man > x86_64-linux-gnu-gcc-11(1)

GCC(1)                                           GNU                                          GCC(1)

NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
           [-g] [-pg] [-Olevel]
           [-Wwarn...] [-Wpedantic]
           [-Idir...] [-Ldir...]
           [-Dmacro[=defn]...] [-Umacro]
           [-foption...] [-mmachine-option...]
           [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the remainder.  g++ accepts
       mostly the same options as gcc.

DESCRIPTION
       When you invoke GCC, it normally does preprocessing, compilation, assembly and linking.  The
       "overall options" allow you to stop this process at an intermediate stage.  For example, the
       -c option says not to run the linker.  Then the output consists of object files output by the
       assembler.

       Other options are passed on to one or more stages of processing.  Some options control the
       preprocessor and others the compiler itself.  Yet other options control the assembler and
       linker; most of these are not documented here, since you rarely need to use any of them.

       Most of the command-line options that you can use with GCC are useful for C programs; when an
       option is only useful with another language (usually C++), the explanation says so
       explicitly.  If the description for a particular option does not mention a source language,
       you can use that option with all supported languages.

       The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-
       compiling, or machine-gcc-version to run a specific version of GCC.  When you compile C++
       programs, you should invoke GCC as g++ instead.

       The gcc program accepts options and file names as operands.  Many options have multi-letter
       names; therefore multiple single-letter options may not be grouped: -dv is very different
       from -d -v.

       You can mix options and other arguments.  For the most part, the order you use doesn't
       matter.  Order does matter when you use several options of the same kind; for example, if you
       specify -L more than once, the directories are searched in the order specified.  Also, the
       placement of the -l option is significant.

       Many options have long names starting with -f or with -W---for example,
       -fmove-loop-invariants, -Wformat and so on.  Most of these have both positive and negative
       forms; the negative form of -ffoo is -fno-foo.  This manual documents only one of these two
       forms, whichever one is not the default.

       Some options take one or more arguments typically separated either by a space or by the
       equals sign (=) from the option name.  Unless documented otherwise, an argument can be either
       numeric or a string.  Numeric arguments must typically be small unsigned decimal or
       hexadecimal integers.  Hexadecimal arguments must begin with the 0x prefix.  Arguments to
       options that specify a size threshold of some sort may be arbitrarily large decimal or
       hexadecimal integers followed by a byte size suffix designating a multiple of bytes such as
       "kB" and "KiB" for kilobyte and kibibyte, respectively, "MB" and "MiB" for megabyte and
       mebibyte, "GB" and "GiB" for gigabyte and gigibyte, and so on.  Such arguments are designated
       by byte-size in the following text.  Refer to the NIST, IEC, and other relevant national and
       international standards for the full listing and explanation of the binary and decimal byte
       size prefixes.

OPTIONS
   Option Summary
       Here is a summary of all the options, grouped by type.  Explanations are in the following
       sections.

       Overall Options
           -c   -S   -E   -o  file -dumpbase dumpbase  -dumpbase-ext auxdropsuf -dumpdir dumppfx  -x
           language -v  -###  --help[=class[,...]]  --target-help  --version -pass-exit-codes  -pipe
           -specs=file       -wrapper      @file       -ffile-prefix-map=old=new       -fplugin=file
           -fplugin-arg-name=arg -fdump-ada-spec[-slim]  -fada-spec-parent=unit  -fdump-go-spec=file

       C Language Options
           -ansi    -std=standard   -fgnu89-inline  -fpermitted-flt-eval-methods=standard  -aux-info
           filename       -fallow-parameterless-variadic-functions      -fno-asm        -fno-builtin
           -fno-builtin-function   -fgimple  -fhosted   -ffreestanding -fopenacc  -fopenacc-dim=geom
           -fopenmp   -fopenmp-simd  -fms-extensions   -fplan9-extensions    -fsso-struct=endianness
           -fallow-single-precision   -fcond-mismatch   -flax-vector-conversions  -fsigned-bitfields
           -fsigned-char -funsigned-bitfields  -funsigned-char

       C++ Language Options
           -fabi-version=n   -fno-access-control   -faligned-new=n    -fargs-in-order=n    -fchar8_t
           -fcheck-new   -fconstexpr-depth=n    -fconstexpr-cache-depth=n   -fconstexpr-loop-limit=n
           -fconstexpr-ops-limit=n -fno-elide-constructors  -fno-enforce-eh-specs  -fno-gnu-keywords
           -fno-implicit-templates       -fno-implicit-inline-templates       -fno-implement-inlines
           -fmodule-header[=kind]      -fmodule-only      -fmodules-ts      -fmodule-implicit-inline
           -fno-module-lazy  -fmodule-mapper=specification  -fmodule-version-ignore  -fms-extensions
           -fnew-inheriting-ctors    -fnew-ttp-matching     -fno-nonansi-builtins      -fnothrow-opt
           -fno-operator-names  -fno-optional-diags   -fpermissive  -fno-pretty-templates  -fno-rtti
           -fsized-deallocation           -ftemplate-backtrace-limit=n            -ftemplate-depth=n
           -fno-threadsafe-statics           -fuse-cxa-atexit         -fno-weak          -nostdinc++
           -fvisibility-inlines-hidden         -fvisibility-ms-compat         -fext-numeric-literals
           -flang-info-include-translate[=header]                  -flang-info-include-translate-not
           -flang-info-module-cmi[=module]   -stdlib=libstdc++,libc++    -Wabi-tag     -Wcatch-value
           -Wcatch-value=n      -Wno-class-conversion       -Wclass-memaccess      -Wcomma-subscript
           -Wconditionally-supported         -Wno-conversion-null           -Wctad-maybe-unsupported
           -Wctor-dtor-privacy   -Wno-delete-incomplete -Wdelete-non-virtual-dtor  -Wdeprecated-copy
           -Wdeprecated-copy-dtor                               -Wno-deprecated-enum-enum-conversion
           -Wno-deprecated-enum-float-conversion      -Weffc++      -Wno-exceptions     -Wextra-semi
           -Wno-inaccessible-base       -Wno-inherited-variadic-ctor         -Wno-init-list-lifetime
           -Winvalid-imported-macros            -Wno-invalid-offsetof            -Wno-literal-suffix
           -Wno-mismatched-new-delete   -Wmismatched-tags    -Wmultiple-inheritance     -Wnamespaces
           -Wnarrowing    -Wnoexcept     -Wnoexcept-type     -Wnon-virtual-dtor   -Wpessimizing-move
           -Wno-placement-new      -Wplacement-new=n     -Wrange-loop-construct     -Wredundant-move
           -Wredundant-tags  -Wreorder   -Wregister  -Wstrict-null-sentinel   -Wno-subobject-linkage
           -Wtemplates     -Wno-non-template-friend       -Wold-style-cast      -Woverloaded-virtual
           -Wno-pmf-conversions     -Wsign-promo    -Wsized-deallocation     -Wsuggest-final-methods
           -Wsuggest-final-types       -Wsuggest-override       -Wno-terminate        -Wuseless-cast
           -Wno-vexing-parse      -Wvirtual-inheritance     -Wno-virtual-move-assign      -Wvolatile
           -Wzero-as-null-pointer-constant

       Objective-C and Objective-C++ Language Options
           -fconstant-string-class=class-name   -fgnu-runtime    -fnext-runtime   -fno-nil-receivers
           -fobjc-abi-version=n   -fobjc-call-cxx-cdtors   -fobjc-direct-dispatch  -fobjc-exceptions
           -fobjc-gc           -fobjc-nilcheck           -fobjc-std=objc1           -fno-local-ivars
           -fivar-visibility=[public|protected|private|package]  -freplace-objc-classes  -fzero-link
           -gen-decls      -Wassign-intercept       -Wno-property-assign-default       -Wno-protocol
           -Wobjc-root-class -Wselector -Wstrict-selector-match -Wundeclared-selector

       Diagnostic Message Formatting Options
           -fmessage-length=n   -fdiagnostics-plain-output  -fdiagnostics-show-location=[once|every-
           line]   -fdiagnostics-color=[auto|never|always]    -fdiagnostics-urls=[auto|never|always]
           -fdiagnostics-format=[text|json]                             -fno-diagnostics-show-option
           -fno-diagnostics-show-caret                                  -fno-diagnostics-show-labels
           -fno-diagnostics-show-line-numbers                              -fno-diagnostics-show-cwe
           -fdiagnostics-minimum-margin-width=width                   -fdiagnostics-parseable-fixits
           -fdiagnostics-generate-patch       -fdiagnostics-show-template-tree       -fno-elide-type
           -fdiagnostics-path-format=[none|separate-events|inline-events]
           -fdiagnostics-show-path-depths -fno-show-column  -fdiagnostics-column-unit=[display|byte]
           -fdiagnostics-column-origin=origin

       Warning Options
           -fsyntax-only   -fmax-errors=n   -Wpedantic  -pedantic-errors -w  -Wextra  -Wall  -Wabi=n
           -Waddress                -Wno-address-of-packed-member                 -Waggregate-return
           -Walloc-size-larger-than=byte-size  -Walloc-zero -Walloca  -Walloca-larger-than=byte-size
           -Wno-aggressive-loop-optimizations  -Warith-conversion  -Warray-bounds   -Warray-bounds=n
           -Wno-attributes     -Wattribute-alias=n    -Wno-attribute-alias    -Wno-attribute-warning
           -Wbool-compare              -Wbool-operation            -Wno-builtin-declaration-mismatch
           -Wno-builtin-macro-redefined    -Wc90-c99-compat     -Wc99-c11-compat    -Wc11-c2x-compat
           -Wc++-compat   -Wc++11-compat  -Wc++14-compat  -Wc++17-compat -Wc++20-compat -Wcast-align
           -Wcast-align=strict   -Wcast-function-type   -Wcast-qual  -Wchar-subscripts   -Wclobbered
           -Wcomment  -Wconversion   -Wno-coverage-mismatch   -Wno-cpp  -Wdangling-else  -Wdate-time
           -Wno-deprecated             -Wno-deprecated-declarations             -Wno-designated-init
           -Wdisabled-optimization     -Wno-discarded-array-qualifiers     -Wno-discarded-qualifiers
           -Wno-div-by-zero      -Wdouble-promotion     -Wduplicated-branches      -Wduplicated-cond
           -Wempty-body   -Wno-endif-labels   -Wenum-compare   -Wenum-conversion  -Werror  -Werror=*
           -Wexpansion-to-defined   -Wfatal-errors   -Wfloat-conversion    -Wfloat-equal    -Wformat
           -Wformat=2     -Wno-format-contains-nul     -Wno-format-extra-args    -Wformat-nonliteral
           -Wformat-overflow=n   -Wformat-security     -Wformat-signedness     -Wformat-truncation=n
           -Wformat-y2k    -Wframe-address  -Wframe-larger-than=byte-size   -Wno-free-nonheap-object
           -Wno-if-not-aligned              -Wno-ignored-attributes             -Wignored-qualifiers
           -Wno-incompatible-pointer-types             -Wimplicit             -Wimplicit-fallthrough
           -Wimplicit-fallthrough=n      -Wno-implicit-function-declaration        -Wno-implicit-int
           -Winit-self          -Winline          -Wno-int-conversion          -Wint-in-bool-context
           -Wno-int-to-pointer-cast   -Wno-invalid-memory-model  -Winvalid-pch    -Wjump-misses-init
           -Wlarger-than=byte-size      -Wlogical-not-parentheses      -Wlogical-op      -Wlong-long
           -Wno-lto-type-mismatch       -Wmain        -Wmaybe-uninitialized        -Wmemset-elt-size
           -Wmemset-transposed-args -Wmisleading-indentation  -Wmissing-attributes  -Wmissing-braces
           -Wmissing-field-initializers       -Wmissing-format-attribute      -Wmissing-include-dirs
           -Wmissing-noreturn     -Wno-missing-profile    -Wno-multichar     -Wmultistatement-macros
           -Wnonnull  -Wnonnull-compare -Wnormalized=[none|id|nfc|nfkc] -Wnull-dereference  -Wno-odr
           -Wopenmp-simd    -Wno-overflow    -Woverlength-strings    -Wno-override-init-side-effects
           -Wpacked   -Wno-packed-bitfield-compat   -Wpacked-not-aligned    -Wpadded   -Wparentheses
           -Wno-pedantic-ms-format  -Wpointer-arith   -Wno-pointer-compare  -Wno-pointer-to-int-cast
           -Wno-pragmas  -Wno-prio-ctor-dtor  -Wredundant-decls  -Wrestrict   -Wno-return-local-addr
           -Wreturn-type   -Wno-scalar-storage-order    -Wsequence-point  -Wshadow   -Wshadow=global
           -Wshadow=local   -Wshadow=compatible-local   -Wno-shadow-ivar   -Wno-shift-count-negative
           -Wno-shift-count-overflow  -Wshift-negative-value -Wno-shift-overflow  -Wshift-overflow=n
           -Wsign-compare      -Wsign-conversion    -Wno-sizeof-array-argument    -Wsizeof-array-div
           -Wsizeof-pointer-div  -Wsizeof-pointer-memaccess  -Wstack-protector   -Wstack-usage=byte-
           size    -Wstrict-aliasing   -Wstrict-aliasing=n   -Wstrict-overflow   -Wstrict-overflow=n
           -Wstring-compare -Wno-stringop-overflow  -Wno-stringop-overread  -Wno-stringop-truncation
           -Wsuggest-attribute=[pure|const|noreturn|format|malloc]     -Wswitch     -Wno-switch-bool
           -Wswitch-default    -Wswitch-enum   -Wno-switch-outside-range     -Wno-switch-unreachable
           -Wsync-nand  -Wsystem-headers   -Wtautological-compare  -Wtrampolines  -Wtrigraphs -Wtsan
           -Wtype-limits  -Wundef  -Wuninitialized   -Wunknown-pragmas  -Wunsuffixed-float-constants
           -Wunused  -Wunused-but-set-parameter   -Wunused-but-set-variable  -Wunused-const-variable
           -Wunused-const-variable=n  -Wunused-function    -Wunused-label    -Wunused-local-typedefs
           -Wunused-macros  -Wunused-parameter  -Wno-unused-result -Wunused-value  -Wunused-variable
           -Wno-varargs         -Wvariadic-macros        -Wvector-operation-performance        -Wvla
           -Wvla-larger-than=byte-size          -Wno-vla-larger-than         -Wvolatile-register-var
           -Wwrite-strings -Wzero-length-bounds

       Static Analyzer Options
           -fanalyzer  -fanalyzer-call-summaries  -fanalyzer-checker=name  -fno-analyzer-feasibility
           -fanalyzer-fine-grained           -fanalyzer-state-merge           -fanalyzer-state-purge
           -fanalyzer-transitivity     -fanalyzer-verbose-edges     -fanalyzer-verbose-state-changes
           -fanalyzer-verbosity=level             -fdump-analyzer             -fdump-analyzer-stderr
           -fdump-analyzer-callgraph  -fdump-analyzer-exploded-graph  -fdump-analyzer-exploded-nodes
           -fdump-analyzer-exploded-nodes-2                         -fdump-analyzer-exploded-nodes-3
           -fdump-analyzer-feasibility       -fdump-analyzer-json        -fdump-analyzer-state-purge
           -fdump-analyzer-supergraph      -Wno-analyzer-double-fclose     -Wno-analyzer-double-free
           -Wno-analyzer-exposure-through-output-file                        -Wno-analyzer-file-leak
           -Wno-analyzer-free-of-non-heap                                  -Wno-analyzer-malloc-leak
           -Wno-analyzer-mismatching-deallocation                        -Wno-analyzer-null-argument
           -Wno-analyzer-null-dereference                       -Wno-analyzer-possible-null-argument
           -Wno-analyzer-possible-null-dereference                -Wno-analyzer-shift-count-negative
           -Wno-analyzer-shift-count-overflow                      -Wno-analyzer-stale-setjmp-buffer
           -Wno-analyzer-tainted-array-index                                  -Wanalyzer-too-complex
           -Wno-analyzer-unsafe-call-within-signal-handler              -Wno-analyzer-use-after-free
           -Wno-analyzer-use-of-pointer-in-stale-stack-frame
           -Wno-analyzer-use-of-uninitialized-value                     -Wno-analyzer-write-to-const
           -Wno-analyzer-write-to-string-literal

       C and Objective-C-only Warning Options
           -Wbad-function-cast             -Wmissing-declarations           -Wmissing-parameter-type
           -Wmissing-prototypes   -Wnested-externs  -Wold-style-declaration   -Wold-style-definition
           -Wstrict-prototypes                 -Wtraditional                -Wtraditional-conversion
           -Wdeclaration-after-statement  -Wpointer-sign

       Debugging Options
           -g      -glevel      -gdwarf       -gdwarf-version      -ggdb       -grecord-gcc-switches
           -gno-record-gcc-switches    -gstabs     -gstabs+     -gstrict-dwarf     -gno-strict-dwarf
           -gas-loc-support    -gno-as-loc-support   -gas-locview-support    -gno-as-locview-support
           -gcolumn-info      -gno-column-info      -gdwarf32     -gdwarf64    -gstatement-frontiers
           -gno-statement-frontiers     -gvariable-location-views       -gno-variable-location-views
           -ginternal-reset-location-views     -gno-internal-reset-location-views    -ginline-points
           -gno-inline-points -gvms  -gxcoff  -gxcoff+   -gz[=type]  -gsplit-dwarf   -gdescribe-dies
           -gno-describe-dies            -fdebug-prefix-map=old=new            -fdebug-types-section
           -fno-eliminate-unused-debug-types                            -femit-struct-debug-baseonly
           -femit-struct-debug-reduced                      -femit-struct-debug-detailed[=spec-list]
           -fno-eliminate-unused-debug-symbols   -femit-class-debug-always  -fno-merge-debug-strings
           -fno-dwarf2-cfi-asm -fvar-tracking  -fvar-tracking-assignments

       Optimization Options
           -faggressive-loop-optimizations                       -falign-functions[=n[:m:[n2[:m2]]]]
           -falign-jumps[=n[:m:[n2[:m2]]]]                          -falign-labels[=n[:m:[n2[:m2]]]]
           -falign-loops[=n[:m:[n2[:m2]]]]        -fno-allocation-dce       -fallow-store-data-races
           -fassociative-math       -fauto-profile        -fauto-profile[=path]       -fauto-inc-dec
           -fbranch-probabilities   -fcaller-saves   -fcombine-stack-adjustments    -fconserve-stack
           -fcompare-elim  -fcprop-registers  -fcrossjumping  -fcse-follow-jumps   -fcse-skip-blocks
           -fcx-fortran-rules    -fcx-limited-range    -fdata-sections     -fdce    -fdelayed-branch
           -fdelete-null-pointer-checks         -fdevirtualize          -fdevirtualize-speculatively
           -fdevirtualize-at-ltrans   -fdse  -fearly-inlining   -fipa-sra  -fexpensive-optimizations
           -ffat-lto-objects         -ffast-math          -ffinite-math-only           -ffloat-store
           -fexcess-precision=style    -ffinite-loops    -fforward-propagate     -ffp-contract=style
           -ffunction-sections     -fgcse       -fgcse-after-reload       -fgcse-las       -fgcse-lm
           -fgraphite-identity  -fgcse-sm   -fhoist-adjacent-loads  -fif-conversion -fif-conversion2
           -findirect-inlining -finline-functions  -finline-functions-called-once   -finline-limit=n
           -finline-small-functions  -fipa-modref  -fipa-cp   -fipa-cp-clone -fipa-bit-cp  -fipa-vrp
           -fipa-pta  -fipa-profile  -fipa-pure-const  -fipa-reference   -fipa-reference-addressable
           -fipa-stack-alignment     -fipa-icf     -fira-algorithm=algorithm   -flive-patching=level
           -fira-region=region  -fira-hoist-pressure -fira-loop-pressure   -fno-ira-share-save-slots
           -fno-ira-share-spill-slots                          -fisolate-erroneous-paths-dereference
           -fisolate-erroneous-paths-attribute           -fivopts            -fkeep-inline-functions
           -fkeep-static-functions          -fkeep-static-consts          -flimit-function-alignment
           -flive-range-shrinkage      -floop-block       -floop-interchange       -floop-strip-mine
           -floop-unroll-and-jam   -floop-nest-optimize  -floop-parallelize-all   -flra-remat  -flto
           -flto-compression-level  -flto-partition=alg    -fmerge-all-constants   -fmerge-constants
           -fmodulo-sched             -fmodulo-sched-allow-regmoves           -fmove-loop-invariants
           -fno-branch-count-reg  -fno-defer-pop    -fno-fp-int-builtin-inexact    -fno-function-cse
           -fno-guess-branch-probability  -fno-inline  -fno-math-errno  -fno-peephole -fno-peephole2
           -fno-printf-return-value     -fno-sched-interblock   -fno-sched-spec    -fno-signed-zeros
           -fno-toplevel-reorder           -fno-trapping-math           -fno-zero-initialized-in-bss
           -fomit-frame-pointer      -foptimize-sibling-calls    -fpartial-inlining     -fpeel-loops
           -fpredictive-commoning    -fprefetch-loop-arrays    -fprofile-correction    -fprofile-use
           -fprofile-use=path               -fprofile-partial-training              -fprofile-values
           -fprofile-reorder-functions      -freciprocal-math        -free        -frename-registers
           -freorder-blocks    -freorder-blocks-algorithm=algorithm   -freorder-blocks-and-partition
           -freorder-functions      -frerun-cse-after-loop       -freschedule-modulo-scheduled-loops
           -frounding-math   -fsave-optimization-record  -fsched2-use-superblocks   -fsched-pressure
           -fsched-spec-load        -fsched-spec-load-dangerous        -fsched-stalled-insns-dep[=n]
           -fsched-stalled-insns[=n]     -fsched-group-heuristic     -fsched-critical-path-heuristic
           -fsched-spec-insn-heuristic       -fsched-rank-heuristic      -fsched-last-insn-heuristic
           -fsched-dep-count-heuristic    -fschedule-fusion    -fschedule-insns    -fschedule-insns2
           -fsection-anchors -fselective-scheduling  -fselective-scheduling2  -fsel-sched-pipelining
           -fsel-sched-pipelining-outer-loops         -fsemantic-interposition         -fshrink-wrap
           -fshrink-wrap-separate            -fsignaling-nans            -fsingle-precision-constant
           -fsplit-ivs-in-unroller        -fsplit-loops       -fsplit-paths       -fsplit-wide-types
           -fsplit-wide-types-early   -fssa-backprop   -fssa-phiopt  -fstdarg-opt    -fstore-merging
           -fstrict-aliasing   -fthread-jumps    -ftracer    -ftree-bit-ccp  -ftree-builtin-call-dce
           -ftree-ccp      -ftree-ch     -ftree-coalesce-vars      -ftree-copy-prop       -ftree-dce
           -ftree-dominator-opts    -ftree-dse     -ftree-forwprop     -ftree-fre    -fcode-hoisting
           -ftree-loop-if-convert     -ftree-loop-im    -ftree-phiprop      -ftree-loop-distribution
           -ftree-loop-distribute-patterns          -ftree-loop-ivcanon           -ftree-loop-linear
           -ftree-loop-optimize   -ftree-loop-vectorize    -ftree-parallelize-loops=n     -ftree-pre
           -ftree-partial-pre     -ftree-pta    -ftree-reassoc     -ftree-scev-cprop     -ftree-sink
           -ftree-slsr    -ftree-sra    -ftree-switch-conversion     -ftree-tail-merge    -ftree-ter
           -ftree-vectorize         -ftree-vrp        -funconstrained-commons       -funit-at-a-time
           -funroll-all-loops  -funroll-loops -funsafe-math-optimizations  -funswitch-loops -fipa-ra
           -fvariable-expansion-in-unroller  -fvect-cost-model  -fvpt -fweb  -fwhole-program   -fwpa
           -fuse-linker-plugin  -fzero-call-used-regs --param name=value -O  -O0  -O1  -O2  -O3  -Os
           -Ofast  -Og

       Program Instrumentation Options
           -p     -pg     -fprofile-arcs      --coverage      -ftest-coverage     -fprofile-abs-path
           -fprofile-dir=path   -fprofile-generate   -fprofile-generate=path  -fprofile-info-section
           -fprofile-info-section=name        -fprofile-note=path         -fprofile-prefix-path=path
           -fprofile-update=method     -fprofile-filter-files=regex    -fprofile-exclude-files=regex
           -fprofile-reproducible=[multithreaded|parallel-runs|serial]              -fsanitize=style
           -fsanitize-recover           -fsanitize-recover=style         -fasan-shadow-offset=number
           -fsanitize-sections=s1,s2,...      -fsanitize-undefined-trap-on-error      -fbounds-check
           -fcf-protection=[full|branch|return|none|check]  -fstack-protector  -fstack-protector-all
           -fstack-protector-strong            -fstack-protector-explicit              -fstack-check
           -fstack-limit-register=reg    -fstack-limit-symbol=sym   -fno-stack-limit   -fsplit-stack
           -fvtable-verify=[std|preinit|none]   -fvtv-counts    -fvtv-debug   -finstrument-functions
           -finstrument-functions-exclude-function-list=sym,sym,...
           -finstrument-functions-exclude-file-list=file,file,...

       Preprocessor Options
           -Aquestion=answer  -A-question[=answer]  -C   -CC  -Dmacro[=defn] -dD  -dI  -dM  -dN  -dU
           -fdebug-cpp     -fdirectives-only     -fdollars-in-identifiers     -fexec-charset=charset
           -fextended-identifiers            -finput-charset=charset            -flarge-source-files
           -fmacro-prefix-map=old=new    -fmax-include-depth=depth     -fno-canonical-system-headers
           -fpch-deps   -fpch-preprocess  -fpreprocessed   -ftabstop=width   -ftrack-macro-expansion
           -fwide-exec-charset=charset  -fworking-directory -H  -imacros file  -include file -M  -MD
           -MF  -MG  -MM  -MMD  -MP  -MQ  -MT -Mno-modules -no-integrated-cpp  -P  -pthread   -remap
           -traditional   -traditional-cpp   -trigraphs  -Umacro   -undef -Wp,option  -Xpreprocessor
           option

       Assembler Options
           -Wa,option  -Xassembler option

       Linker Options
           object-file-name   -fuse-ld=linker   -llibrary  -nostartfiles   -nodefaultlibs    -nolibc
           -nostdlib  -e entry  --entry=entry -pie  -pthread  -r  -rdynamic -s  -static  -static-pie
           -static-libgcc   -static-libstdc++  -static-libasan    -static-libtsan    -static-liblsan
           -static-libubsan  -shared   -shared-libgcc   -symbolic  -T  script   -Wl,option  -Xlinker
           option -u symbol  -z keyword

       Directory Options
           -Bprefix  -Idir   -I-  -idirafter  dir  -imacros  file   -imultilib  dir  -iplugindir=dir
           -iprefix   file   -iquote   dir    -isysroot   dir    -isystem   dir   -iwithprefix   dir
           -iwithprefixbefore  dir  -Ldir   -no-canonical-prefixes   --no-sysroot-suffix   -nostdinc
           -nostdinc++  --sysroot=dir

       Code Generation Options
           -fcall-saved-reg    -fcall-used-reg   -ffixed-reg    -fexceptions   -fnon-call-exceptions
           -fdelete-dead-exceptions   -funwind-tables  -fasynchronous-unwind-tables  -fno-gnu-unique
           -finhibit-size-directive   -fcommon   -fno-ident -fpcc-struct-return  -fpic  -fPIC  -fpie
           -fPIE  -fno-plt -fno-jump-tables -fno-bit-tests -frecord-gcc-switches -freg-struct-return
           -fshort-enums   -fshort-wchar   -fverbose-asm    -fpack-struct[=n]   -fleading-underscore
           -ftls-model=model     -fstack-reuse=reuse_level     -ftrampolines     -ftrapv     -fwrapv
           -fvisibility=[default|internal|hidden|protected]              -fstrict-volatile-bitfields
           -fsync-libcalls

       Developer Options
           -dletters        -dumpspecs        -dumpmachine        -dumpversion      -dumpfullversion
           -fcallgraph-info[=su,da]  -fchecking   -fchecking=n  -fdbg-cnt-list    -fdbg-cnt=counter-
           value-list -fdisable-ipa-pass_name -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-
           list     -fdisable-tree-pass_name     -fdisable-tree-pass-name=range-list    -fdump-debug
           -fdump-earlydebug     -fdump-noaddr       -fdump-unnumbered       -fdump-unnumbered-links
           -fdump-final-insns[=file]     -fdump-ipa-all      -fdump-ipa-cgraph     -fdump-ipa-inline
           -fdump-lang-all               -fdump-lang-switch               -fdump-lang-switch-options
           -fdump-lang-switch-options=filename             -fdump-passes             -fdump-rtl-pass
           -fdump-rtl-pass=filename     -fdump-statistics     -fdump-tree-all     -fdump-tree-switch
           -fdump-tree-switch-options   -fdump-tree-switch-options=filename   -fcompare-debug[=opts]
           -fcompare-debug-second -fenable-kind-pass  -fenable-kind-pass=range-list  -fira-verbose=n
           -flto-report    -flto-report-wpa    -fmem-report-wpa  -fmem-report   -fpre-ipa-mem-report
           -fpost-ipa-mem-report     -fopt-info      -fopt-info-options[=file]      -fprofile-report
           -frandom-seed=string     -fsched-verbose=n    -fsel-sched-verbose    -fsel-sched-dump-cfg
           -fsel-sched-pipelining-verbose        -fstats         -fstack-usage         -ftime-report
           -ftime-report-details             -fvar-tracking-assignments-toggle              -gtoggle
           -print-file-name=library          -print-libgcc-file-name          -print-multi-directory
           -print-multi-lib   -print-multi-os-directory -print-prog-name=program  -print-search-dirs
           -Q    -print-sysroot     -print-sysroot-headers-suffix    -save-temps     -save-temps=cwd
           -save-temps=obj  -time[=file]

       Machine-Dependent Options
           AArch64    Options    -mabi=name    -mbig-endian    -mlittle-endian   -mgeneral-regs-only
           -mcmodel=tiny    -mcmodel=small    -mcmodel=large    -mstrict-align     -mno-strict-align
           -momit-leaf-frame-pointer  -mtls-dialect=desc   -mtls-dialect=traditional -mtls-size=size
           -mfix-cortex-a53-835769         -mfix-cortex-a53-843419        -mlow-precision-recip-sqrt
           -mlow-precision-sqrt            -mlow-precision-div           -mpc-relative-literal-loads
           -msign-return-address=scope  -mbranch-protection=none|standard|pac-ret[+leaf  +b-key]|bti
           -mharden-sls=opts      -march=name      -mcpu=name      -mtune=name     -moverride=string
           -mverbose-cost-dump   -mstack-protector-guard=guard    -mstack-protector-guard-reg=sysreg
           -mstack-protector-guard-offset=offset -mtrack-speculation -moutline-atomics

           Adapteva  Epiphany  Options  -mhalf-reg-file   -mprefer-short-insn-regs -mbranch-cost=num
           -mcmove     -mnops=num     -msoft-cmpsf    -msplit-lohi     -mpost-inc      -mpost-modify
           -mstack-offset=num -mround-nearest  -mlong-calls  -mshort-calls  -msmall16 -mfp-mode=mode
           -mvect-double  -max-vect-align=num -msplit-vecmove-early  -m1reg-reg

           AMD GCN Options -march=gpu -mtune=gpu -mstack-size=bytes

           ARC  Options  -mbarrel-shifter   -mjli-always  -mcpu=cpu   -mA6  -mARC600  -mA7  -mARC700
           -mdpfp  -mdpfp-compact  -mdpfp-fast  -mno-dpfp-lrsr -mea  -mno-mpy   -mmul32x16   -mmul64
           -matomic  -mnorm  -mspfp  -mspfp-compact  -mspfp-fast  -msimd  -msoft-float  -mswap -mcrc
           -mdsp-packa  -mdvbf  -mlock   -mmac-d16   -mmac-24   -mrtsc   -mswape  -mtelephony   -mxy
           -misize    -mannotate-align   -marclinux   -marclinux_prof  -mlong-calls   -mmedium-calls
           -msdata  -mirq-ctrl-saved -mrgf-banked-regs  -mlpc-width=width  -G  num  -mvolatile-cache
           -mtp-regno=regno     -malign-call     -mauto-modify-reg     -mbbit-peephole     -mno-brcc
           -mcase-vector-pcrel  -mcompact-casesi  -mno-cond-exec   -mearly-cbranchsi  -mexpand-adddi
           -mindexed-loads    -mlra    -mlra-priority-none   -mlra-priority-compact   mlra-priority-
           noncompact   -mmillicode  -mmixed-code   -mq-class   -mRcq    -mRcw    -msize-level=level
           -mtune=cpu    -mmultcost=num   -mcode-density-frame  -munalign-prob-threshold=probability
           -mmpy-option=multo -mdiv-rem  -mcode-density  -mll64  -mfpu=fpu  -mrf16  -mbranch-index

           ARM    Options    -mapcs-frame      -mno-apcs-frame     -mabi=name     -mapcs-stack-check
           -mno-apcs-stack-check     -mapcs-reentrant     -mno-apcs-reentrant    -mgeneral-regs-only
           -msched-prolog    -mno-sched-prolog   -mlittle-endian    -mbig-endian    -mbe8     -mbe32
           -mfloat-abi=name  -mfp16-format=name  -mthumb-interwork   -mno-thumb-interwork -mcpu=name
           -march=name   -mfpu=name   -mtune=name    -mprint-tune-info   -mstructure-size-boundary=n
           -mabort-on-noreturn -mlong-calls  -mno-long-calls -msingle-pic-base  -mno-single-pic-base
           -mpic-register=reg  -mnop-fun-dllimport -mpoke-function-name -mthumb  -marm  -mflip-thumb
           -mtpcs-frame  -mtpcs-leaf-frame -mcaller-super-interworking   -mcallee-super-interworking
           -mtp=name        -mtls-dialect=dialect       -mword-relocations      -mfix-cortex-m3-ldrd
           -munaligned-access -mneon-for-64bits -mslow-flash-data -masm-syntax-unified -mrestrict-it
           -mverbose-cost-dump -mpure-code -mcmse -mfix-cmse-cve-2021-35465 -mfdpic

           AVR Options -mmcu=mcu  -mabsdata  -maccumulate-args  -mbranch-cost=cost  -mcall-prologues
           -mgas-isr-prologues      -mint8     -mdouble=bits    -mlong-double=bits    -mn_flash=size
           -mno-interrupts   -mmain-is-OS_task     -mrelax     -mrmw     -mstrict-X     -mtiny-stack
           -mfract-convert-truncate -mshort-calls  -nodevicelib  -nodevicespecs -Waddr-space-convert
           -Wmisspelled-isr

           Blackfin      Options     -mcpu=cpu[-sirevision]     -msim      -momit-leaf-frame-pointer
           -mno-omit-leaf-frame-pointer   -mspecld-anomaly    -mno-specld-anomaly    -mcsync-anomaly
           -mno-csync-anomaly    -mlow-64k    -mno-low64k    -mstack-check-l1    -mid-shared-library
           -mno-id-shared-library           -mshared-library-id=n           -mleaf-id-shared-library
           -mno-leaf-id-shared-library   -msep-data   -mno-sep-data   -mlong-calls   -mno-long-calls
           -mfast-fp  -minline-plt  -mmulticore  -mcorea  -mcoreb  -msdram -micplb

           C6X Options -mbig-endian  -mlittle-endian  -march=cpu -msim  -msdata=sdata-type

           CRIS Options -mcpu=cpu  -march=cpu -mtune=cpu  -mmax-stack-frame=n  -metrax4   -metrax100
           -mpdebug    -mcc-init    -mno-side-effects   -mstack-align   -mdata-align   -mconst-align
           -m32-bit   -m16-bit   -m8-bit   -mno-prologue-epilogue   -melf    -maout    -sim    -sim2
           -mmul-bug-workaround  -mno-mul-bug-workaround

           CR16 Options -mmac -mcr16cplus  -mcr16c -msim  -mint32  -mbit-ops -mdata-model=model

           C-SKY Options -march=arch  -mcpu=cpu -mbig-endian  -EB  -mlittle-endian  -EL -mhard-float
           -msoft-float  -mfpu=fpu  -mdouble-float  -mfdivdu -mfloat-abi=name -melrw  -mistack  -mmp
           -mcp  -mcache  -msecurity  -mtrust -mdsp  -medsp  -mvdsp -mdiv  -msmart  -mhigh-registers
           -manchor  -mpushpop   -mmultiple-stld   -mconstpool  -mstack-size  -mccrt -mbranch-cost=n
           -mcse-cc  -msched-prolog -msim

           Darwin  Options  -all_load   -allowable_client   -arch    -arch_errors_fatal   -arch_only
           -bind_at_load      -bundle      -bundle_loader    -client_name     -compatibility_version
           -current_version  -dead_strip   -dependency-file    -dylib_file    -dylinker_install_name
           -dynamic       -dynamiclib      -exported_symbols_list     -filelist      -flat_namespace
           -force_cpusubtype_ALL  -force_flat_namespace   -headerpad_max_install_names   -iframework
           -image_base  -init  -install_name  -keep_private_externs -multi_module  -multiply_defined
           -multiply_defined_unused  -noall_load    -no_dead_strip_inits_and_terms  -nofixprebinding
           -nomultidefs        -noprebind        -noseglinkedit       -pagezero_size        -prebind
           -prebind_all_twolevel_modules      -private_bundle      -read_only_relocs      -sectalign
           -sectobjectsymbols   -whyload   -seg1addr  -sectcreate   -sectobjectsymbols    -sectorder
           -segaddr         -segs_read_only_addr         -segs_read_write_addr       -seg_addr_table
           -seg_addr_table_filename        -seglinkedit        -segprot         -segs_read_only_addr
           -segs_read_write_addr     -single_module      -static      -sub_library     -sub_umbrella
           -twolevel_namespace         -umbrella         -undefined         -unexported_symbols_list
           -weak_reference_mismatches -whatsloaded  -F  -gused  -gfull  -mmacosx-version-min=version
           -mkernel  -mone-byte-bool

           DEC    Alpha    Options    -mno-fp-regs     -msoft-float    -mieee    -mieee-with-inexact
           -mieee-conformant  -mfp-trap-mode=mode    -mfp-rounding-mode=mode   -mtrap-precision=mode
           -mbuild-constants  -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix -mfloat-vax
           -mfloat-ieee -mexplicit-relocs   -msmall-data   -mlarge-data  -msmall-text   -mlarge-text
           -mmemory-latency=time

           eBPF Options -mbig-endian -mlittle-endian -mkernel=version -mframe-limit=bytes -mxbpf

           FR30 Options -msmall-model  -mno-lsim

           FT32 Options -msim  -mlra  -mnodiv  -mft32b  -mcompress  -mnopm

           FRV  Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float  -msoft-float -malloc-cc
           -mfixed-cc  -mdword   -mno-dword  -mdouble   -mno-double  -mmedia   -mno-media   -mmuladd
           -mno-muladd   -mfdpic    -minline-plt    -mgprel-ro    -multilib-library-pic  -mlinked-fp
           -mlong-calls   -malign-labels   -mlibrary-pic    -macc-4    -macc-8   -mpack    -mno-pack
           -mno-eflags   -mcond-move   -mno-cond-move  -moptimize-membar  -mno-optimize-membar -mscc
           -mno-scc  -mcond-exec  -mno-cond-exec -mvliw-branch   -mno-vliw-branch  -mmulti-cond-exec
           -mno-multi-cond-exec    -mnested-cond-exec  -mno-nested-cond-exec   -mtomcat-stats  -mTLS
           -mtls -mcpu=cpu

           GNU/Linux  Options  -mglibc   -muclibc   -mmusl   -mbionic    -mandroid   -tno-android-cc
           -tno-android-ld

           H8/300 Options -mrelax  -mh  -ms  -mn  -mexr  -mno-exr  -mint32  -malign-300

           HPPA      Options      -march=architecture-type     -mcaller-copies      -mdisable-fpregs
           -mdisable-indexing      -mfast-indirect-calls       -mgas        -mgnu-ld         -mhp-ld
           -mfixed-range=register-range       -mjump-in-delay        -mlinker-opt       -mlong-calls
           -mlong-load-store   -mno-disable-fpregs  -mno-disable-indexing   -mno-fast-indirect-calls
           -mno-gas  -mno-jump-in-delay  -mno-long-load-store -mno-portable-runtime  -mno-soft-float
           -mno-space-regs      -msoft-float      -mpa-risc-1-0     -mpa-risc-1-1      -mpa-risc-2-0
           -mportable-runtime   -mschedule=cpu-type   -mspace-regs   -msio   -mwsio  -munix=unix-std
           -nolibdld  -static  -threads

           IA-64   Options   -mbig-endian     -mlittle-endian     -mgnu-as     -mgnu-ld     -mno-pic
           -mvolatile-asm-stop   -mregister-names   -msdata   -mno-sdata  -mconstant-gp   -mauto-pic
           -mfused-madd    -minline-float-divide-min-latency    -minline-float-divide-max-throughput
           -mno-inline-float-divide                                  -minline-int-divide-min-latency
           -minline-int-divide-max-throughput    -mno-inline-int-divide    -minline-sqrt-min-latency
           -minline-sqrt-max-throughput     -mno-inline-sqrt     -mdwarf2-asm      -mearly-stop-bits
           -mfixed-range=register-range   -mtls-size=tls-size   -mtune=cpu-type    -milp32    -mlp64
           -msched-br-data-spec   -msched-ar-data-spec  -msched-control-spec -msched-br-in-data-spec
           -msched-ar-in-data-spec              -msched-in-control-spec             -msched-spec-ldc
           -msched-spec-control-ldc                               -msched-prefer-non-data-spec-insns
           -msched-prefer-non-control-spec-insns                 -msched-stop-bits-after-every-cycle
           -msched-count-spec-in-critical-path                   -msel-sched-dont-check-control-spec
           -msched-fp-mem-deps-zero-cost                         -msched-max-memory-insns-hard-limit
           -msched-max-memory-insns=max-insns

           LM32     Options     -mbarrel-shift-enabled      -mdivide-enabled      -mmultiply-enabled
           -msign-extend-enabled  -muser-enabled

           M32R/D  Options   -m32r2    -m32rx    -m32r   -mdebug   -malign-loops    -mno-align-loops
           -missue-rate=number  -mbranch-cost=number -mmodel=code-size-model-type -msdata=sdata-type
           -mno-flush-func  -mflush-func=name -mno-flush-trap  -mflush-trap=number -G num

           M32C Options -mcpu=cpu  -msim  -memregs=number

           M680x0  Options  -march=arch   -mcpu=cpu   -mtune=tune   -m68000    -m68020    -m68020-40
           -m68020-60   -m68030   -m68040  -m68060  -mcpu32  -m5200  -m5206e  -m528x  -m5307  -m5407
           -mcfv4e  -mbitfield  -mno-bitfield   -mc68000   -mc68020  -mnobitfield   -mrtd   -mno-rtd
           -mdiv    -mno-div   -mshort  -mno-short   -mhard-float   -m68881   -msoft-float   -mpcrel
           -malign-int     -mstrict-align     -msep-data     -mno-sep-data     -mshared-library-id=n
           -mid-shared-library  -mno-id-shared-library -mxgot  -mno-xgot  -mlong-jump-table-offsets

           MCore    Options    -mhardlit     -mno-hardlit    -mdiv    -mno-div    -mrelax-immediates
           -mno-relax-immediates     -mwide-bitfields      -mno-wide-bitfields     -m4byte-functions
           -mno-4byte-functions  -mcallgraph-data -mno-callgraph-data  -mslow-bytes  -mno-slow-bytes
           -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340  -mstack-increment

           MeP   Options   -mabsdiff   -mall-opts   -maverage   -mbased=n   -mbitops  -mc=n   -mclip
           -mconfig=name  -mcop  -mcop32  -mcop64  -mivc2 -mdc   -mdiv   -meb   -mel   -mio-volatile
           -ml   -mleadz   -mm   -mminmax  -mmult  -mno-opts  -mrepeat  -ms  -msatur  -msdram  -msim
           -msimnovec  -mtf -mtiny=n

           MicroBlaze  Options  -msoft-float   -mhard-float   -msmall-divides   -mcpu=cpu   -mmemcpy
           -mxl-soft-mul   -mxl-soft-div   -mxl-barrel-shift  -mxl-pattern-compare  -mxl-stack-check
           -mxl-gp-opt   -mno-clearbss   -mxl-multiply-high    -mxl-float-convert    -mxl-float-sqrt
           -mbig-endian           -mlittle-endian          -mxl-reorder          -mxl-mode-app-model
           -mpic-data-is-text-relative

           MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2  -mips3   -mips4   -mips32
           -mips32r2   -mips32r3   -mips32r5  -mips32r6   -mips64   -mips64r2   -mips64r3  -mips64r5
           -mips64r6      -mips16       -mno-mips16       -mflip-mips16       -minterlink-compressed
           -mno-interlink-compressed -minterlink-mips16  -mno-interlink-mips16 -mabi=abi  -mabicalls
           -mno-abicalls  -mshared   -mno-shared   -mplt  -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64
           -mfp32    -mfpxx    -mfp64    -mhard-float    -msoft-float   -mno-float    -msingle-float
           -mdouble-float  -modd-spreg   -mno-odd-spreg  -mabs=mode   -mnan=encoding -mdsp  -mno-dsp
           -mdspr2  -mno-dspr2 -mmcu  -mmno-mcu -meva  -mno-eva -mvirt   -mno-virt  -mxpa   -mno-xpa
           -mcrc    -mno-crc   -mginv    -mno-ginv   -mmicromips    -mno-micromips  -mmsa   -mno-msa
           -mloongson-mmi   -mno-loongson-mmi  -mloongson-ext    -mno-loongson-ext   -mloongson-ext2
           -mno-loongson-ext2    -mfpu=fpu-type    -msmartmips     -mno-smartmips    -mpaired-single
           -mno-paired-single   -mdmx   -mno-mdmx  -mips3d   -mno-mips3d   -mmt    -mno-mt    -mllsc
           -mno-llsc  -mlong64  -mlong32  -msym32  -mno-sym32 -Gnum  -mlocal-sdata  -mno-local-sdata
           -mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt -membedded-data  -mno-embedded-data
           -muninit-const-in-rodata        -mno-uninit-const-in-rodata       -mcode-readable=setting
           -msplit-addresses      -mno-split-addresses    -mexplicit-relocs     -mno-explicit-relocs
           -mcheck-zero-division     -mno-check-zero-division    -mdivide-traps      -mdivide-breaks
           -mload-store-pairs     -mno-load-store-pairs    -mmemcpy     -mno-memcpy     -mlong-calls
           -mno-long-calls  -mmad   -mno-mad   -mimadd   -mno-imadd   -mfused-madd   -mno-fused-madd
           -nocpp  -mfix-24k   -mno-fix-24k -mfix-r4000  -mno-fix-r4000  -mfix-r4400  -mno-fix-r4400
           -mfix-r5900  -mno-fix-r5900 -mfix-r10000  -mno-fix-r10000  -mfix-rm7000   -mno-fix-rm7000
           -mfix-vr4120   -mno-fix-vr4120  -mfix-vr4130   -mno-fix-vr4130   -mfix-sb1   -mno-fix-sb1
           -mflush-func=func  -mno-flush-func -mbranch-cost=num  -mbranch-likely  -mno-branch-likely
           -mcompact-branches=policy     -mfp-exceptions      -mno-fp-exceptions      -mvr4130-align
           -mno-vr4130-align   -msynci   -mno-synci -mlxc1-sxc1  -mno-lxc1-sxc1  -mmadd4  -mno-madd4
           -mrelax-pic-calls     -mno-relax-pic-calls     -mmcount-ra-address     -mframe-header-opt
           -mno-frame-header-opt

           MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon  -mabi=gnu -mabi=mmixware
           -mzero-extend       -mknuthdiv       -mtoplevel-symbols      -melf       -mbranch-predict
           -mno-branch-predict       -mbase-addresses       -mno-base-addresses        -msingle-exit
           -mno-single-exit

           MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33  -mam33  -mam33-2  -mam34 -mtune=cpu-
           type -mreturn-pointer-on-d0 -mno-crt0  -mrelax  -mliw  -msetlb

           Moxie Options -meb  -mel  -mmul.x  -mno-crt0

           MSP430  Options  -msim   -masm-hex   -mmcu=  -mcpu=  -mlarge  -msmall  -mrelax -mwarn-mcu
           -mcode-region=   -mdata-region=   -msilicon-errata=    -msilicon-errata-warn=   -mhwmult=
           -minrt  -mtiny-printf  -mmax-inline-shift=

           NDS32 Options -mbig-endian  -mlittle-endian -mreduced-regs  -mfull-regs -mcmov  -mno-cmov
           -mext-perf    -mno-ext-perf  -mext-perf2   -mno-ext-perf2  -mext-string   -mno-ext-string
           -mv3push  -mno-v3push -m16bit   -mno-16bit  -misr-vector-size=num  -mcache-block-size=num
           -march=arch -mcmodel=code-model -mctor-dtor  -mrelax

           Nios   II   Options   -G  num   -mgpopt=option   -mgpopt   -mno-gpopt  -mgprel-sec=regexp
           -mr0rel-sec=regexp  -mel   -meb  -mno-bypass-cache   -mbypass-cache   -mno-cache-volatile
           -mcache-volatile   -mno-fast-sw-div    -mfast-sw-div   -mhw-mul   -mno-hw-mul   -mhw-mulx
           -mno-hw-mulx       -mno-hw-div       -mhw-div      -mcustom-insn=N       -mno-custom-insn
           -mcustom-fpu-cfg=name -mhal  -msmallc  -msys-crt0=name  -msys-lib=name -march=arch  -mbmx
           -mno-bmx  -mcdx  -mno-cdx

           Nvidia PTX Options -m64  -mmainkernel  -moptimize

           OpenRISC  Options  -mboard=name   -mnewlib  -mhard-mul  -mhard-div -msoft-mul  -msoft-div
           -msoft-float   -mhard-float   -mdouble-float  -munordered-float  -mcmov   -mror    -mrori
           -msext  -msfimm  -mshftimm

           PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45  -m10 -mint32  -mno-int16
           -mint16  -mno-int32 -msplit  -munix-asm  -mdec-asm  -mgnu-asm  -mlra

           picoChip      Options      -mae=ae_type       -mvliw-lookahead=N      -msymbol-as-address
           -mno-inefficient-warnings

           PowerPC Options See RS/6000 and PowerPC Options.

           PRU Options -mmcu=mcu  -minrt  -mno-relax  -mloop -mabi=variant

           RISC-V  Options  -mbranch-cost=N-instruction  -mplt   -mno-plt  -mabi=ABI-string   -mfdiv
           -mno-fdiv       -mdiv        -mno-div      -march=ISA-string      -mtune=processor-string
           -mpreferred-stack-boundary=num         -msmall-data-limit=N-bytes          -msave-restore
           -mno-save-restore       -mshorten-memrefs        -mno-shorten-memrefs      -mstrict-align
           -mno-strict-align        -mcmodel=medlow         -mcmodel=medany        -mexplicit-relocs
           -mno-explicit-relocs    -mrelax    -mno-relax   -mriscv-attribute    -mmo-riscv-attribute
           -malign-data=type    -mbig-endian      -mlittle-endian     +-mstack-protector-guard=guard
           -mstack-protector-guard-reg=reg +-mstack-protector-guard-offset=offset

           RL78  Options  -msim   -mmul=none   -mmul=g13   -mmul=g14  -mallregs -mcpu=g10  -mcpu=g13
           -mcpu=g14       -mg10       -mg13       -mg14      -m64bit-doubles        -m32bit-doubles
           -msave-mduc-in-interrupts

           RS/6000   and   PowerPC   Options   -mcpu=cpu-type   -mtune=cpu-type  -mcmodel=code-model
           -mpowerpc64 -maltivec  -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt  -mpowerpc-gfxopt
           -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb  -mno-popcntb  -mpopcntd  -mno-popcntd
           -mfprnd     -mno-fprnd    -mcmpb    -mno-cmpb    -mhard-dfp    -mno-hard-dfp   -mfull-toc
           -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64   -m32   -mxl-compat   -mno-xl-compat
           -mpe -malign-power  -malign-natural -msoft-float  -mhard-float  -mmultiple  -mno-multiple
           -mupdate      -mno-update     -mavoid-indexed-addresses      -mno-avoid-indexed-addresses
           -mfused-madd      -mno-fused-madd      -mbit-align      -mno-bit-align     -mstrict-align
           -mno-strict-align         -mrelocatable        -mno-relocatable         -mrelocatable-lib
           -mno-relocatable-lib -mtoc   -mno-toc   -mlittle   -mlittle-endian   -mbig   -mbig-endian
           -mdynamic-no-pic    -mswdiv    -msingle-pic-base   -mprioritize-restricted-insns=priority
           -msched-costly-dep=dependence_type -minsert-sched-nops=scheme -mcall-aixdesc  -mcall-eabi
           -mcall-freebsd -mcall-linux  -mcall-netbsd  -mcall-openbsd -mcall-sysv   -mcall-sysv-eabi
           -mcall-sysv-noeabi  -mtraceback=traceback_type  -maix-struct-return  -msvr4-struct-return
           -mabi=abi-type  -msecure-plt  -mbss-plt -mlongcall  -mno-longcall  -mpltseq   -mno-pltseq
           -mblock-move-inline-limit=num                            -mblock-compare-inline-limit=num
           -mblock-compare-inline-loop-limit=num                        -mno-block-ops-unaligned-vsx
           -mstring-compare-inline-limit=num   -misel    -mno-isel   -mvrsave   -mno-vrsave  -mmulhw
           -mno-mulhw  -mdlmzb   -mno-dlmzb  -mprototype   -mno-prototype   -msim    -mmvme    -mads
           -myellowknife  -memb  -msdata -msdata=opt  -mreadonly-in-sdata  -mvxworks  -G num -mrecip
           -mrecip=opt   -mno-recip  -mrecip-precision -mno-recip-precision -mveclibabi=type  -mfriz
           -mno-friz        -mpointers-to-nested-functions         -mno-pointers-to-nested-functions
           -msave-toc-indirect     -mno-save-toc-indirect    -mpower8-fusion     -mno-mpower8-fusion
           -mpower8-vector  -mno-power8-vector -mcrypto  -mno-crypto  -mhtm  -mno-htm  -mquad-memory
           -mno-quad-memory    -mquad-memory-atomic    -mno-quad-memory-atomic   -mcompat-align-parm
           -mno-compat-align-parm       -mfloat128         -mno-float128         -mfloat128-hardware
           -mno-float128-hardware  -mgnu-attribute  -mno-gnu-attribute -mstack-protector-guard=guard
           -mstack-protector-guard-reg=reg     -mstack-protector-guard-offset=offset      -mprefixed
           -mno-prefixed   -mpcrel   -mno-pcrel   -mmma   -mno-mmma  -mrop-protect  -mno-rop-protect
           -mprivileged -mno-privileged

           RX  Options  -m64bit-doubles   -m32bit-doubles   -fpu   -nofpu  -mcpu=  -mbig-endian-data
           -mlittle-endian-data   -msmall-data  -msim   -mno-sim  -mas100-syntax   -mno-as100-syntax
           -mrelax     -mmax-constant-size=     -mint-register=      -mpid      -mallow-string-insns
           -mno-allow-string-insns -mjsr -mno-warn-multiple-fast-interrupts -msave-acc-in-interrupts

           S/390  and  zSeries  Options  -mtune=cpu-type  -march=cpu-type -mhard-float  -msoft-float
           -mhard-dfp  -mno-hard-dfp -mlong-double-64  -mlong-double-128 -mbackchain  -mno-backchain
           -mpacked-stack  -mno-packed-stack -msmall-exec  -mno-small-exec  -mmvcle  -mno-mvcle -m64
           -m31   -mdebug   -mno-debug   -mesa    -mzarch   -mhtm    -mvx    -mzvector   -mtpf-trace
           -mno-tpf-trace    -mtpf-trace-skip    -mno-tpf-trace-skip  -mfused-madd   -mno-fused-madd
           -mwarn-framesize         -mwarn-dynamicstack          -mstack-size          -mstack-guard
           -mhotpatch=halfwords,halfwords

           Score Options -meb  -mel -mnhwloop -muls -mmac -mscore5  -mscore5u  -mscore7  -mscore7d

           SH  Options  -m1   -m2   -m2e  -m2a-nofpu   -m2a-single-only  -m2a-single  -m2a -m3  -m3e
           -m4-nofpu  -m4-single-only  -m4-single   -m4  -m4a-nofpu   -m4a-single-only   -m4a-single
           -m4a   -m4al  -mb   -ml   -mdalign   -mrelax -mbigtable  -mfmovd  -mrenesas  -mno-renesas
           -mnomacsave -mieee  -mno-ieee   -mbitops   -misize   -minline-ic_invalidate   -mpadstruct
           -mprefergot     -musermode     -multcost=number    -mdiv=strategy   -mdivsi3_libfunc=name
           -mfixed-range=register-range    -maccumulate-outgoing-args    -matomic-model=atomic-model
           -mbranch-cost=num   -mzdcbranch   -mno-zdcbranch  -mcbranch-force-delay-slot -mfused-madd
           -mno-fused-madd  -mfsca  -mno-fsca  -mfsrra  -mno-fsrra -mpretend-cmove  -mtas

           Solaris  2  Options  -mclear-hwcap   -mno-clear-hwcap   -mimpure-text    -mno-impure-text
           -pthreads

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -mmemory-model=mem-model
           -m32   -m64   -mapp-regs   -mno-app-regs  -mfaster-structs   -mno-faster-structs   -mflat
           -mno-flat    -mfpu     -mno-fpu      -mhard-float      -msoft-float     -mhard-quad-float
           -msoft-quad-float         -mstack-bias         -mno-stack-bias        -mstd-struct-return
           -mno-std-struct-return    -munaligned-doubles      -mno-unaligned-doubles     -muser-mode
           -mno-user-mode   -mv8plus    -mno-v8plus    -mvis   -mno-vis  -mvis2   -mno-vis2   -mvis3
           -mno-vis3 -mvis4  -mno-vis4  -mvis4b  -mno-vis4b -mcbcond  -mno-cbcond  -mfmaf  -mno-fmaf
           -mfsmuld  -mno-fsmuld -mpopc  -mno-popc  -msubxc   -mno-subxc  -mfix-at697f   -mfix-ut699
           -mfix-ut700  -mfix-gr712rc -mlra  -mno-lra

           System V Options -Qy  -Qn  -YP,paths  -Ym,dir

           TILE-Gx Options -mcpu=CPU  -m32  -m64  -mbig-endian  -mlittle-endian -mcmodel=code-model

           TILEPro Options -mcpu=cpu  -m32

           V850    Options    -mlong-calls    -mno-long-calls    -mep    -mno-ep   -mprolog-function
           -mno-prolog-function   -mspace  -mtda=n   -msda=n   -mzda=n   -mapp-regs    -mno-app-regs
           -mdisable-callt   -mno-disable-callt  -mv850e2v3   -mv850e2   -mv850e1   -mv850es -mv850e
           -mv850   -mv850e3v5  -mloop  -mrelax  -mlong-jumps  -msoft-float  -mhard-float  -mgcc-abi
           -mrh850-abi -mbig-switch

           VAX Options -mg  -mgnu  -munix

           Visium Options -mdebug  -msim  -mfpu  -mno-fpu  -mhard-float  -msoft-float -mcpu=cpu-type
           -mtune=cpu-type  -msv-mode  -muser-mode

           VMS Options -mvms-return-codes  -mdebug-main=prefix  -mmalloc64 -mpointer-size=size

           VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic -Xbind-lazy  -Xbind-now

           x86      Options      -mtune=cpu-type       -march=cpu-type      -mtune-ctrl=feature-list
           -mdump-tune-features   -mno-default  -mfpmath=unit   -masm=dialect    -mno-fancy-math-387
           -mno-fp-ret-in-387    -m80387    -mhard-float    -msoft-float  -mno-wide-multiply   -mrtd
           -malign-double -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mcld  -mcx16
           -msahf  -mmovbe   -mcrc32  -mmwait  -mrecip   -mrecip=opt  -mvzeroupper   -mprefer-avx128
           -mprefer-vector-width=opt  -mmmx   -msse   -msse2   -msse3   -mssse3   -msse4.1  -msse4.2
           -msse4   -mavx  -mavx2   -mavx512f   -mavx512pf    -mavx512er    -mavx512cd    -mavx512vl
           -mavx512bw   -mavx512dq   -mavx512ifma   -mavx512vbmi   -msha  -maes -mpclmul  -mfsgsbase
           -mrdrnd  -mf16c  -mfma   -mpconfig   -mwbnoinvd  -mptwrite   -mprefetchwt1   -mclflushopt
           -mclwb   -mxsavec   -mxsaves  -msse4a   -m3dnow   -m3dnowa  -mpopcnt  -mabm  -mbmi  -mtbm
           -mfma4  -mxop -madx  -mlzcnt  -mbmi2  -mfxsr  -mxsave  -mxsaveopt   -mrtm   -mhle   -mlwp
           -mmwaitx   -mclzero   -mpku   -mthreads  -mgfni  -mvaes  -mwaitpkg -mshstk -mmanual-endbr
           -mforce-indirect-call  -mavx512vbmi2 -mavx512bf16 -menqcmd  -mvpclmulqdq   -mavx512bitalg
           -mmovdiri   -mmovdir64b   -mavx512vpopcntdq  -mavx5124fmaps  -mavx512vnni  -mavx5124vnniw
           -mprfchw  -mrdpid -mrdseed  -msgx -mavx512vp2intersect -mserialize -mtsxldtrk  -mamx-tile
           -mamx-int8     -mamx-bf16   -muintr   -mhreset   -mavxvnni   -mcldemote    -mms-bitfields
           -mno-align-stringops         -minline-all-stringops        -minline-stringops-dynamically
           -mstringop-strategy=alg          -mkl         -mwidekl         -mmemcpy-strategy=strategy
           -mmemset-strategy=strategy -mpush-args  -maccumulate-outgoing-args   -m128bit-long-double
           -m96bit-long-double   -mlong-double-64  -mlong-double-80  -mlong-double-128 -mregparm=num
           -msseregparm  -mveclibabi=type   -mvect8-ret-in-mem  -mpc32   -mpc64   -mpc80   -mdaz-ftz
           -mstackrealign    -momit-leaf-frame-pointer     -mno-red-zone    -mno-tls-direct-seg-refs
           -mcmodel=code-model  -mabi=name  -maddress-mode=mode -m32   -m64   -mx32   -m16   -miamcu
           -mlarge-data-threshold=num    -msse2avx     -mfentry     -mrecord-mcount     -mnop-mcount
           -m8bit-idiv     -minstrument-return=type     -mfentry-name=name     -mfentry-section=name
           -mavx256-split-unaligned-load       -mavx256-split-unaligned-store      -malign-data=type
           -mstack-protector-guard=guard                             -mstack-protector-guard-reg=reg
           -mstack-protector-guard-offset=offset               -mstack-protector-guard-symbol=symbol
           -mgeneral-regs-only            -mcall-ms2sysv-xlogues            -mindirect-branch=choice
           -mfunction-return=choice          -mindirect-branch-register          -mharden-sls=choice
           -mindirect-branch-cs-prefix -mneeded

           x86 Windows Options -mconsole  -mcygwin  -mno-cygwin  -mdll -mnop-fun-dllimport  -mthread
           -municode  -mwin32  -mwindows  -fno-set-stack-executable

           Xstormy16 Options -msim

           Xtensa  Options  -mconst16   -mno-const16  -mfused-madd   -mno-fused-madd  -mforce-no-pic
           -mserialize-volatile            -mno-serialize-volatile           -mtext-section-literals
           -mno-text-section-literals     -mauto-litpools      -mno-auto-litpools     -mtarget-align
           -mno-target-align -mlongcalls  -mno-longcalls -mabi=abi-type

           zSeries Options See S/390 and zSeries Options.

   Options Controlling the Kind of Output
       Compilation  can  involve  up to four stages: preprocessing, compilation proper, assembly and
       linking, always in that order.  GCC is capable of preprocessing and compiling  several  files
       either  into  several  assembler  input  files,  or  into one assembler input file; then each
       assembler input file produces an object file, and  linking  combines  all  the  object  files
       (those newly compiled, and those specified as input) into an executable file.

       For any given input file, the file name suffix determines what kind of compilation is done:

       file.c
           C source code that must be preprocessed.

       file.i
           C source code that should not be preprocessed.

       file.ii
           C++ source code that should not be preprocessed.

       file.m
           Objective-C  source  code.   Note  that you must link with the libobjc library to make an
           Objective-C program work.

       file.mi
           Objective-C source code that should not be preprocessed.

       file.mm
       file.M
           Objective-C++ source code.  Note that you must link with the libobjc library to  make  an
           Objective-C++ program work.  Note that .M refers to a literal capital M.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.h
           C,  C++,  Objective-C or Objective-C++ header file to be turned into a precompiled header
           (default), or C, C++ header file to be turned into an Ada spec (via  the  -fdump-ada-spec
           switch).

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
           C++  source code that must be preprocessed.  Note that in .cxx, the last two letters must
           both be literally x.  Likewise, .C refers to a literal capital C.

       file.mm
       file.M
           Objective-C++ source code that must be preprocessed.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
           C++ header file to be turned into a precompiled header or Ada spec.

       file.f
       file.for
       file.ftn
           Fixed form Fortran source code that should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
           Fixed  form  Fortran  source  code  that  must  be  preprocessed  (with  the  traditional
           preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
           Free form Fortran source code that should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
           Free   form  Fortran  source  code  that  must  be  preprocessed  (with  the  traditional
           preprocessor).

       file.go
           Go source code.

       file.brig
           BRIG files (binary representation of HSAIL).

       file.d
           D source code.

       file.di
           D interface file.

       file.dd
           D documentation code (Ddoc).

       file.ads
           Ada source code file that contains  a  library  unit  declaration  (a  declaration  of  a
           package,  subprogram, or generic, or a generic instantiation), or a library unit renaming
           declaration (a package, generic, or subprogram renaming  declaration).   Such  files  are
           also called specs.

       file.adb
           Ada source code file containing a library unit body (a subprogram or package body).  Such
           files are also called bodies.

       file.s
           Assembler code.

       file.S
       file.sx
           Assembler code that must be preprocessed.

       other
           An  object file to be fed straight into linking.  Any file name with no recognized suffix
           is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
           Specify explicitly the language for the following input files (rather  than  letting  the
           compiler  choose  a  default  based on the file name suffix).  This option applies to all
           following input files until the next -x option.  Possible values for language are:

                   c  c-header  cpp-output
                   c++  c++-header  c++-system-header c++-user-header c++-cpp-output
                   objective-c  objective-c-header  objective-c-cpp-output
                   objective-c++ objective-c++-header objective-c++-cpp-output
                   assembler  assembler-with-cpp
                   ada
                   d
                   f77  f77-cpp-input f95  f95-cpp-input
                   go
                   brig

       -x none
           Turn off any specification of a language, so that subsequent files are handled  according
           to their file name suffixes (as they are if -x has not been used at all).

       If  you only want some of the stages of compilation, you can use -x (or filename suffixes) to
       tell gcc where to start, and one of the options -c, -S, or -E to say where gcc  is  to  stop.
       Note  that  some  combinations  (for example, -x cpp-output -E) instruct gcc to do nothing at
       all.

       -c  Compile or assemble the source files, but do not link.  The linking stage simply  is  not
           done.  The ultimate output is in the form of an object file for each source file.

           By  default,  the  object file name for a source file is made by replacing the suffix .c,
           .i, .s, etc., with .o.

           Unrecognized input files, not requiring compilation or assembly, are ignored.

       -S  Stop after the stage of compilation proper; do not assemble.  The output is in  the  form
           of an assembler code file for each non-assembler input file specified.

           By default, the assembler file name for a source file is made by replacing the suffix .c,
           .i, etc., with .s.

           Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler proper.  The output is in the
           form of preprocessed source code, which is sent to the standard output.

           Input files that don't require preprocessing are ignored.

       -o file
           Place  the primary output in file file.  This applies to whatever sort of output is being
           produced, whether it be an  executable  file,  an  object  file,  an  assembler  file  or
           preprocessed C code.

           If  -o  is  not  specified, the default is to put an executable file in a.out, the object
           file for source.suffix in source.o, its assembler file in source.s, a precompiled  header
           file in source.suffix.gch, and all preprocessed C source on standard output.

           Though -o names only the primary output, it also affects the naming of auxiliary and dump
           outputs.   See  the  examples  below.  Unless overridden, both auxiliary outputs and dump
           outputs are placed in the same directory as the primary output.   In  auxiliary  outputs,
           the  suffix of the input file is replaced with that of the auxiliary output file type; in
           dump outputs, the suffix of the dump file is appended  to  the  input  file  suffix.   In
           compilation  commands,  the  base  name of both auxiliary and dump outputs is that of the
           primary output; in compile  and  link  commands,  the  primary  output  name,  minus  the
           executable  suffix,  is  combined  with the input file name.  If both share the same base
           name, disregarding the  suffix,  the  result  of  the  combination  is  that  base  name,
           otherwise, they are concatenated, separated by a dash.

                   gcc -c foo.c ...

           will  use  foo.o as the primary output, and place aux outputs and dumps next to it, e.g.,
           aux file foo.dwo for -gsplit-dwarf, and dump file foo.c.???r.final for -fdump-rtl-final.

           If a non-linker output file is explicitly specified, aux and dump files by  default  take
           the same base name:

                   gcc -c foo.c -o dir/foobar.o ...

           will name aux outputs dir/foobar.* and dump outputs dir/foobar.c.*.

           A linker output will instead prefix aux and dump outputs:

                   gcc foo.c bar.c -o dir/foobar ...

           will  generally  name aux outputs dir/foobar-foo.* and dir/foobar-bar.*, and dump outputs
           dir/foobar-foo.c.* and dir/foobar-bar.c.*.

           The one exception to the above is when the executable  shares  the  base  name  with  the
           single input:

                   gcc foo.c -o dir/foo ...

           in which case aux outputs are named dir/foo.* and dump outputs named dir/foo.c.*.

           The  location  and the names of auxiliary and dump outputs can be adjusted by the options
           -dumpbase, -dumpbase-ext, -dumpdir, -save-temps=cwd, and -save-temps=obj.

       -dumpbase dumpbase
           This option sets the base name for auxiliary and dump output files.  It does  not  affect
           the  name  of  the  primary  output  file.  Intermediate outputs, when preserved, are not
           regarded as primary outputs, but as auxiliary outputs:

                   gcc -save-temps -S foo.c

           saves the (no longer) temporary preprocessed file in foo.i,  and  then  compiles  to  the
           (implied) output file foo.s, whereas:

                   gcc -save-temps -dumpbase save-foo -c foo.c

           preprocesses  to  in  save-foo.i,  compiles  to  save-foo.s  (now  an  intermediate, thus
           auxiliary output), and then assembles to the (implied) output file foo.o.

           Absent this option, dump and aux files take their names from the input file, or from  the
           (non-linker)  output  file, if one is explicitly specified: dump output files (e.g. those
           requested by -fdump-* options) with the input name suffix, and aux  output  files  (those
           requested    by    other   non-dump   options,   e.g.   "-save-temps",   "-gsplit-dwarf",
           "-fcallgraph-info") without it.

           Similar suffix differentiation of dump and aux outputs can be  attained  for  explicitly-
           given -dumpbase basename.suf by also specifying -dumpbase-ext .suf.

           If   dumpbase   is  explicitly  specified  with  any  directory  component,  any  dumppfx
           specification (e.g. -dumpdir or -save-temps=*) is ignored, and instead  of  appending  to
           it, dumpbase fully overrides it:

                   gcc foo.c -c -o dir/foo.o -dumpbase alt/foo \
                     -dumpdir pfx- -save-temps=cwd ...

           creates  auxiliary  and  dump  outputs  named  alt/foo.*, disregarding dir/ in -o, the ./
           prefix implied by -save-temps=cwd, and pfx- in -dumpdir.

           When -dumpbase is specified in a command that compiles multiple inputs, or that  compiles
           and then links, it may be combined with dumppfx, as specified under -dumpdir.  Then, each
           input  file  is  compiled using the combined dumppfx, and default values for dumpbase and
           auxdropsuf are computed for each input file:

                   gcc foo.c bar.c -c -dumpbase main ...

           creates foo.o and bar.o as primary outputs, and avoids overwriting the auxiliary and dump
           outputs by using the dumpbase as a prefix, creating  auxiliary  and  dump  outputs  named
           main-foo.*  and main-bar.*.

           An  empty string specified as dumpbase avoids the influence of the output basename in the
           naming of auxiliary and dump outputs during compilation, computing default values :

                   gcc -c foo.c -o dir/foobar.o -dumpbase " ...

           will name aux outputs dir/foo.* and dump outputs dir/foo.c.*.  Note how  their  basenames
           are taken from the input name, but the directory still defaults to that of the output.

           The  empty-string  dumpbase  does  not prevent the use of the output basename for outputs
           during linking:

                   gcc foo.c bar.c -o dir/foobar -dumpbase " -flto ...

           The compilation of the source files will name auxiliary outputs dir/foo.* and  dir/bar.*,
           and  dump outputs dir/foo.c.* and dir/bar.c.*.  LTO recompilation during linking will use
           dir/foobar. as the prefix for dumps and auxiliary files.

       -dumpbase-ext auxdropsuf
           When forming the name of an auxiliary  (but  not  a  dump)  output  file,  drop  trailing
           auxdropsuf  from  dumpbase  before appending any suffixes.  If not specified, this option
           defaults to the suffix of a default dumpbase, i.e., the suffix of  the  input  file  when
           -dumpbase is not present in the command line, or dumpbase is combined with dumppfx.

                   gcc foo.c -c -o dir/foo.o -dumpbase x-foo.c -dumpbase-ext .c ...

           creates  dir/foo.o  as  the  main output, and generates auxiliary outputs in dir/x-foo.*,
           taking the location of the primary output, and dropping the .c suffix from the  dumpbase.
           Dump outputs retain the suffix: dir/x-foo.c.*.

           This  option  is  disregarded  if  it  does not match the suffix of a specified dumpbase,
           except as an alternative to the executable suffix when appending the linker  output  base
           name to dumppfx, as specified below:

                   gcc foo.c bar.c -o main.out -dumpbase-ext .out ...

           creates  main.out  as  the  primary output, and avoids overwriting the auxiliary and dump
           outputs by using the executable name minus auxdropsuf as  a  prefix,  creating  auxiliary
           outputs  named  main-foo.*  and  main-bar.*  and  dump  outputs  named  main-foo.c.*  and
           main-bar.c.*.

       -dumpdir dumppfx
           When forming the name of an auxiliary or dump output file, use dumppfx as a prefix:

                   gcc -dumpdir pfx- -c foo.c ...

           creates foo.o as the primary output, and auxiliary outputs named pfx-foo.*, combining the
           given dumppfx with the default dumpbase derived from the default primary output,  derived
           in turn from the input name.  Dump outputs also take the input name suffix: pfx-foo.c.*.

           If dumppfx is to be used as a directory name, it must end with a directory separator:

                   gcc -dumpdir dir/ -c foo.c -o obj/bar.o ...

           creates obj/bar.o as the primary output, and auxiliary outputs named dir/bar.*, combining
           the  given  dumppfx with the default dumpbase derived from the primary output name.  Dump
           outputs also take the input name suffix: dir/bar.c.*.

           It defaults to the location of the output file, unless the output file is a special  file
           like "/dev/null". Options -save-temps=cwd and -save-temps=obj override this default, just
           like  an explicit -dumpdir option.  In case multiple such options are given, the last one
           prevails:

                   gcc -dumpdir pfx- -c foo.c -save-temps=obj ...

           outputs foo.o, with auxiliary outputs named foo.*  because  -save-temps=*  overrides  the
           dumppfx  given  by  the  earlier  -dumpdir  option.   It does not matter that =obj is the
           default for -save-temps,  nor  that  the  output  directory  is  implicitly  the  current
           directory.  Dump outputs are named foo.c.*.

           When  compiling  from  multiple input files, if -dumpbase is specified, dumpbase, minus a
           auxdropsuf suffix, and a dash are appended to (or override, if containing  any  directory
           components)  an  explicit or defaulted dumppfx, so that each of the multiple compilations
           gets differently-named aux and dump outputs.

                   gcc foo.c bar.c -c -dumpdir dir/pfx- -dumpbase main ...

           outputs auxiliary dumps to dir/pfx-main-foo.* and dir/pfx-main-bar.*, appending dumpbase-
           to dumppfx.  Dump  outputs  retain  the  input  file  suffix:  dir/pfx-main-foo.c.*   and
           dir/pfx-main-bar.c.*, respectively.  Contrast with the single-input compilation:

                   gcc foo.c -c -dumpdir dir/pfx- -dumpbase main ...

           that,  applying  -dumpbase  to  a  single  source, does not compute and append a separate
           dumpbase per input file.  Its auxiliary and dump outputs go in dir/pfx-main.*.

           When compiling and then linking from multiple input  files,  a  defaulted  or  explicitly
           specified dumppfx also undergoes the dumpbase- transformation above (e.g. the compilation
           of  foo.c and bar.c above, but without -c).  If neither -dumpdir nor -dumpbase are given,
           the linker output base name, minus auxdropsuf, if specified,  or  the  executable  suffix
           otherwise,  plus  a dash is appended to the default dumppfx instead.  Note, however, that
           unlike earlier cases of linking:

                   gcc foo.c bar.c -dumpdir dir/pfx- -o main ...

           does not append  the  output  name  main  to  dumppfx,  because  -dumpdir  is  explicitly
           specified.   The  goal is that the explicitly-specified dumppfx may contain the specified
           output name as part of the prefix, if desired;  only  an  explicitly-specified  -dumpbase
           would be combined with it, in order to avoid simply discarding a meaningful option.

           When  compiling  and  then  linking from a single input file, the linker output base name
           will only be appended to the default dumppfx as above if it does not share the base  name
           with  the  single  input  file name.  This has been covered in single-input linking cases
           above, but not  with  an  explicit  -dumpdir  that  inhibits  the  combination,  even  if
           overridden by -save-temps=*:

                   gcc foo.c -dumpdir alt/pfx- -o dir/main.exe -save-temps=cwd ...

           Auxiliary  outputs  are  named  foo.*,  and  dump outputs foo.c.*, in the current working
           directory as ultimately requested by -save-temps=cwd.

           Summing it all up for an intuitive though  slightly  imprecise  data  flow:  the  primary
           output  name  is  broken into a directory part and a basename part; dumppfx is set to the
           former, unless overridden by -dumpdir or  -save-temps=*,  and  dumpbase  is  set  to  the
           latter,  unless  overriden  by  -dumpbase.  If there are multiple inputs or linking, this
           dumpbase may be combined with dumppfx and taken from each input file.   Auxiliary  output
           names  for  each  input  are  formed by combining dumppfx, dumpbase minus suffix, and the
           auxiliary output suffix; dump output names are only different in  that  the  suffix  from
           dumpbase is retained.

           When  it  comes  to  auxiliary  and  dump  outputs  created  during  LTO recompilation, a
           combination of dumppfx and dumpbase, as given or as derived from the linker  output  name
           but  not from inputs, even in cases in which this combination would not otherwise be used
           as such, is passed down with a trailing period replacing the compiler-added dash, if any,
           as a -dumpdir option to lto-wrapper; being involved in linking,  this  program  does  not
           normally get any -dumpbase and -dumpbase-ext, and it ignores them.

           When  running sub-compilers, lto-wrapper appends LTO stage names to the received dumppfx,
           ensures it contains a directory component so that it overrides any -dumpdir,  and  passes
           that as -dumpbase to sub-compilers.

       -v  Print  (on standard error output) the commands executed to run the stages of compilation.
           Also print the version number of the compiler driver program and of the preprocessor  and
           the compiler proper.

       -###
           Like -v except the commands are not executed and arguments are quoted unless they contain
           only  alphanumeric characters or "./-_".  This is useful for shell scripts to capture the
           driver-generated command lines.

       --help
           Print (on the standard output) a description of the command-line  options  understood  by
           gcc.   If  the  -v  option is also specified then --help is also passed on to the various
           processes invoked by gcc, so that they can display the command-line options they  accept.
           If the -Wextra option has also been specified (prior to the --help option), then command-
           line options that have no documentation associated with them are also displayed.

       --target-help
           Print  (on the standard output) a description of target-specific command-line options for
           each tool.  For some targets extra target-specific information may also be printed.

       --help={class|[^]qualifier}[,...]
           Print (on the standard output) a description of the command-line  options  understood  by
           the compiler that fit into all specified classes and qualifiers.  These are the supported
           classes:

           optimizers
               Display all of the optimization options supported by the compiler.

           warnings
               Display all of the options controlling warning messages produced by the compiler.

           target
               Display  target-specific  options.   Unlike the --target-help option however, target-
               specific options of the linker and assembler are  not  displayed.   This  is  because
               those tools do not currently support the extended --help= syntax.

           params
               Display the values recognized by the --param option.

           language
               Display  the options supported for language, where language is the name of one of the
               languages supported in this version of  GCC.   If  an  option  is  supported  by  all
               languages, one needs to select common class.

           common
               Display the options that are common to all languages.

           These are the supported qualifiers:

           undocumented
               Display only those options that are undocumented.

           joined
               Display  options  taking  an  argument  that  appears after an equal sign in the same
               continuous piece of text, such as: --help=target.

           separate
               Display options taking an argument that appears as  a  separate  word  following  the
               original option, such as: -o output-file.

           Thus  for  example  to display all the undocumented target-specific switches supported by
           the compiler, use:

                   --help=target,undocumented

           The sense of a qualifier can be inverted by prefixing it with the  ^  character,  so  for
           example  to  display all binary warning options (i.e., ones that are either on or off and
           that do not take an argument) that have a description, use:

                   --help=warnings,^joined,^undocumented

           The argument to --help= should not consist solely of inverted qualifiers.

           Combining several classes is possible, although this usually restricts the output so much
           that there is nothing to display.  One case where it does work, however, is when  one  of
           the  classes  is  target.   For  example, to display all the target-specific optimization
           options, use:

                   --help=target,optimizers

           The --help= option can be repeated on the command line.  Each successive use displays its
           requested class of options, skipping those that have already been displayed.   If  --help
           is  also  specified  anywhere  on  the  command  line then this takes precedence over any
           --help= option.

           If the -Q option appears on  the  command  line  before  the  --help=  option,  then  the
           descriptive  text  displayed  by --help= is changed.  Instead of describing the displayed
           options, an indication is given as to whether the option is enabled, disabled or set to a
           specific value (assuming that the compiler knows this at  the  point  where  the  --help=
           option is used).

           Here is a truncated example from the ARM port of gcc:

                     % gcc -Q -mabi=2 --help=target -c
                     The following options are target specific:
                     -mabi=                                2
                     -mabort-on-noreturn                   [disabled]
                     -mapcs                                [disabled]

           The  output  is sensitive to the effects of previous command-line options, so for example
           it is possible to find out which optimizations are enabled at -O2 by using:

                   -Q -O2 --help=optimizers

           Alternatively you can discover which binary optimizations are enabled by -O3 by using:

                   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                   diff /tmp/O2-opts /tmp/O3-opts | grep enabled

       --version
           Display the version number and copyrights of the invoked GCC.

       -pass-exit-codes
           Normally the gcc program exits with the code of 1 if any phase of the compiler returns  a
           non-success  return  code.   If  you  specify  -pass-exit-codes,  the gcc program instead
           returns with the numerically highest error produced  by  any  phase  returning  an  error
           indication.  The C, C++, and Fortran front ends return 4 if an internal compiler error is
           encountered.

       -pipe
           Use  pipes  rather  than  temporary files for communication between the various stages of
           compilation.  This fails to work on some systems where the assembler is  unable  to  read
           from a pipe; but the GNU assembler has no trouble.

       -specs=file
           Process  file  after  the compiler reads in the standard specs file, in order to override
           the defaults which the gcc driver program uses when determining what switches to pass  to
           cc1,  cc1plus,  as,  ld,  etc.  More than one -specs=file can be specified on the command
           line, and they are processed in order, from left to right.

       -wrapper
           Invoke all subcommands under a wrapper program.  The name of the wrapper program and  its
           parameters are passed as a comma separated list.

                   gcc -c t.c -wrapper gdb,--args

           This  invokes  all subprograms of gcc under gdb --args, thus the invocation of cc1 is gdb
           --args cc1 ....

       -ffile-prefix-map=old=new
           When compiling files residing in directory old, record any  references  to  them  in  the
           result  of  the compilation as if the files resided in directory new instead.  Specifying
           this option is equivalent to specifying all the individual -f*-prefix-map options.   This
           can  be  used  to  make  reproducible  builds  that  are  location independent.  See also
           -fmacro-prefix-map and -fdebug-prefix-map.

       -fplugin=name.so
           Load the plugin code in file name.so, assumed to be a shared object to be dlopen'd by the
           compiler.  The base name of the shared object file is used to identify the plugin for the
           purposes of argument parsing (See -fplugin-arg-name-key=value below).  Each plugin should
           define the callback functions specified in the Plugins API.

       -fplugin-arg-name-key=value
           Define an argument called key with a value of value for the plugin called name.

       -fdump-ada-spec[-slim]
           For C and C++ source and include files, generate corresponding Ada specs.

       -fada-spec-parent=unit
           In conjunction with -fdump-ada-spec[-slim] above, generate Ada specs as  child  units  of
           parent unit.

       -fdump-go-spec=file
           For  input  files  in any language, generate corresponding Go declarations in file.  This
           generates Go "const", "type", "var", and "func" declarations which may be a useful way to
           start writing a Go interface to code written in some other language.

       @file
           Read command-line options from file.  The options read  are  inserted  in  place  of  the
           original  @file  option.  If file does not exist, or cannot be read, then the option will
           be treated literally, and not removed.

           Options in file are separated by whitespace.  A whitespace character may be  included  in
           an  option  by  surrounding  the  entire  option  in either single or double quotes.  Any
           character (including a backslash) may be  included  by  prefixing  the  character  to  be
           included  with  a  backslash.   The file may itself contain additional @file options; any
           such options will be processed recursively.

   Compiling C++ Programs
       C++ source files conventionally use one of the suffixes .C, .cc, .cpp, .CPP,  .c++,  .cp,  or
       .cxx;  C++  header  files  often  use  .hh, .hpp, .H, or (for shared template code) .tcc; and
       preprocessed C++ files use the suffix  .ii.   GCC  recognizes  files  with  these  names  and
       compiles  them  as C++ programs even if you call the compiler the same way as for compiling C
       programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program that  calls  GCC  and
       automatically  specifies  linking  against the C++ library.  It treats .c, .h and .i files as
       C++ source files instead of C source files unless -x is used.  This program  is  also  useful
       when  precompiling  a C header file with a .h extension for use in C++ compilations.  On many
       systems, g++ is also installed with the name c++.

       When you compile C++ programs, you may specify many of the same command-line options that you
       use for compiling programs in any language; or command-line  options  meaningful  for  C  and
       related languages; or options that are meaningful only for C++ programs.

   Options Controlling C Dialect
       The  following  options  control  the dialect of C (or languages derived from C, such as C++,
       Objective-C and Objective-C++) that the compiler accepts:

       -ansi
           In C mode, this is equivalent to -std=c90. In C++ mode, it is equivalent to -std=c++98.

           This turns off certain features of GCC that are incompatible with ISO C90 (when compiling
           C code), or of standard C++ (when compiling C++ code), such as  the  "asm"  and  "typeof"
           keywords, and predefined macros such as "unix" and "vax" that identify the type of system
           you  are  using.   It  also enables the undesirable and rarely used ISO trigraph feature.
           For the C compiler, it disables recognition of C++ style  //  comments  as  well  as  the
           "inline" keyword.

           The alternate keywords "__asm__", "__extension__", "__inline__" and "__typeof__" continue
           to  work  despite  -ansi.  You would not want to use them in an ISO C program, of course,
           but it is useful to put them in header files that might be included in compilations  done
           with  -ansi.   Alternate  predefined  macros  such  as  "__unix__" and "__vax__" are also
           available, with or without -ansi.

           The -ansi option does not cause non-ISO programs to be rejected gratuitously.  For  that,
           -Wpedantic is required in addition to -ansi.

           The  macro  "__STRICT_ANSI__"  is  predefined when the -ansi option is used.  Some header
           files may notice this macro and refrain from  declaring  certain  functions  or  defining
           certain  macros that the ISO standard doesn't call for; this is to avoid interfering with
           any programs that might use these names for other things.

           Functions that are normally built in but do not have semantics defined by ISO C (such  as
           "alloca" and "ffs") are not built-in functions when -ansi is used.

       -std=
           Determine the language standard.   This option is currently only supported when compiling
           C or C++.

           The compiler can accept several base standards, such as c90 or c++98, and GNU dialects of
           those  standards,  such  as  gnu90  or  gnu++98.   When a base standard is specified, the
           compiler accepts all programs following that standard plus  those  using  GNU  extensions
           that  do not contradict it.  For example, -std=c90 turns off certain features of GCC that
           are incompatible with ISO C90, such as the "asm" and "typeof" keywords, but not other GNU
           extensions that do not have a meaning in ISO C90, such as omitting the middle term  of  a
           "?:"  expression.  On  the other hand, when a GNU dialect of a standard is specified, all
           features supported by the compiler are enabled,  even  when  those  features  change  the
           meaning  of  the  base  standard.   As  a  result, some strict-conforming programs may be
           rejected.  The particular standard is used by -Wpedantic to identify which  features  are
           GNU  extensions  given  that  version  of the standard. For example -std=gnu90 -Wpedantic
           warns about C++ style // comments, while -std=gnu99 -Wpedantic does not.

           A value for this option must be provided; possible values are

           c90
           c89
           iso9899:1990
               Support all ISO C90 programs (certain GNU extensions that conflict with ISO  C90  are
               disabled). Same as -ansi for C code.

           iso9899:199409
               ISO C90 as modified in amendment 1.

           c99
           c9x
           iso9899:1999
           iso9899:199x
               ISO  C99.   This  standard  is  substantially  completely  supported, modulo bugs and
               floating-point issues (mainly but not entirely relating to optional C99 features from
               Annexes F and G).  See <http://gcc.gnu.org/c99status.html> for more information.  The
               names c9x and iso9899:199x are deprecated.

           c11
           c1x
           iso9899:2011
               ISO C11, the 2011 revision of the ISO C standard.   This  standard  is  substantially
               completely  supported,  modulo  bugs,  floating-point issues (mainly but not entirely
               relating to optional C11 features from Annexes F and G) and the  optional  Annexes  K
               (Bounds-checking interfaces) and L (Analyzability).  The name c1x is deprecated.

           c17
           c18
           iso9899:2017
           iso9899:2018
               ISO  C17, the 2017 revision of the ISO C standard (published in 2018).  This standard
               is same as C11 except for corrections of defects (all of which are also applied  with
               -std=c11)  and  a  new  value  of "__STDC_VERSION__", and so is supported to the same
               extent as C11.

           c2x The next version of the ISO C standard, still under  development.   The  support  for
               this version is experimental and incomplete.

           gnu90
           gnu89
               GNU dialect of ISO C90 (including some C99 features).

           gnu99
           gnu9x
               GNU dialect of ISO C99.  The name gnu9x is deprecated.

           gnu11
           gnu1x
               GNU dialect of ISO C11.  The name gnu1x is deprecated.

           gnu17
           gnu18
               GNU dialect of ISO C17.  This is the default for C code.

           gnu2x
               The next version of the ISO C standard, still under development, plus GNU extensions.
               The support for this version is experimental and incomplete.

           c++98
           c++03
               The  1998  ISO  C++  standard plus the 2003 technical corrigendum and some additional
               defect reports. Same as -ansi for C++ code.

           gnu++98
           gnu++03
               GNU dialect of -std=c++98.

           c++11
           c++0x
               The 2011 ISO C++ standard plus amendments.  The name c++0x is deprecated.

           gnu++11
           gnu++0x
               GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

           c++14
           c++1y
               The 2014 ISO C++ standard plus amendments.  The name c++1y is deprecated.

           gnu++14
           gnu++1y
               GNU dialect of -std=c++14.  The name gnu++1y is deprecated.

           c++17
           c++1z
               The 2017 ISO C++ standard plus amendments.  The name c++1z is deprecated.

           gnu++17
           gnu++1z
               GNU dialect of -std=c++17.  This is the default for C++ code.  The  name  gnu++1z  is
               deprecated.

           c++20
           c++2a
               The 2020 ISO C++ standard plus amendments.  Support is experimental, and could change
               in incompatible ways in future releases.  The name c++2a is deprecated.

           gnu++20
           gnu++2a
               GNU dialect of -std=c++20.  Support is experimental, and could change in incompatible
               ways in future releases.  The name gnu++2a is deprecated.

           c++2b
           c++23
               The  next  revision  of  the  ISO  C++ standard, planned for 2023.  Support is highly
               experimental, and will  almost  certainly  change  in  incompatible  ways  in  future
               releases.

           gnu++2b
           gnu++23
               GNU dialect of -std=c++2b.  Support is highly experimental, and will almost certainly
               change in incompatible ways in future releases.

       -fgnu89-inline
           The  option  -fgnu89-inline  tells  GCC to use the traditional GNU semantics for "inline"
           functions when in C99 mode.

           Using this option is roughly equivalent to adding the "gnu_inline" function attribute  to
           all inline functions.

           The  option  -fno-gnu89-inline explicitly tells GCC to use the C99 semantics for "inline"
           when in C99 or gnu99 mode (i.e., it specifies the default behavior).  This option is  not
           supported in -std=c90 or -std=gnu90 mode.

           The  preprocessor  macros "__GNUC_GNU_INLINE__" and "__GNUC_STDC_INLINE__" may be used to
           check which semantics are in effect for "inline" functions.

       -fpermitted-flt-eval-methods=style
           ISO/IEC TS 18661-3 defines new permissible values  for  "FLT_EVAL_METHOD"  that  indicate
           that  operations  and  constants  with a semantic type that is an interchange or extended
           format should be evaluated to the precision and range of that type.  These new values are
           a superset of those permitted under C99/C11, which does not specify the meaning of  other
           positive  values of "FLT_EVAL_METHOD".  As such, code conforming to C11 may not have been
           written expecting the possibility of the new values.

           -fpermitted-flt-eval-methods specifies whether the compiler should allow only the  values
           of  "FLT_EVAL_METHOD"  specified  in  C99/C11, or the extended set of values specified in
           ISO/IEC TS 18661-3.

           style is either "c11" or "ts-18661-3" as appropriate.

           The  default  when  in  a   standards   compliant   mode   (-std=c11   or   similar)   is
           -fpermitted-flt-eval-methods=c11.   The  default  when  in  a  GNU dialect (-std=gnu11 or
           similar) is -fpermitted-flt-eval-methods=ts-18661-3.

       -aux-info filename
           Output to the given filename prototyped declarations for all  functions  declared  and/or
           defined  in a translation unit, including those in header files.  This option is silently
           ignored in any language other than C.

           Besides declarations, the file indicates, in comments, the  origin  of  each  declaration
           (source  file and line), whether the declaration was implicit, prototyped or unprototyped
           (I, N for new or O for old, respectively, in the first character after  the  line  number
           and  the  colon),  and  whether  it  came  from  a  declaration  or a definition (C or F,
           respectively, in the following character).   In  the  case  of  function  definitions,  a
           K&R-style  list  of  arguments  followed  by  their declarations is also provided, inside
           comments, after the declaration.

       -fallow-parameterless-variadic-functions
           Accept variadic functions without named parameters.

           Although it is possible to define such a function, this is not very useful as it  is  not
           possible  to  read  the  arguments.   This  is  only supported for C as this construct is
           allowed by C++.

       -fno-asm
           Do not recognize "asm", "inline" or "typeof" as a keyword, so that  code  can  use  these
           words  as identifiers.  You can use the keywords "__asm__", "__inline__" and "__typeof__"
           instead.  -ansi implies -fno-asm.

           In C++, this switch only affects the "typeof"  keyword,  since  "asm"  and  "inline"  are
           standard keywords.  You may want to use the -fno-gnu-keywords flag instead, which has the
           same  effect.   In  C99 mode (-std=c99 or -std=gnu99), this switch only affects the "asm"
           and "typeof" keywords, since "inline" is a standard keyword in ISO C99.

       -fno-builtin
       -fno-builtin-function
           Don't recognize built-in functions that do not begin with __builtin_ as prefix.

           GCC  normally  generates  special  code  to  handle  certain  built-in   functions   more
           efficiently;  for instance, calls to "alloca" may become single instructions which adjust
           the stack directly, and calls to "memcpy" may become inline copy  loops.   The  resulting
           code  is  often both smaller and faster, but since the function calls no longer appear as
           such, you cannot set a breakpoint on those calls, nor can you change the behavior of  the
           functions  by  linking  with  a  different  library.   In  addition,  when  a function is
           recognized as a built-in function, GCC may use information about that  function  to  warn
           about  problems  with calls to that function, or to generate more efficient code, even if
           the resulting code still contains calls to that  function.   For  example,  warnings  are
           given  with  -Wformat for bad calls to "printf" when "printf" is built in and "strlen" is
           known not to modify global memory.

           With the -fno-builtin-function option only the built-in function  function  is  disabled.
           function  must not begin with __builtin_.  If a function is named that is not built-in in
           this  version  of  GCC,  this   option   is   ignored.    There   is   no   corresponding
           -fbuiltin-function  option;  if  you  wish  to enable built-in functions selectively when
           using -fno-builtin or -ffreestanding, you may define macros such as:

                   #define abs(n)          __builtin_abs ((n))
                   #define strcpy(d, s)    __builtin_strcpy ((d), (s))

       -fgimple
           Enable parsing of function definitions marked with "__GIMPLE".  This is  an  experimental
           feature that allows unit testing of GIMPLE passes.

       -fhosted
           Assert  that compilation targets a hosted environment.  This implies -fbuiltin.  A hosted
           environment is one in which the entire standard library is available, and in which "main"
           has a return type of "int".  Examples are nearly everything except  a  kernel.   This  is
           equivalent to -fno-freestanding.

       -ffreestanding
           Assert  that  compilation targets a freestanding environment.  This implies -fno-builtin.
           A freestanding environment is one in which  the  standard  library  may  not  exist,  and
           program  startup  may  not  necessarily  be at "main".  The most obvious example is an OS
           kernel.  This is equivalent to -fno-hosted.

       -fopenacc
           Enable handling of OpenACC directives "#pragma acc" in  C/C++  and  "!$acc"  in  Fortran.
           When  -fopenacc  is  specified,  the compiler generates accelerated code according to the
           OpenACC Application Programming Interface v2.6  <https://www.openacc.org>.   This  option
           implies -pthread, and thus is only supported on targets that have support for -pthread.

       -fopenacc-dim=geom
           Specify  default  compute  dimensions for parallel offload regions that do not explicitly
           specify.  The geom value is a triple of ':'-separated sizes, in  order  'gang',  'worker'
           and, 'vector'.  A size can be omitted, to use a target-specific default value.

       -fopenmp
           Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran.  When
           -fopenmp  is  specified,  the  compiler  generates  parallel code according to the OpenMP
           Application  Program  Interface  v4.5  <https://www.openmp.org>.   This  option   implies
           -pthread,  and thus is only supported on targets that have support for -pthread. -fopenmp
           implies -fopenmp-simd.

       -fopenmp-simd
           Enable handling of OpenMP's SIMD directives with "#pragma omp" in C/C++  and  "!$omp"  in
           Fortran. Other OpenMP directives are ignored.

       -fgnu-tm
           When  the option -fgnu-tm is specified, the compiler generates code for the Linux variant
           of Intel's current Transactional Memory ABI specification document (Revision 1.1,  May  6
           2009).   This is an experimental feature whose interface may change in future versions of
           GCC, as the official specification changes.  Please note that not all  architectures  are
           supported for this feature.

           For more information on GCC's support for transactional memory,

           Note  that  the  transactional  memory  feature is not supported with non-call exceptions
           (-fnon-call-exceptions).

       -fms-extensions
           Accept some non-standard constructs used in Microsoft header files.

           In C++ code, this allows member names in structures  to  be  similar  to  previous  types
           declarations.

                   typedef int UOW;
                   struct ABC {
                     UOW UOW;
                   };

           Some cases of unnamed fields in structures and unions are only accepted with this option.

           Note that this option is off for all targets except for x86 targets using ms-abi.

       -fplan9-extensions
           Accept some non-standard constructs used in Plan 9 code.

           This  enables  -fms-extensions,  permits  passing  pointers  to structures with anonymous
           fields to functions that expect pointers to elements  of  the  type  of  the  field,  and
           permits referring to anonymous fields declared using a typedef.    This is only supported
           for C, not C++.

       -fcond-mismatch
           Allow  conditional  expressions  with mismatched types in the second and third arguments.
           The value of such an expression is void.  This option is not supported for C++.

       -flax-vector-conversions
           Allow implicit conversions between vectors with  differing  numbers  of  elements  and/or
           incompatible element types.  This option should not be used for new code.

       -funsigned-char
           Let the type "char" be unsigned, like "unsigned char".

           Each  kind  of  machine  has  a  default  for  what  "char" should be.  It is either like
           "unsigned char" by default or like "signed char" by default.

           Ideally, a portable program should always use "signed char" or "unsigned  char"  when  it
           depends on the signedness of an object.  But many programs have been written to use plain
           "char" and expect it to be signed, or expect it to be unsigned, depending on the machines
           they  were  written  for.  This option, and its inverse, let you make such a program work
           with the opposite default.

           The type "char" is always a distinct type from each of "signed char" or "unsigned  char",
           even though its behavior is always just like one of those two.

       -fsigned-char
           Let the type "char" be signed, like "signed char".

           Note  that  this  is  equivalent  to  -fno-unsigned-char,  which  is the negative form of
           -funsigned-char.  Likewise, the option -fno-signed-char is equivalent to -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
           These options control whether a bit-field is signed or  unsigned,  when  the  declaration
           does  not  use  either  "signed"  or "unsigned".  By default, such a bit-field is signed,
           because this is consistent: the basic integer types such as "int" are signed types.

       -fsso-struct=endianness
           Set the  default  scalar  storage  order  of  structures  and  unions  to  the  specified
           endianness.   The accepted values are big-endian, little-endian and native for the native
           endianness of the target (the default).  This option is not supported for C++.

           Warning: the -fsso-struct  switch  causes  GCC  to  generate  code  that  is  not  binary
           compatible  with  code generated without it if the specified endianness is not the native
           endianness of the target.

   Options Controlling C++ Dialect
       This section describes the command-line options that are only meaningful  for  C++  programs.
       You can also use most of the GNU compiler options regardless of what language your program is
       in.  For example, you might compile a file firstClass.C like this:

               g++ -g -fstrict-enums -O -c firstClass.C

       In  this  example,  only -fstrict-enums is an option meant only for C++ programs; you can use
       the other options with any language supported by GCC.

       Some options for compiling C programs, such as -std, are also relevant for C++ programs.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
           Use version n of the C++ ABI.  The default is version 0.

           Version 0 refers to the version conforming most closely to  the  C++  ABI  specification.
           Therefore,  the  ABI obtained using version 0 will change in different versions of G++ as
           ABI bugs are fixed.

           Version 1 is the version of the C++ ABI that first appeared in G++ 3.2.

           Version 2 is the version of the C++ ABI that first appeared  in  G++  3.4,  and  was  the
           default through G++ 4.9.

           Version 3 corrects an error in mangling a constant address as a template argument.

           Version  4,  which  first  appeared in G++ 4.5, implements a standard mangling for vector
           types.

           Version 5,  which  first  appeared  in  G++  4.6,  corrects  the  mangling  of  attribute
           const/volatile on function pointer types, decltype of a plain decl, and use of a function
           parameter in the declaration of another parameter.

           Version  6,  which  first  appeared  in G++ 4.7, corrects the promotion behavior of C++11
           scoped enums and the mangling of template argument packs,  const/static_cast,  prefix  ++
           and --, and a class scope function used as a template argument.

           Version  7,  which first appeared in G++ 4.8, that treats nullptr_t as a builtin type and
           corrects the mangling of lambdas in default argument scope.

           Version 8, which first appeared  in  G++  4.9,  corrects  the  substitution  behavior  of
           function types with function-cv-qualifiers.

           Version 9, which first appeared in G++ 5.2, corrects the alignment of "nullptr_t".

           Version 10, which first appeared in G++ 6.1, adds mangling of attributes that affect type
           identity, such as ia32 calling convention attributes (e.g. stdcall).

           Version 11, which first appeared in G++ 7, corrects the mangling of sizeof... expressions
           and operator names.  For multiple entities with the same name within a function, that are
           declared  in  different  scopes,  the  mangling  now  changes  starting  with the twelfth
           occurrence.  It also implies -fnew-inheriting-ctors.

           Version 12, which first appeared in G++ 8, corrects the  calling  conventions  for  empty
           classes  on  the  x86_64 target and for classes with only deleted copy/move constructors.
           It  accidentally  changes  the  calling  convention  for  classes  with  a  deleted  copy
           constructor and a trivial move constructor.

           Version 13, which first appeared in G++ 8.2, fixes the accidental change in version 12.

           Version  14,  which  first  appeared  in  G++  10,  corrects  the mangling of the nullptr
           expression.

           Version 15, which first appeared in G++ 11, changes the mangling of "__alignof__"  to  be
           distinct from that of "alignof", and dependent operator names.

           See also -Wabi.

       -fabi-compat-version=n
           On  targets that support strong aliases, G++ works around mangling changes by creating an
           alias with the correct mangled name when defining a  symbol  with  an  incorrect  mangled
           name.  This switch specifies which ABI version to use for the alias.

           With  -fabi-version=0  (the  default),  this  defaults  to  11 (GCC 7 compatibility).  If
           another ABI version is explicitly selected, this defaults to 0.  For  compatibility  with
           GCC versions 3.2 through 4.9, use -fabi-compat-version=2.

           If  this  option  is  not provided but -Wabi=n is, that version is used for compatibility
           aliases.  If this option is provided along with -Wabi (without the version), the  version
           from this option is used for the warning.

       -fno-access-control
           Turn  off  all  access checking.  This switch is mainly useful for working around bugs in
           the access control code.

       -faligned-new
           Enable support for  C++17  "new"  of  types  that  require  more  alignment  than  "void*
           ::operator new(std::size_t)" provides.  A numeric argument such as "-faligned-new=32" can
           be  used  to  specify how much alignment (in bytes) is provided by that function, but few
           users will need to override the default of alignof(std::max_align_t).

           This flag is enabled by default for -std=c++17.

       -fchar8_t
       -fno-char8_t
           Enable support for "char8_t" as adopted for C++20.  This includes the addition of  a  new
           "char8_t"  fundamental type, changes to the types of UTF-8 string and character literals,
           new signatures for user-defined literals, associated standard library  updates,  and  new
           "__cpp_char8_t" and "__cpp_lib_char8_t" feature test macros.

           This option enables functions to be overloaded for ordinary and UTF-8 strings:

                   int f(const char *);    // #1
                   int f(const char8_t *); // #2
                   int v1 = f("text");     // Calls #1
                   int v2 = f(u8"text");   // Calls #2

           and introduces new signatures for user-defined literals:

                   int operator""_udl1(char8_t);
                   int v3 = u8'x'_udl1;
                   int operator""_udl2(const char8_t*, std::size_t);
                   int v4 = u8"text"_udl2;
                   template<typename T, T...> int operator""_udl3();
                   int v5 = u8"text"_udl3;

           The   change   to   the   types   of  UTF-8  string  and  character  literals  introduces
           incompatibilities with ISO C++11 and later standards.  For example, the following code is
           well-formed under ISO C++11, but is ill-formed when -fchar8_t is specified.

                   char ca[] = u8"xx";     // error: char-array initialized from wide
                                           //        string
                   const char *cp = u8"xx";// error: invalid conversion from
                                           //        `const char8_t*' to `const char*'
                   int f(const char*);
                   auto v = f(u8"xx");     // error: invalid conversion from
                                           //        `const char8_t*' to `const char*'
                   std::string s{u8"xx"};  // error: no matching function for call to
                                           //        `std::basic_string<char>::basic_string()'
                   using namespace std::literals;
                   s = u8"xx"s;            // error: conversion from
                                           //        `basic_string<char8_t>' to non-scalar
                                           //        type `basic_string<char>' requested

       -fcheck-new
           Check that the pointer returned by "operator new" is non-null before attempting to modify
           the storage allocated.  This check is  normally  unnecessary  because  the  C++  standard
           specifies that "operator new" only returns 0 if it is declared throw(), in which case the
           compiler  always  checks  the return value even without this option.  In all other cases,
           when "operator new"  has  a  non-empty  exception  specification,  memory  exhaustion  is
           signalled by throwing "std::bad_alloc".  See also new (nothrow).

       -fconcepts
       -fconcepts-ts
           Below  -std=c++20,  -fconcepts  enables  support  for  the  C++  Extensions  for Concepts
           Technical Specification, ISO 19217 (2015).

           With -std=c++20 and above, Concepts are part of  the  language  standard,  so  -fconcepts
           defaults  to  on.   But the standard specification of Concepts differs significantly from
           the TS, so some constructs that were allowed in the  TS  but  didn't  make  it  into  the
           standard can still be enabled by -fconcepts-ts.

       -fconstexpr-depth=n
           Set  the  maximum nested evaluation depth for C++11 constexpr functions to n.  A limit is
           needed to detect endless recursion during constant expression  evaluation.   The  minimum
           specified by the standard is 512.

       -fconstexpr-cache-depth=n
           Set  the maximum level of nested evaluation depth for C++11 constexpr functions that will
           be cached to n.  This is a heuristic that trades off compilation speed  (when  the  cache
           avoids repeated calculations) against memory consumption (when the cache grows very large
           from highly recursive evaluations).  The default is 8.  Very few users are likely to want
           to  adjust  it,  but  if  your  code  does heavy constexpr calculations you might want to
           experiment to find which value works best for you.

       -fconstexpr-loop-limit=n
           Set the maximum number of iterations for a loop in C++14 constexpr  functions  to  n.   A
           limit  is  needed  to  detect  infinite loops during constant expression evaluation.  The
           default is 262144 (1<<18).

       -fconstexpr-ops-limit=n
           Set the maximum number of operations during a single  constexpr  evaluation.   Even  when
           number  of  iterations  of  a  single  loop is limited with the above limit, if there are
           several nested loops and each of them has many iterations  but  still  smaller  than  the
           above  limit, or if in a body of some loop or even outside of a loop too many expressions
           need to be evaluated, the resulting  constexpr  evaluation  might  take  too  long.   The
           default is 33554432 (1<<25).

       -fcoroutines
           Enable support for the C++ coroutines extension (experimental).

       -fno-elide-constructors
           The  C++ standard allows an implementation to omit creating a temporary that is only used
           to initialize another object of the same type.   Specifying  this  option  disables  that
           optimization, and forces G++ to call the copy constructor in all cases.  This option also
           causes G++ to call trivial member functions which otherwise would be expanded inline.

           In  C++17,  the  compiler  is  required  to omit these temporaries, but this option still
           affects trivial member functions.

       -fno-enforce-eh-specs
           Don't generate code to check for violation of exception specifications at run time.  This
           option violates the C++ standard, but may be useful for reducing code size in  production
           builds,  much  like  defining "NDEBUG".  This does not give user code permission to throw
           exceptions in violation of the exception specifications;  the  compiler  still  optimizes
           based  on  the  specifications,  so throwing an unexpected exception results in undefined
           behavior at run time.

       -fextern-tls-init
       -fno-extern-tls-init
           The C++11 and OpenMP standards allow "thread_local" and "threadprivate" variables to have
           dynamic (runtime) initialization.  To support this, any  use  of  such  a  variable  goes
           through  a wrapper function that performs any necessary initialization.  When the use and
           definition of the variable are in  the  same  translation  unit,  this  overhead  can  be
           optimized  away, but when the use is in a different translation unit there is significant
           overhead even if the variable doesn't  actually  need  dynamic  initialization.   If  the
           programmer  can be sure that no use of the variable in a non-defining TU needs to trigger
           dynamic initialization (either because the variable is statically initialized, or  a  use
           of  the variable in the defining TU will be executed before any uses in another TU), they
           can avoid this overhead with the -fno-extern-tls-init option.

           On targets that support symbol aliases, the default  is  -fextern-tls-init.   On  targets
           that do not support symbol aliases, the default is -fno-extern-tls-init.

       -fno-gnu-keywords
           Do  not recognize "typeof" as a keyword, so that code can use this word as an identifier.
           You can use the keyword "__typeof__" instead.  This option is implied by the  strict  ISO
           C++ dialects: -ansi, -std=c++98, -std=c++11, etc.

       -fno-implicit-templates
           Never  emit code for non-inline templates that are instantiated implicitly (i.e. by use);
           only emit code for explicit instantiations.  If you use this option, you must  take  care
           to  structure  your  code  to  include all the necessary explicit instantiations to avoid
           getting undefined symbols at link time.

       -fno-implicit-inline-templates
           Don't emit code for implicit instantiations of inline templates, either.  The default  is
           to  handle  inlines  differently  so that compiles with and without optimization need the
           same set of explicit instantiations.

       -fno-implement-inlines
           To save space, do not emit out-of-line copies of inline functions controlled by  "#pragma
           implementation".  This causes linker errors if these functions are not inlined everywhere
           they are called.

       -fmodules-ts
       -fno-modules-ts
           Enable  support for C++20 modules   The -fno-modules-ts is usually not needed, as that is
           the default.  Even though this is a C++20 feature, it is not currently implicitly enabled
           by selecting that standard version.

       -fmodule-header
       -fmodule-header=user
       -fmodule-header=system
           Compile a header file to create an importable header unit.

       -fmodule-implicit-inline
           Member functions defined in their class definitions are not implicitly inline for modular
           code.  This is different to traditional C++ behavior, for good reasons.  However, it  may
           result  in a difficulty during code porting.  This option makes such function definitions
           implicitly inline.  It does however generate an ABI incompatibility, so you must  use  it
           everywhere  or  nowhere.   (Such  definitions outside of a named module remain implicitly
           inline, regardless.)

       -fno-module-lazy
           Disable lazy module importing and module mapper creation.

       -fmodule-mapper=[hostname]:port[?ident]
       -fmodule-mapper=|program[?ident] args...
       -fmodule-mapper==socket[?ident]
       -fmodule-mapper=<>[inout][?ident]
       -fmodule-mapper=<in>out[?ident]
       -fmodule-mapper=file[?ident]
           An  oracle  to  query  for  module  name  to  filename  mappings.   If  unspecified   the
           CXX_MODULE_MAPPER  environment  variable  is  used,  and  if that is unset, an in-process
           default is provided.

       -fmodule-only
           Only emit the Compiled Module Interface, inhibiting any object file.

       -fms-extensions
           Disable Wpedantic warnings about constructs used in MFC, such as implicit int and getting
           a pointer to member function via non-standard syntax.

       -fnew-inheriting-ctors
           Enable the P0136 adjustment to the semantics of C++11 constructor inheritance.   This  is
           part  of  C++17  but also considered to be a Defect Report against C++11 and C++14.  This
           flag is enabled by default unless -fabi-version=10 or lower is specified.

       -fnew-ttp-matching
           Enable the P0522 resolution to Core issue 150, template template parameters  and  default
           arguments:  this  allows  a template with default template arguments as an argument for a
           template template parameter with fewer template parameters.   This  flag  is  enabled  by
           default for -std=c++17.

       -fno-nonansi-builtins
           Disable  built-in  declarations  of functions that are not mandated by ANSI/ISO C.  These
           include "ffs", "alloca", "_exit", "index", "bzero", "conjf", and other related functions.

       -fnothrow-opt
           Treat a throw() exception specification as if  it  were  a  "noexcept"  specification  to
           reduce  or  eliminate  the  text  size  overhead relative to a function with no exception
           specification.   If  the  function  has  local  variables  of  types   with   non-trivial
           destructors,  the exception specification actually makes the function smaller because the
           EH cleanups for those variables can be optimized away.  The semantic effect  is  that  an
           exception thrown out of a function with such an exception specification results in a call
           to "terminate" rather than "unexpected".

       -fno-operator-names
           Do  not  treat  the operator name keywords "and", "bitand", "bitor", "compl", "not", "or"
           and "xor" as synonyms as keywords.

       -fno-optional-diags
           Disable diagnostics that the standard says a compiler does not need to issue.  Currently,
           the only such diagnostic issued by G++ is the one for a  name  having  multiple  meanings
           within a class.

       -fpermissive
           Downgrade some diagnostics about nonconformant code from errors to warnings.  Thus, using
           -fpermissive allows some nonconforming code to compile.

       -fno-pretty-templates
           When  an  error  message  refers to a specialization of a function template, the compiler
           normally prints the signature of the template followed by the template arguments and  any
           typedefs or typenames in the signature (e.g. "void f(T) [with T = int]" rather than "void
           f(int)")  so that it's clear which template is involved.  When an error message refers to
           a specialization of a class template, the compiler  omits  any  template  arguments  that
           match  the  default  template  arguments for that template.  If either of these behaviors
           make it harder  to  understand  the  error  message  rather  than  easier,  you  can  use
           -fno-pretty-templates to disable them.

       -fno-rtti
           Disable generation of information about every class with virtual functions for use by the
           C++  run-time  type  identification features ("dynamic_cast" and "typeid").  If you don't
           use those parts of the language, you can save some space by using this flag.   Note  that
           exception  handling  uses  the  same  information,  but  G++  generates it as needed. The
           "dynamic_cast" operator can still be used for casts that do  not  require  run-time  type
           information, i.e. casts to "void *" or to unambiguous base classes.

           Mixing  code  compiled  with  -frtti with that compiled with -fno-rtti may not work.  For
           example, programs may fail to link if a class compiled with -fno-rtti is used as  a  base
           for a class compiled with -frtti.

       -fsized-deallocation
           Enable the built-in global declarations

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           as  introduced  in  C++14.   This  is  useful  for  user-defined replacement deallocation
           functions that, for example, use the size of the  object  to  make  deallocation  faster.
           Enabled by default under -std=c++14 and above.  The flag -Wsized-deallocation warns about
           places that might want to add a definition.

       -fstrict-enums
           Allow  the  compiler to optimize using the assumption that a value of enumerated type can
           only be one of the values of the enumeration (as defined in the C++ standard;  basically,
           a value that can be represented in the minimum number of bits needed to represent all the
           enumerators).   This assumption may not be valid if the program uses a cast to convert an
           arbitrary integer value to the enumerated type.

       -fstrong-eval-order
           Evaluate member access, array subscripting, and shift expressions in left-to-right order,
           and evaluate assignment in right-to-left order, as adopted for C++17.  Enabled by default
           with -std=c++17.  -fstrong-eval-order=some enables just the ordering of member access and
           shift expressions, and is the default without -std=c++17.

       -ftemplate-backtrace-limit=n
           Set the maximum number of template instantiation notes for a single warning or  error  to
           n.  The default value is 10.

       -ftemplate-depth=n
           Set  the  maximum instantiation depth for template classes to n.  A limit on the template
           instantiation depth  is  needed  to  detect  endless  recursions  during  template  class
           instantiation.  ANSI/ISO C++ conforming programs must not rely on a maximum depth greater
           than  17  (changed  to 1024 in C++11).  The default value is 900, as the compiler can run
           out of stack space before hitting 1024 in some situations.

       -fno-threadsafe-statics
           Do not emit the extra code to use the routines specified in the C++ ABI  for  thread-safe
           initialization of local statics.  You can use this option to reduce code size slightly in
           code that doesn't need to be thread-safe.

       -fuse-cxa-atexit
           Register  destructors  for  objects  with static storage duration with the "__cxa_atexit"
           function rather than the "atexit" function.  This option is required for fully standards-
           compliant handling of static destructors, but only  works  if  your  C  library  supports
           "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
           Don't    use    the    "__cxa_get_exception_ptr"    runtime    routine.     This   causes
           "std::uncaught_exception" to be incorrect, but is necessary if the runtime routine is not
           available.

       -fvisibility-inlines-hidden
           This switch declares that the user  does  not  attempt  to  compare  pointers  to  inline
           functions  or  methods  where  the  addresses of the two functions are taken in different
           shared objects.

           The effect of this is that GCC may, effectively, mark inline methods with  "__attribute__
           ((visibility ("hidden")))" so that they do not appear in the export table of a DSO and do
           not  require a PLT indirection when used within the DSO.  Enabling this option can have a
           dramatic effect on load and link times of a DSO as it massively reduces the size  of  the
           dynamic export table when the library makes heavy use of templates.

           The  behavior  of  this  switch  is  not  quite the same as marking the methods as hidden
           directly, because it does not affect static variables local to the function or cause  the
           compiler to deduce that the function is defined in only one shared object.

           You  may  mark  a  method  as  having a visibility explicitly to negate the effect of the
           switch for that method.  For example, if you do want to compare pointers to a  particular
           inline  method,  you  might  mark it as having default visibility.  Marking the enclosing
           class with explicit visibility has no effect.

           Explicitly instantiated inline methods are unaffected by this  option  as  their  linkage
           might otherwise cross a shared library boundary.

       -fvisibility-ms-compat
           This  flag attempts to use visibility settings to make GCC's C++ linkage model compatible
           with that of Microsoft Visual Studio.

           The flag makes these changes to GCC's linkage model:

           1.  It sets the default visibility to "hidden", like -fvisibility=hidden.

           2.  Types, but not their members, are not hidden by default.

           3.  The  One  Definition  Rule  is  relaxed  for  types   without   explicit   visibility
               specifications  that  are  defined in more than one shared object: those declarations
               are permitted if they are permitted when this option is not used.

           In new code it is better to use -fvisibility=hidden and export  those  classes  that  are
           intended  to  be  externally  visible.   Unfortunately  it  is possible for code to rely,
           perhaps accidentally, on the Visual Studio behavior.

           Among the consequences of these changes are that static data members  of  the  same  type
           with the same name but defined in different shared objects are different, so changing one
           does  not  change  the  other; and that pointers to function members defined in different
           shared objects may not compare equal.  When this flag is given, it is a violation of  the
           ODR to define types with the same name differently.

       -fno-weak
           Do  not  use  weak symbol support, even if it is provided by the linker.  By default, G++
           uses weak symbols if they are available.  This option exists only for testing, and should
           not be used by end-users; it results in inferior code and has no benefits.   This  option
           may be removed in a future release of G++.

       -fext-numeric-literals (C++ and Objective-C++ only)
           Accept  imaginary,  fixed-point,  or  machine-defined  literal  number  suffixes  as  GNU
           extensions.  When this option is turned off these suffixes are  treated  as  C++11  user-
           defined  literal  numeric suffixes.  This is on by default for all pre-C++11 dialects and
           all GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++14.  This  option  is
           off by default for ISO C++11 onwards (-std=c++11, ...).

       -nostdinc++
           Do  not search for header files in the standard directories specific to C++, but do still
           search the other standard directories.  (This  option  is  used  when  building  the  C++
           library.)

       -flang-info-include-translate
       -flang-info-include-translate-not
       -flang-info-include-translate=header
           Inform of include translation events.  The first will note accepted include translations,
           the  second  will  note  declined  include  translations.  The header form will inform of
           include translations relating to that specific header.  If header is of the  form  "user"
           or  "<system>"  it will be resolved to a specific user or system header using the include
           path.

       -flang-info-module-cmi
       -flang-info-module-cmi=module
           Inform of Compiled Module  Interface  pathnames.   The  first  will  note  all  read  CMI
           pathnames.   The  module  form will not reading a specific module's CMI.  module may be a
           named module or a header-unit (the latter indicated by either being a pathname containing
           directory separators or enclosed in "<>" or "").

       -stdlib=libstdc++,libc++
           When G++ is configured to support this option, it allows specification of  alternate  C++
           runtime libraries.  Two options are available: libstdc++ (the default, native C++ runtime
           for  G++)  and  libc++ which is the C++ runtime installed on some operating systems (e.g.
           Darwin versions from Darwin11 onwards).  The option switches G++ to use the headers  from
           the  specified library and to emit "-lstdc++" or "-lc++" respectively, when a C++ runtime
           is required for linking.

       In addition, these warning options have meanings only for C++ programs:

       -Wabi-tag (C++ and Objective-C++ only)
           Warn when a type with an ABI tag is used in a context that does not have  that  ABI  tag.
           See C++ Attributes for more information about ABI tags.

       -Wcomma-subscript (C++ and Objective-C++ only)
           Warn  about  uses of a comma expression within a subscripting expression.  This usage was
           deprecated in C++20.  However, a comma expression wrapped in "(  )"  is  not  deprecated.
           Example:

                   void f(int *a, int b, int c) {
                       a[b,c];     // deprecated
                       a[(b,c)];   // OK
                   }

           Enabled by default with -std=c++20.

       -Wctad-maybe-unsupported (C++ and Objective-C++ only)
           Warn  when  performing  class  template  argument  deduction  (CTAD)  on  a  type with no
           explicitly written deduction guides.  This  warning  will  point  out  cases  where  CTAD
           succeeded  only  because  the  compiler  synthesized the implicit deduction guides, which
           might not be what the programmer intended.  Certain style guides allow CTAD only on types
           that specifically "opt-in"; i.e., on types that  are  designed  to  support  CTAD.   This
           warning can be suppressed with the following pattern:

                   struct allow_ctad_t; // any name works
                   template <typename T> struct S {
                     S(T) { }
                   };
                   S(allow_ctad_t) -> S<void>; // guide with incomplete parameter type will never be considered

       -Wctor-dtor-privacy (C++ and Objective-C++ only)
           Warn  when  a  class  seems  unusable because all the constructors or destructors in that
           class are private, and it has neither friends nor public static member  functions.   Also
           warn  if  there  are  no  non-private  methods,  and  there's at least one private member
           function that isn't a constructor or destructor.

       -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
           Warn when "delete" is used to destroy an instance of a class that has  virtual  functions
           and non-virtual destructor. It is unsafe to delete an instance of a derived class through
           a  pointer  to  a  base class if the base class does not have a virtual destructor.  This
           warning is enabled by -Wall.

       -Wdeprecated-copy (C++ and Objective-C++ only)
           Warn that the implicit declaration of a copy constructor or copy assignment  operator  is
           deprecated if the class has a user-provided copy constructor or copy assignment operator,
           in  C++11 and up.  This warning is enabled by -Wextra.  With -Wdeprecated-copy-dtor, also
           deprecate if the class has a user-provided destructor.

       -Wno-deprecated-enum-enum-conversion (C++ and Objective-C++ only)
           Disable the warning about the case when the usual arithmetic conversions are  applied  on
           operands  where  one  is  of enumeration type and the other is of a different enumeration
           type.  This conversion was deprecated in C++20.  For example:

                   enum E1 { e };
                   enum E2 { f };
                   int k = f - e;

           -Wdeprecated-enum-enum-conversion is enabled by default with  -std=c++20.   In  pre-C++20
           dialects, this warning can be enabled by -Wenum-conversion.

       -Wno-deprecated-enum-float-conversion (C++ and Objective-C++ only)
           Disable  the  warning about the case when the usual arithmetic conversions are applied on
           operands where one is of enumeration type and the other  is  of  a  floating-point  type.
           This conversion was deprecated in C++20.  For example:

                   enum E1 { e };
                   enum E2 { f };
                   bool b = e <= 3.7;

           -Wdeprecated-enum-float-conversion  is  enabled by default with -std=c++20.  In pre-C++20
           dialects, this warning can be enabled by -Wenum-conversion.

       -Wno-init-list-lifetime (C++ and Objective-C++ only)
           Do not warn about uses of "std::initializer_list" that are likely to result  in  dangling
           pointers.   Since the underlying array for an "initializer_list" is handled like a normal
           C++ temporary object, it is easy to inadvertently keep a pointer to the  array  past  the
           end of the array's lifetime.  For example:

           *   If  a  function returns a temporary "initializer_list", or a local "initializer_list"
               variable, the array's lifetime ends at the end of the return statement, so the  value
               returned has a dangling pointer.

           *   If a new-expression creates an "initializer_list", the array only lives until the end
               of  the  enclosing  full-expression,  so  the  "initializer_list"  in  the heap has a
               dangling pointer.

           *   When an "initializer_list" variable is assigned  from  a  brace-enclosed  initializer
               list,  the  temporary  array  created for the right side of the assignment only lives
               until the end of the full-expression, so at the next statement the "initializer_list"
               variable has a dangling pointer.

                       // li's initial underlying array lives as long as li
                       std::initializer_list<int> li = { 1,2,3 };
                       // assignment changes li to point to a temporary array
                       li = { 4, 5 };
                       // now the temporary is gone and li has a dangling pointer
                       int i = li.begin()[0] // undefined behavior

           *   When a list constructor  stores  the  "begin"  pointer  from  the  "initializer_list"
               argument,  this  doesn't  extend the lifetime of the array, so if a class variable is
               constructed from a temporary "initializer_list", the pointer is left dangling by  the
               end of the variable declaration statement.

       -Winvalid-imported-macros
           Verify  all  imported macro definitions are valid at the end of compilation.  This is not
           enabled by default, as it requires additional processing to determine.  It may be  useful
           when preparing sets of header-units to ensure consistent macros.

       -Wno-literal-suffix (C++ and Objective-C++ only)
           Do  not warn when a string or character literal is followed by a ud-suffix which does not
           begin with an underscore.  As  a  conforming  extension,  GCC  treats  such  suffixes  as
           separate preprocessing tokens in order to maintain backwards compatibility with code that
           uses formatting macros from "<inttypes.h>".  For example:

                   #define __STDC_FORMAT_MACROS
                   #include <inttypes.h>
                   #include <stdio.h>

                   int main() {
                     int64_t i64 = 123;
                     printf("My int64: %" PRId64"\n", i64);
                   }

           In this case, "PRId64" is treated as a separate preprocessing token.

           This  option also controls warnings when a user-defined literal operator is declared with
           a literal suffix identifier  that  doesn't  begin  with  an  underscore.  Literal  suffix
           identifiers that don't begin with an underscore are reserved for future standardization.

           These warnings are enabled by default.

       -Wno-narrowing (C++ and Objective-C++ only)
           For  C++11  and  later  standards,  narrowing  conversions  are  diagnosed by default, as
           required by the standard.  A narrowing conversion from a constant produces an error,  and
           a  narrowing  conversion  from  a  non-constant  produces  a  warning, but -Wno-narrowing
           suppresses the diagnostic.  Note that this does not affect  the  meaning  of  well-formed
           code; narrowing conversions are still considered ill-formed in SFINAE contexts.

           With  -Wnarrowing  in  C++98, warn when a narrowing conversion prohibited by C++11 occurs
           within { }, e.g.

                   int i = { 2.2 }; // error: narrowing from double to int

           This flag is included in -Wall and -Wc++11-compat.

       -Wnoexcept (C++ and Objective-C++ only)
           Warn when a noexcept-expression evaluates to false because of a call to a  function  that
           does  not have a non-throwing exception specification (i.e. throw() or "noexcept") but is
           known by the compiler to never throw an exception.

       -Wnoexcept-type (C++ and Objective-C++ only)
           Warn if the C++17 feature making "noexcept" part of a function type changes  the  mangled
           name of a symbol relative to C++14.  Enabled by -Wabi and -Wc++17-compat.

           As an example:

                   template <class T> void f(T t) { t(); };
                   void g() noexcept;
                   void h() { f(g); }

           In C++14, "f" calls "f<void(*)()>", but in C++17 it calls "f<void(*)()noexcept>".

       -Wclass-memaccess (C++ and Objective-C++ only)
           Warn when the destination of a call to a raw memory function such as "memset" or "memcpy"
           is  an  object of class type, and when writing into such an object might bypass the class
           non-trivial or deleted constructor  or  copy  assignment,  violate  const-correctness  or
           encapsulation,  or  corrupt virtual table pointers.  Modifying the representation of such
           objects may violate invariants maintained by member functions of the class.  For example,
           the call to "memset" below is undefined because it modifies a  non-trivial  class  object
           and  is, therefore, diagnosed.  The safe way to either initialize or clear the storage of
           objects of such types is by using the appropriate constructor or assignment operator,  if
           one is available.

                   std::string str = "abc";
                   memset (&str, 0, sizeof str);

           The  -Wclass-memaccess option is enabled by -Wall.  Explicitly casting the pointer to the
           class object to "void *" or to a type that can be  safely  accessed  by  the  raw  memory
           function suppresses the warning.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
           Warn  when  a class has virtual functions and an accessible non-virtual destructor itself
           or in an accessible polymorphic base class, in which case it is possible  but  unsafe  to
           delete  an  instance  of  a  derived  class through a pointer to the class itself or base
           class.  This warning is automatically enabled if -Weffc++ is specified.

       -Wregister (C++ and Objective-C++ only)
           Warn on uses of the "register" storage class specifier, except when it is part of the GNU
           Explicit Register Variables extension.  The use of  the  "register"  keyword  as  storage
           class  specifier  has  been deprecated in C++11 and removed in C++17.  Enabled by default
           with -std=c++17.

       -Wreorder (C++ and Objective-C++ only)
           Warn when the order of member initializers given in the code does not match the order  in
           which they must be executed.  For instance:

                   struct A {
                     int i;
                     int j;
                     A(): j (0), i (1) { }
                   };

           The  compiler rearranges the member initializers for "i" and "j" to match the declaration
           order of the members, emitting a warning to that effect.   This  warning  is  enabled  by
           -Wall.

       -Wno-pessimizing-move (C++ and Objective-C++ only)
           This  warning warns when a call to "std::move" prevents copy elision.  A typical scenario
           when copy elision can occur is when returning in a function with  a  class  return  type,
           when the expression being returned is the name of a non-volatile automatic object, and is
           not a function parameter, and has the same type as the function return type.

                   struct T {
                   ...
                   };
                   T fn()
                   {
                     T t;
                     ...
                     return std::move (t);
                   }

           But in this example, the "std::move" call prevents copy elision.

           This warning is enabled by -Wall.

       -Wno-redundant-move (C++ and Objective-C++ only)
           This  warning  warns about redundant calls to "std::move"; that is, when a move operation
           would have been performed even without the "std::move" call.  This  happens  because  the
           compiler is forced to treat the object as if it were an rvalue in certain situations such
           as returning a local variable, where copy elision isn't applicable.  Consider:

                   struct T {
                   ...
                   };
                   T fn(T t)
                   {
                     ...
                     return std::move (t);
                   }

           Here, the "std::move" call is redundant.  Because G++ implements Core Issue 1579, another
           example is:

                   struct T { // convertible to U
                   ...
                   };
                   struct U {
                   ...
                   };
                   U fn()
                   {
                     T t;
                     ...
                     return std::move (t);
                   }

           In  this  example, copy elision isn't applicable because the type of the expression being
           returned and the function return type differ, yet G++ treats the return value  as  if  it
           were designated by an rvalue.

           This warning is enabled by -Wextra.

       -Wrange-loop-construct (C++ and Objective-C++ only)
           This warning warns when a C++ range-based for-loop is creating an unnecessary copy.  This
           can  happen  when  the range declaration is not a reference, but probably should be.  For
           example:

                   struct S { char arr[128]; };
                   void fn () {
                     S arr[5];
                     for (const auto x : arr) { ... }
                   }

           It does not warn when the type being copied is a trivially-copyable type  whose  size  is
           less than 64 bytes.

           This  warning  also  warns  when a loop variable in a range-based for-loop is initialized
           with a value of a different type resulting in a copy.  For example:

                   void fn() {
                     int arr[10];
                     for (const double &x : arr) { ... }
                   }

           In the example above, in every iteration of the loop a temporary value of  type  "double"
           is created and destroyed, to which the reference "const double &" is bound.

           This warning is enabled by -Wall.

       -Wredundant-tags (C++ and Objective-C++ only)
           Warn  about  redundant class-key and enum-key in references to class types and enumerated
           types in contexts where the key can be eliminated  without  causing  an  ambiguity.   For
           example:

                   struct foo;
                   struct foo *p;   // warn that keyword struct can be eliminated

           On the other hand, in this example there is no warning:

                   struct foo;
                   void foo ();   // "hides" struct foo
                   void bar (struct foo&);  // no warning, keyword struct is necessary

       -Wno-subobject-linkage (C++ and Objective-C++ only)
           Do not warn if a class type has a base or a field whose type uses the anonymous namespace
           or  depends  on  a  type  with  no  linkage.   If a type A depends on a type B with no or
           internal linkage, defining it in multiple translation units would  be  an  ODR  violation
           because  the  meaning of B is different in each translation unit.  If A only appears in a
           single translation unit, the best way to silence the  warning  is  to  give  it  internal
           linkage  by putting it in an anonymous namespace as well.  The compiler doesn't give this
           warning for types defined in the main .C file, as those are  unlikely  to  have  multiple
           definitions.  -Wsubobject-linkage is enabled by default.

       -Weffc++ (C++ and Objective-C++ only)
           Warn  about violations of the following style guidelines from Scott Meyers' Effective C++
           series of books:

           *   Define a copy constructor and an assignment operator for  classes  with  dynamically-
               allocated memory.

           *   Prefer initialization to assignment in constructors.

           *   Have "operator=" return a reference to *this.

           *   Don't try to return a reference when you must return an object.

           *   Distinguish between prefix and postfix forms of increment and decrement operators.

           *   Never overload "&&", "||", or ",".

           This  option  also  enables  -Wnon-virtual-dtor,  which  is also one of the effective C++
           recommendations.  However, the check is extended  to  warn  about  the  lack  of  virtual
           destructor in accessible non-polymorphic bases classes too.

           When selecting this option, be aware that the standard library headers do not obey all of
           these guidelines; use grep -v to filter out those warnings.

       -Wno-exceptions (C++ and Objective-C++ only)
           Disable  the  warning  about  the  case  when an exception handler is shadowed by another
           handler, which can point out a wrong ordering of exception handlers.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
           Warn about the use of an uncasted "NULL" as sentinel.  When compiling only with GCC  this
           is  a  valid  sentinel,  as "NULL" is defined to "__null".  Although it is a null pointer
           constant rather than a null pointer, it is guaranteed  to  be  of  the  same  size  as  a
           pointer.  But this use is not portable across different compilers.

       -Wno-non-template-friend (C++ and Objective-C++ only)
           Disable  warnings  when non-template friend functions are declared within a template.  In
           very old versions of GCC that predate implementation of the  ISO  standard,  declarations
           such  as friend int foo(int), where the name of the friend is an unqualified-id, could be
           interpreted as a particular specialization of a template function; the warning exists  to
           diagnose compatibility problems, and is enabled by default.

       -Wold-style-cast (C++ and Objective-C++ only)
           Warn if an old-style (C-style) cast to a non-void type is used within a C++ program.  The
           new-style casts ("dynamic_cast", "static_cast", "reinterpret_cast", and "const_cast") are
           less vulnerable to unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
           Warn when a function declaration hides virtual functions from a base class.  For example,
           in:

                   struct A {
                     virtual void f();
                   };

                   struct B: public A {
                     void f(int);
                   };

           the "A" class version of "f" is hidden in "B", and code like:

                   B* b;
                   b->f();

           fails to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
           Disable  the  diagnostic  for  converting  a  bound pointer to member function to a plain
           pointer.

       -Wsign-promo (C++ and Objective-C++ only)
           Warn when overload resolution chooses a promotion from unsigned or enumerated type  to  a
           signed  type,  over a conversion to an unsigned type of the same size.  Previous versions
           of G++ tried to preserve unsignedness, but the standard mandates the current behavior.

       -Wtemplates (C++ and Objective-C++ only)
           Warn when a primary template declaration is  encountered.   Some  coding  rules  disallow
           templates,  and  this may be used to enforce that rule.  The warning is inactive inside a
           system header file, such as the STL, so  one  can  still  use  the  STL.   One  may  also
           instantiate or specialize templates.

       -Wno-mismatched-new-delete (C++ and Objective-C++ only)
           Warn  for  mismatches  between  calls  to  "operator  new"  or  "operator delete" and the
           corresponding call to the allocation or deallocation function.  This includes invocations
           of C++ "operator delete" with pointers returned from either mismatched forms of "operator
           new", or from other functions that allocate objects for which the "operator delete" isn't
           a suitable deallocator, as well as calls to other deallocation  functions  with  pointers
           returned from "operator new" for which the deallocation function isn't suitable.

           For  example,  the  "delete"  expression  in  the  function below is diagnosed because it
           doesn't match the array form of the "new" expression the pointer  argument  was  returned
           from.  Similarly, the call to "free" is also diagnosed.

                   void f ()
                   {
                     int *a = new int[n];
                     delete a;   // warning: mismatch in array forms of expressions

                     char *p = new char[n];
                     free (p);   // warning: mismatch between new and free
                   }

           The  related  option  -Wmismatched-dealloc  diagnoses mismatches involving allocation and
           deallocation functions other than "operator new" and "operator delete".

           -Wmismatched-new-delete is enabled by default.

       -Wmismatched-tags (C++ and Objective-C++ only)
           Warn for declarations of structs, classes, and class templates and their  specializations
           with a class-key that does not match either the definition or the first declaration if no
           definition is provided.

           For  example,  the declaration of "struct Object" in the argument list of "draw" triggers
           the warning.  To avoid it, either remove the redundant class-key "struct" or  replace  it
           with "class" to match its definition.

                   class Object {
                   public:
                     virtual ~Object () = 0;
                   };
                   void draw (struct Object*);

           It  is  not  wrong  to  declare  a class with the class-key "struct" as the example above
           shows.  The -Wmismatched-tags option is intended to help achieve a  consistent  style  of
           class  declarations.   In code that is intended to be portable to Windows-based compilers
           the warning helps prevent unresolved references due to the difference in the mangling  of
           symbols  declared with different class-keys.  The option can be used either on its own or
           in conjunction with -Wredundant-tags.

       -Wmultiple-inheritance (C++ and Objective-C++ only)
           Warn when a class is defined with  multiple  direct  base  classes.   Some  coding  rules
           disallow multiple inheritance, and this may be used to enforce that rule.  The warning is
           inactive inside a system header file, such as the STL, so one can still use the STL.  One
           may also define classes that indirectly use multiple inheritance.

       -Wvirtual-inheritance
           Warn  when  a  class  is  defined  with  a  virtual direct base class.  Some coding rules
           disallow multiple inheritance, and this may be used to enforce that rule.  The warning is
           inactive inside a system header file, such as the STL, so one can still use the STL.  One
           may also define classes that indirectly use virtual inheritance.

       -Wno-virtual-move-assign
           Suppress warnings about inheriting from a virtual base  with  a  non-trivial  C++11  move
           assignment  operator.   This  is dangerous because if the virtual base is reachable along
           more than one path, it is moved multiple times, which can mean both objects end up in the
           moved-from state.  If the move assignment operator is written  to  avoid  moving  from  a
           moved-from object, this warning can be disabled.

       -Wnamespaces
           Warn  when  a namespace definition is opened.  Some coding rules disallow namespaces, and
           this may be used to enforce that rule.  The warning is inactive inside  a  system  header
           file,  such  as the STL, so one can still use the STL.  One may also use using directives
           and qualified names.

       -Wno-terminate (C++ and Objective-C++ only)
           Disable the warning about a throw-expression that will immediately result in  a  call  to
           "terminate".

       -Wno-vexing-parse (C++ and Objective-C++ only)
           Warn  about the most vexing parse syntactic ambiguity.  This warns about the cases when a
           declaration looks like a variable definition, but the C++  language  requires  it  to  be
           interpreted as a function declaration.  For instance:

                   void f(double a) {
                     int i();        // extern int i (void);
                     int n(int(a));  // extern int n (int);
                   }

           Another example:

                   struct S { S(int); };
                   void f(double a) {
                     S x(int(a));   // extern struct S x (int);
                     S y(int());    // extern struct S y (int (*) (void));
                     S z();         // extern struct S z (void);
                   }

           The warning will suggest options how to deal with such an ambiguity; e.g., it can suggest
           removing the parentheses or using braces instead.

           This warning is enabled by default.

       -Wno-class-conversion (C++ and Objective-C++ only)
           Do  not  warn  when  a conversion function converts an object to the same type, to a base
           class of that type, or to void; such a conversion function will never be called.

       -Wvolatile (C++ and Objective-C++ only)
           Warn about deprecated uses of the "volatile" qualifier.  This includes postfix and prefix
           "++" and "--" expressions of "volatile"-qualified types, using simple  assignments  where
           the  left  operand  is  a  "volatile"-qualified  non-class type for their value, compound
           assignments  where  the  left  operand  is   a   "volatile"-qualified   non-class   type,
           "volatile"-qualified  function  return  type,  "volatile"-qualified  parameter  type, and
           structured bindings of a "volatile"-qualified type.  This usage was deprecated in C++20.

           Enabled by default with -std=c++20.

       -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
           Warn when a literal 0 is used as null pointer constant.  This can be useful to facilitate
           the conversion to "nullptr" in C++11.

       -Waligned-new
           Warn about  a  new-expression  of  a  type  that  requires  greater  alignment  than  the
           alignof(std::max_align_t)  but  uses an allocation function without an explicit alignment
           parameter. This option is enabled by -Wall.

           Normally this only warns about global allocation functions,  but  -Waligned-new=all  also
           warns about class member allocation functions.

       -Wno-placement-new
       -Wplacement-new=n
           Warn  about  placement  new  expressions with undefined behavior, such as constructing an
           object in a buffer that is smaller than  the  type  of  the  object.   For  example,  the
           placement  new expression below is diagnosed because it attempts to construct an array of
           64 integers in a buffer only 64 bytes large.

                   char buf [64];
                   new (buf) int[64];

           This warning is enabled by default.

           -Wplacement-new=1
               This is the default warning level of -Wplacement-new.  At this level the  warning  is
               not  issued  for some strictly undefined constructs that GCC allows as extensions for
               compatibility with legacy code.  For example, the following "new" expression  is  not
               diagnosed  at  this  level even though it has undefined behavior according to the C++
               standard because it writes past the end of the one-element array.

                       struct S { int n, a[1]; };
                       S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
                       new (s->a)int [32]();

           -Wplacement-new=2
               At this level, in addition to diagnosing all the same constructs as  at  level  1,  a
               diagnostic  is  also issued for placement new expressions that construct an object in
               the last member of structure whose type is an array of a  single  element  and  whose
               size  is  less  than  the  size  of the object being constructed.  While the previous
               example would be diagnosed, the following construct makes use of the flexible  member
               array extension to avoid the warning at level 2.

                       struct S { int n, a[]; };
                       S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
                       new (s->a)int [32]();

       -Wcatch-value
       -Wcatch-value=n (C++ and Objective-C++ only)
           Warn  about  catch  handlers  that  do not catch via reference.  With -Wcatch-value=1 (or
           -Wcatch-value for short) warn about polymorphic class types that  are  caught  by  value.
           With  -Wcatch-value=2  warn  about  all  class  types  that  are  caught  by  value. With
           -Wcatch-value=3 warn about all types that are not caught by reference.  -Wcatch-value  is
           enabled by -Wall.

       -Wconditionally-supported (C++ and Objective-C++ only)
           Warn for conditionally-supported (C++11 [intro.defs]) constructs.

       -Wno-delete-incomplete (C++ and Objective-C++ only)
           Do  not  warn  when  deleting  a  pointer  to  incomplete type, which may cause undefined
           behavior at runtime.  This warning is enabled by default.

       -Wextra-semi (C++, Objective-C++ only)
           Warn about redundant semicolons after in-class function definitions.

       -Wno-inaccessible-base (C++, Objective-C++ only)
           This option controls warnings when a base class is inaccessible in a class  derived  from
           it  due  to  ambiguity.   The  warning  is enabled by default.  Note that the warning for
           ambiguous virtual bases is enabled by the -Wextra option.

                   struct A { int a; };

                   struct B : A { };

                   struct C : B, A { };

       -Wno-inherited-variadic-ctor
           Suppress warnings about  use  of  C++11  inheriting  constructors  when  the  base  class
           inherited  from  has  a  C variadic constructor; the warning is on by default because the
           ellipsis is not inherited.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
           Suppress warnings from applying the "offsetof" macro to a non-POD type.  According to the
           2014 ISO C++ standard, applying "offsetof" to a non-standard-layout  type  is  undefined.
           In  existing C++ implementations, however, "offsetof" typically gives meaningful results.
           This flag is for users who are aware that they are writing nonportable code and who  have
           deliberately chosen to ignore the warning about it.

           The restrictions on "offsetof" may be relaxed in a future version of the C++ standard.

       -Wsized-deallocation (C++ and Objective-C++ only)
           Warn about a definition of an unsized deallocation function

                   void operator delete (void *) noexcept;
                   void operator delete[] (void *) noexcept;

           without a definition of the corresponding sized deallocation function

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           or vice versa.  Enabled by -Wextra along with -fsized-deallocation.

       -Wsuggest-final-types
           Warn  about  types  with virtual methods where code quality would be improved if the type
           were declared with the C++11 "final" specifier, or, if possible, declared in an anonymous
           namespace. This allows GCC to more aggressively devirtualize the polymorphic calls.  This
           warning  is  more  effective with link-time optimization, where the information about the
           class hierarchy graph is more complete.

       -Wsuggest-final-methods
           Warn about virtual methods where code quality  would  be  improved  if  the  method  were
           declared  with the C++11 "final" specifier, or, if possible, its type were declared in an
           anonymous namespace or with the "final" specifier.  This warning is more  effective  with
           link-time  optimization,  where  the  information about the class hierarchy graph is more
           complete. It is recommended to first consider suggestions  of  -Wsuggest-final-types  and
           then rebuild with new annotations.

       -Wsuggest-override
           Warn about overriding virtual functions that are not marked with the "override" keyword.

       -Wuseless-cast (C++ and Objective-C++ only)
           Warn when an expression is casted to its own type.

       -Wno-conversion-null (C++ and Objective-C++ only)
           Do  not  warn  for conversions between "NULL" and non-pointer types. -Wconversion-null is
           enabled by default.

   Options Controlling Objective-C and Objective-C++ Dialects
       (NOTE: This manual does not describe the Objective-C and Objective-C++ languages themselves.

       This section describes the command-line options that are only meaningful for Objective-C  and
       Objective-C++  programs.   You  can  also  use  most of the language-independent GNU compiler
       options.  For example, you might compile a file some_class.m like this:

               gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant  only  for  Objective-C  and  Objective-C++
       programs; you can use the other options with any language supported by GCC.

       Note  that  since Objective-C is an extension of the C language, Objective-C compilations may
       also use options specific to the C front-end (e.g., -Wtraditional).  Similarly, Objective-C++
       compilations may use C++-specific options (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and Objective-C++ programs:

       -fconstant-string-class=class-name
           Use class-name as the name of the class to instantiate for each literal string  specified
           with  the  syntax  "@"..."".   The  default  class  name is "NXConstantString" if the GNU
           runtime is being used, and "NSConstantString" if the NeXT  runtime  is  being  used  (see
           below).   On  Darwin (macOS, MacOS X) platforms, the -fconstant-cfstrings option, if also
           present, overrides the -fconstant-string-class setting and cause "@"..."" literals to  be
           laid  out as constant CoreFoundation strings.  Note that -fconstant-cfstrings is an alias
           for the target-specific -mconstant-cfstrings equivalent.

       -fgnu-runtime
           Generate object code compatible with the standard GNU Objective-C runtime.  This  is  the
           default for most types of systems.

       -fnext-runtime
           Generate  output  compatible  with  the NeXT runtime.  This is the default for NeXT-based
           systems, including Darwin and Mac OS X.  The macro "__NEXT_RUNTIME__"  is  predefined  if
           (and only if) this option is used.

       -fno-nil-receivers
           Assume  that  all  Objective-C  message  dispatches  ("[receiver  message:arg]")  in this
           translation unit ensure that the receiver is not "nil".  This allows for  more  efficient
           entry  points  in  the  runtime to be used.  This option is only available in conjunction
           with the NeXT runtime and ABI version 0 or 1.

       -fobjc-abi-version=n
           Use version n of the Objective-C ABI for the selected runtime.  This option is  currently
           supported only for the NeXT runtime.  In that case, Version 0 is the traditional (32-bit)
           ABI without support for properties and other Objective-C 2.0 additions.  Version 1 is the
           traditional (32-bit) ABI with support for properties and other Objective-C 2.0 additions.
           Version  2 is the modern (64-bit) ABI.  If nothing is specified, the default is Version 0
           on 32-bit target machines, and Version 2 on 64-bit target machines.

       -fobjc-call-cxx-cdtors
           For each Objective-C class, check if any of its instance variables is a C++ object with a
           non-trivial default constructor.  If so, synthesize a  special  "-  (id)  .cxx_construct"
           instance  method  which  runs  non-trivial  default  constructors  on  any  such instance
           variables, in order, and then return "self".  Similarly, check if any  instance  variable
           is  a C++ object with a non-trivial destructor, and if so, synthesize a special "- (void)
           .cxx_destruct" method which runs all such default destructors, in reverse order.

           The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods  thusly  generated  only
           operate  on  instance  variables declared in the current Objective-C class, and not those
           inherited from superclasses.  It is the responsibility  of  the  Objective-C  runtime  to
           invoke   all   such   methods   in  an  object's  inheritance  hierarchy.   The  "-  (id)
           .cxx_construct" methods are invoked  by  the  runtime  immediately  after  a  new  object
           instance  is  allocated;  the  "-  (void)  .cxx_destruct" methods are invoked immediately
           before the runtime deallocates an object instance.

           As of this writing, only the NeXT runtime on Mac OS X 10.4  and  later  has  support  for
           invoking the "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods.

       -fobjc-direct-dispatch
           Allow  fast jumps to the message dispatcher.  On Darwin this is accomplished via the comm
           page.

       -fobjc-exceptions
           Enable syntactic support for structured exception handling  in  Objective-C,  similar  to
           what  is  offered  by C++.  This option is required to use the Objective-C keywords @try,
           @throw, @catch, @finally and @synchronized.  This option is available with both  the  GNU
           runtime  and  the NeXT runtime (but not available in conjunction with the NeXT runtime on
           Mac OS X 10.2 and earlier).

       -fobjc-gc
           Enable garbage collection (GC) in Objective-C and Objective-C++ programs.  This option is
           only available with the NeXT runtime; the GNU runtime has a different garbage  collection
           implementation that does not require special compiler flags.

       -fobjc-nilcheck
           For  the  NeXT  runtime  with  version  2  of the ABI, check for a nil receiver in method
           invocations before doing the actual method call.  This is the default and can be disabled
           using -fno-objc-nilcheck.  Class methods and super calls are never  checked  for  nil  in
           this  way  no matter what this flag is set to.  Currently this flag does nothing when the
           GNU runtime, or an older version of the NeXT runtime ABI, is used.

       -fobjc-std=objc1
           Conform to the language syntax of Objective-C 1.0, the language recognized  by  GCC  4.0.
           This  only  affects  the  Objective-C additions to the C/C++ language; it does not affect
           conformance to C/C++ standards, which is controlled by the separate C/C++ dialect  option
           flags.   When  this  option  is  used with the Objective-C or Objective-C++ compiler, any
           Objective-C syntax that is not recognized by GCC 4.0 is rejected.  This is useful if  you
           need to make sure that your Objective-C code can be compiled with older versions of GCC.

       -freplace-objc-classes
           Emit  a  special  marker instructing ld(1) not to statically link in the resulting object
           file, and allow dyld(1) to load it in at run time instead.  This is used  in  conjunction
           with  the  Fix-and-Continue  debugging  mode,  where  the  object file in question may be
           recompiled and dynamically reloaded in the course of program execution, without the  need
           to  restart  the  program  itself.   Currently,  Fix-and-Continue  functionality  is only
           available in conjunction with the NeXT runtime on Mac OS X 10.3 and later.

       -fzero-link
           When  compiling  for  the  NeXT  runtime,  the  compiler  ordinarily  replaces  calls  to
           objc_getClass("...")  (when  the  name of the class is known at compile time) with static
           class references that get initialized at load time, which improves run-time  performance.
           Specifying   the   -fzero-link   flag  suppresses  this  behavior  and  causes  calls  to
           objc_getClass("...")  to be retained.  This is useful in Zero-Link debugging mode,  since
           it  allows  for individual class implementations to be modified during program execution.
           The GNU runtime currently always retains calls to  objc_get_class("...")   regardless  of
           command-line options.

       -fno-local-ivars
           By  default  instance  variables  in  Objective-C  can  be accessed as if they were local
           variables from within the methods of the class they're declared in.   This  can  lead  to
           shadowing between instance variables and other variables declared either locally inside a
           class  method  or  globally  with  the  same  name.  Specifying the -fno-local-ivars flag
           disables this behavior thus avoiding variable shadowing issues.

       -fivar-visibility=[public|protected|private|package]
           Set the default instance variable visibility to the specified  option  so  that  instance
           variables  declared  outside  the  scope of any access modifier directives default to the
           specified visibility.

       -gen-decls
           Dump interface declarations for all classes seen in the  source  file  to  a  file  named
           sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
           Warn whenever an Objective-C assignment is being intercepted by the garbage collector.

       -Wno-property-assign-default (Objective-C and Objective-C++ only)
           Do not warn if a property for an Objective-C object has no assign semantics specified.

       -Wno-protocol (Objective-C and Objective-C++ only)
           If  a  class is declared to implement a protocol, a warning is issued for every method in
           the protocol that is not implemented by the class.  The default behavior is  to  issue  a
           warning  for  every  method  not  explicitly  implemented  in the class, even if a method
           implementation is inherited from the superclass.  If you use  the  -Wno-protocol  option,
           then  methods  inherited  from  the  superclass  are considered to be implemented, and no
           warning is issued for them.

       -Wobjc-root-class (Objective-C and Objective-C++ only)
           Warn if a class interface lacks a superclass. Most classes will inherit  from  "NSObject"
           (or  "Object")  for  example.   When  declaring  classes intended to be root classes, the
           warning    can     be     suppressed     by     marking     their     interfaces     with
           "__attribute__((objc_root_class))".

       -Wselector (Objective-C and Objective-C++ only)
           Warn  if  multiple  methods  of  different  types  for the same selector are found during
           compilation.  The check is performed on the  list  of  methods  in  the  final  stage  of
           compilation.   Additionally,  a  check  is  performed  for  each  selector appearing in a
           @selector(...)  expression, and a corresponding method for that selector has  been  found
           during  compilation.   Because  these  checks  scan  the  method table only at the end of
           compilation, these warnings are not produced if the final stage  of  compilation  is  not
           reached,  for  example  because  an  error  is  found  during compilation, or because the
           -fsyntax-only option is being used.

       -Wstrict-selector-match (Objective-C and Objective-C++ only)
           Warn if multiple methods with differing argument and/or return  types  are  found  for  a
           given  selector  when  attempting  to send a message using this selector to a receiver of
           type "id" or "Class".  When this flag  is  off  (which  is  the  default  behavior),  the
           compiler  omits  such  warnings if any differences found are confined to types that share
           the same size and alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
           Warn if a @selector(...) expression referring to an  undeclared  selector  is  found.   A
           selector  is  considered  undeclared if no method with that name has been declared before
           the  @selector(...)  expression,  either  explicitly  in  an  @interface   or   @protocol
           declaration,  or  implicitly  in an @implementation section.  This option always performs
           its checks as soon as  a  @selector(...)  expression  is  found,  while  -Wselector  only
           performs  its  checks  in  the final stage of compilation.  This also enforces the coding
           style convention that methods and selectors must be declared before being used.

       -print-objc-runtime-info
           Generate C header describing the largest structure that is passed by value, if any.

   Options to Control Diagnostic Messages Formatting
       Traditionally, diagnostic messages have been formatted irrespective of  the  output  device's
       aspect  (e.g.  its  width,  ...).   You  can  use  the options described below to control the
       formatting algorithm for diagnostic messages, e.g. how many characters per  line,  how  often
       source  location  information should be reported.  Note that some language front ends may not
       honor these options.

       -fmessage-length=n
           Try to format error messages so that they fit on lines of about n characters.   If  n  is
           zero,  then  no line-wrapping is done; each error message appears on a single line.  This
           is the default for all front ends.

           Note - this option also affects the display of  the  #error  and  #warning  pre-processor
           directives,  and  the  deprecated  function/type/variable attribute.  It does not however
           affect the pragma GCC warning and pragma GCC error pragmas.

       -fdiagnostics-plain-output
           This option requests that diagnostic output look as  plain  as  possible,  which  may  be
           useful  when running dejagnu or other utilities that need to parse diagnostics output and
           prefer that it remain more stable over  time.   -fdiagnostics-plain-output  is  currently
           equivalent      to      the      following      options:      -fno-diagnostics-show-caret
           -fno-diagnostics-show-line-numbers   -fdiagnostics-color=never   -fdiagnostics-urls=never
           -fdiagnostics-path-format=separate-events  In  the  future,  if  GCC  changes the default
           appearance of its diagnostics, the corresponding option to disable the new behavior  will
           be added to this list.

       -fdiagnostics-show-location=once
           Only  meaningful  in  line-wrapping  mode.  Instructs the diagnostic messages reporter to
           emit source location information once; that is, in case the message is too long to fit on
           a single physical line and has to be wrapped, the source location won't  be  emitted  (as
           prefix)  again,  over  and  over,  in subsequent continuation lines.  This is the default
           behavior.

       -fdiagnostics-show-location=every-line
           Only meaningful in line-wrapping mode.  Instructs the  diagnostic  messages  reporter  to
           emit the same source location information (as prefix) for physical lines that result from
           the process of breaking a message which is too long to fit on a single line.

       -fdiagnostics-color[=WHEN]
       -fno-diagnostics-color
           Use  color  in  diagnostics.  WHEN is never, always, or auto.  The default depends on how
           the compiler has been configured, it can be any of the above WHEN options or  also  never
           if  GCC_COLORS environment variable isn't present in the environment, and auto otherwise.
           auto makes GCC use color only when the  standard  error  is  a  terminal,  and  when  not
           executing  in  an  emacs shell.  The forms -fdiagnostics-color and -fno-diagnostics-color
           are aliases for -fdiagnostics-color=always and -fdiagnostics-color=never, respectively.

           The colors are defined by the environment variable GCC_COLORS.  Its  value  is  a  colon-
           separated  list  of  capabilities  and  Select  Graphic  Rendition  (SGR) substrings. SGR
           commands are interpreted by the terminal or terminal emulator.  (See the section  in  the
           documentation  of your text terminal for permitted values and their meanings as character
           attributes.)  These substring values are integers in decimal representation  and  can  be
           concatenated  with  semicolons.   Common  values to concatenate include 1 for bold, 4 for
           underline, 5 for blink, 7 for inverse, 39 for default foreground  color,  30  to  37  for
           foreground  colors,  90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for
           88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47
           for background colors, 100 to 107 for 16-color mode  background  colors,  and  48;5;0  to
           48;5;255 for 88-color and 256-color modes background colors.

           The default GCC_COLORS is

                   error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\
                   quote=01:path=01;36:fixit-insert=32:fixit-delete=31:\
                   diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\
                   type-diff=01;32

           where  01;31  is  bold red, 01;35 is bold magenta, 01;36 is bold cyan, 32 is green, 34 is
           blue, 01 is bold, and 31 is red.  Setting GCC_COLORS to the empty string disables colors.
           Supported capabilities are as follows.

           "error="
               SGR substring for error: markers.

           "warning="
               SGR substring for warning: markers.

           "note="
               SGR substring for note: markers.

           "path="
               SGR  substring  for  colorizing  paths  of  control-flow  events   as   printed   via
               -fdiagnostics-path-format=,  such  as  the identifiers of individual events and lines
               indicating interprocedural calls and returns.

           "range1="
               SGR substring for first additional range.

           "range2="
               SGR substring for second additional range.

           "locus="
               SGR substring for location information, file:line or file:line:column etc.

           "quote="
               SGR substring for information printed within quotes.

           "fixit-insert="
               SGR substring for fix-it hints suggesting text to be inserted or replaced.

           "fixit-delete="
               SGR substring for fix-it hints suggesting text to be deleted.

           "diff-filename="
               SGR substring for filename headers within generated patches.

           "diff-hunk="
               SGR substring for the starts of hunks within generated patches.

           "diff-delete="
               SGR substring for deleted lines within generated patches.

           "diff-insert="
               SGR substring for inserted lines within generated patches.

           "type-diff="
               SGR substring for highlighting mismatching types within template arguments in the C++
               frontend.

       -fdiagnostics-urls[=WHEN]
           Use   escape   sequences   to   embed   URLs   in   diagnostics.    For   example,   when
           -fdiagnostics-show-option  emits  text  showing  the  command-line  option  controlling a
           diagnostic, embed a URL for documentation of that option.

           WHEN is never, always, or auto.  auto makes GCC use URL escape sequences  only  when  the
           standard  error  is a terminal, and when not executing in an emacs shell or any graphical
           terminal which is known to be incompatible with this feature, see below.

           The default depends on how the compiler has been configured.  It can be any of the  above
           WHEN options.

           GCC  can  also  be configured (via the --with-diagnostics-urls=auto-if-env configure-time
           option) so that  the  default  is  affected  by  environment  variables.   Under  such  a
           configuration,  GCC  defaults  to  using auto if either GCC_URLS or TERM_URLS environment
           variables are present and non-empty in the environment  of  the  compiler,  or  never  if
           neither are.

           However,   even  with  -fdiagnostics-urls=always  the  behavior  is  dependent  on  those
           environment variables: If GCC_URLS  is  set  to  empty  or  no,  do  not  embed  URLs  in
           diagnostics.   If  set  to st, URLs use ST escape sequences.  If set to bel, the default,
           URLs use BEL escape sequences.  Any  other  non-empty  value  enables  the  feature.   If
           GCC_URLS  is  not set, use TERM_URLS as a fallback.  Note: ST is an ANSI escape sequence,
           string terminator ESC \, BEL is an ASCII character, CTRL-G that  usually  sounds  like  a
           beep.

           At this time GCC tries to detect also a few terminals that are known to not implement the
           URL  feature,  and have bugs or at least had bugs in some versions that are still in use,
           where the URL escapes are likely to misbehave, i.e. print garbage on  the  screen.   That
           list  is currently xfce4-terminal, certain known to be buggy gnome-terminal versions, the
           linux console, and mingw.  This check can be skipped with the -fdiagnostics-urls=always.

       -fno-diagnostics-show-option
           By default, each diagnostic emitted includes text indicating the command-line option that
           directly controls  the  diagnostic  (if  such  an  option  is  known  to  the  diagnostic
           machinery).  Specifying the -fno-diagnostics-show-option flag suppresses that behavior.

       -fno-diagnostics-show-caret
           By  default,  each  diagnostic  emitted  includes  the original source line and a caret ^
           indicating the column.  This option suppresses this  information.   The  source  line  is
           truncated to n characters, if the -fmessage-length=n option is given.  When the output is
           done  to the terminal, the width is limited to the width given by the COLUMNS environment
           variable or, if not set, to the terminal width.

       -fno-diagnostics-show-labels
           By default, when printing source code  (via  -fdiagnostics-show-caret),  diagnostics  can
           label ranges of source code with pertinent information, such as the types of expressions:

                       printf ("foo %s bar", long_i + long_j);
                                    ~^       ~~~~~~~~~~~~~~~
                                     |              |
                                     char *         long int

           This  option  suppresses the printing of these labels (in the example above, the vertical
           bars and the "char *" and "long int" text).

       -fno-diagnostics-show-cwe
           Diagnostic       messages       can       optionally       have       an       associated
           @url{https://cwe.mitre.org/index.html,  CWE}  identifier.   GCC itself only provides such
           metadata  for  some  of  the  -fanalyzer  diagnostics.   GCC  plugins  may  also  provide
           diagnostics  with  such metadata.  By default, if this information is present, it will be
           printed with the diagnostic.  This option suppresses the printing of this metadata.

       -fno-diagnostics-show-line-numbers
           By default, when printing source code (via -fdiagnostics-show-caret), a  left  margin  is
           printed, showing line numbers.  This option suppresses this left margin.

       -fdiagnostics-minimum-margin-width=width
           This   option   controls   the   minimum   width   of   the   left   margin   printed  by
           -fdiagnostics-show-line-numbers.  It defaults to 6.

       -fdiagnostics-parseable-fixits
           Emit fix-it hints in a machine-parseable format, suitable for consumption by  IDEs.   For
           each  fix-it,  a  line  will  be printed after the relevant diagnostic, starting with the
           string "fix-it:".  For example:

                   fix-it:"test.c":{45:3-45:21}:"gtk_widget_show_all"

           The location is expressed as a half-open range, expressed as a count of  bytes,  starting
           at byte 1 for the initial column.  In the above example, bytes 3 through 20 of line 45 of
           "test.c" are to be replaced with the given string:

                   00000000011111111112222222222
                   12345678901234567890123456789
                     gtk_widget_showall (dlg);
                     ^^^^^^^^^^^^^^^^^^
                     gtk_widget_show_all

           The  filename  and  replacement  string escape backslash as "\\", tab as "\t", newline as
           "\n", double quotes as "\"", non-printable characters as  octal  (e.g.  vertical  tab  as
           "\013").

           An  empty  replacement  string indicates that the given range is to be removed.  An empty
           range (e.g. "45:3-45:3") indicates that the  string  is  to  be  inserted  at  the  given
           position.

       -fdiagnostics-generate-patch
           Print  fix-it  hints to stderr in unified diff format, after any diagnostics are printed.
           For example:

                   --- test.c
                   +++ test.c
                   @ -42,5 +42,5 @

                    void show_cb(GtkDialog *dlg)
                    {
                   -  gtk_widget_showall(dlg);
                   +  gtk_widget_show_all(dlg);
                    }

           The diff may or may not be colorized, following the same rules as  for  diagnostics  (see
           -fdiagnostics-color).

       -fdiagnostics-show-template-tree
           In  the  C++ frontend, when printing diagnostics showing mismatching template types, such
           as:

                     could not convert 'std::map<int, std::vector<double> >()'
                       from 'map<[...],vector<double>>' to 'map<[...],vector<float>>

           the -fdiagnostics-show-template-tree flag enables printing a tree-like structure  showing
           the common and differing parts of the types, such as:

                     map<
                       [...],
                       vector<
                         [double != float]>>

           The parts that differ are highlighted with color ("double" and "float" in this case).

       -fno-elide-type
           By  default  when the C++ frontend prints diagnostics showing mismatching template types,
           common parts of the types are printed as "[...]" to  simplify  the  error  message.   For
           example:

                     could not convert 'std::map<int, std::vector<double> >()'
                       from 'map<[...],vector<double>>' to 'map<[...],vector<float>>

           Specifying the -fno-elide-type flag suppresses that behavior.  This flag also affects the
           output of the -fdiagnostics-show-template-tree flag.

       -fdiagnostics-path-format=KIND
           Specify  how  to print paths of control-flow events for diagnostics that have such a path
           associated with them.

           KIND is none, separate-events, or inline-events, the default.

           none means to not print diagnostic paths.

           separate-events means to print a separate "note" diagnostic for  each  event  within  the
           diagnostic.  For example:

                   test.c:29:5: error: passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter
                   test.c:25:10: note: (1) when 'PyList_New' fails, returning NULL
                   test.c:27:3: note: (2) when 'i < count'
                   test.c:29:5: note: (3) when calling 'PyList_Append', passing NULL from (1) as argument 1

           inline-events  means  to  print  the  events  "inline" within the source code.  This view
           attempts to consolidate the events into runs of sufficiently-close events, printing  them
           as labelled ranges within the source.

           For example, the same events as above might be printed as:

                     'test': events 1-3
                       |
                       |   25 |   list = PyList_New(0);
                       |      |          ^~~~~~~~~~~~~
                       |      |          |
                       |      |          (1) when 'PyList_New' fails, returning NULL
                       |   26 |
                       |   27 |   for (i = 0; i < count; i++) {
                       |      |   ~~~
                       |      |   |
                       |      |   (2) when 'i < count'
                       |   28 |     item = PyLong_FromLong(random());
                       |   29 |     PyList_Append(list, item);
                       |      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
                       |      |     |
                       |      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
                       |

           Interprocedural  control  flow  is shown by grouping the events by stack frame, and using
           indentation to show how stack frames are nested, pushed, and popped.

           For example:

                     'test': events 1-2
                       |
                       |  133 | {
                       |      | ^
                       |      | |
                       |      | (1) entering 'test'
                       |  134 |   boxed_int *obj = make_boxed_int (i);
                       |      |                    ~~~~~~~~~~~~~~~~~~
                       |      |                    |
                       |      |                    (2) calling 'make_boxed_int'
                       |
                       +--> 'make_boxed_int': events 3-4
                              |
                              |  120 | {
                              |      | ^
                              |      | |
                              |      | (3) entering 'make_boxed_int'
                              |  121 |   boxed_int *result = (boxed_int *)wrapped_malloc (sizeof (boxed_int));
                              |      |                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                              |      |                                    |
                              |      |                                    (4) calling 'wrapped_malloc'
                              |
                              +--> 'wrapped_malloc': events 5-6
                                     |
                                     |    7 | {
                                     |      | ^
                                     |      | |
                                     |      | (5) entering 'wrapped_malloc'
                                     |    8 |   return malloc (size);
                                     |      |          ~~~~~~~~~~~~~
                                     |      |          |
                                     |      |          (6) calling 'malloc'
                                     |
                       <-------------+
                       |
                    'test': event 7
                       |
                       |  138 |   free_boxed_int (obj);
                       |      |   ^~~~~~~~~~~~~~~~~~~~
                       |      |   |
                       |      |   (7) calling 'free_boxed_int'
                       |
                   (etc)

       -fdiagnostics-show-path-depths
           This option provides additional information when printing control-flow  paths  associated
           with a diagnostic.

           If this is option is provided then the stack depth will be printed for each run of events
           within -fdiagnostics-path-format=separate-events.

           This  is  intended  for  use  by  GCC  developers  and  plugin  developers when debugging
           diagnostics that report interprocedural control flow.

       -fno-show-column
           Do not print column numbers in diagnostics.  This may be  necessary  if  diagnostics  are
           being scanned by a program that does not understand the column numbers, such as dejagnu.

       -fdiagnostics-column-unit=UNIT
           Select  the  units  for  the column number.  This affects traditional diagnostics (in the
           absence of -fno-show-column), as well as JSON format diagnostics if requested.

           The default UNIT, display, considers the number  of  display  columns  occupied  by  each
           character.  This may be larger than the number of bytes required to encode the character,
           in the case of tab characters, or it may be smaller, in the case of multibyte characters.
           For  example, the character "GREEK SMALL LETTER PI (U+03C0)" occupies one display column,
           and its  UTF-8  encoding  requires  two  bytes;  the  character  "SLIGHTLY  SMILING  FACE
           (U+1F642)" occupies two display columns, and its UTF-8 encoding requires four bytes.

           Setting UNIT to byte changes the column number to the raw byte count in all cases, as was
           traditionally output by GCC prior to version 11.1.0.

       -fdiagnostics-column-origin=ORIGIN
           Select  the  origin  for  column  numbers,  i.e.  the column number assigned to the first
           column.  The default value of 1 corresponds to traditional GCC behavior and  to  the  GNU
           style  guide.   Some  utilities  may perform better with an origin of 0; any non-negative
           value may be specified.

       -fdiagnostics-format=FORMAT
           Select a different format for printing diagnostics.  FORMAT is text or json.  The default
           is text.

           The json format consists of a top-level JSON array containing JSON  objects  representing
           the diagnostics.

           The  JSON  is  emitted  as  one  line,  without  formatting; the examples below have been
           formatted for clarity.

           Diagnostics can have child diagnostics.  For example, this error and note:

                   misleading-indentation.c:15:3: warning: this 'if' clause does not
                     guard... [-Wmisleading-indentation]
                      15 |   if (flag)
                         |   ^~
                   misleading-indentation.c:17:5: note: ...this statement, but the latter
                     is misleadingly indented as if it were guarded by the 'if'
                      17 |     y = 2;
                         |     ^

           might be printed in JSON form (after formatting) like this:

                   [
                       {
                           "kind": "warning",
                           "locations": [
                               {
                                   "caret": {
                                       "display-column": 3,
                                       "byte-column": 3,
                                       "column": 3,
                                       "file": "misleading-indentation.c",
                                       "line": 15
                                   },
                                   "finish": {
                                       "display-column": 4,
                                       "byte-column": 4,
                                       "column": 4,
                                       "file": "misleading-indentation.c",
                                       "line": 15
                                   }
                               }
                           ],
                           "message": "this \u2018if\u2019 clause does not guard...",
                           "option": "-Wmisleading-indentation",
                           "option_url": "https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmisleading-indentation",
                           "children": [
                               {
                                   "kind": "note",
                                   "locations": [
                                       {
                                           "caret": {
                                               "display-column": 5,
                                               "byte-column": 5,
                                               "column": 5,
                                               "file": "misleading-indentation.c",
                                               "line": 17
                                           }
                                       }
                                   ],
                                   "message": "...this statement, but the latter is ..."
                               }
                           ]
                           "column-origin": 1,
                       },
                       ...
                   ]

           where the "note" is a child of the "warning".

           A diagnostic has a "kind".   If  this  is  "warning",  then  there  is  an  "option"  key
           describing the command-line option controlling the warning.

           A  diagnostic  can contain zero or more locations.  Each location has an optional "label"
           string and up to three positions within it: a "caret" position and optional  "start"  and
           "finish" positions.  A position is described by a "file" name, a "line" number, and three
           numbers indicating a column position:

           *   "display-column"   counts   display   columns,  accounting  for  tabs  and  multibyte
               characters.

           *   "byte-column" counts raw bytes.

           *   "column"  is  equal  to   one   of   the   previous   two,   as   dictated   by   the
               -fdiagnostics-column-unit option.

           All  three  columns  are relative to the origin specified by -fdiagnostics-column-origin,
           which is typically equal to 1 but may be set, for instance, to 0 for  compatibility  with
           other  utilities  that  number columns from 0.  The column origin is recorded in the JSON
           output in the "column-origin" tag.  In the remaining examples  below,  the  extra  column
           number outputs have been omitted for brevity.

           For example, this error:

                   bad-binary-ops.c:64:23: error: invalid operands to binary + (have 'S' {aka
                      'struct s'} and 'T' {aka 'struct t'})
                      64 |   return callee_4a () + callee_4b ();
                         |          ~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
                         |          |              |
                         |          |              T {aka struct t}
                         |          S {aka struct s}

           has  three locations.  Its primary location is at the "+" token at column 23.  It has two
           secondary locations, describing the left and right-hand sides of  the  expression,  which
           have labels.  It might be printed in JSON form as:

                       {
                           "children": [],
                           "kind": "error",
                           "locations": [
                               {
                                   "caret": {
                                       "column": 23, "file": "bad-binary-ops.c", "line": 64
                                   }
                               },
                               {
                                   "caret": {
                                       "column": 10, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "finish": {
                                       "column": 21, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "label": "S {aka struct s}"
                               },
                               {
                                   "caret": {
                                       "column": 25, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "finish": {
                                       "column": 36, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "label": "T {aka struct t}"
                               }
                           ],
                           "message": "invalid operands to binary + ..."
                       }

           If  a  diagnostic contains fix-it hints, it has a "fixits" array, consisting of half-open
           intervals, similar to the output of -fdiagnostics-parseable-fixits.   For  example,  this
           diagnostic with a replacement fix-it hint:

                   demo.c:8:15: error: 'struct s' has no member named 'colour'; did you
                     mean 'color'?
                       8 |   return ptr->colour;
                         |               ^~~~~~
                         |               color

           might be printed in JSON form as:

                       {
                           "children": [],
                           "fixits": [
                               {
                                   "next": {
                                       "column": 21,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "start": {
                                       "column": 15,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "string": "color"
                               }
                           ],
                           "kind": "error",
                           "locations": [
                               {
                                   "caret": {
                                       "column": 15,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "finish": {
                                       "column": 20,
                                       "file": "demo.c",
                                       "line": 8
                                   }
                               }
                           ],
                           "message": "\u2018struct s\u2019 has no member named ..."
                       }

           where  the  fix-it  hint suggests replacing the text from "start" up to but not including
           "next" with "string"'s value.  Deletions are expressed via an empty value  for  "string",
           insertions by having "start" equal "next".

           If  the  diagnostic has a path of control-flow events associated with it, it has a "path"
           array of objects representing the events.  Each event object has a "description"  string,
           a "location" object, along with a "function" string and a "depth" number for representing
           interprocedural paths.  The "function" represents the current function at that event, and
           the  "depth"  represents  the stack depth relative to some baseline: the higher, the more
           frames are within the stack.

           For example, the intraprocedural example shown for -fdiagnostics-path-format= might  have
           this JSON for its path:

                       "path": [
                           {
                               "depth": 0,
                               "description": "when 'PyList_New' fails, returning NULL",
                               "function": "test",
                               "location": {
                                   "column": 10,
                                   "file": "test.c",
                                   "line": 25
                               }
                           },
                           {
                               "depth": 0,
                               "description": "when 'i < count'",
                               "function": "test",
                               "location": {
                                   "column": 3,
                                   "file": "test.c",
                                   "line": 27
                               }
                           },
                           {
                               "depth": 0,
                               "description": "when calling 'PyList_Append', passing NULL from (1) as argument 1",
                               "function": "test",
                               "location": {
                                   "column": 5,
                                   "file": "test.c",
                                   "line": 29
                               }
                           }
                       ]

   Options to Request or Suppress Warnings
       Warnings  are diagnostic messages that report constructions that are not inherently erroneous
       but that are risky or suggest there may have been an error.

       The following language-independent options do not enable specific warnings  but  control  the
       kinds of diagnostics produced by GCC.

       -fsyntax-only
           Check the code for syntax errors, but don't do anything beyond that.

       -fmax-errors=n
           Limits  the  maximum  number  of error messages to n, at which point GCC bails out rather
           than attempting to continue processing the source code.  If n is 0 (the  default),  there
           is  no  limit  on  the  number  of  error  messages  produced.  If -Wfatal-errors is also
           specified, then -Wfatal-errors takes precedence over this option.

       -w  Inhibit all warning messages.

       -Werror
           Make all warnings into errors.

       -Werror=
           Make the specified warning into an error.  The specifier for a warning is  appended;  for
           example  -Werror=switch  turns  the  warnings  controlled  by -Wswitch into errors.  This
           switch takes a negative form, to be used to negate -Werror  for  specific  warnings;  for
           example  -Wno-error=switch makes -Wswitch warnings not be errors, even when -Werror is in
           effect.

           The warning message for each controllable warning includes the option that  controls  the
           warning.   That option can then be used with -Werror= and -Wno-error= as described above.
           (Printing  of  the  option  in  the  warning  message   can   be   disabled   using   the
           -fno-diagnostics-show-option flag.)

           Note  that  specifying  -Werror=foo automatically implies -Wfoo.  However, -Wno-error=foo
           does not imply anything.

       -Wfatal-errors
           This option causes the compiler to abort compilation on the first error  occurred  rather
           than trying to keep going and printing further error messages.

       You can request many specific warnings with options beginning with -W, for example -Wimplicit
       to  request  warnings  on implicit declarations.  Each of these specific warning options also
       has a negative form beginning -Wno- to turn off warnings; for example,  -Wno-implicit.   This
       manual  lists only one of the two forms, whichever is not the default.  For further language-
       specific options also refer to C++ Dialect Options and Objective-C and Objective-C++  Dialect
       Options.  Additional warnings can be produced by enabling the static analyzer;

       Some  options,  such as -Wall and -Wextra, turn on other options, such as -Wunused, which may
       turn on further options, such as -Wunused-value. The combined effect of positive and negative
       forms is that more specific options have priority over less specific ones,  independently  of
       their  position  in the command-line. For options of the same specificity, the last one takes
       effect. Options enabled or disabled via pragmas take effect as if they appeared at the end of
       the command-line.

       When an unrecognized warning option is  requested  (e.g.,  -Wunknown-warning),  GCC  emits  a
       diagnostic  stating  that  the option is not recognized.  However, if the -Wno- form is used,
       the behavior is slightly different: no diagnostic is produced for -Wno-unknown-warning unless
       other diagnostics are being produced.  This allows the use of  new  -Wno-  options  with  old
       compilers,  but  if  something  goes wrong, the compiler warns that an unrecognized option is
       present.

       The effectiveness of some warnings depends on optimizations also being enabled.  For  example
       -Wsuggest-final-types is more effective with link-time optimization and -Wmaybe-uninitialized
       does not warn at all unless optimization is enabled.

       -Wpedantic
       -pedantic
           Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use
           forbidden  extensions, and some other programs that do not follow ISO C and ISO C++.  For
           ISO C, follows the version of the ISO C standard specified by any -std option used.

           Valid ISO C and ISO C++ programs should compile properly  with  or  without  this  option
           (though  a rare few require -ansi or a -std option specifying the required version of ISO
           C).  However, without this option, certain GNU  extensions  and  traditional  C  and  C++
           features are supported as well.  With this option, they are rejected.

           -Wpedantic  does not cause warning messages for use of the alternate keywords whose names
           begin and end with __.  This alternate format can also be used to  disable  warnings  for
           non-ISO  __intN  types,  i.e.  __intN__.   Pedantic  warnings  are  also  disabled in the
           expression that follows "__extension__".  However, only system header  files  should  use
           these escape routes; application programs should avoid them.

           Some  users  try  to use -Wpedantic to check programs for strict ISO C conformance.  They
           soon find that it does not do quite what they want: it finds some non-ISO practices,  but
           not  all---only  those  for  which ISO C requires a diagnostic, and some others for which
           diagnostics have been added.

           A feature to report any failure to conform to ISO C might be useful  in  some  instances,
           but  would  require  considerable  additional  work  and  would  be  quite different from
           -Wpedantic.  We don't have plans to support such a feature in the near future.

           Where the standard specified with -std represents a GNU extended dialect of  C,  such  as
           gnu90 or gnu99, there is a corresponding base standard, the version of ISO C on which the
           GNU  extended  dialect  is  based.   Warnings  from  -Wpedantic  are given where they are
           required by the base standard.  (It does not make sense for such  warnings  to  be  given
           only  for  features  not  in  the  specified  GNU  C dialect, since by definition the GNU
           dialects of C include all features the compiler supports with the given option, and there
           would be nothing to warn about.)

       -pedantic-errors
           Give an error whenever the base standard (see -Wpedantic) requires a diagnostic, in  some
           cases  where  there is undefined behavior at compile-time and in some other cases that do
           not prevent compilation of programs that are valid according to the standard. This is not
           equivalent to -Werror=pedantic, since there are errors enabled by  this  option  and  not
           enabled by the latter and vice versa.

       -Wall
           This  enables all the warnings about constructions that some users consider questionable,
           and that are easy to avoid (or modify to prevent the warning), even in  conjunction  with
           macros.   This  also  enables  some  language-specific  warnings described in C++ Dialect
           Options and Objective-C and Objective-C++ Dialect Options.

           -Wall turns on the following warning flags:

           -Waddress -Warray-bounds=1 (only with -O2) -Warray-parameter=2 (C and  Objective-C  only)
           -Wbool-compare  -Wbool-operation  -Wc++11-compat   -Wc++14-compat  -Wcatch-value (C++ and
           Objective-C++  only)  -Wchar-subscripts  -Wcomment  -Wduplicate-decl-specifier   (C   and
           Objective-C  only)  -Wenum-compare  (in  C/ObjC;  this  is on by default in C++) -Wformat
           -Wformat-overflow -Wformat-truncation -Wint-in-bool-context -Wimplicit (C and Objective-C
           only) -Wimplicit-int (C and  Objective-C  only)  -Wimplicit-function-declaration  (C  and
           Objective-C  only)  -Winit-self (only for C++) -Wlogical-not-parentheses -Wmain (only for
           C/ObjC    and    unless    -ffreestanding)    -Wmaybe-uninitialized     -Wmemset-elt-size
           -Wmemset-transposed-args  -Wmisleading-indentation  (only for C/C++) -Wmissing-attributes
           -Wmissing-braces (only for C/ObjC) -Wmultistatement-macros  -Wnarrowing  (only  for  C++)
           -Wnonnull -Wnonnull-compare -Wopenmp-simd -Wparentheses -Wpessimizing-move (only for C++)
           -Wpointer-sign  -Wrange-loop-construct  (only for C++) -Wreorder -Wrestrict -Wreturn-type
           -Wsequence-point -Wsign-compare (only  in  C++)  -Wsizeof-array-div  -Wsizeof-pointer-div
           -Wsizeof-pointer-memaccess       -Wstrict-aliasing      -Wstrict-overflow=1      -Wswitch
           -Wtautological-compare -Wtrigraphs  -Wuninitialized  -Wunknown-pragmas  -Wunused-function
           -Wunused-label  -Wunused-value -Wunused-variable -Wvla-parameter (C and Objective-C only)
           -Wvolatile-register-var -Wzero-length-bounds

           Note that some warning flags  are  not  implied  by  -Wall.   Some  of  them  warn  about
           constructions  that  users generally do not consider questionable, but which occasionally
           you might wish to check for; others warn about constructions that are necessary  or  hard
           to  avoid  in  some  cases, and there is no simple way to modify the code to suppress the
           warning. Some of  them  are  enabled  by  -Wextra  but  many  of  them  must  be  enabled
           individually.

       -Wextra
           This enables some extra warning flags that are not enabled by -Wall. (This option used to
           be  called  -W.   The  older  name  is  still  supported,  but  the  newer  name  is more
           descriptive.)

           -Wclobbered    -Wcast-function-type    -Wdeprecated-copy    (C++    only)    -Wempty-body
           -Wenum-conversion      (C     only)     -Wignored-qualifiers     -Wimplicit-fallthrough=3
           -Wmissing-field-initializers -Wmissing-parameter-type (C only) -Wold-style-declaration (C
           only) -Woverride-init -Wsign-compare (C only) -Wstring-compare -Wredundant-move (only for
           C++) -Wtype-limits -Wuninitialized -Wshift-negative-value (in C++11 to C++17 and  in  C99
           and  newer)  -Wunused-parameter  (only with -Wunused or -Wall) -Wunused-but-set-parameter
           (only with -Wunused or -Wall)

           The option -Wextra also prints warning messages for the following cases:

           *   A pointer is compared against integer zero with "<", "<=", ">", or ">=".

           *   (C++  only)  An  enumerator  and  a  non-enumerator  both  appear  in  a  conditional
               expression.

           *   (C++ only) Ambiguous virtual bases.

           *   (C++ only) Subscripting an array that has been declared "register".

           *   (C++ only) Taking the address of a variable that has been declared "register".

           *   (C++  only)  A  base  class  is  not initialized in the copy constructor of a derived
               class.

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
           Warn about code affected by ABI changes.  This includes code that may not  be  compatible
           with the vendor-neutral C++ ABI as well as the psABI for the particular target.

           Since  G++ now defaults to updating the ABI with each major release, normally -Wabi warns
           only about C++ ABI compatibility problems if there is a check added later  in  a  release
           series  for  an  ABI  issue discovered since the initial release.  -Wabi warns about more
           things if an older ABI version is selected (with -fabi-version=n).

           -Wabi can  also  be  used  with  an  explicit  version  number  to  warn  about  C++  ABI
           compatibility  with  a particular -fabi-version level, e.g. -Wabi=2 to warn about changes
           relative to -fabi-version=2.

           If an explicit version number is provided and -fabi-compat-version is not specified,  the
           version  number  from  this  option  is  used  for compatibility aliases.  If no explicit
           version number is provided with this option, but -fabi-compat-version is specified,  that
           version number is used for C++ ABI warnings.

           Although  an  effort  has been made to warn about all such cases, there are probably some
           cases that are not warned about, even though G++ is generating incompatible code.   There
           may  also  be  cases where warnings are emitted even though the code that is generated is
           compatible.

           You should rewrite your code to avoid these warnings if you are concerned about the  fact
           that  code  generated  by  G++  may not be binary compatible with code generated by other
           compilers.

           Known incompatibilities in -fabi-version=2 (which was the default from GCC  3.4  to  4.9)
           include:

           *   A  template  with  a  non-type  template  parameter  of  reference  type  was mangled
               incorrectly:

                       extern int N;
                       template <int &> struct S {};
                       void n (S<N>) {2}

               This was fixed in -fabi-version=3.

           *   SIMD vector types declared using "__attribute ((vector_size))" were mangled in a non-
               standard way that does not allow for  overloading  of  functions  taking  vectors  of
               different sizes.

               The mangling was changed in -fabi-version=4.

           *   "__attribute   ((const))"  and  "noreturn"  were  mangled  as  type  qualifiers,  and
               "decltype" of a plain declaration was folded away.

               These mangling issues were fixed in -fabi-version=5.

           *   Scoped enumerators passed as arguments to  a  variadic  function  are  promoted  like
               unscoped  enumerators,  causing  "va_arg" to complain.  On most targets this does not
               actually affect the parameter passing ABI, as there is no way  to  pass  an  argument
               smaller than "int".

               Also,  the  ABI  changed  the  mangling  of  template  argument  packs, "const_cast",
               "static_cast", prefix increment/decrement, and a  class  scope  function  used  as  a
               template argument.

               These issues were corrected in -fabi-version=6.

           *   Lambdas  in  default argument scope were mangled incorrectly, and the ABI changed the
               mangling of "nullptr_t".

               These issues were corrected in -fabi-version=7.

           *   When mangling a function type with function-cv-qualifiers, the un-qualified  function
               type was incorrectly treated as a substitution candidate.

               This was fixed in -fabi-version=8, the default for GCC 5.1.

           *   decltype(nullptr)  incorrectly  had an alignment of 1, leading to unaligned accesses.
               Note that this did not affect the ABI of a function with a "nullptr_t" parameter,  as
               parameters have a minimum alignment.

               This was fixed in -fabi-version=9, the default for GCC 5.2.

           *   Target-specific  attributes  that affect the identity of a type, such as ia32 calling
               conventions on a function type (stdcall, regparm, etc.), did not affect  the  mangled
               name,  leading  to  name  collisions  when  function  pointers  were used as template
               arguments.

               This was fixed in -fabi-version=10, the default for GCC 6.1.

           This option also enables warnings about psABI-related changes.  The known  psABI  changes
           at this point include:

           *   For  SysV/x86-64, unions with "long double" members are passed in memory as specified
               in psABI.  Prior to GCC 4.4, this was not the case.  For example:

                       union U {
                         long double ld;
                         int i;
                       };

               "union U" is now always passed in memory.

       -Wchar-subscripts
           Warn if an array subscript has type  "char".   This  is  a  common  cause  of  error,  as
           programmers  often  forget  that  this  type is signed on some machines.  This warning is
           enabled by -Wall.

       -Wno-coverage-mismatch
           Warn if feedback profiles do not match when using the -fprofile-use option.  If a  source
           file  is  changed  between  compiling with -fprofile-generate and with -fprofile-use, the
           files with the profile feedback can fail to match the source file and GCC cannot use  the
           profile  feedback  information.  By default, this warning is enabled and is treated as an
           error.    -Wno-coverage-mismatch   can   be   used   to   disable    the    warning    or
           -Wno-error=coverage-mismatch  can  be used to disable the error.  Disabling the error for
           this warning can result in poorly optimized code and is useful only in the case  of  very
           minor  changes  such  as  bug  fixes  to an existing code-base.  Completely disabling the
           warning is not recommended.

       -Wno-cpp
           (C, Objective-C, C++, Objective-C++ and Fortran only) Suppress warning  messages  emitted
           by "#warning" directives.

       -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
           Give  a  warning  when  a value of type "float" is implicitly promoted to "double".  CPUs
           with a 32-bit "single-precision" floating-point unit implement "float" in  hardware,  but
           emulate  "double"  in  software.   On  such  a machine, doing computations using "double"
           values is much more expensive because of the overhead required for software emulation.

           It is easy to accidentally do computations with "double" because floating-point  literals
           are implicitly of type "double".  For example, in:

                   float area(float radius)
                   {
                      return 3.14159 * radius * radius;
                   }

           the  compiler  performs  the  entire computation with "double" because the floating-point
           literal is a "double".

       -Wduplicate-decl-specifier (C and Objective-C only)
           Warn if  a  declaration  has  duplicate  "const",  "volatile",  "restrict"  or  "_Atomic"
           specifier.  This warning is enabled by -Wall.

       -Wformat
       -Wformat=n
           Check  calls to "printf" and "scanf", etc., to make sure that the arguments supplied have
           types appropriate to the format string specified, and that the conversions  specified  in
           the  format string make sense.  This includes standard functions, and others specified by
           format attributes,  in  the  "printf",  "scanf",  "strftime"  and  "strfmon"  (an  X/Open
           extension,  not  in  the C standard) families (or other target-specific families).  Which
           functions are checked without format attributes having  been  specified  depends  on  the
           standard  version  selected, and such checks of functions without the attribute specified
           are disabled by -ffreestanding or -fno-builtin.

           The formats are checked against the format features supported by GNU  libc  version  2.2.
           These  include  all  ISO  C90  and C99 features, as well as features from the Single Unix
           Specification and some BSD and GNU extensions.  Other  library  implementations  may  not
           support  all these features; GCC does not support warning about features that go beyond a
           particular library's limitations.  However, if -Wpedantic is used with -Wformat, warnings
           are given about format features not  in  the  selected  standard  version  (but  not  for
           "strfmon" formats, since those are not in any version of the C standard).

           -Wformat=1
           -Wformat
               Option  -Wformat  is  equivalent  to  -Wformat=1,  and  -Wno-format  is equivalent to
               -Wformat=0.  Since -Wformat  also  checks  for  null  format  arguments  for  several
               functions,  -Wformat  also  implies  -Wnonnull.  Some aspects of this level of format
               checking   can   be    disabled    by    the    options:    -Wno-format-contains-nul,
               -Wno-format-extra-args, and -Wno-format-zero-length.  -Wformat is enabled by -Wall.

           -Wformat=2
               Enable  -Wformat  plus  additional  format  checks.  Currently equivalent to -Wformat
               -Wformat-nonliteral -Wformat-security -Wformat-y2k.

       -Wno-format-contains-nul
           If -Wformat is specified, do not warn about format strings that contain NUL bytes.

       -Wno-format-extra-args
           If -Wformat is specified, do not warn about excess arguments to  a  "printf"  or  "scanf"
           format function.  The C standard specifies that such arguments are ignored.

           Where  the  unused arguments lie between used arguments that are specified with $ operand
           number specifications, normally warnings are still given, since the implementation  could
           not  know  what  type  to pass to "va_arg" to skip the unused arguments.  However, in the
           case of "scanf" formats, this option suppresses the warning if the unused  arguments  are
           all  pointers,  since  the  Single Unix Specification says that such unused arguments are
           allowed.

       -Wformat-overflow
       -Wformat-overflow=level
           Warn about calls to formatted input/output functions such  as  "sprintf"  and  "vsprintf"
           that  might overflow the destination buffer.  When the exact number of bytes written by a
           format directive cannot be determined at compile-time it is estimated based on heuristics
           that depend on the level argument and on optimization.  While enabling optimization  will
           in most cases improve the accuracy of the warning, it may also result in false positives.

           -Wformat-overflow
           -Wformat-overflow=1
               Level 1 of -Wformat-overflow enabled by -Wformat employs a conservative approach that
               warns  only about calls that most likely overflow the buffer.  At this level, numeric
               arguments to format directives with unknown values are assumed to have the  value  of
               one,  and strings of unknown length to be empty.  Numeric arguments that are known to
               be bounded to a subrange of their type, or string arguments whose output  is  bounded
               either  by  their  directive's  precision  or by a finite set of string literals, are
               assumed to take on the value within the range that  results  in  the  most  bytes  on
               output.  For example, the call to "sprintf" below is diagnosed because even with both
               a  and b equal to zero, the terminating NUL character ('\0') appended by the function
               to the destination buffer will be written past its end.  Increasing the size  of  the
               buffer  by  a  single  byte  is sufficient to avoid the warning, though it may not be
               sufficient to avoid the overflow.

                       void f (int a, int b)
                       {
                         char buf [13];
                         sprintf (buf, "a = %i, b = %i\n", a, b);
                       }

           -Wformat-overflow=2
               Level 2 warns also about calls that might overflow the destination  buffer  given  an
               argument  of  sufficient  length or magnitude.  At level 2, unknown numeric arguments
               are assumed to have the minimum representable value for signed types with a precision
               greater than 1, and  the  maximum  representable  value  otherwise.   Unknown  string
               arguments  whose  length  cannot  be  assumed to be bounded either by the directive's
               precision, or by a finite set of  string  literals  they  may  evaluate  to,  or  the
               character array they may point to, are assumed to be 1 character long.

               At  level  2, the call in the example above is again diagnosed, but this time because
               with a equal to a 32-bit "INT_MIN" the first %i directive  will  write  some  of  its
               digits beyond the end of the destination buffer.  To make the call safe regardless of
               the values of the two variables, the size of the destination buffer must be increased
               to  at  least  34  bytes.   GCC  includes  the  minimum  size  of  the  buffer  in an
               informational note following the warning.

               An alternative to increasing the size of the destination buffer is to  constrain  the
               range  of formatted values.  The maximum length of string arguments can be bounded by
               specifying the precision in the format directive.  When numeric arguments  of  format
               directives  can  be  assumed  to be bounded by less than the precision of their type,
               choosing an appropriate length modifier to  the  format  specifier  will  reduce  the
               required buffer size.  For example, if a and b in the example above can be assumed to
               be  within  the  precision  of  the "short int" type then using either the %hi format
               directive or casting the argument to "short" reduces the maximum required size of the
               buffer to 24 bytes.

                       void f (int a, int b)
                       {
                         char buf [23];
                         sprintf (buf, "a = %hi, b = %i\n", a, (short)b);
                       }

       -Wno-format-zero-length
           If -Wformat is specified,  do  not  warn  about  zero-length  formats.   The  C  standard
           specifies that zero-length formats are allowed.

       -Wformat-nonliteral
           If  -Wformat  is specified, also warn if the format string is not a string literal and so
           cannot be checked, unless the format function takes its format arguments as a "va_list".

       -Wformat-security
           If -Wformat is specified, also  warn  about  uses  of  format  functions  that  represent
           possible  security  problems.  At present, this warns about calls to "printf" and "scanf"
           functions where the format string is not  a  string  literal  and  there  are  no  format
           arguments,  as in "printf (foo);".  This may be a security hole if the format string came
           from  untrusted  input  and  contains  %n.   (This  is  currently  a   subset   of   what
           -Wformat-nonliteral warns about, but in future warnings may be added to -Wformat-security
           that are not included in -Wformat-nonliteral.)

       -Wformat-signedness
           If  -Wformat  is  specified, also warn if the format string requires an unsigned argument
           and the argument is signed and vice versa.

       -Wformat-truncation
       -Wformat-truncation=level
           Warn about calls to formatted input/output functions such as "snprintf"  and  "vsnprintf"
           that  might  result  in  output  truncation.  When the exact number of bytes written by a
           format directive cannot be determined at compile-time it is estimated based on heuristics
           that depend on the level argument and on optimization.  While enabling optimization  will
           in most cases improve the accuracy of the warning, it may also result in false positives.
           Except as noted otherwise, the option uses the same logic -Wformat-overflow.

           -Wformat-truncation
           -Wformat-truncation=1
               Level  1  of  -Wformat-truncation enabled by -Wformat employs a conservative approach
               that warns only about calls to bounded functions whose return  value  is  unused  and
               that will most likely result in output truncation.

           -Wformat-truncation=2
               Level  2  warns  also about calls to bounded functions whose return value is used and
               that might result in truncation given an argument of sufficient length or magnitude.

       -Wformat-y2k
           If -Wformat is specified, also warn about "strftime" formats that may yield only  a  two-
           digit year.

       -Wnonnull
           Warn  about  passing a null pointer for arguments marked as requiring a non-null value by
           the "nonnull" function attribute.

           -Wnonnull is included in -Wall and -Wformat.  It can be disabled  with  the  -Wno-nonnull
           option.

       -Wnonnull-compare
           Warn when comparing an argument marked with the "nonnull" function attribute against null
           inside the function.

           -Wnonnull-compare is included in -Wall.  It can be disabled with the -Wno-nonnull-compare
           option.

       -Wnull-dereference
           Warn  if  the  compiler detects paths that trigger erroneous or undefined behavior due to
           dereferencing    a    null    pointer.     This    option    is    only    active    when
           -fdelete-null-pointer-checks  is  active,  which  is  enabled  by  optimizations  in most
           targets.  The precision of the warnings depends on the optimization options used.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
           Warn about uninitialized variables that  are  initialized  with  themselves.   Note  this
           option can only be used with the -Wuninitialized option.

           For  example,  GCC warns about "i" being uninitialized in the following snippet only when
           -Winit-self has been specified:

                   int f()
                   {
                     int i = i;
                     return i;
                   }

           This warning is enabled by -Wall in C++.

       -Wno-implicit-int (C and Objective-C only)
           This option controls warnings when a declaration does not specify a type.   This  warning
           is enabled by default in C99 and later dialects of C, and also by -Wall.

       -Wno-implicit-function-declaration (C and Objective-C only)
           This  option  controls  warnings  when  a  function  is used before being declared.  This
           warning is enabled by default in C99 and later dialects of C, and  also  by  -Wall.   The
           warning is made into an error by -pedantic-errors.

       -Wimplicit (C and Objective-C only)
           Same  as  -Wimplicit-int and -Wimplicit-function-declaration.  This warning is enabled by
           -Wall.

       -Wimplicit-fallthrough
           -Wimplicit-fallthrough    is     the     same     as     -Wimplicit-fallthrough=3     and
           -Wno-implicit-fallthrough is the same as -Wimplicit-fallthrough=0.

       -Wimplicit-fallthrough=n
           Warn when a switch case falls through.  For example:

                   switch (cond)
                     {
                     case 1:
                       a = 1;
                       break;
                     case 2:
                       a = 2;
                     case 3:
                       a = 3;
                       break;
                     }

           This  warning  does  not warn when the last statement of a case cannot fall through, e.g.
           when there is a return statement or  a  call  to  function  declared  with  the  noreturn
           attribute.  -Wimplicit-fallthrough= also takes into account control flow statements, such
           as ifs, and only warns when appropriate.  E.g.

                   switch (cond)
                     {
                     case 1:
                       if (i > 3) {
                         bar (5);
                         break;
                       } else if (i < 1) {
                         bar (0);
                       } else
                         return;
                     default:
                       ...
                     }

           Since  there are occasions where a switch case fall through is desirable, GCC provides an
           attribute, "__attribute__ ((fallthrough))",  that  is  to  be  used  along  with  a  null
           statement to suppress this warning that would normally occur:

                   switch (cond)
                     {
                     case 1:
                       bar (0);
                       __attribute__ ((fallthrough));
                     default:
                       ...
                     }

           C++17  provides  a  standard  way  to  suppress  the -Wimplicit-fallthrough warning using
           "[[fallthrough]];" instead of the GNU  attribute.   In  C++11  or  C++14  users  can  use
           "[[gnu::fallthrough]];",  which  is  a GNU extension.  Instead of these attributes, it is
           also possible to add a fallthrough comment to silence the warning.  The whole body of the
           C or C++ style comment should match the given  regular  expressions  listed  below.   The
           option argument n specifies what kind of comments are accepted:

           *<-Wimplicit-fallthrough=0 disables the warning altogether.>
           *<-Wimplicit-fallthrough=1 matches ".*" regular>
               expression, any comment is used as fallthrough comment.

           *<-Wimplicit-fallthrough=2 case insensitively matches>
               ".*falls?[ \t-]*thr(ough|u).*" regular expression.

           *<-Wimplicit-fallthrough=3 case sensitively matches one of the>
               following regular expressions:

               *<"-fallthrough">
               *<"@fallthrough@">
               *<"lint -fallthrough[ \t]*">
               *<"[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S | |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?">
               *<"[ \t.!]*(Else,? |Intentional(ly)? )?Fall((s | |-)[Tt]|t)hr(ough|u)[
               \t.!]*(-[^\n\r]*)?">
               *<"[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?fall(s | |-)?thr(ough|u)[
               \t.!]*(-[^\n\r]*)?">
           *<-Wimplicit-fallthrough=4 case sensitively matches one of the>
               following regular expressions:

               *<"-fallthrough">
               *<"@fallthrough@">
               *<"lint -fallthrough[ \t]*">
               *<"[ \t]*FALLTHR(OUGH|U)[ \t]*">
           *<-Wimplicit-fallthrough=5 doesn't recognize any comments as>
               fallthrough comments, only attributes disable the warning.

           The  comment  needs to be followed after optional whitespace and other comments by "case"
           or "default" keywords or by a user label that precedes some "case" or "default" label.

                   switch (cond)
                     {
                     case 1:
                       bar (0);
                       /* FALLTHRU */
                     default:
                       ...
                     }

           The -Wimplicit-fallthrough=3 warning is enabled by -Wextra.

       -Wno-if-not-aligned (C, C++, Objective-C and Objective-C++ only)
           Control if warnings triggered by the "warn_if_not_aligned" attribute  should  be  issued.
           These warnings are enabled by default.

       -Wignored-qualifiers (C and C++ only)
           Warn  if  the  return type of a function has a type qualifier such as "const".  For ISO C
           such a type qualifier has no effect, since the value returned by a  function  is  not  an
           lvalue.   For  C++,  the  warning  is  only  emitted  for  scalar types or "void".  ISO C
           prohibits qualified "void" return types on function definitions,  so  such  return  types
           always receive a warning even without this option.

           This warning is also enabled by -Wextra.

       -Wno-ignored-attributes (C and C++ only)
           This  option  controls warnings when an attribute is ignored.  This is different from the
           -Wattributes option in that it warns whenever the compiler decides to drop an  attribute,
           not  that  the  attribute is either unknown, used in a wrong place, etc.  This warning is
           enabled by default.

       -Wmain
           Warn if the type of "main" is suspicious.  "main" should  be  a  function  with  external
           linkage,  returning  int,  taking  either  zero  arguments,  two,  or  three arguments of
           appropriate types.  This warning is enabled by default in C++ and is  enabled  by  either
           -Wall or -Wpedantic.

       -Wmisleading-indentation (C and C++ only)
           Warn   when   the  indentation  of  the  code  does  not  reflect  the  block  structure.
           Specifically, a warning is issued for "if", "else", "while", and  "for"  clauses  with  a
           guarded  statement  that does not use braces, followed by an unguarded statement with the
           same indentation.

           In the following example, the call to "bar"  is  misleadingly  indented  as  if  it  were
           guarded by the "if" conditional.

                     if (some_condition ())
                       foo ();
                       bar ();  /* Gotcha: this is not guarded by the "if".  */

           In the case of mixed tabs and spaces, the warning uses the -ftabstop= option to determine
           if the statements line up (defaulting to 8).

           The  warning  is  not  issued for code involving multiline preprocessor logic such as the
           following example.

                     if (flagA)
                       foo (0);
                   #if SOME_CONDITION_THAT_DOES_NOT_HOLD
                     if (flagB)
                   #endif
                       foo (1);

           The warning is not issued after a  "#line"  directive,  since  this  typically  indicates
           autogenerated  code, and no assumptions can be made about the layout of the file that the
           directive references.

           This warning is enabled by -Wall in C and C++.

       -Wmissing-attributes
           Warn when a declaration of a function is missing one or more attributes  that  a  related
           function  is  declared  with  and  whose  absence may adversely affect the correctness or
           efficiency of generated code.  For example, the warning is  issued  for  declarations  of
           aliases  that use attributes to specify less restrictive requirements than those of their
           targets.  This typically represents a potential optimization opportunity.   By  contrast,
           the   -Wattribute-alias=2  option  controls  warnings  issued  when  the  alias  is  more
           restrictive than the target, which could lead to incorrect code  generation.   Attributes
           considered include "alloc_align", "alloc_size", "cold", "const", "hot", "leaf", "malloc",
           "nonnull", "noreturn", "nothrow", "pure", "returns_nonnull", and "returns_twice".

           In  C++,  the  warning  is  issued  when an explicit specialization of a primary template
           declared  with  attribute  "alloc_align",   "alloc_size",   "assume_aligned",   "format",
           "format_arg",  "malloc",  or  "nonnull" is declared without it.  Attributes "deprecated",
           "error", and "warning" suppress the warning..

           You can use the "copy" attribute to apply the same set of attributes to a declaration  as
           that on another declaration without explicitly enumerating the attributes. This attribute
           can be applied to declarations of functions, variables, or types.

           -Wmissing-attributes is enabled by -Wall.

           For  example,  since  the declaration of the primary function template below makes use of
           both attribute "malloc" and "alloc_size" the declaration of the  explicit  specialization
           of the template is diagnosed because it is missing one of the attributes.

                   template <class T>
                   T* __attribute__ ((malloc, alloc_size (1)))
                   allocate (size_t);

                   template <>
                   void* __attribute__ ((malloc))   // missing alloc_size
                   allocate<void> (size_t);

       -Wmissing-braces
           Warn  if  an  aggregate  or  union  initializer is not fully bracketed.  In the following
           example, the initializer for "a" is not fully  bracketed,  but  that  for  "b"  is  fully
           bracketed.

                   int a[2][2] = { 0, 1, 2, 3 };
                   int b[2][2] = { { 0, 1 }, { 2, 3 } };

           This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
           Warn if a user-supplied include directory does not exist.

       -Wno-missing-profile
           This   option  controls  warnings  if  feedback  profiles  are  missing  when  using  the
           -fprofile-use option.  This option diagnoses those cases where a new function  or  a  new
           file  is  added between compiling with -fprofile-generate and with -fprofile-use, without
           regenerating the profiles.  In these cases,  the  profile  feedback  data  files  do  not
           contain   any  profile  feedback  information  for  the  newly  added  function  or  file
           respectively.  Also, in the case when profile count data (.gcda) files are  removed,  GCC
           cannot  use any profile feedback information.  In all these cases, warnings are issued to
           inform you that a profile generation step is due.  Ignoring the  warning  can  result  in
           poorly optimized code.  -Wno-missing-profile can be used to disable the warning, but this
           is not recommended and should be done only when non-existent profile data is justified.

       -Wno-mismatched-dealloc
           Warn  for  calls  to  deallocation  functions  with  pointer arguments returned from from
           allocations functions for which the former isn't  a  suitable  deallocator.   A  pair  of
           functions  can  be associated as matching allocators and deallocators by use of attribute
           "malloc".  Unless disabled by the -fno-builtin option the  standard  functions  "calloc",
           "malloc", "realloc", and "free", as well as the corresponding forms of C++ "operator new"
           and  "operator delete" are implicitly associated as matching allocators and deallocators.
           In the following example "mydealloc"  is  the  deallocator  for  pointers  returned  from
           "myalloc".

                   void mydealloc (void*);

                   __attribute__ ((malloc (mydealloc, 1))) void*
                   myalloc (size_t);

                   void f (void)
                   {
                     void *p = myalloc (32);
                     // ...use p...
                     free (p);   // warning: not a matching deallocator for myalloc
                     mydealloc (p);   // ok
                   }

           In  C++, the related option -Wmismatched-new-delete diagnoses mismatches involving either
           "operator new" or "operator delete".

           Option -Wmismatched-dealloc is enabled by default.

       -Wmultistatement-macros
           Warn about unsafe multiple statement macros that appear to be guarded by a clause such as
           "if", "else", "for", "switch", or "while", in which only the first statement is  actually
           guarded after the macro is expanded.

           For example:

                   #define DOIT x++; y++
                   if (c)
                     DOIT;

           will increment "y" unconditionally, not just when "c" holds.  The can usually be fixed by
           wrapping the macro in a do-while loop:

                   #define DOIT do { x++; y++; } while (0)
                   if (c)
                     DOIT;

           This warning is enabled by -Wall in C and C++.

       -Wparentheses
           Warn  if parentheses are omitted in certain contexts, such as when there is an assignment
           in a context where a truth  value  is  expected,  or  when  operators  are  nested  whose
           precedence people often get confused about.

           Also  warn  if a comparison like "x<=y<=z" appears; this is equivalent to "(x<=y ? 1 : 0)
           <= z", which is a different interpretation from that of ordinary mathematical notation.

           Also warn for dangerous uses of the GNU extension to "?:" with  omitted  middle  operand.
           When  the  condition  in  the "?": operator is a boolean expression, the omitted value is
           always 1.  Often programmers expect it to be a  value  computed  inside  the  conditional
           expression instead.

           For  C++ this also warns for some cases of unnecessary parentheses in declarations, which
           can indicate an attempt at a function call instead of a declaration:

                   {
                     // Declares a local variable called mymutex.
                     std::unique_lock<std::mutex> (mymutex);
                     // User meant std::unique_lock<std::mutex> lock (mymutex);
                   }

           This warning is enabled by -Wall.

       -Wsequence-point
           Warn about code that may have undefined semantics because of violations of sequence point
           rules in the C and C++ standards.

           The C and C++ standards define the order in which expressions  in  a  C/C++  program  are
           evaluated  in  terms  of  sequence points, which represent a partial ordering between the
           execution of parts of the program: those executed before the sequence  point,  and  those
           executed  after  it.  These occur after the evaluation of a full expression (one which is
           not part of a larger expression), after the evaluation of the first operand  of  a  "&&",
           "||",  "?  :"  or  ","  (comma)  operator,  before  a  function  is called (but after the
           evaluation of its arguments and the expression denoting  the  called  function),  and  in
           certain  other places.  Other than as expressed by the sequence point rules, the order of
           evaluation of subexpressions of an expression is not specified.  All these rules describe
           only a partial order rather than a total order, since, for example, if two functions  are
           called  within one expression with no sequence point between them, the order in which the
           functions are called is not specified.  However, the standards committee have ruled  that
           function calls do not overlap.

           It  is  not specified when between sequence points modifications to the values of objects
           take effect.  Programs whose behavior depends on this have undefined behavior; the C  and
           C++  standards specify that "Between the previous and next sequence point an object shall
           have its stored value  modified  at  most  once  by  the  evaluation  of  an  expression.
           Furthermore,  the  prior  value shall be read only to determine the value to be stored.".
           If a program breaks these  rules,  the  results  on  any  particular  implementation  are
           entirely unpredictable.

           Examples  of  code  with undefined behavior are "a = a++;", "a[n] = b[n++]" and "a[i++] =
           i;".  Some more complicated cases are not diagnosed by this option, and it  may  give  an
           occasional  false  positive  result, but in general it has been found fairly effective at
           detecting this sort of problem in programs.

           The C++17 standard will define the order of evaluation of  operands  in  more  cases:  in
           particular  it requires that the right-hand side of an assignment be evaluated before the
           left-hand side, so the above examples are no longer  undefined.   But  this  option  will
           still  warn  about  them,  to  help  people avoid writing code that is undefined in C and
           earlier revisions of C++.

           The standard is worded confusingly, therefore there  is  some  debate  over  the  precise
           meaning  of  the  sequence  point  rules  in  subtle  cases.  Links to discussions of the
           problem, including proposed formal definitions, may be found on the GCC readings page, at
           <http://gcc.gnu.org/readings.html>.

           This warning is enabled by -Wall for C and C++.

       -Wno-return-local-addr
           Do not warn about returning a pointer (or in C++, a reference) to a  variable  that  goes
           out of scope after the function returns.

       -Wreturn-type
           Warn whenever a function is defined with a return type that defaults to "int".  Also warn
           about  any "return" statement with no return value in a function whose return type is not
           "void" (falling off the end of the  function  body  is  considered  returning  without  a
           value).

           For C only, warn about a "return" statement with an expression in a function whose return
           type  is  "void",  unless  the  expression  type is also "void".  As a GNU extension, the
           latter case is accepted without a warning unless -Wpedantic is used.  Attempting  to  use
           the  return  value  of  a non-"void" function other than "main" that flows off the end by
           reaching the closing curly brace that terminates the function is undefined.

           Unlike in C, in C++, flowing off the end of  a  non-"void"  function  other  than  "main"
           results in undefined behavior even when the value of the function is not used.

           This warning is enabled by default in C++ and by -Wall otherwise.

       -Wno-shift-count-negative
           Controls warnings if a shift count is negative.  This warning is enabled by default.

       -Wno-shift-count-overflow
           Controls warnings if a shift count is greater than or equal to the bit width of the type.
           This warning is enabled by default.

       -Wshift-negative-value
           Warn  if  left shifting a negative value.  This warning is enabled by -Wextra in C99 (and
           newer) and C++11 to C++17 modes.

       -Wno-shift-overflow
       -Wshift-overflow=n
           These options control warnings about left shift overflows.

           -Wshift-overflow=1
               This is the warning level of -Wshift-overflow and is enabled by default  in  C99  and
               C++11 modes (and newer).  This warning level does not warn about left-shifting 1 into
               the  sign  bit.  (However, in C, such an overflow is still rejected in contexts where
               an integer constant expression is required.)  No warning is  emitted  in  C++20  mode
               (and newer), as signed left shifts always wrap.

           -Wshift-overflow=2
               This  warning  level also warns about left-shifting 1 into the sign bit, unless C++14
               mode (or newer) is active.

       -Wswitch
           Warn whenever a "switch" statement has an index of enumerated type and lacks a "case" for
           one or more of the named codes of that enumeration.  (The presence of a  "default"  label
           prevents  this  warning.)   "case"  labels  outside  the  enumeration  range also provoke
           warnings when this option is used (even if there is a "default" label).  This warning  is
           enabled by -Wall.

       -Wswitch-default
           Warn whenever a "switch" statement does not have a "default" case.

       -Wswitch-enum
           Warn whenever a "switch" statement has an index of enumerated type and lacks a "case" for
           one  or  more  of  the  named  codes  of  that  enumeration.   "case"  labels outside the
           enumeration range also provoke warnings when this option is used.   The  only  difference
           between  -Wswitch  and  this  option is that this option gives a warning about an omitted
           enumeration code even if there is a "default" label.

       -Wno-switch-bool
           Do not warn when a "switch" statement has an index of boolean type and  the  case  values
           are  outside  the  range  of  a boolean type.  It is possible to suppress this warning by
           casting the controlling expression to a type other than "bool".  For example:

                   switch ((int) (a == 4))
                     {
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wno-switch-outside-range
           This option controls warnings when a "switch" case has a value that  is  outside  of  its
           respective type range.  This warning is enabled by default for C and C++ programs.

       -Wno-switch-unreachable
           Do  not  warn  when  a  "switch"  statement  contains  statements between the controlling
           expression and the first case label, which will never be executed.  For example:

                   switch (cond)
                     {
                      i = 15;
                     ...
                      case 5:
                     ...
                     }

           -Wswitch-unreachable does not warn if the statement between  the  controlling  expression
           and the first case label is just a declaration:

                   switch (cond)
                     {
                      int i;
                     ...
                      case 5:
                      i = 5;
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wsync-nand (C and C++ only)
           Warn  when  "__sync_fetch_and_nand"  and  "__sync_nand_and_fetch"  built-in functions are
           used.  These functions changed semantics in GCC 4.4.

       -Wunused-but-set-parameter
           Warn whenever a function parameter is assigned to, but otherwise unused (aside  from  its
           declaration).

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused together with -Wextra.

       -Wunused-but-set-variable
           Warn  whenever  a  local  variable  is  assigned to, but otherwise unused (aside from its
           declaration).  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused, which is enabled by -Wall.

       -Wunused-function
           Warn whenever a static function is declared  but  not  defined  or  a  non-inline  static
           function is unused.  This warning is enabled by -Wall.

       -Wunused-label
           Warn whenever a label is declared but not used.  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
           Warn  when  a typedef locally defined in a function is not used.  This warning is enabled
           by -Wall.

       -Wunused-parameter
           Warn whenever a function parameter is unused aside from its declaration.

           To suppress this warning use the "unused" attribute.

       -Wno-unused-result
           Do not warn if a caller of a function marked with attribute "warn_unused_result" does not
           use its return value. The default is -Wunused-result.

       -Wunused-variable
           Warn whenever a local or static variable is  unused  aside  from  its  declaration.  This
           option  implies -Wunused-const-variable=1 for C, but not for C++. This warning is enabled
           by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-const-variable
       -Wunused-const-variable=n
           Warn  whenever  a  constant  static  variable  is  unused  aside  from  its  declaration.
           -Wunused-const-variable=1  is  enabled  by -Wunused-variable for C, but not for C++. In C
           this declares variable storage, but in C++ this is not an  error  since  const  variables
           take the place of "#define"s.

           To suppress this warning use the "unused" attribute.

           -Wunused-const-variable=1
               This  is the warning level that is enabled by -Wunused-variable for C.  It warns only
               about unused static const variables defined in the main  compilation  unit,  but  not
               about static const variables declared in any header included.

           -Wunused-const-variable=2
               This  warning  level  also  warns  for  unused  constant  static variables in headers
               (excluding system headers).  This is the warning level of -Wunused-const-variable and
               must be explicitly requested since in C++ this isn't an error and in C  it  might  be
               harder to clean up all headers included.

       -Wunused-value
           Warn whenever a statement computes a result that is explicitly not used. To suppress this
           warning  cast  the  unused expression to "void". This includes an expression-statement or
           the left-hand side of a comma expression that contains no side effects. For  example,  an
           expression such as "x[i,j]" causes a warning, while "x[(void)i,j]" does not.

           This warning is enabled by -Wall.

       -Wunused
           All the above -Wunused options combined.

           In  order  to  get  a warning about an unused function parameter, you must either specify
           -Wextra  -Wunused  (note  that   -Wall   implies   -Wunused),   or   separately   specify
           -Wunused-parameter.

       -Wuninitialized
           Warn  if  an  object  with automatic or allocated storage duration is used without having
           been initialized.  In C++, also warn if a  non-static  reference  or  non-static  "const"
           member appears in a class without constructors.

           In  addition,  passing a pointer (or in C++, a reference) to an uninitialized object to a
           "const"-qualified argument of a built-in function  known  to  read  the  object  is  also
           diagnosed by this warning.  (-Wmaybe-uninitialized is issued for ordinary functions.)

           If  you  want to warn about code that uses the uninitialized value of the variable in its
           own initializer, use the -Winit-self option.

           These warnings occur for individual uninitialized elements of structure, union  or  array
           variables  as well as for variables that are uninitialized as a whole.  They do not occur
           for variables  or  elements  declared  "volatile".   Because  these  warnings  depend  on
           optimization,  the exact variables or elements for which there are warnings depend on the
           precise optimization options and version of GCC used.

           Note that there may be no warning about a variable that is used only to compute  a  value
           that itself is never used, because such computations may be deleted by data flow analysis
           before the warnings are printed.

       -Wno-invalid-memory-model
           This  option controls warnings for invocations of __atomic Builtins, __sync Builtins, and
           the C11 atomic generic functions with  a  memory  consistency  argument  that  is  either
           invalid  for  the  operation  or  outside  the  range  of  values  of  the "memory_order"
           enumeration.  For example, since the "__atomic_store"  and  "__atomic_store_n"  built-ins
           are  only defined for the relaxed, release, and sequentially consistent memory orders the
           following code is diagnosed:

                   void store (int *i)
                   {
                     __atomic_store_n (i, 0, memory_order_consume);
                   }

           -Winvalid-memory-model is enabled by default.

       -Wmaybe-uninitialized
           For an object with automatic or allocated storage duration, if there exists a  path  from
           the function entry to a use of the object that is initialized, but there exist some other
           paths  for which the object is not initialized, the compiler emits a warning if it cannot
           prove the uninitialized paths are not executed at run time.

           In addition, passing a pointer (or in C++, a reference) to an uninitialized object  to  a
           "const"-qualified  function argument is also diagnosed by this warning.  (-Wuninitialized
           is issued for built-in functions known to read the object.)  Annotating the function with
           attribute "access (none)" indicates that the argument isn't used to access the object and
           avoids the warning.

           These warnings are only possible in optimizing compilation, because  otherwise  GCC  does
           not keep track of the state of variables.

           These  warnings  are made optional because GCC may not be able to determine when the code
           is correct in spite of appearing to have an error.  Here is one example of how  this  can
           happen:

                   {
                     int x;
                     switch (y)
                       {
                       case 1: x = 1;
                         break;
                       case 2: x = 4;
                         break;
                       case 3: x = 5;
                       }
                     foo (x);
                   }

           If  the value of "y" is always 1, 2 or 3, then "x" is always initialized, but GCC doesn't
           know this. To suppress the warning, you need to provide a default case with assert(0)  or
           similar code.

           This  option also warns when a non-volatile automatic variable might be changed by a call
           to "longjmp".  The compiler sees only the  calls  to  "setjmp".   It  cannot  know  where
           "longjmp"  will  be  called;  in fact, a signal handler could call it at any point in the
           code.  As a result, you may get a warning even when there is in fact no  problem  because
           "longjmp" cannot in fact be called at the place that would cause a problem.

           Some spurious warnings can be avoided if you declare all the functions you use that never
           return as "noreturn".

           This warning is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
           Warn  when  a  "#pragma" directive is encountered that is not understood by GCC.  If this
           command-line option is used, warnings are even  issued  for  unknown  pragmas  in  system
           header  files.   This  is  not  the  case  if  the warnings are only enabled by the -Wall
           command-line option.

       -Wno-pragmas
           Do not warn about misuses of pragmas, such as incorrect parameters,  invalid  syntax,  or
           conflicts between pragmas.  See also -Wunknown-pragmas.

       -Wno-prio-ctor-dtor
           Do  not  warn if a priority from 0 to 100 is used for constructor or destructor.  The use
           of constructor  and  destructor  attributes  allow  you  to  assign  a  priority  to  the
           constructor/destructor to control its order of execution before "main" is called or after
           it  returns.   The  priority  values  must  be  greater than 100 as the compiler reserves
           priority values between 0--100 for the implementation.

       -Wstrict-aliasing
           This option is only active when -fstrict-aliasing is active.  It warns  about  code  that
           might  break  the strict aliasing rules that the compiler is using for optimization.  The
           warning does not catch all cases, but does attempt to catch the more common pitfalls.  It
           is included in -Wall.  It is equivalent to -Wstrict-aliasing=3

       -Wstrict-aliasing=n
           This option is only active when -fstrict-aliasing is active.  It warns  about  code  that
           might  break  the  strict  aliasing  rules  that  the compiler is using for optimization.
           Higher levels correspond to higher accuracy (fewer false positives).  Higher levels  also
           correspond  to more effort, similar to the way -O works.  -Wstrict-aliasing is equivalent
           to -Wstrict-aliasing=3.

           Level 1: Most aggressive, quick, least accurate.  Possibly useful when higher  levels  do
           not warn but -fstrict-aliasing still breaks the code, as it has very few false negatives.
           However, it has many false positives.  Warns for all pointer conversions between possibly
           incompatible types, even if never dereferenced.  Runs in the front end only.

           Level 2: Aggressive, quick, not too precise.  May still have many false positives (not as
           many  as  level  1  though),  and  few  false negatives (but possibly more than level 1).
           Unlike level 1, it only warns when an address is taken.  Warns  about  incomplete  types.
           Runs in the front end only.

           Level  3  (default  for  -Wstrict-aliasing): Should have very few false positives and few
           false negatives.  Slightly slower than levels 1 or 2 when optimization is enabled.  Takes
           care of the common pun+dereference pattern in the front  end:  "*(int*)&some_float".   If
           optimization  is  enabled,  it  also  runs  in the back end, where it deals with multiple
           statement  cases  using  flow-sensitive  points-to  information.   Only  warns  when  the
           converted pointer is dereferenced.  Does not warn about incomplete types.

       -Wstrict-overflow
       -Wstrict-overflow=n
           This option is only active when signed overflow is undefined.  It warns about cases where
           the compiler optimizes based on the assumption that signed overflow does not occur.  Note
           that  it does not warn about all cases where the code might overflow: it only warns about
           cases where the compiler implements some optimization.  Thus this warning depends on  the
           optimization level.

           An optimization that assumes that signed overflow does not occur is perfectly safe if the
           values  of  the  variables  involved  are  such that overflow never does, in fact, occur.
           Therefore this warning can easily give a false positive: a warning about code that is not
           actually a problem.  To help focus  on  important  issues,  several  warning  levels  are
           defined.  No warnings are issued for the use of undefined signed overflow when estimating
           how  many  iterations a loop requires, in particular when determining whether a loop will
           be executed at all.

           -Wstrict-overflow=1
               Warn about cases that are both questionable and  easy  to  avoid.   For  example  the
               compiler  simplifies "x + 1 > x" to 1.  This level of -Wstrict-overflow is enabled by
               -Wall; higher levels are not, and must be explicitly requested.

           -Wstrict-overflow=2
               Also warn about other cases where a comparison is  simplified  to  a  constant.   For
               example: "abs (x) >= 0".  This can only be simplified when signed integer overflow is
               undefined,  because  "abs (INT_MIN)" overflows to "INT_MIN", which is less than zero.
               -Wstrict-overflow (with no level) is the same as -Wstrict-overflow=2.

           -Wstrict-overflow=3
               Also warn about other cases where a comparison is simplified.  For example: "x + 1  >
               1" is simplified to "x > 0".

           -Wstrict-overflow=4
               Also  warn  about other simplifications not covered by the above cases.  For example:
               "(x * 10) / 5" is simplified to "x * 2".

           -Wstrict-overflow=5
               Also warn about cases where the compiler reduces the magnitude of a constant involved
               in a comparison.  For example: "x + 2 > y" is simplified to "x + 1 >=  y".   This  is
               reported  only  at  the  highest warning level because this simplification applies to
               many comparisons, so this warning level gives a very large number of false positives.

       -Wstring-compare
           Warn for calls to "strcmp" and "strncmp" whose result is determined to be either zero  or
           non-zero  in  tests  for  such equality owing to the length of one argument being greater
           than the size of the array the other argument is stored in (or the bound in the  case  of
           "strncmp").   Such  calls  could be mistakes.  For example, the call to "strcmp" below is
           diagnosed because its result is necessarily non-zero irrespective of the contents of  the
           array "a".

                   extern char a[4];
                   void f (char *d)
                   {
                     strcpy (d, "string");
                     ...
                     if (0 == strcmp (a, d))   // cannot be true
                       puts ("a and d are the same");
                   }

           -Wstring-compare is enabled by -Wextra.

       -Wno-stringop-overflow
       -Wstringop-overflow
       -Wstringop-overflow=type
           Warn  for  calls  to string manipulation functions such as "memcpy" and "strcpy" that are
           determined to overflow the destination buffer.  The optional argument is one greater than
           the type of Object Size Checking to perform to determine the  size  of  the  destination.
           The  argument  is  meaningful only for functions that operate on character arrays but not
           for raw memory functions like "memcpy" which always make use of Object Size type-0.   The
           option  also warns for calls that specify a size in excess of the largest possible object
           or at most "SIZE_MAX / 2" bytes.  The option produces the best results with  optimization
           enabled  but  can  detect  a  small  subset  of  simple  buffer  overflows  even  without
           optimization in  calls  to  the  GCC  built-in  functions  like  "__builtin_memcpy"  that
           correspond  to the standard functions.  In any case, the option warns about just a subset
           of buffer overflows detected by  the  corresponding  overflow  checking  built-ins.   For
           example,  the  option  issues  a warning for the "strcpy" call below because it copies at
           least 5 characters (the string "blue" including the terminating NUL) into the  buffer  of
           size 4.

                   enum Color { blue, purple, yellow };
                   const char* f (enum Color clr)
                   {
                     static char buf [4];
                     const char *str;
                     switch (clr)
                       {
                         case blue: str = "blue"; break;
                         case purple: str = "purple"; break;
                         case yellow: str = "yellow"; break;
                       }

                     return strcpy (buf, str);   // warning here
                   }

           Option -Wstringop-overflow=2 is enabled by default.

           -Wstringop-overflow
           -Wstringop-overflow=1
               The -Wstringop-overflow=1 option uses type-zero Object Size Checking to determine the
               sizes  of  destination  objects.  At this setting the option does not warn for writes
               past the end of subobjects of larger objects accessed by pointers unless the size  of
               the  largest surrounding object is known.  When the destination may be one of several
               objects it is assumed to be  the  largest  one  of  them.   On  Linux  systems,  when
               optimization  is  enabled  at this setting the option warns for the same code as when
               the "_FORTIFY_SOURCE" macro is defined to a non-zero value.

           -Wstringop-overflow=2
               The -Wstringop-overflow=2 option uses type-one Object Size Checking to determine  the
               sizes  of destination objects.  At this setting the option warns about overflows when
               writing to members of the  largest  complete  objects  whose  exact  size  is  known.
               However, it does not warn for excessive writes to the same members of unknown objects
               referenced  by  pointers since they may point to arrays containing unknown numbers of
               elements.  This is the default setting of the option.

           -Wstringop-overflow=3
               The -Wstringop-overflow=3 option uses type-two Object Size Checking to determine  the
               sizes of destination objects.  At this setting the option warns about overflowing the
               smallest  object  or data member.  This is the most restrictive setting of the option
               that may result in warnings for safe code.

           -Wstringop-overflow=4
               The -Wstringop-overflow=4 option uses type-three Object Size  Checking  to  determine
               the sizes of destination objects.  At this setting the option warns about overflowing
               any data members, and when the destination is one of several objects it uses the size
               of  the  largest  of  them  to  decide  whether  to  issue  a  warning.  Similarly to
               -Wstringop-overflow=3 this setting of the option may result in  warnings  for  benign
               code.

       -Wno-stringop-overread
           Warn  for  calls  to string manipulation functions such as "memchr", or "strcpy" that are
           determined to read past the end of the source sequence.

           Option -Wstringop-overread is enabled by default.

       -Wno-stringop-truncation
           Do not warn for calls  to  bounded  string  manipulation  functions  such  as  "strncat",
           "strncpy",  and  "stpncpy"  that  may  either  truncate  the  copied  string or leave the
           destination unchanged.

           In the following example, the call to "strncat" specifies a bound that is less  than  the
           length  of  the source string.  As a result, the copy of the source will be truncated and
           so the call is diagnosed.  To avoid the warning use "bufsize - strlen (buf) - 1)" as  the
           bound.

                   void append (char *buf, size_t bufsize)
                   {
                     strncat (buf, ".txt", 3);
                   }

           As  another  example,  the following call to "strncpy" results in copying to "d" just the
           characters preceding the terminating NUL, without appending the NUL to the end.  Assuming
           the result of "strncpy" is necessarily a NUL-terminated string is a common  mistake,  and
           so  the  call  is  diagnosed.  To avoid the warning when the result is not expected to be
           NUL-terminated, call "memcpy" instead.

                   void copy (char *d, const char *s)
                   {
                     strncpy (d, s, strlen (s));
                   }

           In the following example, the call to "strncpy" specifies the  size  of  the  destination
           buffer as the bound.  If the length of the source string is equal to or greater than this
           size  the  result  of  the  copy will not be NUL-terminated.  Therefore, the call is also
           diagnosed.  To avoid the warning, specify "sizeof buf - 1" as the bound and set the  last
           element of the buffer to "NUL".

                   void copy (const char *s)
                   {
                     char buf[80];
                     strncpy (buf, s, sizeof buf);
                     ...
                   }

           In  situations  where  a character array is intended to store a sequence of bytes with no
           terminating "NUL" such an array may be annotated with attribute "nonstring" to avoid this
           warning.  Such arrays, however, are not  suitable  arguments  to  functions  that  expect
           "NUL"-terminated  strings.   To  help detect accidental misuses of such arrays GCC issues
           warnings unless it can prove that the use is safe.

       -Wsuggest-attribute=[pure|const|noreturn|format|cold|malloc]
           Warn for cases where adding an attribute may  be  beneficial.  The  attributes  currently
           supported are listed below.

           -Wsuggest-attribute=pure
           -Wsuggest-attribute=const
           -Wsuggest-attribute=noreturn
           -Wmissing-noreturn
           -Wsuggest-attribute=malloc
               Warn  about  functions  that  might  be  candidates for attributes "pure", "const" or
               "noreturn" or "malloc". The compiler  only  warns  for  functions  visible  in  other
               compilation  units or (in the case of "pure" and "const") if it cannot prove that the
               function returns normally. A function returns  normally  if  it  doesn't  contain  an
               infinite  loop  or  return abnormally by throwing, calling "abort" or trapping.  This
               analysis requires option -fipa-pure-const, which is enabled  by  default  at  -O  and
               higher.  Higher optimization levels improve the accuracy of the analysis.

           -Wsuggest-attribute=format
           -Wmissing-format-attribute
               Warn  about function pointers that might be candidates for "format" attributes.  Note
               these are only possible candidates, not absolute ones.   GCC  guesses  that  function
               pointers  with  "format"  attributes  that  are  used  in assignment, initialization,
               parameter passing or return statements should have a corresponding "format" attribute
               in the resulting type.  I.e. the left-hand side of the assignment or  initialization,
               the  type  of  the  parameter variable, or the return type of the containing function
               respectively should also have a "format" attribute to avoid the warning.

               GCC also warns about function definitions  that  might  be  candidates  for  "format"
               attributes.   Again,  these  are only possible candidates.  GCC guesses that "format"
               attributes might be appropriate for any function that calls a function like "vprintf"
               or "vscanf", but this might not always be the case,  and  some  functions  for  which
               "format" attributes are appropriate may not be detected.

           -Wsuggest-attribute=cold
               Warn about functions that might be candidates for "cold" attribute.  This is based on
               static  detection  and  generally  only warns about functions which always leads to a
               call to another "cold" function such as  wrappers  of  C++  "throw"  or  fatal  error
               reporting functions leading to "abort".

       -Walloc-zero
           Warn  about  calls  to  allocation  functions  decorated with attribute "alloc_size" that
           specify  zero  bytes,  including  those  to  the  built-in   forms   of   the   functions
           "aligned_alloc",  "alloca",  "calloc",  "malloc", and "realloc".  Because the behavior of
           these functions when called with a zero size differs among implementations  (and  in  the
           case  of  "realloc"  has  been deprecated) relying on it may result in subtle portability
           bugs and should be avoided.

       -Walloc-size-larger-than=byte-size
           Warn about calls to functions decorated  with  attribute  "alloc_size"  that  attempt  to
           allocate  objects  larger  than the specified number of bytes, or where the result of the
           size computation in an integer type with infinite precision would  exceed  the  value  of
           PTRDIFF_MAX  on  the target.  -Walloc-size-larger-than=PTRDIFF_MAX is enabled by default.
           Warnings controlled by the option can be  disabled  either  by  specifying  byte-size  of
           SIZE_MAX or more or by -Wno-alloc-size-larger-than.

       -Wno-alloc-size-larger-than
           Disable    -Walloc-size-larger-than=    warnings.     The   option   is   equivalent   to
           -Walloc-size-larger-than=SIZE_MAX or larger.

       -Walloca
           This option warns on all uses of "alloca" in the source.

       -Walloca-larger-than=byte-size
           This option warns on calls to "alloca" with an integer argument  whose  value  is  either
           zero,  or that is not bounded by a controlling predicate that limits its value to at most
           byte-size.  It also warns for calls  to  "alloca"  where  the  bound  value  is  unknown.
           Arguments  of  non-integer  types  are  considered  unbounded  even  if they appear to be
           constrained to the expected range.

           For example, a bounded case of "alloca" could be:

                   void func (size_t n)
                   {
                     void *p;
                     if (n <= 1000)
                       p = alloca (n);
                     else
                       p = malloc (n);
                     f (p);
                   }

           In the above example, passing  "-Walloca-larger-than=1000"  would  not  issue  a  warning
           because  the  call  to  "alloca"  is  known  to  be  at  most  1000  bytes.   However, if
           "-Walloca-larger-than=500" were passed, the compiler would emit a warning.

           Unbounded uses, on the other hand, are uses of "alloca"  with  no  controlling  predicate
           constraining its integer argument.  For example:

                   void func ()
                   {
                     void *p = alloca (n);
                     f (p);
                   }

           If  "-Walloca-larger-than=500"  were  passed, the above would trigger a warning, but this
           time because of the lack of bounds checking.

           Note, that even seemingly correct code involving signed integers could cause a warning:

                   void func (signed int n)
                   {
                     if (n < 500)
                       {
                         p = alloca (n);
                         f (p);
                       }
                   }

           In the above example, n could be negative, causing a larger than expected argument to  be
           implicitly cast into the "alloca" call.

           This option also warns when "alloca" is used in a loop.

           -Walloca-larger-than=PTRDIFF_MAX  is  enabled  by  default  but is usually only effective
           when -ftree-vrp is active (default for -O2 and above).

           See also -Wvla-larger-than=byte-size.

       -Wno-alloca-larger-than
           Disable    -Walloca-larger-than=    warnings.     The    option    is    equivalent    to
           -Walloca-larger-than=SIZE_MAX or larger.

       -Warith-conversion
           Do warn about implicit conversions from arithmetic operations even when conversion of the
           operands  to  the  same  type  cannot  change  their  values.  This affects warnings from
           -Wconversion, -Wfloat-conversion, and -Wsign-conversion.

                   void f (char c, int i)
                   {
                     c = c + i; // warns with B<-Wconversion>
                     c = c + 1; // only warns with B<-Warith-conversion>
                   }

       -Warray-bounds
       -Warray-bounds=n
           This option is only active when -ftree-vrp is active (default  for  -O2  and  above).  It
           warns  about  subscripts to arrays that are always out of bounds. This warning is enabled
           by -Wall.

           -Warray-bounds=1
               This is the warning level of -Warray-bounds and is enabled by  -Wall;  higher  levels
               are not, and must be explicitly requested.

           -Warray-bounds=2
               This  warning  level also warns about out of bounds access for arrays at the end of a
               struct and for arrays accessed through pointers. This warning level may give a larger
               number of false positives and is deactivated by default.

       -Warray-parameter
       -Warray-parameter=n
           Warn about redeclarations of functions involving arguments of array or pointer  types  of
           inconsistent  kinds  or forms, and enable the detection of out-of-bounds accesses to such
           parameters by warnings such as -Warray-bounds.

           If the first function declaration uses the array form the bound specified in the array is
           assumed to be the minimum number of elements expected to be  provided  in  calls  to  the
           function and the maximum number of elements accessed by it.  Failing to provide arguments
           of sufficient size or accessing more than the maximum number of elements may be diagnosed
           by  warnings  such  as  -Warray-bounds.  At level 1 the warning diagnoses inconsistencies
           involving array parameters declared using the "T[static N]" form.

           For example, the warning triggers for the following redeclarations because the first  one
           allows  an  array  of  any size to be passed to "f" while the second one with the keyword
           "static" specifies that the array argument must have at least four elements.

                   void f (int[static 4]);
                   void f (int[]);           // warning (inconsistent array form)

                   void g (void)
                   {
                     int *p = (int *)malloc (4);
                     f (p);                  // warning (array too small)
                     ...
                   }

           At level 2 the warning also triggers for redeclarations involving any other inconsistency
           in array or pointer  argument  forms  denoting  array  sizes.   Pointers  and  arrays  of
           unspecified bound are considered equivalent and do not trigger a warning.

                   void g (int*);
                   void g (int[]);     // no warning
                   void g (int[8]);    // warning (inconsistent array bound)

           -Warray-parameter=2  is  included in -Wall.  The -Wvla-parameter option triggers warnings
           for similar inconsistencies involving Variable Length Array arguments.

       -Wattribute-alias=n
       -Wno-attribute-alias
           Warn about declarations  using  the  "alias"  and  similar  attributes  whose  target  is
           incompatible with the type of the alias.

           -Wattribute-alias=1
               The default warning level of the -Wattribute-alias option diagnoses incompatibilities
               between   the   type  of  the  alias  declaration  and  that  of  its  target.   Such
               incompatibilities are typically indicative of bugs.

           -Wattribute-alias=2
               At this level -Wattribute-alias also diagnoses cases  where  the  attributes  of  the
               alias  declaration  are  more  restrictive than the attributes applied to its target.
               These mismatches can potentially result in incorrect code generation.  In other cases
               they may be benign and could be resolved simply by adding the  missing  attribute  to
               the  target.   For  comparison,  see  the -Wmissing-attributes option, which controls
               diagnostics when the alias declaration is less restrictive than  the  target,  rather
               than more restrictive.

               Attributes  considered  include  "alloc_align", "alloc_size", "cold", "const", "hot",
               "leaf", "malloc", "nonnull", "noreturn", "nothrow",  "pure",  "returns_nonnull",  and
               "returns_twice".

           -Wattribute-alias  is  equivalent  to -Wattribute-alias=1.  This is the default.  You can
           disable these warnings with either -Wno-attribute-alias or -Wattribute-alias=0.

       -Wbool-compare
           Warn  about  boolean  expression  compared  with  an   integer   value   different   from
           "true"/"false".  For instance, the following comparison is always false:

                   int n = 5;
                   ...
                   if ((n > 1) == 2) { ... }

           This warning is enabled by -Wall.

       -Wbool-operation
           Warn about suspicious operations on expressions of a boolean type.  For instance, bitwise
           negation  of  a  boolean  is  very likely a bug in the program.  For C, this warning also
           warns about incrementing or decrementing a boolean, which rarely makes sense.   (In  C++,
           decrementing  a  boolean  is always invalid.  Incrementing a boolean is invalid in C++17,
           and deprecated otherwise.)

           This warning is enabled by -Wall.

       -Wduplicated-branches
           Warn when an if-else has identical branches.  This warning detects cases like

                   if (p != NULL)
                     return 0;
                   else
                     return 0;

           It doesn't warn when both branches contain just a null statement.  This warning also warn
           for conditional operators:

                     int i = x ? *p : *p;

       -Wduplicated-cond
           Warn about duplicated conditions in an if-else-if chain.   For  instance,  warn  for  the
           following code:

                   if (p->q != NULL) { ... }
                   else if (p->q != NULL) { ... }

       -Wframe-address
           Warn  when  the  __builtin_frame_address  or  __builtin_return_address  is called with an
           argument greater than 0.  Such  calls  may  return  indeterminate  values  or  crash  the
           program.  The warning is included in -Wall.

       -Wno-discarded-qualifiers (C and Objective-C only)
           Do  not warn if type qualifiers on pointers are being discarded.  Typically, the compiler
           warns if a "const char *" variable is  passed  to  a  function  that  takes  a  "char  *"
           parameter.  This option can be used to suppress such a warning.

       -Wno-discarded-array-qualifiers (C and Objective-C only)
           Do  not  warn if type qualifiers on arrays which are pointer targets are being discarded.
           Typically, the compiler warns if a "const int (*)[]" variable is  passed  to  a  function
           that takes a "int (*)[]" parameter.  This option can be used to suppress such a warning.

       -Wno-incompatible-pointer-types (C and Objective-C only)
           Do  not  warn  when  there is a conversion between pointers that have incompatible types.
           This warning is for cases not covered  by  -Wno-pointer-sign,  which  warns  for  pointer
           argument passing or assignment with different signedness.

       -Wno-int-conversion (C and Objective-C only)
           Do  not  warn  about  incompatible integer to pointer and pointer to integer conversions.
           This warning is  about  implicit  conversions;  for  explicit  conversions  the  warnings
           -Wno-int-to-pointer-cast and -Wno-pointer-to-int-cast may be used.

       -Wzero-length-bounds
           Warn  about  accesses  to  elements of zero-length array members that might overlap other
           members of the same object.  Declaring interior zero-length arrays is discouraged because
           accesses to them are undefined.  See

           For example, the first two stores in function  "bad"  are  diagnosed  because  the  array
           elements  overlap  the  subsequent  members "b" and "c".  The third store is diagnosed by
           -Warray-bounds because it is beyond the bounds of the enclosing object.

                   struct X { int a[0]; int b, c; };
                   struct X x;

                   void bad (void)
                   {
                     x.a[0] = 0;   // -Wzero-length-bounds
                     x.a[1] = 1;   // -Wzero-length-bounds
                     x.a[2] = 2;   // -Warray-bounds
                   }

           Option -Wzero-length-bounds is enabled by -Warray-bounds.

       -Wno-div-by-zero
           Do not warn about compile-time integer division by zero.  Floating-point division by zero
           is not warned about, as it can be a legitimate way of obtaining infinities and NaNs.

       -Wsystem-headers
           Print warning messages for constructs found in system header files.  Warnings from system
           headers are normally suppressed, on the assumption that they usually do not indicate real
           problems and would only make the compiler output harder to read.  Using this command-line
           option tells GCC to emit warnings from system headers as if they occurred in  user  code.
           However,  note  that  using  -Wall  in  conjunction  with this option does not warn about
           unknown pragmas in system headers---for that, -Wunknown-pragmas must also be used.

       -Wtautological-compare
           Warn if a self-comparison always evaluates  to  true  or  false.   This  warning  detects
           various mistakes such as:

                   int i = 1;
                   ...
                   if (i > i) { ... }

           This  warning also warns about bitwise comparisons that always evaluate to true or false,
           for instance:

                   if ((a & 16) == 10) { ... }

           will always be false.

           This warning is enabled by -Wall.

       -Wtrampolines
           Warn about trampolines generated for pointers to nested functions.   A  trampoline  is  a
           small  piece of data or code that is created at run time on the stack when the address of
           a nested function is taken, and is used to call the nested function indirectly.  For some
           targets, it is made up of data only and thus requires no  special  treatment.   But,  for
           most  targets, it is made up of code and thus requires the stack to be made executable in
           order for the program to work properly.

       -Wfloat-equal
           Warn if floating-point values are used in equality comparisons.

           The idea behind this is that sometimes it is convenient (for the programmer) to  consider
           floating-point  values  as approximations to infinitely precise real numbers.  If you are
           doing this, then you need to compute (by analyzing the code, or in some  other  way)  the
           maximum  or  likely  maximum error that the computation introduces, and allow for it when
           performing comparisons (and when producing output, but that's a different  problem).   In
           particular,  instead  of  testing  for  equality, you should check to see whether the two
           values have ranges that overlap; and this is  done  with  the  relational  operators,  so
           equality comparisons are probably mistaken.

       -Wtraditional (C and Objective-C only)
           Warn  about  certain  constructs  that behave differently in traditional and ISO C.  Also
           warn about ISO C constructs that have no traditional  C  equivalent,  and/or  problematic
           constructs that should be avoided.

           *   Macro  parameters  that  appear  within  string  literals  in  the  macro  body.   In
               traditional C macro replacement takes place within string literals, but in ISO  C  it
               does not.

           *   In   traditional   C,  some  preprocessor  directives  did  not  exist.   Traditional
               preprocessors only considered a line to be a directive if the # appeared in column  1
               on  the  line.   Therefore  -Wtraditional  warns  about directives that traditional C
               understands but ignores because the # does not appear as the first character  on  the
               line.   It  also  suggests  you  hide  directives  like  "#pragma"  not understood by
               traditional C by indenting them.  Some traditional implementations do  not  recognize
               "#elif", so this option suggests avoiding it altogether.

           *   A function-like macro that appears without arguments.

           *   The unary plus operator.

           *   The  U  integer  constant  suffix,  or  the  F or L floating-point constant suffixes.
               (Traditional C does support the L suffix on integer constants.)  Note, these suffixes
               appear in macros defined in the system headers  of  most  modern  systems,  e.g.  the
               _MIN/_MAX  macros  in  "<limits.h>".  Use of these macros in user code might normally
               lead to spurious warnings, however GCC's integrated preprocessor has  enough  context
               to avoid warning in these cases.

           *   A function declared external in one block and then used after the end of the block.

           *   A "switch" statement has an operand of type "long".

           *   A  non-"static"  function  declaration follows a "static" one.  This construct is not
               accepted by some traditional C compilers.

           *   The ISO type of an integer constant has a different  width  or  signedness  from  its
               traditional  type.   This  warning is only issued if the base of the constant is ten.
               I.e. hexadecimal or octal values, which typically represent  bit  patterns,  are  not
               warned about.

           *   Usage of ISO string concatenation is detected.

           *   Initialization of automatic aggregates.

           *   Identifier  conflicts  with  labels.   Traditional  C  lacks a separate namespace for
               labels.

           *   Initialization of unions.  If the initializer is zero, the warning is omitted.   This
               is  done  under  the  assumption  that  the  zero  initializer  in  user code appears
               conditioned on e.g. "__STDC__" to avoid missing initializer warnings  and  relies  on
               default initialization to zero in the traditional C case.

           *   Conversions  by  prototypes  between fixed/floating-point values and vice versa.  The
               absence of  these  prototypes  when  compiling  with  traditional  C  causes  serious
               problems.  This is a subset of the possible conversion warnings; for the full set use
               -Wtraditional-conversion.

           *   Use  of  ISO  C style function definitions.  This warning intentionally is not issued
               for prototype declarations or variadic functions because these ISO C features  appear
               in  your code when using libiberty's traditional C compatibility macros, "PARAMS" and
               "VPARAMS".  This warning is also bypassed for nested functions because  that  feature
               is already a GCC extension and thus not relevant to traditional C compatibility.

       -Wtraditional-conversion (C and Objective-C only)
           Warn  if a prototype causes a type conversion that is different from what would happen to
           the same argument in the absence of a prototype.   This  includes  conversions  of  fixed
           point  to  floating and vice versa, and conversions changing the width or signedness of a
           fixed-point argument except when the same as the default promotion.

       -Wdeclaration-after-statement (C and Objective-C only)
           Warn when a declaration is found after a statement in a  block.   This  construct,  known
           from  C++,  was  introduced  with  ISO  C99  and is by default allowed in GCC.  It is not
           supported by ISO C90.

       -Wshadow
           Warn whenever a local variable or type declaration shadows another  variable,  parameter,
           type, class member (in C++), or instance variable (in Objective-C) or whenever a built-in
           function  is  shadowed.  Note that in C++, the compiler warns if a local variable shadows
           an explicit typedef, but not if it shadows  a  struct/class/enum.   If  this  warning  is
           enabled,   it   includes  also  all  instances  of  local  shadowing.   This  means  that
           -Wno-shadow=local and -Wno-shadow=compatible-local are ignored  when  -Wshadow  is  used.
           Same as -Wshadow=global.

       -Wno-shadow-ivar (Objective-C only)
           Do  not  warn  whenever  a  local variable shadows an instance variable in an Objective-C
           method.

       -Wshadow=global
           Warn for any shadowing.  Same as -Wshadow.

       -Wshadow=local
           Warn when a local variable shadows another local variable or parameter.

       -Wshadow=compatible-local
           Warn when a local variable shadows another local variable  or  parameter  whose  type  is
           compatible  with  that  of the shadowing variable.  In C++, type compatibility here means
           the type of the shadowing variable can be converted to that  of  the  shadowed  variable.
           The  creation of this flag (in addition to -Wshadow=local) is based on the idea that when
           a local variable shadows another one of incompatible type, it is most likely intentional,
           not a bug or typo, as shown in the following example:

                   for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i)
                   {
                     for (int i = 0; i < N; ++i)
                     {
                       ...
                     }
                     ...
                   }

           Since the two variable "i" in the example above have incompatible  types,  enabling  only
           -Wshadow=compatible-local does not emit a warning.  Because their types are incompatible,
           if a programmer accidentally uses one in place of the other, type checking is expected to
           catch  that and emit an error or warning.  Use of this flag instead of -Wshadow=local can
           possibly reduce the number of warnings triggered by  intentional  shadowing.   Note  that
           this also means that shadowing "const char *i" by "char *i" does not emit a warning.

           This warning is also enabled by -Wshadow=local.

       -Wlarger-than=byte-size
           Warn    whenever    an    object    is    defined    whose    size   exceeds   byte-size.
           -Wlarger-than=PTRDIFF_MAX is enabled by default.  Warnings controlled by the  option  can
           be disabled either by specifying byte-size of SIZE_MAX or more or by -Wno-larger-than.

           Also  warn  for  calls  to bounded functions such as "memchr" or "strnlen" that specify a
           bound greater than the largest possible object, which is PTRDIFF_MAX  bytes  by  default.
           These warnings can only be disabled by -Wno-larger-than.

       -Wno-larger-than
           Disable  -Wlarger-than=  warnings.  The option is equivalent to -Wlarger-than=SIZE_MAX or
           larger.

       -Wframe-larger-than=byte-size
           Warn if the size of  a  function  frame  exceeds  byte-size.   The  computation  done  to
           determine  the  stack  frame  size  is  approximate  and  not  conservative.   The actual
           requirements may be somewhat greater than byte-size even if you do not get a warning.  In
           addition, any space allocated via "alloca", variable-length arrays, or related constructs
           is not included by the compiler when determining whether  or  not  to  issue  a  warning.
           -Wframe-larger-than=PTRDIFF_MAX is enabled by default.  Warnings controlled by the option
           can   be   disabled   either   by   specifying  byte-size  of  SIZE_MAX  or  more  or  by
           -Wno-frame-larger-than.

       -Wno-frame-larger-than
           Disable    -Wframe-larger-than=    warnings.     The    option    is    equivalent     to
           -Wframe-larger-than=SIZE_MAX or larger.

       -Wno-free-nonheap-object
           Warn  when  attempting to deallocate an object that was either not allocated on the heap,
           or by using a pointer that was not returned  from  a  prior  call  to  the  corresponding
           allocation  function.  For example, because the call to "stpcpy" returns a pointer to the
           terminating nul character and not to the begginning of the object,  the  call  to  "free"
           below is diagnosed.

                   void f (char *p)
                   {
                     p = stpcpy (p, "abc");
                     // ...
                     free (p);   // warning
                   }

           -Wfree-nonheap-object is enabled by default.

       -Wstack-usage=byte-size
           Warn  if  the  stack usage of a function might exceed byte-size.  The computation done to
           determine the stack usage is conservative.  Any space allocated via  "alloca",  variable-
           length arrays, or related constructs is included by the compiler when determining whether
           or not to issue a warning.

           The message is in keeping with the output of -fstack-usage.

           *   If the stack usage is fully static but exceeds the specified amount, it's:

                         warning: stack usage is 1120 bytes

           *   If the stack usage is (partly) dynamic but bounded, it's:

                         warning: stack usage might be 1648 bytes

           *   If the stack usage is (partly) dynamic and not bounded, it's:

                         warning: stack usage might be unbounded

           -Wstack-usage=PTRDIFF_MAX  is  enabled by default.  Warnings controlled by the option can
           be disabled either by specifying byte-size of SIZE_MAX or more or by -Wno-stack-usage.

       -Wno-stack-usage
           Disable -Wstack-usage= warnings.  The option is equivalent to  -Wstack-usage=SIZE_MAX  or
           larger.

       -Wunsafe-loop-optimizations
           Warn  if  the loop cannot be optimized because the compiler cannot assume anything on the
           bounds of the loop indices.  With -funsafe-loop-optimizations warn if the compiler  makes
           such assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
           When  used in combination with -Wformat and -pedantic without GNU extensions, this option
           disables the warnings about non-ISO "printf" / "scanf"  format  width  specifiers  "I32",
           "I64", and "I" used on Windows targets, which depend on the MS runtime.

       -Wpointer-arith
           Warn  about  anything  that depends on the "size of" a function type or of "void".  GNU C
           assigns these types a size of 1, for convenience in calculations with "void  *"  pointers
           and  pointers  to  functions.   In  C++,  warn also when an arithmetic operation involves
           "NULL".  This warning is also enabled by -Wpedantic.

       -Wno-pointer-compare
           Do not warn if a pointer is compared with a zero character constant.  This usually  means
           that the pointer was meant to be dereferenced.  For example:

                   const char *p = foo ();
                   if (p == '\0')
                     return 42;

           Note that the code above is invalid in C++11.

           This warning is enabled by default.

       -Wtsan
           Warn about unsupported features in ThreadSanitizer.

           ThreadSanitizer   does  not  support  "std::atomic_thread_fence"  and  can  report  false
           positives.

           This warning is enabled by default.

       -Wtype-limits
           Warn if a comparison is always true or always false due to the limited range of the  data
           type,  but  do  not  warn  for  constant  expressions.   For example, warn if an unsigned
           variable is compared against zero with "<" or ">=".  This  warning  is  also  enabled  by
           -Wextra.

       -Wabsolute-value (C and Objective-C only)
           Warn  for calls to standard functions that compute the absolute value of an argument when
           a more appropriate standard  function  is  available.   For  example,  calling  abs(3.14)
           triggers  the  warning  because  the appropriate function to call to compute the absolute
           value of a double argument is  "fabs".   The  option  also  triggers  warnings  when  the
           argument  in  a  call  to  such  a  function  has  an unsigned type.  This warning can be
           suppressed with an explicit type cast and it is also enabled by -Wextra.

       -Wcomment
       -Wcomments
           Warn whenever a comment-start sequence  /*  appears  in  a  /*  comment,  or  whenever  a
           backslash-newline appears in a // comment.  This warning is enabled by -Wall.

       -Wtrigraphs
           Warn  if  any  trigraphs  are  encountered  that might change the meaning of the program.
           Trigraphs within comments are not warned about, except  those  that  would  form  escaped
           newlines.

           This  option  is  implied  by -Wall.  If -Wall is not given, this option is still enabled
           unless trigraphs are enabled.  To get trigraph conversion without warnings, but  get  the
           other -Wall warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wundef
           Warn if an undefined identifier is evaluated in an "#if" directive.  Such identifiers are
           replaced with zero.

       -Wexpansion-to-defined
           Warn  whenever  defined  is  encountered  in the expansion of a macro (including the case
           where the macro is expanded by an #if directive).  Such  usage  is  not  portable.   This
           warning is also enabled by -Wpedantic and -Wextra.

       -Wunused-macros
           Warn  about  macros  defined  in the main file that are unused.  A macro is used if it is
           expanded or tested for existence at least once.  The preprocessor also warns if the macro
           has not been used at the time it is redefined or undefined.

           Built-in macros, macros defined on the command line, and macros defined in include  files
           are not warned about.

           Note:  If a macro is actually used, but only used in skipped conditional blocks, then the
           preprocessor reports it as unused.  To avoid the  warning  in  such  a  case,  you  might
           improve  the  scope  of  the macro's definition by, for example, moving it into the first
           skipped block.  Alternatively, you could provide a dummy use with something like:

                   #if defined the_macro_causing_the_warning
                   #endif

       -Wno-endif-labels
           Do not warn whenever an "#else" or an "#endif" are  followed  by  text.   This  sometimes
           happens in older programs with code of the form

                   #if FOO
                   ...
                   #else FOO
                   ...
                   #endif FOO

           The second and third "FOO" should be in comments.  This warning is on by default.

       -Wbad-function-cast (C and Objective-C only)
           Warn when a function call is cast to a non-matching type.  For example, warn if a call to
           a function returning an integer type is cast to a pointer type.

       -Wc90-c99-compat (C and Objective-C only)
           Warn  about  features not present in ISO C90, but present in ISO C99.  For instance, warn
           about use of variable length arrays, "long long" type, "bool"  type,  compound  literals,
           designated  initializers,  and  so on.  This option is independent of the standards mode.
           Warnings are disabled in the expression that follows "__extension__".

       -Wc99-c11-compat (C and Objective-C only)
           Warn about features not present in ISO C99, but present in ISO C11.  For  instance,  warn
           about  use  of anonymous structures and unions, "_Atomic" type qualifier, "_Thread_local"
           storage-class specifier, "_Alignas" specifier, "Alignof"  operator,  "_Generic"  keyword,
           and  so  on.  This option is independent of the standards mode.  Warnings are disabled in
           the expression that follows "__extension__".

       -Wc11-c2x-compat (C and Objective-C only)
           Warn about features not present in ISO C11, but present in ISO C2X.  For  instance,  warn
           about  omitting the string in "_Static_assert", use of [[]] syntax for attributes, use of
           decimal floating-point types, and so on.  This option is  independent  of  the  standards
           mode.  Warnings are disabled in the expression that follows "__extension__".

       -Wc++-compat (C and Objective-C only)
           Warn  about  ISO C constructs that are outside of the common subset of ISO C and ISO C++,
           e.g. request for implicit conversion from "void *" to a pointer to non-"void" type.

       -Wc++11-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 1998 and  ISO  C++  2011,
           e.g.,  identifiers in ISO C++ 1998 that are keywords in ISO C++ 2011.  This warning turns
           on -Wnarrowing and is enabled by -Wall.

       -Wc++14-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2011 and  ISO  C++  2014.
           This warning is enabled by -Wall.

       -Wc++17-compat (C++ and Objective-C++ only)
           Warn  about  C++  constructs whose meaning differs between ISO C++ 2014 and ISO C++ 2017.
           This warning is enabled by -Wall.

       -Wc++20-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2017 and  ISO  C++  2020.
           This warning is enabled by -Wall.

       -Wcast-qual
           Warn  whenever  a  pointer is cast so as to remove a type qualifier from the target type.
           For example, warn if a "const char *" is cast to an ordinary "char *".

           Also warn when making a cast that introduces a type qualifier  in  an  unsafe  way.   For
           example, casting "char **" to "const char **" is unsafe, as in this example:

                     /* p is char ** value.  */
                     const char **q = (const char **) p;
                     /* Assignment of readonly string to const char * is OK.  */
                     *q = "string";
                     /* Now char** pointer points to read-only memory.  */
                     **p = 'b';

       -Wcast-align
           Warn  whenever  a  pointer  is  cast  such  that  the required alignment of the target is
           increased.  For example, warn if a "char *" is cast to  an  "int  *"  on  machines  where
           integers can only be accessed at two- or four-byte boundaries.

       -Wcast-align=strict
           Warn  whenever  a  pointer  is  cast  such  that  the required alignment of the target is
           increased.  For example, warn if a "char *" is cast to  an  "int  *"  regardless  of  the
           target machine.

       -Wcast-function-type
           Warn  when  a  function  pointer  is cast to an incompatible function pointer.  In a cast
           involving function types with  a  variable  argument  list  only  the  types  of  initial
           arguments  that  are  provided are considered.  Any parameter of pointer-type matches any
           other pointer-type.  Any benign differences in integral types are ignored, like "int" vs.
           "long" on ILP32 targets.  Likewise type qualifiers are ignored.  The function type  "void
           (*)  (void)"  is  special  and  matches  everything,  which  can be used to suppress this
           warning.  In a cast involving pointer to member types this  warning  warns  whenever  the
           type cast is changing the pointer to member type.  This warning is enabled by -Wextra.

       -Wwrite-strings
           When compiling C, give string constants the type "const char[length]" so that copying the
           address  of  one  into a non-"const" "char *" pointer produces a warning.  These warnings
           help you find at compile time code that can try to write into a string constant, but only
           if you have been very  careful  about  using  "const"  in  declarations  and  prototypes.
           Otherwise,  it  is  just  a  nuisance.  This  is  why we did not make -Wall request these
           warnings.

           When compiling C++, warn about the deprecated conversion from string  literals  to  "char
           *".  This warning is enabled by default for C++ programs.

       -Wclobbered
           Warn  for  variables that might be changed by "longjmp" or "vfork".  This warning is also
           enabled by -Wextra.

       -Wconversion
           Warn for implicit conversions that may alter a value. This includes  conversions  between
           real  and  integer,  like  "abs (x)" when "x" is "double"; conversions between signed and
           unsigned, like "unsigned ui = -1"; and conversions to smaller types, like "sqrtf (M_PI)".
           Do not warn for explicit casts like "abs ((int) x)" and "ui = (unsigned) -1", or  if  the
           value  is  not changed by the conversion like in "abs (2.0)".  Warnings about conversions
           between signed and unsigned integers can be disabled by using -Wno-sign-conversion.

           For C++, also warn for confusing overload resolution for  user-defined  conversions;  and
           conversions  that  never  use a type conversion operator: conversions to "void", the same
           type, a base class or a reference to them. Warnings about conversions between signed  and
           unsigned  integers  are disabled by default in C++ unless -Wsign-conversion is explicitly
           enabled.

           Warnings about conversion from arithmetic on a small type back  to  that  type  are  only
           given with -Warith-conversion.

       -Wdangling-else
           Warn  about  constructions where there may be confusion to which "if" statement an "else"
           branch belongs.  Here is an example of such a case:

                   {
                     if (a)
                       if (b)
                         foo ();
                     else
                       bar ();
                   }

           In C/C++, every "else" branch belongs to the innermost possible "if" statement, which  in
           this example is "if (b)".  This is often not what the programmer expected, as illustrated
           in  the  above  example by indentation the programmer chose.  When there is the potential
           for this confusion, GCC issues a warning when this flag is specified.  To  eliminate  the
           warning,  add  explicit braces around the innermost "if" statement so there is no way the
           "else" can belong to the enclosing "if".  The resulting code looks like this:

                   {
                     if (a)
                       {
                         if (b)
                           foo ();
                         else
                           bar ();
                       }
                   }

           This warning is enabled by -Wparentheses.

       -Wdate-time
           Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are encountered as they  might
           prevent bit-wise-identical reproducible compilations.

       -Wempty-body
           Warn if an empty body occurs in an "if", "else" or "do while" statement.  This warning is
           also enabled by -Wextra.

       -Wno-endif-labels
           Do not warn about stray tokens after "#else" and "#endif".

       -Wenum-compare
           Warn  about a comparison between values of different enumerated types.  In C++ enumerated
           type mismatches in conditional expressions are also diagnosed and the warning is  enabled
           by default.  In C this warning is enabled by -Wall.

       -Wenum-conversion
           Warn  when  a  value of enumerated type is implicitly converted to a different enumerated
           type.  This warning is enabled by -Wextra in C.

       -Wjump-misses-init (C, Objective-C only)
           Warn  if  a  "goto"  statement  or  a  "switch"  statement  jumps  forward   across   the
           initialization  of  a  variable, or jumps backward to a label after the variable has been
           initialized.  This only  warns  about  variables  that  are  initialized  when  they  are
           declared.   This  warning  is  only  supported for C and Objective-C; in C++ this sort of
           branch is an error in any case.

           -Wjump-misses-init  is  included  in  -Wc++-compat.   It  can  be   disabled   with   the
           -Wno-jump-misses-init option.

       -Wsign-compare
           Warn  when  a  comparison  between  signed and unsigned values could produce an incorrect
           result when the signed value is converted to unsigned.  In  C++,  this  warning  is  also
           enabled by -Wall.  In C, it is also enabled by -Wextra.

       -Wsign-conversion
           Warn  for  implicit  conversions  that  may  change  the  sign  of an integer value, like
           assigning a signed integer expression to an unsigned integer variable. An  explicit  cast
           silences the warning. In C, this option is enabled also by -Wconversion.

       -Wfloat-conversion
           Warn  for  implicit conversions that reduce the precision of a real value.  This includes
           conversions from real to integer, and from higher precision real to lower precision  real
           values.  This option is also enabled by -Wconversion.

       -Wno-scalar-storage-order
           Do not warn on suspicious constructs involving reverse scalar storage order.

       -Wsizeof-array-div
           Warn  about  divisions  of two sizeof operators when the first one is applied to an array
           and the divisor does not equal the size of the  array  element.   In  such  a  case,  the
           computation  will not yield the number of elements in the array, which is likely what the
           user intended.  This warning warns e.g. about

                   int fn ()
                   {
                     int arr[10];
                     return sizeof (arr) / sizeof (short);
                   }

           This warning is enabled by -Wall.

       -Wsizeof-pointer-div
           Warn for suspicious divisions of two sizeof expressions that divide the pointer  size  by
           the  element  size,  which  is the usual way to compute the array size but won't work out
           correctly with pointers.  This warning warns e.g. about "sizeof (ptr) / sizeof  (ptr[0])"
           if "ptr" is not an array, but a pointer.  This warning is enabled by -Wall.

       -Wsizeof-pointer-memaccess
           Warn  for suspicious length parameters to certain string and memory built-in functions if
           the argument uses "sizeof".  This warning triggers  for  example  for  "memset  (ptr,  0,
           sizeof  (ptr));" if "ptr" is not an array, but a pointer, and suggests a possible fix, or
           about "memcpy (&foo, ptr, sizeof (&foo));".  -Wsizeof-pointer-memaccess also warns  about
           calls  to  bounded  string copy functions like "strncat" or "strncpy" that specify as the
           bound a "sizeof" expression of the source array.  For example, in the following  function
           the  call  to  "strncat"  specifies  the size of the source string as the bound.  That is
           almost certainly a mistake and so the call is diagnosed.

                   void make_file (const char *name)
                   {
                     char path[PATH_MAX];
                     strncpy (path, name, sizeof path - 1);
                     strncat (path, ".text", sizeof ".text");
                     ...
                   }

           The -Wsizeof-pointer-memaccess option is enabled by -Wall.

       -Wno-sizeof-array-argument
           Do not warn when the "sizeof" operator is applied to a parameter that is declared  as  an
           array  in  a  function  definition.   This  warning  is  enabled by default for C and C++
           programs.

       -Wmemset-elt-size
           Warn for suspicious calls to the  "memset"  built-in  function,  if  the  first  argument
           references  an array, and the third argument is a number equal to the number of elements,
           but not equal to the size of the array in memory.   This  indicates  that  the  user  has
           omitted a multiplication by the element size.  This warning is enabled by -Wall.

       -Wmemset-transposed-args
           Warn  for suspicious calls to the "memset" built-in function where the second argument is
           not zero and the third argument is zero.  For example, the call "memset (buf, sizeof buf,
           0)" is diagnosed because "memset (buf, 0, sizeof buf)" was meant instead.  The diagnostic
           is only emitted if the third argument  is  a  literal  zero.   Otherwise,  if  it  is  an
           expression  that is folded to zero, or a cast of zero to some type, it is far less likely
           that the arguments have been mistakenly transposed  and  no  warning  is  emitted.   This
           warning is enabled by -Wall.

       -Waddress
           Warn  about  suspicious  uses  of  memory addresses. These include using the address of a
           function in  a  conditional  expression,  such  as  "void  func(void);  if  (func)",  and
           comparisons  against  the  memory address of a string literal, such as "if (x == "abc")".
           Such uses typically indicate a  programmer  error:  the  address  of  a  function  always
           evaluates  to  true,  so  their use in a conditional usually indicate that the programmer
           forgot the parentheses in a function call; and comparisons against string literals result
           in unspecified behavior and are not portable in C, so  they  usually  indicate  that  the
           programmer intended to use "strcmp".  This warning is enabled by -Wall.

       -Wno-address-of-packed-member
           Do  not warn when the address of packed member of struct or union is taken, which usually
           results in an unaligned pointer value.  This is enabled by default.

       -Wlogical-op
           Warn about suspicious uses of logical operators  in  expressions.   This  includes  using
           logical  operators  in contexts where a bit-wise operator is likely to be expected.  Also
           warns when the operands of a logical operator are the same:

                   extern int a;
                   if (a < 0 && a < 0) { ... }

       -Wlogical-not-parentheses
           Warn about logical not used on the left hand side operand of a comparison.   This  option
           does not warn if the right operand is considered to be a boolean expression.  Its purpose
           is to detect suspicious code like the following:

                   int a;
                   ...
                   if (!a > 1) { ... }

           It is possible to suppress the warning by wrapping the LHS into parentheses:

                   if ((!a) > 1) { ... }

           This warning is enabled by -Wall.

       -Waggregate-return
           Warn  if  any  functions  that  return  structures  or unions are defined or called.  (In
           languages where you can return an array, this also elicits a warning.)

       -Wno-aggressive-loop-optimizations
           Warn if in a loop with constant number  of  iterations  the  compiler  detects  undefined
           behavior in some statement during one or more of the iterations.

       -Wno-attributes
           Do  not  warn  if an unexpected "__attribute__" is used, such as unrecognized attributes,
           function attributes applied to variables, etc.  This does not stop errors  for  incorrect
           use of supported attributes.

       -Wno-builtin-declaration-mismatch
           Warn  if  a  built-in  function  is  declared with an incompatible signature or as a non-
           function, or when a built-in function declared with  a  type  that  does  not  include  a
           prototype  is  called  with arguments whose promoted types do not match those expected by
           the function.  When -Wextra is specified, also warn when a built-in function  that  takes
           arguments is declared without a prototype.  The -Wbuiltin-declaration-mismatch warning is
           enabled  by  default.   To  avoid the warning include the appropriate header to bring the
           prototypes of built-in functions into scope.

           For example, the call to "memset" below is diagnosed by the warning because the  function
           expects  a  value  of  type  "size_t"  as its argument but the type of 32 is "int".  With
           -Wextra, the declaration of the function is diagnosed as well.

                   extern void* memset ();
                   void f (void *d)
                   {
                     memset (d, '\0', 32);
                   }

       -Wno-builtin-macro-redefined
           Do not warn if certain built-in macros  are  redefined.   This  suppresses  warnings  for
           redefinition of "__TIMESTAMP__", "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
           Warn  if  a  function  is declared or defined without specifying the argument types.  (An
           old-style function definition is permitted without a warning if preceded by a declaration
           that specifies the argument types.)

       -Wold-style-declaration (C and Objective-C only)
           Warn for obsolescent usages, according to the C Standard, in a declaration. For  example,
           warn if storage-class specifiers like "static" are not the first things in a declaration.
           This warning is also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
           Warn  if an old-style function definition is used.  A warning is given even if there is a
           previous prototype.  A definition using () is not considered an old-style  definition  in
           C2X mode, because it is equivalent to (void) in that case, but is considered an old-style
           definition for older standards.

       -Wmissing-parameter-type (C and Objective-C only)
           A function parameter is declared without a type specifier in K&R-style functions:

                   void foo(bar) { }

           This warning is also enabled by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
           Warn  if  a  global  function  is defined without a previous prototype declaration.  This
           warning is issued even if the definition itself provides a prototype.  Use this option to
           detect global functions that do not have a matching prototype  declaration  in  a  header
           file.   This  option  is  not  valid  for  C++  because all function declarations provide
           prototypes and a non-matching declaration declares an overload rather than conflict  with
           an  earlier  declaration.   Use  -Wmissing-declarations to detect missing declarations in
           C++.

       -Wmissing-declarations
           Warn if a global function is defined without a previous declaration.  Do so even  if  the
           definition  itself provides a prototype.  Use this option to detect global functions that
           are not declared in header files.  In C,  no  warnings  are  issued  for  functions  with
           previous   non-prototype   declarations;   use  -Wmissing-prototypes  to  detect  missing
           prototypes.  In C++, no warnings  are  issued  for  function  templates,  or  for  inline
           functions, or for functions in anonymous namespaces.

       -Wmissing-field-initializers
           Warn  if  a  structure's initializer has some fields missing.  For example, the following
           code causes such a warning, because "x.h" is implicitly zero:

                   struct s { int f, g, h; };
                   struct s x = { 3, 4 };

           This option does not warn about designated initializers, so  the  following  modification
           does not trigger a warning:

                   struct s { int f, g, h; };
                   struct s x = { .f = 3, .g = 4 };

           In C this option does not warn about the universal zero initializer { 0 }:

                   struct s { int f, g, h; };
                   struct s x = { 0 };

           Likewise, in C++ this option does not warn about the empty { } initializer, for example:

                   struct s { int f, g, h; };
                   s x = { };

           This warning is included in -Wextra.  To get other -Wextra warnings without this one, use
           -Wextra -Wno-missing-field-initializers.

       -Wno-multichar
           Do  not warn if a multicharacter constant ('FOOF') is used.  Usually they indicate a typo
           in the user's code, as they have implementation-defined values, and should not be used in
           portable code.

       -Wnormalized=[none|id|nfc|nfkc]
           In ISO C and ISO C++, two identifiers are different if they are  different  sequences  of
           characters.  However, sometimes when characters outside the basic ASCII character set are
           used,  you  can  have  two  different  character  sequences that look the same.  To avoid
           confusion, the ISO 10646 standard sets out some normalization rules  which  when  applied
           ensure  that two sequences that look the same are turned into the same sequence.  GCC can
           warn you if you are using identifiers that have not been normalized; this option controls
           that warning.

           There are four levels of warning supported by  GCC.   The  default  is  -Wnormalized=nfc,
           which  warns  about any identifier that is not in the ISO 10646 "C" normalized form, NFC.
           NFC is the recommended form for most uses.  It is equivalent to -Wnormalized.

           Unfortunately, there are some characters allowed in identifiers by  ISO  C  and  ISO  C++
           that,  when  turned into NFC, are not allowed in identifiers.  That is, there's no way to
           use these symbols in portable ISO C  or  C++  and  have  all  your  identifiers  in  NFC.
           -Wnormalized=id  suppresses  the  warning  for these characters.  It is hoped that future
           versions of the standards involved will correct this, which is why this option is not the
           default.

           You can switch the warning  off  for  all  characters  by  writing  -Wnormalized=none  or
           -Wno-normalized.   You  should  only  do  this  if you are using some other normalization
           scheme (like "D"), because otherwise you  can  easily  create  bugs  that  are  literally
           impossible to see.

           Some  characters  in ISO 10646 have distinct meanings but look identical in some fonts or
           display methodologies,  especially  once  formatting  has  been  applied.   For  instance
           "\u207F",  "SUPERSCRIPT  LATIN SMALL LETTER N", displays just like a regular "n" that has
           been placed in a superscript.  ISO 10646 defines the NFKC normalization scheme to convert
           all these into a standard form as well, and GCC warns if your code is not in NFKC if  you
           use -Wnormalized=nfkc.  This warning is comparable to warning about every identifier that
           contains  the  letter  O because it might be confused with the digit 0, and so is not the
           default, but may be useful as a local coding convention if  the  programming  environment
           cannot be fixed to display these characters distinctly.

       -Wno-attribute-warning
           Do not warn about usage of functions declared with "warning" attribute.  By default, this
           warning  is  enabled.   -Wno-attribute-warning  can  be  used  to  disable the warning or
           -Wno-error=attribute-warning can be used to disable the error when compiled with  -Werror
           flag.

       -Wno-deprecated
           Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
           Do  not  warn about uses of functions, variables, and types marked as deprecated by using
           the "deprecated" attribute.

       -Wno-overflow
           Do not warn about compile-time overflow in constant expressions.

       -Wno-odr
           Warn about One Definition Rule violations  during  link-time  optimization.   Enabled  by
           default.

       -Wopenmp-simd
           Warn  if  the vectorizer cost model overrides the OpenMP simd directive set by user.  The
           -fsimd-cost-model=unlimited option can be used to relax the cost model.

       -Woverride-init (C and Objective-C only)
           Warn if an initialized field without side effects is  overridden  when  using  designated
           initializers.

           This warning is included in -Wextra.  To get other -Wextra warnings without this one, use
           -Wextra -Wno-override-init.

       -Wno-override-init-side-effects (C and Objective-C only)
           Do not warn if an initialized field with side effects is overridden when using designated
           initializers.  This warning is enabled by default.

       -Wpacked
           Warn if a structure is given the packed attribute, but the packed attribute has no effect
           on  the  layout  or size of the structure.  Such structures may be mis-aligned for little
           benefit.  For instance, in this code, the variable "f.x" in "struct  bar"  is  misaligned
           even though "struct bar" does not itself have the packed attribute:

                   struct foo {
                     int x;
                     char a, b, c, d;
                   } __attribute__((packed));
                   struct bar {
                     char z;
                     struct foo f;
                   };

       -Wnopacked-bitfield-compat
           The  4.1,  4.2  and 4.3 series of GCC ignore the "packed" attribute on bit-fields of type
           "char".  This was fixed in GCC 4.4  but  the  change  can  lead  to  differences  in  the
           structure  layout.   GCC  informs  you when the offset of such a field has changed in GCC
           4.4.  For example there is no longer a 4-bit padding between field "a" and  "b"  in  this
           structure:

                   struct foo
                   {
                     char a:4;
                     char b:8;
                   } __attribute__ ((packed));

           This  warning  is  enabled  by  default.  Use -Wno-packed-bitfield-compat to disable this
           warning.

       -Wpacked-not-aligned (C, C++, Objective-C and Objective-C++ only)
           Warn if a structure field with explicitly specified alignment in a packed struct or union
           is misaligned.  For example, a warning will be issued  on  "struct  S",  like,  "warning:
           alignment 1 of 'struct S' is less than 8", in this code:

                   struct __attribute__ ((aligned (8))) S8 { char a[8]; };
                   struct __attribute__ ((packed)) S {
                     struct S8 s8;
                   };

           This warning is enabled by -Wall.

       -Wpadded
           Warn  if  padding is included in a structure, either to align an element of the structure
           or to align the whole structure.  Sometimes when this happens it is possible to rearrange
           the fields of the structure to reduce the padding and so make the structure smaller.

       -Wredundant-decls
           Warn if anything is declared more than once in  the  same  scope,  even  in  cases  where
           multiple declaration is valid and changes nothing.

       -Wrestrict
           Warn  when  an  object  referenced  by  a  "restrict"-qualified  parameter (or, in C++, a
           "__restrict"-qualified parameter) is aliased by another argument, or when copies  between
           such  objects  overlap.  For example, the call to the "strcpy" function below attempts to
           truncate the string by replacing its initial characters with  the  last  four.   However,
           because  the call writes the terminating NUL into "a[4]", the copies overlap and the call
           is diagnosed.

                   void foo (void)
                   {
                     char a[] = "abcd1234";
                     strcpy (a, a + 4);
                     ...
                   }

           The -Wrestrict option detects some instances of simple overlap even without  optimization
           but works best at -O2 and above.  It is included in -Wall.

       -Wnested-externs (C and Objective-C only)
           Warn if an "extern" declaration is encountered within a function.

       -Winline
           Warn  if a function that is declared as inline cannot be inlined.  Even with this option,
           the compiler does not warn about failures to inline functions declared in system headers.

           The compiler uses a variety of heuristics  to  determine  whether  or  not  to  inline  a
           function.   For  example,  the compiler takes into account the size of the function being
           inlined and the amount of inlining that has already been done in  the  current  function.
           Therefore,  seemingly  insignificant changes in the source program can cause the warnings
           produced by -Winline to appear or disappear.

       -Wint-in-bool-context
           Warn for suspicious use of integer values where boolean  values  are  expected,  such  as
           conditional expressions (?:) using non-boolean integer constants in boolean context, like
           "if (a <= b ? 2 : 3)".  Or left shifting of signed integers in boolean context, like "for
           (a = 0; 1 << a; a++);".  Likewise for all kinds of multiplications regardless of the data
           type.  This warning is enabled by -Wall.

       -Wno-int-to-pointer-cast
           Suppress  warnings  from casts to pointer type of an integer of a different size. In C++,
           casting to a pointer type of smaller size is an error. Wint-to-pointer-cast is enabled by
           default.

       -Wno-pointer-to-int-cast (C and Objective-C only)
           Suppress warnings from casts from a pointer to an integer type of a different size.

       -Winvalid-pch
           Warn if a precompiled header is found in the search path but cannot be used.

       -Wlong-long
           Warn if "long long" type is used.  This is enabled by either -Wpedantic or  -Wtraditional
           in ISO C90 and C++98 modes.  To inhibit the warning messages, use -Wno-long-long.

       -Wvariadic-macros
           Warn  if variadic macros are used in ISO C90 mode, or if the GNU alternate syntax is used
           in ISO C99 mode.  This is enabled by either -Wpedantic or -Wtraditional.  To inhibit  the
           warning messages, use -Wno-variadic-macros.

       -Wno-varargs
           Do  not warn upon questionable usage of the macros used to handle variable arguments like
           "va_start".  These warnings are enabled by default.

       -Wvector-operation-performance
           Warn if vector operation is not implemented via SIMD capabilities  of  the  architecture.
           Mainly   useful  for  the  performance  tuning.   Vector  operation  can  be  implemented
           "piecewise", which means that the scalar operation is performed on every vector  element;
           "in  parallel",  which  means  that  the vector operation is implemented using scalars of
           wider type, which normally is more performance efficient; and "as a single scalar", which
           means that vector fits into a scalar type.

       -Wvla
           Warn if a variable-length array is used in the code.  -Wno-vla  prevents  the  -Wpedantic
           warning of the variable-length array.

       -Wvla-larger-than=byte-size
           If  this  option  is  used, the compiler warns for declarations of variable-length arrays
           whose size is either unbounded, or bounded by an argument that allows the array  size  to
           exceed byte-size bytes.  This is similar to how -Walloca-larger-than=byte-size works, but
           with variable-length arrays.

           Note  that  GCC  may  optimize  small  variable-length arrays of a known value into plain
           arrays, so this warning may not get triggered for such arrays.

           -Wvla-larger-than=PTRDIFF_MAX is enabled by default but is typically only effective  when
           -ftree-vrp is active (default for -O2 and above).

           See also -Walloca-larger-than=byte-size.

       -Wno-vla-larger-than
           Disable     -Wvla-larger-than=     warnings.      The    option    is    equivalent    to
           -Wvla-larger-than=SIZE_MAX or larger.

       -Wvla-parameter
           Warn about redeclarations of functions involving arguments of Variable Length Array types
           of inconsistent kinds or forms, and enable the detection  of  out-of-bounds  accesses  to
           such parameters by warnings such as -Warray-bounds.

           If  the  first function declaration uses the VLA form the bound specified in the array is
           assumed to be the minimum number of elements expected to be  provided  in  calls  to  the
           function and the maximum number of elements accessed by it.  Failing to provide arguments
           of  sufficient  size  or  accessing  more  than  the  maximum  number  of elements may be
           diagnosed.

           For example, the warning triggers for the following redeclarations because the first  one
           allows  an  array of any size to be passed to "f" while the second one specifies that the
           array argument must have at least "n"  elements.   In  addition,  calling  "f"  with  the
           assotiated  VLA  bound  parameter in excess of the actual VLA bound triggers a warning as
           well.

                   void f (int n, int[n]);
                   void f (int, int[]);     // warning: argument 2 previously declared as a VLA

                   void g (int n)
                   {
                       if (n > 4)
                         return;
                       int a[n];
                       f (sizeof a, a);     // warning: access to a by f may be out of bounds
                     ...
                   }

           -Wvla-parameter is included in -Wall.  The -Warray-parameter option triggers warnings for
           similar problems involving ordinary array arguments.

       -Wvolatile-register-var
           Warn if a register variable is declared volatile.  The volatile modifier does not inhibit
           all optimizations that may eliminate reads and/or writes  to  register  variables.   This
           warning is enabled by -Wall.

       -Wdisabled-optimization
           Warn  if  a  requested  optimization  pass  is disabled.  This warning does not generally
           indicate that there is anything wrong with your code;  it  merely  indicates  that  GCC's
           optimizers  are  unable  to handle the code effectively.  Often, the problem is that your
           code is too big or too complex; GCC refuses to optimize programs  when  the  optimization
           itself is likely to take inordinate amounts of time.

       -Wpointer-sign (C and Objective-C only)
           Warn  for  pointer argument passing or assignment with different signedness.  This option
           is only supported for C and Objective-C.  It is implied by -Wall and by -Wpedantic, which
           can be disabled with -Wno-pointer-sign.

       -Wstack-protector
           This option is only active when -fstack-protector is active.  It  warns  about  functions
           that are not protected against stack smashing.

       -Woverlength-strings
           Warn  about  string constants that are longer than the "minimum maximum" length specified
           in the C standard.  Modern compilers generally  allow  string  constants  that  are  much
           longer  than  the standard's minimum limit, but very portable programs should avoid using
           longer strings.

           The limit applies after string constant concatenation, and does not  count  the  trailing
           NUL.   In  C90,  the limit was 509 characters; in C99, it was raised to 4095.  C++98 does
           not specify a normative minimum maximum, so we do not diagnose overlength strings in C++.

           This option is implied by -Wpedantic, and can be disabled with -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
           Issue a warning for any floating constant  that  does  not  have  a  suffix.   When  used
           together  with  -Wsystem-headers  it  warns  about such constants in system header files.
           This can be useful when preparing code to use  with  the  "FLOAT_CONST_DECIMAL64"  pragma
           from the decimal floating-point extension to C99.

       -Wno-lto-type-mismatch
           During  the  link-time  optimization,  do  not  warn  about  type  mismatches  in  global
           declarations from different compilation units.  Requires -flto to be enabled.  Enabled by
           default.

       -Wno-designated-init (C and Objective-C only)
           Suppress warnings when a positional initializer is used to initialize  a  structure  that
           has been marked with the "designated_init" attribute.

   Options That Control Static Analysis
       -fanalyzer
           This  option  enables  an  static  analysis of program flow which looks for "interesting"
           interprocedural paths through the code, and issues warnings for problems found on them.

           This analysis is much more expensive than other GCC warnings.

           Enabling this option effectively enables the following warnings:

           -Wanalyzer-double-fclose  -Wanalyzer-double-free  -Wanalyzer-exposure-through-output-file
           -Wanalyzer-file-leak          -Wanalyzer-free-of-non-heap          -Wanalyzer-malloc-leak
           -Wanalyzer-mismatching-deallocation                     -Wanalyzer-possible-null-argument
           -Wanalyzer-possible-null-dereference -Wanalyzer-null-argument -Wanalyzer-null-dereference
           -Wanalyzer-shift-count-negative                           -Wanalyzer-shift-count-overflow
           -Wanalyzer-stale-setjmp-buffer                             -Wanalyzer-tainted-array-index
           -Wanalyzer-unsafe-call-within-signal-handler                    -Wanalyzer-use-after-free
           -Wanalyzer-use-of-pointer-in-stale-stack-frame                  -Wanalyzer-write-to-const
           -Wanalyzer-write-to-string-literal

           This option is only available if GCC was configured with analyzer support enabled.

       -Wanalyzer-too-complex
           If  -fanalyzer is enabled, the analyzer uses various heuristics to attempt to explore the
           control flow and data flow in the program, but these  can  be  defeated  by  sufficiently
           complicated code.

           By  default,  the analysis silently stops if the code is too complicated for the analyzer
           to fully explore and it reaches an internal  limit.   The  -Wanalyzer-too-complex  option
           warns if this occurs.

       -Wno-analyzer-double-fclose
           This  warning  requires  -fanalyzer, which enables it; use -Wno-analyzer-double-fclose to
           disable it.

           This diagnostic warns for paths through the code in which a "FILE *"  can  have  "fclose"
           called on it more than once.

       -Wno-analyzer-double-free
           This  warning  requires  -fanalyzer,  which  enables it; use -Wno-analyzer-double-free to
           disable it.

           This diagnostic warns for  paths  through  the  code  in  which  a  pointer  can  have  a
           deallocator  called  on  it more than once, either "free", or a deallocator referenced by
           attribute "malloc".

       -Wno-analyzer-exposure-through-output-file
           This     warning      requires      -fanalyzer,      which      enables      it;      use
           -Wno-analyzer-exposure-through-output-file to disable it.

           This  diagnostic  warns for paths through the code in which a security-sensitive value is
           written to an output file (such as writing a password to a log file).

       -Wno-analyzer-file-leak
           This warning requires  -fanalyzer,  which  enables  it;  use  -Wno-analyzer-file-leak  to
           disable it.

           This  diagnostic  warns for paths through the code in which a "<stdio.h>" "FILE *" stream
           object is leaked.

       -Wno-analyzer-free-of-non-heap
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-free-of-non-heap to
           disable it.

           This diagnostic warns for paths through the code in which "free" is called on a  non-heap
           pointer (e.g. an on-stack buffer, or a global).

       -Wno-analyzer-malloc-leak
           This  warning  requires  -fanalyzer,  which  enables it; use -Wno-analyzer-malloc-leak to
           disable it.

           This diagnostic warns for paths through the code in which  a  pointer  allocated  via  an
           allocator is leaked: either "malloc", or a function marked with attribute "malloc".

       -Wno-analyzer-mismatching-deallocation
           This      warning      requires      -fanalyzer,      which      enables      it;     use
           -Wno-analyzer-mismatching-deallocation to disable it.

           This diagnostic warns for paths through the code in which the wrong deallocation function
           is called on a pointer value, based on which function was used to  allocate  the  pointer
           value.   The  diagnostic  will  warn about mismatches between "free", scalar "delete" and
           vector "delete[]", and  those  marked  as  allocator/deallocator  pairs  using  attribute
           "malloc".

       -Wno-analyzer-possible-null-argument
           This      warning      requires      -fanalyzer,      which      enables      it;     use
           -Wno-analyzer-possible-null-argument to disable it.

           This diagnostic warns for paths through the code in which a possibly-NULL value is passed
           to a function argument marked with "__attribute__((nonnull))"  as  requiring  a  non-NULL
           value.

       -Wno-analyzer-possible-null-dereference
           This      warning      requires      -fanalyzer,      which      enables      it;     use
           -Wno-analyzer-possible-null-dereference to disable it.

           This diagnostic warns for paths through the  code  in  which  a  possibly-NULL  value  is
           dereferenced.

       -Wno-analyzer-null-argument
           This  warning  requires  -fanalyzer, which enables it; use -Wno-analyzer-null-argument to
           disable it.

           This diagnostic warns for paths through the code in which a value known  to  be  NULL  is
           passed  to a function argument marked with "__attribute__((nonnull))" as requiring a non-
           NULL value.

       -Wno-analyzer-null-dereference
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-null-dereference to
           disable it.

           This diagnostic warns for paths through the code in which a value known  to  be  NULL  is
           dereferenced.

       -Wno-analyzer-shift-count-negative
           This      warning      requires      -fanalyzer,      which      enables      it;     use
           -Wno-analyzer-shift-count-negative to disable it.

           This diagnostic warns for paths through the code in which a shift  is  attempted  with  a
           negative  count.  It is analogous to the -Wshift-count-negative diagnostic implemented in
           the C/C++ front ends, but is implemented based on analyzing interprocedural paths, rather
           than merely parsing the syntax tree.  However, the analyzer does not prioritize detection
           of such paths, so false negatives are more likely relative to other warnings.

       -Wno-analyzer-shift-count-overflow
           This     warning      requires      -fanalyzer,      which      enables      it;      use
           -Wno-analyzer-shift-count-overflow to disable it.

           This  diagnostic  warns  for  paths through the code in which a shift is attempted with a
           count greater than or equal to the precision of the operand's type.  It is  analogous  to
           the  -Wshift-count-overflow  diagnostic  implemented  in  the  C/C++  front  ends, but is
           implemented based on analyzing interprocedural paths,  rather  than  merely  parsing  the
           syntax tree.  However, the analyzer does not prioritize detection of such paths, so false
           negatives are more likely relative to other warnings.

       -Wno-analyzer-stale-setjmp-buffer
           This warning requires -fanalyzer, which enables it; use -Wno-analyzer-stale-setjmp-buffer
           to disable it.

           This  diagnostic  warns for paths through the code in which "longjmp" is called to rewind
           to a "jmp_buf" relating to a "setjmp" call in a function that has returned.

           When "setjmp" is called on a "jmp_buf" to record a rewind location, it records the  stack
           frame.   The  stack  frame becomes invalid when the function containing the "setjmp" call
           returns.  Attempting to rewind to it via "longjmp" would reference a stack frame that  no
           longer exists, and likely lead to a crash (or worse).

       -Wno-analyzer-tainted-array-index
           This  warning  requires  both  -fanalyzer  and -fanalyzer-checker=taint to enable it; use
           -Wno-analyzer-tainted-array-index to disable it.

           This diagnostic warns for paths through the code in which a value that could be under  an
           attacker's control is used as the index of an array access without being sanitized.

       -Wno-analyzer-unsafe-call-within-signal-handler
           This      warning      requires      -fanalyzer,      which      enables      it;     use
           -Wno-analyzer-unsafe-call-within-signal-handler to disable it.

           This diagnostic warns for paths through the code in which a function known to  be  async-
           signal-unsafe (such as "fprintf") is called from a signal handler.

       -Wno-analyzer-use-after-free
           This  warning  requires -fanalyzer, which enables it; use -Wno-analyzer-use-after-free to
           disable it.

           This diagnostic warns for paths through the code in which  a  pointer  is  used  after  a
           deallocator  is  called  on  it:  either "free", or a deallocator referenced by attribute
           "malloc".

       -Wno-analyzer-use-of-pointer-in-stale-stack-frame
           This     warning      requires      -fanalyzer,      which      enables      it;      use
           -Wno-analyzer-use-of-pointer-in-stale-stack-frame to disable it.

           This  diagnostic warns for paths through the code in which a pointer is dereferenced that
           points to a variable in a stale stack frame.

       -Wno-analyzer-write-to-const
           This warning requires -fanalyzer, which enables it; use  -Wno-analyzer-write-to-const  to
           disable it.

           This diagnostic warns for paths through the code in which the analyzer detects an attempt
           to  write  through  a  pointer  to  a  "const"  object.   However,  the analyzer does not
           prioritize detection of such paths, so false negatives are more likely relative to  other
           warnings.

       -Wno-analyzer-write-to-string-literal
           This      warning      requires      -fanalyzer,      which      enables      it;     use
           -Wno-analyzer-write-to-string-literal to disable it.

           This diagnostic warns for paths through the code in which the analyzer detects an attempt
           to write through a  pointer  to  a  string  literal.   However,  the  analyzer  does  not
           prioritize  detection of such paths, so false negatives are more likely relative to other
           warnings.

       Pertinent     parameters     for     controlling     the     exploration     are:     --param
       analyzer-bb-explosion-factor=value,    --param   analyzer-max-enodes-per-program-point=value,
       --param             analyzer-max-recursion-depth=value,              and              --param
       analyzer-min-snodes-for-call-summary=value.

       The following options control the analyzer.

       -fanalyzer-call-summaries
           Simplify  interprocedural  analysis by computing the effect of certain calls, rather than
           exploring all paths through the function from callsite to each possible return.

           If enabled, call summaries are only used for functions with more than one call site,  and
           that        are        sufficiently        complicated        (as       per       --param
           analyzer-min-snodes-for-call-summary=value).

       -fanalyzer-checker=name
           Restrict the analyzer to run just the named checker, and enable it.

           Some checkers are disabled by default (even with -fanalyzer), such as the "taint" checker
           that implements -Wanalyzer-tainted-array-index, and this option  is  required  to  enable
           them.

       -fno-analyzer-feasibility
           This option is intended for analyzer developers.

           By  default  the  analyzer  verifies  that there is a feasible control flow path for each
           diagnostic  it  emits:  that  the  conditions  that  hold  are  not  mutually  exclusive.
           Diagnostics  for which no feasible path can be found are rejected.  This filtering can be
           suppressed with -fno-analyzer-feasibility, for debugging issues in this code.

       -fanalyzer-fine-grained
           This option is intended for analyzer developers.

           Internally the analyzer builds an "exploded graph" that combines control flow graphs with
           data flow information.

           By default, an edge in this graph can contain the effects of a run of multiple statements
           within a basic block.  With -fanalyzer-fine-grained, each statement gets its own edge.

       -fanalyzer-show-duplicate-count
           This option is intended for  analyzer  developers:  if  multiple  diagnostics  have  been
           detected  as  being  duplicates  of  each  other, it emits a note when reporting the best
           diagnostic, giving the number of additional  diagnostics  that  were  suppressed  by  the
           deduplication logic.

       -fno-analyzer-state-merge
           This option is intended for analyzer developers.

           By  default  the  analyzer  attempts to simplify analysis by merging sufficiently similar
           states  at  each   program   point   as   it   builds   its   "exploded   graph".    With
           -fno-analyzer-state-merge  this  merging  can be suppressed, for debugging state-handling
           issues.

       -fno-analyzer-state-purge
           This option is intended for analyzer developers.

           By default the analyzer attempts to simplify analysis by purging aspects of  state  at  a
           program  point that appear to no longer be relevant e.g. the values of locals that aren't
           accessed later in the function and which aren't relevant to leak analysis.

           With -fno-analyzer-state-purge this purging of state can  be  suppressed,  for  debugging
           state-handling issues.

       -fanalyzer-transitivity
           This option enables transitivity of constraints within the analyzer.

       -fanalyzer-verbose-edges
           This  option  is  intended for analyzer developers.  It enables more verbose, lower-level
           detail in the descriptions of control flow within diagnostic paths.

       -fanalyzer-verbose-state-changes
           This option is intended for analyzer developers.  It enables  more  verbose,  lower-level
           detail in the descriptions of events relating to state machines within diagnostic paths.

       -fanalyzer-verbosity=level
           This  option  controls  the  complexity  of  the  control flow paths that are emitted for
           analyzer diagnostics.

           The level can be one of:

           0   At this level, interprocedural call and return events are displayed, along  with  the
               most  pertinent  state-change  events  relating  to a diagnostic.  For example, for a
               double-"free" diagnostic, both calls to "free" will be shown.

           1   As per the previous level, but also show events for the entry to each function.

           2   As per the previous level, but also show events relating to  control  flow  that  are
               significant to triggering the issue (e.g. "true path taken" at a conditional).

               This level is the default.

           3   As  per  the  previous  level, but show all control flow events, not just significant
               ones.

           4   This level is intended for analyzer developers; it adds various other events intended
               for debugging the analyzer.

       -fdump-analyzer
           Dump internal details about what the analyzer is doing to file.analyzer.txt.  This option
           is overridden by -fdump-analyzer-stderr.

       -fdump-analyzer-stderr
           Dump internal details about what the analyzer is doing to stderr.  This option  overrides
           -fdump-analyzer.

       -fdump-analyzer-callgraph
           Dump  a  representation  of  the  call  graph  suitable  for  viewing  with  GraphViz  to
           file.callgraph.dot.

       -fdump-analyzer-exploded-graph
           Dump a representation of the "exploded graph"  suitable  for  viewing  with  GraphViz  to
           file.eg.dot.   Nodes  are  color-coded  based  on state-machine states to emphasize state
           changes.

       -fdump-analyzer-exploded-nodes
           Emit diagnostics showing where nodes in the "exploded  graph"  are  in  relation  to  the
           program source.

       -fdump-analyzer-exploded-nodes-2
           Dump a textual representation of the "exploded graph" to file.eg.txt.

       -fdump-analyzer-exploded-nodes-3
           Dump  a  textual  representation  of  the  "exploded graph" to one dump file per node, to
           file.eg-id.txt.  This is typically a large number of dump files.

       -fdump-analyzer-feasibility
           Dump internal details about the analyzer's search for feasible paths.   The  details  are
           written  in  a  form  suitable  for  viewing  with  GraphViz  to  filenames  of  the form
           file.*.fg.dot and file.*.tg.dot.

       -fdump-analyzer-json
           Dump a compressed JSON representation of  analyzer  internals  to  file.analyzer.json.gz.
           The precise format is subject to change.

       -fdump-analyzer-state-purge
           As per -fdump-analyzer-supergraph, dump a representation of the "supergraph" suitable for
           viewing  with  GraphViz,  but  annotate  the graph with information on what state will be
           purged at each node.  The graph is written to file.state-purge.dot.

       -fdump-analyzer-supergraph
           Dump  representations  of  the  "supergraph"  suitable  for  viewing  with  GraphViz   to
           file.supergraph.dot  and  to  file.supergraph-eg.dot.  These show all of the control flow
           graphs in the program, with interprocedural edges for calls and returns.  The second dump
           contains annotations showing nodes in the "exploded  graph"  and  diagnostics  associated
           with them.

   Options for Debugging Your Program
       To  tell  GCC  to  emit extra information for use by a debugger, in almost all cases you need
       only to add -g to your other options.

       GCC allows you to use -g with -O.  The shortcuts taken by optimized code may occasionally  be
       surprising:  some  variables  you  declared may not exist at all; flow of control may briefly
       move where you did not expect it; some statements may not be executed  because  they  compute
       constant  results  or  their  values  are  already  at  hand;  some statements may execute in
       different places because they have been moved out of loops.  Nevertheless it is  possible  to
       debug  optimized  output.   This  makes  it reasonable to use the optimizer for programs that
       might have bugs.

       If you are not using some other optimization option, consider using -Og with -g.  With no  -O
       option  at all, some compiler passes that collect information useful for debugging do not run
       at all, so that -Og may result in a better debugging experience.

       -g  Produce debugging information in the  operating  system's  native  format  (stabs,  COFF,
           XCOFF, or DWARF).  GDB can work with this debugging information.

           On most systems that use stabs format, -g enables use of extra debugging information that
           only  GDB can use; this extra information makes debugging work better in GDB but probably
           makes other debuggers crash or refuse to read the program.  If you want  to  control  for
           certain  whether  to  generate  the  extra  information, use -gstabs+, -gstabs, -gxcoff+,
           -gxcoff, or -gvms (see below).

       -ggdb
           Produce debugging information for use by GDB.  This means  to  use  the  most  expressive
           format  available (DWARF, stabs, or the native format if neither of those are supported),
           including GDB extensions if at all possible.

       -gdwarf
       -gdwarf-version
           Produce debugging information in DWARF format (if  that  is  supported).   The  value  of
           version  may  be either 2, 3, 4 or 5; the default version for most targets is 5 (with the
           exception of VxWorks, TPF and Darwin/Mac OS X, which default to version 2, and AIX, which
           defaults to version 4).

           Note that with DWARF Version 2, some ports require and always  use  some  non-conflicting
           DWARF 3 extensions in the unwind tables.

           Version 4 may require GDB 7.0 and -fvar-tracking-assignments for maximum benefit. Version
           5 requires GDB 8.0 or higher.

           GCC  no  longer supports DWARF Version 1, which is substantially different than Version 2
           and  later.   For  historical  reasons,  some  other  DWARF-related   options   such   as
           -fno-dwarf2-cfi-asm)  retain  a reference to DWARF Version 2 in their names, but apply to
           all currently-supported versions of DWARF.

       -gstabs
           Produce debugging information in  stabs  format  (if  that  is  supported),  without  GDB
           extensions.   This  is  the  format  used by DBX on most BSD systems.  On MIPS, Alpha and
           System V Release 4 systems this option  produces  stabs  debugging  output  that  is  not
           understood by DBX.  On System V Release 4 systems this option requires the GNU assembler.

       -gstabs+
           Produce  debugging  information  in  stabs  format  (if  that  is  supported),  using GNU
           extensions understood only by the GNU debugger (GDB).  The use  of  these  extensions  is
           likely to make other debuggers crash or refuse to read the program.

       -gxcoff
           Produce debugging information in XCOFF format (if that is supported).  This is the format
           used by the DBX debugger on IBM RS/6000 systems.

       -gxcoff+
           Produce  debugging  information  in  XCOFF  format  (if  that  is  supported),  using GNU
           extensions understood only by the GNU debugger (GDB).  The use  of  these  extensions  is
           likely  to  make  other  debuggers  crash  or  refuse  to read the program, and may cause
           assemblers other than the GNU assembler (GAS) to fail with an error.

       -gvms
           Produce debugging information in Alpha/VMS debug format (if that is supported).  This  is
           the format used by DEBUG on Alpha/VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gxcofflevel
       -gvmslevel
           Request  debugging  information  and also use level to specify how much information.  The
           default level is 2.

           Level 0 produces no debug information at all.  Thus, -g0 negates -g.

           Level 1 produces minimal information, enough  for  making  backtraces  in  parts  of  the
           program  that  you  don't  plan  to  debug.   This includes descriptions of functions and
           external variables, and line number tables, but no information about local variables.

           Level 3 includes extra information, such as all the  macro  definitions  present  in  the
           program.  Some debuggers support macro expansion when you use -g3.

           If  you  use  multiple -g options, with or without level numbers, the last such option is
           the one that is effective.

           -gdwarf  does  not  accept  a  concatenated  debug  level,  to   avoid   confusion   with
           -gdwarf-level.   Instead  use  an additional -glevel option to change the debug level for
           DWARF.

       -fno-eliminate-unused-debug-symbols
           By default, no debug information is produced for symbols that are not actually used.  Use
           this option if you want debug information for all symbols.

       -femit-class-debug-always
           Instead  of  emitting debugging information for a C++ class in only one object file, emit
           it in all object files using the class.  This option should be used only  with  debuggers
           that  are  unable  to handle the way GCC normally emits debugging information for classes
           because using this option increases the size of debugging information by  as  much  as  a
           factor of two.

       -fno-merge-debug-strings
           Direct  the  linker  to  not merge together strings in the debugging information that are
           identical in different object files.  Merging is  not  supported  by  all  assemblers  or
           linkers.   Merging  decreases the size of the debug information in the output file at the
           cost of increasing link processing time.  Merging is enabled by default.

       -fdebug-prefix-map=old=new
           When compiling files residing in directory old, record debugging  information  describing
           them  as  if  the  files resided in directory new instead.  This can be used to replace a
           build-time path with an install-time path in the debug info.  It  can  also  be  used  to
           change  an  absolute  path  to  a  relative  path by using . for new.  This can give more
           reproducible builds, which are location independent, but may require an extra command  to
           tell GDB where to find the source files. See also -ffile-prefix-map.

       -fvar-tracking
           Run  variable  tracking pass.  It computes where variables are stored at each position in
           code.  Better debugging information is  then  generated  (if  the  debugging  information
           format supports this information).

           It  is enabled by default when compiling with optimization (-Os, -O, -O2, ...), debugging
           information (-g) and the debug info format supports it.

       -fvar-tracking-assignments
           Annotate assignments to user variables early in the compilation and attempt to carry  the
           annotations  over  throughout  the  compilation  all the way to the end, in an attempt to
           improve debug information while optimizing.  Use of -gdwarf-4 is recommended  along  with
           it.

           It can be enabled even if var-tracking is disabled, in which case annotations are created
           and maintained, but discarded at the end.  By default, this flag is enabled together with
           -fvar-tracking, except when selective scheduling is enabled.

       -gsplit-dwarf
           If  DWARF  debugging  information  is  enabled, separate as much debugging information as
           possible into a separate output file with the extension .dwo.   This  option  allows  the
           build  system  to  avoid linking files with debug information.  To be useful, this option
           requires a debugger capable of reading .dwo files.

       -gdwarf32
       -gdwarf64
           If DWARF debugging information is enabled, the -gdwarf32 selects the 32-bit DWARF  format
           and  the  -gdwarf64  selects the 64-bit DWARF format.  The default is target specific, on
           most targets it is -gdwarf32 though.  The 32-bit  DWARF  format  is  smaller,  but  can't
           support  more  than  2GiB  of  debug  information  in  any of the DWARF debug information
           sections.  The 64-bit DWARF format allows larger debug information and might not be  well
           supported by all consumers yet.

       -gdescribe-dies
           Add  description  attributes  to  some  DWARF  DIEs  that have no name attribute, such as
           artificial variables, external references and call site parameter DIEs.

       -gpubnames
           Generate DWARF ".debug_pubnames" and ".debug_pubtypes" sections.

       -ggnu-pubnames
           Generate ".debug_pubnames" and  ".debug_pubtypes"  sections  in  a  format  suitable  for
           conversion  into  a GDB index.  This option is only useful with a linker that can produce
           GDB index version 7.

       -fdebug-types-section
           When using DWARF Version 4 or higher, type DIEs can be put into their own  ".debug_types"
           section  instead  of making them part of the ".debug_info" section.  It is more efficient
           to put them in a separate comdat section since the linker  can  then  remove  duplicates.
           But  not  all  DWARF  consumers  support  ".debug_types" sections yet and on some objects
           ".debug_types" produces larger instead of smaller debugging information.

       -grecord-gcc-switches
       -gno-record-gcc-switches
           This switch causes the command-line options used to invoke the compiler that  may  affect
           code  generation  to  be  appended  to  the  DW_AT_producer  attribute in DWARF debugging
           information.  The options are concatenated with spaces separating them  from  each  other
           and from the compiler version.  It is enabled by default.  See also -frecord-gcc-switches
           for another way of storing compiler options into the object file.

       -gstrict-dwarf
           Disallow   using   extensions   of  later  DWARF  standard  version  than  selected  with
           -gdwarf-version.  On most targets  using  non-conflicting  DWARF  extensions  from  later
           standard versions is allowed.

       -gno-strict-dwarf
           Allow   using   extensions   of   later   DWARF   standard  version  than  selected  with
           -gdwarf-version.

       -gas-loc-support
           Inform the compiler that the assembler supports ".loc" directives.  It may then use  them
           for the assembler to generate DWARF2+ line number tables.

           This  is  generally  desirable,  because assembler-generated line-number tables are a lot
           more compact than those the compiler can generate itself.

           This option will be enabled by default if, at GCC configure time, the assembler was found
           to support such directives.

       -gno-as-loc-support
           Force GCC to generate DWARF2+ line number  tables  internally,  if  DWARF2+  line  number
           tables are to be generated.

       -gas-locview-support
           Inform  the  compiler  that  the assembler supports "view" assignment and reset assertion
           checking in ".loc" directives.

           This option will be enabled by default if, at GCC configure time, the assembler was found
           to support them.

       -gno-as-locview-support
           Force GCC to assign view numbers internally, if -gvariable-location-views are  explicitly
           requested.

       -gcolumn-info
       -gno-column-info
           Emit  location column information into DWARF debugging information, rather than just file
           and line.  This option is enabled by default.

       -gstatement-frontiers
       -gno-statement-frontiers
           This option causes GCC to create markers in the internal representation at the  beginning
           of  statements,  and  to keep them roughly in place throughout compilation, using them to
           guide the output of "is_stmt" markers in the line  number  table.   This  is  enabled  by
           default  when  compiling  with  optimization  (-Os, -O, -O2, ...), and outputting DWARF 2
           debug information at the normal level.

       -gvariable-location-views
       -gvariable-location-views=incompat5
       -gno-variable-location-views
           Augment variable location lists with progressive  view  numbers  implied  from  the  line
           number  table.   This  enables  debug  information  consumers to inspect state at certain
           points of the program, even if no instructions associated with the  corresponding  source
           locations  are present at that point.  If the assembler lacks support for view numbers in
           line number tables, this will cause the compiler to emit the  line  number  table,  which
           generally  makes  them  somewhat  less  compact.   The  augmented  line number tables and
           location  lists  are  fully  backward-compatible,  so  they  can  be  consumed  by  debug
           information  consumers  that  are not aware of these augmentations, but they won't derive
           any benefit from them either.

           This is enabled by default when outputting DWARF 2 debug information at the normal level,
           as long  as  there  is  assembler  support,  -fvar-tracking-assignments  is  enabled  and
           -gstrict-dwarf  is  not.   When  assembler  support  is  not available, this may still be
           enabled,  but  it  will  force  GCC  to  output  internal  line  number  tables,  and  if
           -ginternal-reset-location-views is not enabled, that will most certainly lead to silently
           mismatching location views.

           There  is a proposed representation for view numbers that is not backward compatible with
           the  location  list  format  introduced  in  DWARF  5,   that   can   be   enabled   with
           -gvariable-location-views=incompat5.   This  option may be removed in the future, is only
           provided as a reference implementation of the proposed representation.  Debug information
           consumers are not expected to support this extended format, and they  would  be  rendered
           unable to decode location lists using it.

       -ginternal-reset-location-views
       -gno-internal-reset-location-views
           Attempt  to  determine location views that can be omitted from location view lists.  This
           requires the compiler to have very accurate insn length estimates, which isn't always the
           case, and it may cause incorrect view lists  to  be  generated  silently  when  using  an
           assembler  that  does  not  support location view lists.  The GNU assembler will flag any
           such error as a "view number mismatch".  This is only enabled  on  ports  that  define  a
           reliable estimation function.

       -ginline-points
       -gno-inline-points
           Generate  extended  debug  information  for  inlined  functions.   Location view tracking
           markers are inserted at inlined entry points, so that address and  view  numbers  can  be
           computed  and output in debug information.  This can be enabled independently of location
           views, in which case the view numbers won't be output, but it can only be  enabled  along
           with  statement  frontiers,  and  it  is  only  enabled  by default if location views are
           enabled.

       -gz[=type]
           Produce compressed debug sections in DWARF format, if that is supported.  If type is  not
           given,  the  default  type  depends on the capabilities of the assembler and linker used.
           type may be one of none (don't compress debug sections), zlib (use  zlib  compression  in
           ELF  gABI  format), or zlib-gnu (use zlib compression in traditional GNU format).  If the
           linker doesn't support  writing  compressed  debug  sections,  the  option  is  rejected.
           Otherwise, if the assembler does not support them, -gz is silently ignored when producing
           object files.

       -femit-struct-debug-baseonly
           Emit  debug  information for struct-like types only when the base name of the compilation
           source file matches the base name of file in which the struct is defined.

           This option substantially reduces the size of debugging information, but  at  significant
           potential  loss in type information to the debugger.  See -femit-struct-debug-reduced for
           a less aggressive option.  See -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF debug output.

       -femit-struct-debug-reduced
           Emit debug information for struct-like types only when the base name of  the  compilation
           source file matches the base name of file in which the type is defined, unless the struct
           is a template or defined in a system header.

           This  option significantly reduces the size of debugging information, with some potential
           loss in type information to the debugger.  See -femit-struct-debug-baseonly  for  a  more
           aggressive option.  See -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF debug output.

       -femit-struct-debug-detailed[=spec-list]
           Specify  the  struct-like  types for which the compiler generates debug information.  The
           intent is to reduce duplicate struct debug information  between  different  object  files
           within the same program.

           This    option    is    a    detailed    version   of   -femit-struct-debug-reduced   and
           -femit-struct-debug-baseonly, which serves for most needs.

           A specification has the syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

           The optional first word limits the specification to structs that are used directly (dir:)
           or used indirectly (ind:).  A struct type is used directly when  it  is  the  type  of  a
           variable, member.  Indirect uses arise through pointers to structs.  That is, when use of
           an  incomplete  struct  is  valid, the use is indirect.  An example is struct one direct;
           struct two * indirect;.

           The optional second word limits the specification to ordinary structs (ord:)  or  generic
           structs  (gen:).   Generic  structs are a bit complicated to explain.  For C++, these are
           non-explicit specializations of template classes,  or  non-template  classes  within  the
           above.   Other programming languages have generics, but -femit-struct-debug-detailed does
           not yet implement them.

           The third word specifies the source files for those structs for which the compiler should
           emit debug information.  The values none and any have the normal meaning.  The value base
           means that the base of name of the file in which the type declaration appears must  match
           the  base  of  the  name of the main compilation file.  In practice, this means that when
           compiling foo.c, debug information is generated for  types  declared  in  that  file  and
           foo.h,  but  not  other header files.  The value sys means those types satisfying base or
           declared in system or compiler headers.

           You may need to experiment to determine the best settings for your application.

           The default is -femit-struct-debug-detailed=all.

           This option works only with DWARF debug output.

       -fno-dwarf2-cfi-asm
           Emit DWARF unwind info as compiler generated ".eh_frame" section  instead  of  using  GAS
           ".cfi_*" directives.

       -fno-eliminate-unused-debug-types
           Normally, when producing DWARF output, GCC avoids producing debug symbol output for types
           that  are nowhere used in the source file being compiled.  Sometimes it is useful to have
           GCC emit debugging information for all types declared in a compilation  unit,  regardless
           of whether or not they are actually used in that compilation unit, for example if, in the
           debugger,  you  want  to cast a value to a type that is not actually used in your program
           (but is declared).  More often, however, this results in a significant amount  of  wasted
           space.

   Options That Control Optimization
       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the cost of compilation and
       to  make debugging produce the expected results.  Statements are independent: if you stop the
       program with a breakpoint between statements, you can then assign a new value to any variable
       or change the program counter to any other statement in the  function  and  get  exactly  the
       results you expect from the source code.

       Turning  on  optimization  flags makes the compiler attempt to improve the performance and/or
       code size at the expense of compilation time and possibly the ability to debug the program.

       The compiler performs optimization based on the knowledge it has of the  program.   Compiling
       multiple  files  at  once to a single output file mode allows the compiler to use information
       gained from all of the files when compiling each of them.

       Not all optimizations are controlled directly by a flag.  Only optimizations that have a flag
       are listed in this section.

       Most optimizations are completely disabled at -O0 or if an -O level is not set on the command
       line, even if individual optimization flags are specified.  Similarly,  -Og  suppresses  many
       optimization passes.

       Depending on the target and how GCC was configured, a slightly different set of optimizations
       may  be  enabled  at  each  -O  level  than  those  listed  here.  You can invoke GCC with -Q
       --help=optimizers to find out the exact set of optimizations that are enabled at each level.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a lot more memory  for  a
           large function.

           With  -O,  the  compiler tries to reduce code size and execution time, without performing
           any optimizations that take a great deal of compilation time.

           -O turns on the following optimization flags:

           -fauto-inc-dec     -fbranch-count-reg     -fcombine-stack-adjustments      -fcompare-elim
           -fcprop-registers    -fdce   -fdefer-pop   -fdelayed-branch   -fdse   -fforward-propagate
           -fguess-branch-probability                -fif-conversion                -fif-conversion2
           -finline-functions-called-once      -fipa-modref      -fipa-profile      -fipa-pure-const
           -fipa-reference  -fipa-reference-addressable   -fmerge-constants   -fmove-loop-invariants
           -fomit-frame-pointer      -freorder-blocks      -fshrink-wrap      -fshrink-wrap-separate
           -fsplit-wide-types  -fssa-backprop  -fssa-phiopt  -ftree-bit-ccp   -ftree-ccp   -ftree-ch
           -ftree-coalesce-vars   -ftree-copy-prop   -ftree-dce   -ftree-dominator-opts   -ftree-dse
           -ftree-forwprop  -ftree-fre  -ftree-phiprop  -ftree-pta   -ftree-scev-cprop   -ftree-sink
           -ftree-slsr -ftree-sra -ftree-ter -funit-at-a-time

       -O2 Optimize  even more.  GCC performs nearly all supported optimizations that do not involve
           a space-speed tradeoff.  As compared to -O, this option increases both  compilation  time
           and the performance of the generated code.

           -O2  turns  on  all  optimization  flags specified by -O.  It also turns on the following
           optimization flags:

           -falign-functions     -falign-jumps    -falign-labels     -falign-loops    -fcaller-saves
           -fcode-hoisting        -fcrossjumping        -fcse-follow-jumps         -fcse-skip-blocks
           -fdelete-null-pointer-checks         -fdevirtualize          -fdevirtualize-speculatively
           -fexpensive-optimizations   -ffinite-loops   -fgcse    -fgcse-lm   -fhoist-adjacent-loads
           -finline-functions -finline-small-functions  -findirect-inlining  -fipa-bit-cp   -fipa-cp
           -fipa-icf    -fipa-ra     -fipa-sra     -fipa-vrp   -fisolate-erroneous-paths-dereference
           -flra-remat  -foptimize-sibling-calls  -foptimize-strlen  -fpartial-inlining  -fpeephole2
           -freorder-blocks-algorithm=stc     -freorder-blocks-and-partition     -freorder-functions
           -frerun-cse-after-loop     -fschedule-insns      -fschedule-insns2     -fsched-interblock
           -fsched-spec  -fstore-merging  -fstrict-aliasing  -fthread-jumps  -ftree-builtin-call-dce
           -ftree-pre -ftree-switch-conversion  -ftree-tail-merge -ftree-vrp

           Please note the warning under -fgcse about invoking -O2 on  programs  that  use  computed
           gotos.

           NOTE:  In  Ubuntu 8.10 and later versions, -D_FORTIFY_SOURCE=2, in Ubuntu 24.04 and later
           versions, -D_FORTIFY_SOURCE=3, is set by default, and is activated when -O is set to 2 or
           higher.  This enables additional  compile-time  and  run-time  checks  for  several  libc
           functions.  To disable, specify either -U_FORTIFY_SOURCE or -D_FORTIFY_SOURCE=0.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2 and also turns on the
           following optimization flags:

           -fgcse-after-reload  -fipa-cp-clone -floop-interchange -floop-unroll-and-jam -fpeel-loops
           -fpredictive-commoning     -fsplit-loops      -fsplit-paths      -ftree-loop-distribution
           -ftree-loop-vectorize     -ftree-partial-pre     -ftree-slp-vectorize    -funswitch-loops
           -fvect-cost-model -fvect-cost-model=dynamic -fversion-loops-for-strides

       -O0 Reduce compilation time and make debugging produce the expected  results.   This  is  the
           default.

       -Os Optimize  for  size.   -Os enables all -O2 optimizations except those that often increase
           code size:

           -falign-functions   -falign-jumps  -falign-labels   -falign-loops  -fprefetch-loop-arrays
           -freorder-blocks-algorithm=stc

           It also enables -finline-functions, causes the compiler to tune for code size rather than
           execution speed, and performs further optimizations designed to reduce code size.

       -Ofast
           Disregard  strict  standards  compliance.  -Ofast enables all -O3 optimizations.  It also
           enables optimizations that are not valid for all standard-compliant programs.   It  turns
           on  -ffast-math, -fallow-store-data-races and the Fortran-specific -fstack-arrays, unless
           -fmax-stack-var-size is specified, and -fno-protect-parens.

       -Og Optimize debugging experience.  -Og should be the optimization level of  choice  for  the
           standard  edit-compile-debug  cycle,  offering  a  reasonable level of optimization while
           maintaining fast compilation and a good debugging experience.  It is a better choice than
           -O0 for producing debuggable  code  because  some  compiler  passes  that  collect  debug
           information are disabled at -O0.

           Like  -O0,  -Og  completely  disables  a number of optimization passes so that individual
           options controlling them have no effect.  Otherwise  -Og  enables  all  -O1  optimization
           flags except for those that may interfere with debugging:

           -fbranch-count-reg     -fdelayed-branch    -fdse     -fif-conversion     -fif-conversion2
           -finline-functions-called-once   -fmove-loop-invariants    -fssa-phiopt    -ftree-bit-ccp
           -ftree-dse  -ftree-pta  -ftree-sra

       If  you  use  multiple -O options, with or without level numbers, the last such option is the
       one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most flags have both  positive
       and  negative forms; the negative form of -ffoo is -fno-foo.  In the table below, only one of
       the forms is listed---the one you typically use.  You can figure out the other form by either
       removing no- or adding it.

       The following options control specific  optimizations.   They  are  either  activated  by  -O
       options  or  are related to ones that are.  You can use the following flags in the rare cases
       when "fine-tuning" of optimizations to be performed is desired.

       -fno-defer-pop
           For machines that must pop arguments after a function call, always pop the  arguments  as
           soon  as  each  function  returns.  At levels -O1 and higher, -fdefer-pop is the default;
           this allows the compiler to let arguments accumulate on the stack  for  several  function
           calls and pop them all at once.

       -fforward-propagate
           Perform  a  forward  propagation pass on RTL.  The pass tries to combine two instructions
           and checks if the result can be simplified.  If loop unrolling is active, two passes  are
           performed and the second is scheduled after loop unrolling.

           This option is enabled by default at optimization levels -O, -O2, -O3, -Os.

       -ffp-contract=style
           -ffp-contract=off  disables  floating-point  expression  contraction.  -ffp-contract=fast
           enables floating-point expression contraction  such  as  forming  of  fused  multiply-add
           operations if the target has native support for them.  -ffp-contract=on enables floating-
           point  expression contraction if allowed by the language standard.  This is currently not
           implemented and treated equal to -ffp-contract=off.

           The default is -ffp-contract=fast.

       -fomit-frame-pointer
           Omit the frame pointer in functions that don't need one.  This avoids the instructions to
           save, set up and restore the frame pointer; on  many  targets  it  also  makes  an  extra
           register available.

           On some targets this flag has no effect because the standard calling sequence always uses
           a frame pointer, so it cannot be omitted.

           Note  that  -fno-omit-frame-pointer  doesn't  guarantee  the frame pointer is used in all
           functions.  Several targets always omit the frame pointer in leaf functions.

           Enabled by default at -O and higher.

       -foptimize-sibling-calls
           Optimize sibling and tail recursive calls.

           Enabled at levels -O2, -O3, -Os.

       -foptimize-strlen
           Optimize various standard C string functions (e.g. "strlen", "strchr"  or  "strcpy")  and
           their "_FORTIFY_SOURCE" counterparts into faster alternatives.

           Enabled at levels -O2, -O3.

       -fno-inline
           Do  not  expand  any  functions  inline  apart from those marked with the "always_inline"
           attribute.  This is the default when not optimizing.

           Single functions can be exempted from  inlining  by  marking  them  with  the  "noinline"
           attribute.

       -finline-small-functions
           Integrate  functions into their callers when their body is smaller than expected function
           call code (so overall size of program gets smaller).  The compiler heuristically  decides
           which  functions  are  simple  enough to be worth integrating in this way.  This inlining
           applies to all functions, even those not declared inline.

           Enabled at levels -O2, -O3, -Os.

       -findirect-inlining
           Inline also indirect calls that are discovered to be known  at  compile  time  thanks  to
           previous  inlining.  This option has any effect only when inlining itself is turned on by
           the -finline-functions or -finline-small-functions options.

           Enabled at levels -O2, -O3, -Os.

       -finline-functions
           Consider all functions for inlining, even if they are not declared inline.  The  compiler
           heuristically decides which functions are worth integrating in this way.

           If  all  calls to a given function are integrated, and the function is declared "static",
           then the function is normally not output as assembler code in its own right.

           Enabled at levels -O2, -O3, -Os.  Also enabled by -fprofile-use and -fauto-profile.

       -finline-functions-called-once
           Consider all "static" functions called once for inlining into their caller even  if  they
           are  not marked "inline".  If a call to a given function is integrated, then the function
           is not output as assembler code in its own right.

           Enabled at levels -O1, -O2, -O3 and -Os, but not -Og.

       -fearly-inlining
           Inline functions marked by "always_inline" and functions whose body  seems  smaller  than
           the function call overhead early before doing -fprofile-generate instrumentation and real
           inlining  pass.   Doing  so  makes  profiling  significantly cheaper and usually inlining
           faster on programs having large chains of nested wrapper functions.

           Enabled by default.

       -fipa-sra
           Perform interprocedural scalar replacement of aggregates, removal  of  unused  parameters
           and replacement of parameters passed by reference by parameters passed by value.

           Enabled at levels -O2, -O3 and -Os.

       -finline-limit=n
           By  default,  GCC  limits  the  size  of functions that can be inlined.  This flag allows
           coarse control of this limit.  n is the size of functions that can be inlined  in  number
           of pseudo instructions.

           Inlining  is  actually  controlled  by  a  number  of  parameters, which may be specified
           individually by using --param name=value.  The -finline-limit=n option sets some of these
           parameters as follows:

           max-inline-insns-single
               is set to n/2.

           max-inline-insns-auto
               is set to n/2.

           See below for a documentation of the individual parameters controlling inlining  and  for
           the defaults of these parameters.

           Note: there may be no value to -finline-limit that results in default behavior.

           Note:  pseudo instruction represents, in this particular context, an abstract measurement
           of function's size.  In no way does it represent a count of assembly instructions and  as
           such its exact meaning might change from one release to an another.

       -fno-keep-inline-dllexport
           This  is  a  more  fine-grained version of -fkeep-inline-functions, which applies only to
           functions that are declared using the "dllexport" attribute or declspec.

       -fkeep-inline-functions
           In C, emit "static" functions that are declared "inline" into the object  file,  even  if
           the  function  has  been  inlined  into  all of its callers.  This switch does not affect
           functions using the "extern inline" extension in GNU C90.   In  C++,  emit  any  and  all
           inline functions into the object file.

       -fkeep-static-functions
           Emit "static" functions into the object file, even if the function is never used.

       -fkeep-static-consts
           Emit  variables  declared  "static  const" when optimization isn't turned on, even if the
           variables aren't referenced.

           GCC enables this option by default.  If you want to force the  compiler  to  check  if  a
           variable  is  referenced, regardless of whether or not optimization is turned on, use the
           -fno-keep-static-consts option.

       -fmerge-constants
           Attempt to merge identical constants  (string  constants  and  floating-point  constants)
           across compilation units.

           This  option is the default for optimized compilation if the assembler and linker support
           it.  Use -fno-merge-constants to inhibit this behavior.

           Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
           Attempt to merge identical constants and identical variables.

           This option implies -fmerge-constants.  In addition to -fmerge-constants  this  considers
           e.g.  even constant initialized arrays or initialized constant variables with integral or
           floating-point types.  Languages like C or C++ require each variable, including  multiple
           instances  of  the same variable in recursive calls, to have distinct locations, so using
           this option results in non-conforming behavior.

       -fmodulo-sched
           Perform swing modulo scheduling immediately before the first scheduling pass.  This  pass
           looks  at  innermost  loops  and  reorders  their  instructions  by overlapping different
           iterations.

       -fmodulo-sched-allow-regmoves
           Perform more aggressive SMS-based modulo scheduling  with  register  moves  allowed.   By
           setting  this  flag  certain  anti-dependences  edges  are  deleted,  which  triggers the
           generation of reg-moves based on the life-range analysis.  This option is effective  only
           with -fmodulo-sched enabled.

       -fno-branch-count-reg
           Disable  the optimization pass that scans for opportunities to use "decrement and branch"
           instructions on a count register  instead  of  instruction  sequences  that  decrement  a
           register, compare it against zero, and then branch based upon the result.  This option is
           only  meaningful  on  architectures  that  support  such instructions, which include x86,
           PowerPC, IA-64 and S/390.  Note that the -fno-branch-count-reg option doesn't remove  the
           decrement  and  branch  instructions  from the generated instruction stream introduced by
           other optimization passes.

           The default is -fbranch-count-reg at -O1 and higher, except for -Og.

       -fno-function-cse
           Do not put function addresses in registers; make each instruction that calls  a  constant
           function contain the function's address explicitly.

           This  option  results  in  less  efficient  code,  but  some strange hacks that alter the
           assembler output may be confused by the optimizations performed when this option  is  not
           used.

           The default is -ffunction-cse

       -fno-zero-initialized-in-bss
           If  the target supports a BSS section, GCC by default puts variables that are initialized
           to zero into BSS.  This can save space in the resulting code.

           This option turns off this behavior because some programs explicitly  rely  on  variables
           going to the data section---e.g., so that the resulting executable can find the beginning
           of that section and/or make assumptions based on that.

           The default is -fzero-initialized-in-bss.

       -fthread-jumps
           Perform  optimizations  that  check to see if a jump branches to a location where another
           comparison subsumed by the first is found.  If so, the  first  branch  is  redirected  to
           either  the  destination  of  the  second  branch  or  a  point immediately following it,
           depending on whether the condition is known to be true or false.

           Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
           When using a type that occupies multiple registers, such  as  "long  long"  on  a  32-bit
           system,  split  the  registers  apart  and  allocate  them  independently.  This normally
           generates better code for those types, but may make debugging more difficult.

           Enabled at levels -O, -O2, -O3, -Os.

       -fsplit-wide-types-early
           Fully split wide types early, instead of very late.  This option  has  no  effect  unless
           -fsplit-wide-types is turned on.

           This is the default on some targets.

       -fcse-follow-jumps
           In common subexpression elimination (CSE), scan through jump instructions when the target
           of  the  jump is not reached by any other path.  For example, when CSE encounters an "if"
           statement with an "else" clause, CSE follows the jump when the condition tested is false.

           Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
           This is similar to -fcse-follow-jumps, but causes CSE to follow jumps that  conditionally
           skip  over  blocks.   When  CSE  encounters  a simple "if" statement with no else clause,
           -fcse-skip-blocks causes CSE to follow the jump around the body of the "if".

           Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
           Re-run common subexpression elimination after loop optimizations are performed.

           Enabled at levels -O2, -O3, -Os.

       -fgcse
           Perform a global common subexpression elimination pass.  This pass also  performs  global
           constant and copy propagation.

           Note:  When compiling a program using computed gotos, a GCC extension, you may get better
           run-time performance if you disable the global common subexpression elimination  pass  by
           adding -fno-gcse to the command line.

           Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
           When -fgcse-lm is enabled, global common subexpression elimination attempts to move loads
           that  are  only  killed  by  stores  into  themselves.   This  allows a loop containing a
           load/store sequence to be changed to a load outside the loop, and a copy/store within the
           loop.

           Enabled by default when -fgcse is enabled.

       -fgcse-sm
           When -fgcse-sm is enabled, a store motion pass is run after global  common  subexpression
           elimination.   This  pass attempts to move stores out of loops.  When used in conjunction
           with -fgcse-lm, loops containing a load/store sequence can be changed to  a  load  before
           the loop and a store after the loop.

           Not enabled at any optimization level.

       -fgcse-las
           When  -fgcse-las  is enabled, the global common subexpression elimination pass eliminates
           redundant loads that come after stores to the same memory location (both partial and full
           redundancies).

           Not enabled at any optimization level.

       -fgcse-after-reload
           When -fgcse-after-reload is enabled, a redundant load elimination pass is performed after
           reload.  The purpose of this pass is to clean up redundant spilling.

           Enabled by -fprofile-use and -fauto-profile.

       -faggressive-loop-optimizations
           This option tells the loop optimizer to use language constraints to derive bounds for the
           number of iterations of a loop.  This assumes that loop code does  not  invoke  undefined
           behavior  by for example causing signed integer overflows or out-of-bound array accesses.
           The bounds for the number of iterations of a loop are used to guide  loop  unrolling  and
           peeling and loop exit test optimizations.  This option is enabled by default.

       -funconstrained-commons
           This  option  tells  the compiler that variables declared in common blocks (e.g. Fortran)
           may later be overridden with longer trailing arrays. This prevents certain  optimizations
           that depend on knowing the array bounds.

       -fcrossjumping
           Perform  cross-jumping  transformation.   This transformation unifies equivalent code and
           saves code size.  The resulting code may or may not perform better  than  without  cross-
           jumping.

           Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
           Combine  increments or decrements of addresses with memory accesses.  This pass is always
           skipped on architectures that do not have  instructions  to  support  this.   Enabled  by
           default at -O and higher on architectures that support this.

       -fdce
           Perform dead code elimination (DCE) on RTL.  Enabled by default at -O and higher.

       -fdse
           Perform dead store elimination (DSE) on RTL.  Enabled by default at -O and higher.

       -fif-conversion
           Attempt  to  transform conditional jumps into branch-less equivalents.  This includes use
           of conditional moves, min, max, set flags and abs instructions, and some tricks doable by
           standard arithmetics.  The use of conditional execution on chips where it is available is
           controlled by -fif-conversion2.

           Enabled at levels -O, -O2, -O3, -Os, but not with -Og.

       -fif-conversion2
           Use conditional execution (where available) to transform conditional jumps  into  branch-
           less equivalents.

           Enabled at levels -O, -O2, -O3, -Os, but not with -Og.

       -fdeclone-ctor-dtor
           The  C++  ABI  requires multiple entry points for constructors and destructors: one for a
           base subobject, one for a complete object, and one for a virtual  destructor  that  calls
           operator  delete  afterwards.   For a hierarchy with virtual bases, the base and complete
           variants are clones, which means two copies of the function.  With this option, the  base
           and complete variants are changed to be thunks that call a common implementation.

           Enabled by -Os.

       -fdelete-null-pointer-checks
           Assume  that  programs  cannot safely dereference null pointers, and that no code or data
           element  resides  at  address  zero.   This  option  enables  simple   constant   folding
           optimizations  at all optimization levels.  In addition, other optimization passes in GCC
           use this flag to control global dataflow analyses that eliminate useless checks for  null
           pointers;  these assume that a memory access to address zero always results in a trap, so
           that if a pointer is checked after it has already been dereferenced, it cannot be null.

           Note  however  that  in  some  environments   this   assumption   is   not   true.    Use
           -fno-delete-null-pointer-checks  to disable this optimization for programs that depend on
           that behavior.

           This option is enabled by default on most targets.  On Nios II ELF, it defaults  to  off.
           On AVR, CR16, and MSP430, this option is completely disabled.

           Passes  that  use  the  dataflow  information  are  enabled  independently  at  different
           optimization levels.

       -fdevirtualize
           Attempt to convert calls to virtual functions to direct calls.  This is done both  within
           a  procedure and interprocedurally as part of indirect inlining (-findirect-inlining) and
           interprocedural constant propagation (-fipa-cp).  Enabled at levels -O2, -O3, -Os.

       -fdevirtualize-speculatively
           Attempt to convert calls to virtual functions to speculative direct calls.  Based on  the
           analysis  of  the  type  inheritance  graph, determine for a given call the set of likely
           targets. If the set is small, preferably of size 1, change the call  into  a  conditional
           deciding   between  direct  and  indirect  calls.   The  speculative  calls  enable  more
           optimizations, such as inlining.  When they seem useless after further optimization, they
           are converted back into original form.

       -fdevirtualize-at-ltrans
           Stream extra information needed for aggressive devirtualization when  running  the  link-
           time  optimizer  in local transformation mode.  This option enables more devirtualization
           but significantly increases the size of streamed data. For this reason it is disabled  by
           default.

       -fexpensive-optimizations
           Perform a number of minor optimizations that are relatively expensive.

           Enabled at levels -O2, -O3, -Os.

       -free
           Attempt  to  remove redundant extension instructions.  This is especially helpful for the
           x86-64 architecture, which implicitly zero-extends in 64-bit registers after  writing  to
           their lower 32-bit half.

           Enabled for Alpha, AArch64 and x86 at levels -O2, -O3, -Os.

       -fno-lifetime-dse
           In  C++  the value of an object is only affected by changes within its lifetime: when the
           constructor begins, the object has an indeterminate value, and  any  changes  during  the
           lifetime  of  the  object  are  dead  when  the object is destroyed.  Normally dead store
           elimination will take advantage of this; if your code relies on the value of  the  object
           storage  persisting  beyond  the lifetime of the object, you can use this flag to disable
           this optimization.  To preserve stores before the constructor starts (e.g.  because  your
           operator  new  clears  the  object  storage) but still treat the object as dead after the
           destructor, you can  use  -flifetime-dse=1.   The  default  behavior  can  be  explicitly
           selected with -flifetime-dse=2.  -flifetime-dse=0 is equivalent to -fno-lifetime-dse.

       -flive-range-shrinkage
           Attempt  to  decrease  register  pressure through register live range shrinkage.  This is
           helpful for fast processors with small or moderate size register sets.

       -fira-algorithm=algorithm
           Use the  specified  coloring  algorithm  for  the  integrated  register  allocator.   The
           algorithm  argument  can  be  priority,  which specifies Chow's priority coloring, or CB,
           which specifies Chaitin-Briggs coloring.  Chaitin-Briggs coloring is not implemented  for
           all architectures, but for those targets that do support it, it is the default because it
           generates better code.

       -fira-region=region
           Use  specified regions for the integrated register allocator.  The region argument should
           be one of the following:

           all Use all loops as register allocation regions.  This can give  the  best  results  for
               machines with a small and/or irregular register set.

           mixed
               Use  all  loops  except  for loops with small register pressure as the regions.  This
               value usually gives the best results in most cases and for most architectures, and is
               enabled by default when compiling with optimization for speed (-O, -O2, ...).

           one Use all functions as a single region.  This typically results in  the  smallest  code
               size, and is enabled by default for -Os or -O0.

       -fira-hoist-pressure
           Use  IRA  to  evaluate register pressure in the code hoisting pass for decisions to hoist
           expressions.  This option usually results in smaller code, but it can slow  the  compiler
           down.

           This option is enabled at level -Os for all targets.

       -fira-loop-pressure
           Use  IRA  to  evaluate  register pressure in loops for decisions to move loop invariants.
           This option usually results in generation of faster and smaller  code  on  machines  with
           large register files (>= 32 registers), but it can slow the compiler down.

           This option is enabled at level -O3 for some targets.

       -fno-ira-share-save-slots
           Disable  sharing of stack slots used for saving call-used hard registers living through a
           call.  Each hard register gets a separate stack slot, and  as  a  result  function  stack
           frames are larger.

       -fno-ira-share-spill-slots
           Disable sharing of stack slots allocated for pseudo-registers.  Each pseudo-register that
           does  not  get a hard register gets a separate stack slot, and as a result function stack
           frames are larger.

       -flra-remat
           Enable CFG-sensitive rematerialization in LRA.  Instead  of  loading  values  of  spilled
           pseudos, LRA tries to rematerialize (recalculate) values if it is profitable.

           Enabled at levels -O2, -O3, -Os.

       -fdelayed-branch
           If  supported  for  the  target  machine,  attempt  to  reorder  instructions  to exploit
           instruction slots available after delayed branch instructions.

           Enabled at levels -O, -O2, -O3, -Os, but not at -Og.

       -fschedule-insns
           If supported for the  target  machine,  attempt  to  reorder  instructions  to  eliminate
           execution  stalls  due to required data being unavailable.  This helps machines that have
           slow floating point or memory load instructions by  allowing  other  instructions  to  be
           issued until the result of the load or floating-point instruction is required.

           Enabled at levels -O2, -O3.

       -fschedule-insns2
           Similar  to  -fschedule-insns,  but requests an additional pass of instruction scheduling
           after register allocation has been done.  This is especially useful on  machines  with  a
           relatively  small  number  of registers and where memory load instructions take more than
           one cycle.

           Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
           Disable instruction scheduling across  basic  blocks,  which  is  normally  enabled  when
           scheduling before register allocation, i.e.  with -fschedule-insns or at -O2 or higher.

       -fno-sched-spec
           Disable  speculative  motion  of  non-load  instructions,  which is normally enabled when
           scheduling before register allocation, i.e.  with -fschedule-insns or at -O2 or higher.

       -fsched-pressure
           Enable register pressure sensitive insn scheduling before register allocation.  This only
           makes  sense  when  scheduling  before  register  allocation  is   enabled,   i.e.   with
           -fschedule-insns  or  at  -O2  or higher.  Usage of this option can improve the generated
           code and decrease its size by preventing register pressure increase above the  number  of
           available hard registers and subsequent spills in register allocation.

       -fsched-spec-load
           Allow  speculative  motion  of  some  load  instructions.   This  only  makes  sense when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
           Allow speculative  motion  of  more  load  instructions.   This  only  makes  sense  when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
           Define  how  many insns (if any) can be moved prematurely from the queue of stalled insns
           into the ready list during the second scheduling  pass.   -fno-sched-stalled-insns  means
           that  no  insns are moved prematurely, -fsched-stalled-insns=0 means there is no limit on
           how many queued insns can be moved prematurely.  -fsched-stalled-insns without a value is
           equivalent to -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
           Define how many insn groups (cycles) are examined for a dependency on a stalled insn that
           is a candidate for premature removal from the queue of stalled insns.  This has an effect
           only during the second scheduling  pass,  and  only  if  -fsched-stalled-insns  is  used.
           -fno-sched-stalled-insns-dep     is     equivalent     to    -fsched-stalled-insns-dep=0.
           -fsched-stalled-insns-dep without a value is equivalent to -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
           When scheduling after register allocation, use superblock scheduling.  This allows motion
           across  basic  block  boundaries,  resulting  in  faster  schedules.   This   option   is
           experimental, as not all machine descriptions used by GCC model the CPU closely enough to
           avoid unreliable results from the algorithm.

           This   only   makes   sense   when   scheduling  after  register  allocation,  i.e.  with
           -fschedule-insns2 or at -O2 or higher.

       -fsched-group-heuristic
           Enable the group heuristic in the scheduler.  This heuristic favors the instruction  that
           belongs to a schedule group.  This is enabled by default when scheduling is enabled, i.e.
           with -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-critical-path-heuristic
           Enable  the critical-path heuristic in the scheduler.  This heuristic favors instructions
           on the critical path.  This is enabled by default when scheduling is enabled,  i.e.  with
           -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-spec-insn-heuristic
           Enable  the  speculative  instruction  heuristic in the scheduler.  This heuristic favors
           speculative instructions with greater dependency weakness.  This is  enabled  by  default
           when scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or
           higher.

       -fsched-rank-heuristic
           Enable  the  rank  heuristic  in  the  scheduler.   This heuristic favors the instruction
           belonging to a basic block with greater size or frequency.  This is  enabled  by  default
           when scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or
           higher.

       -fsched-last-insn-heuristic
           Enable  the  last-instruction  heuristic  in  the  scheduler.   This heuristic favors the
           instruction that is less dependent on the last instruction scheduled.  This is enabled by
           default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at
           -O2 or higher.

       -fsched-dep-count-heuristic
           Enable the dependent-count  heuristic  in  the  scheduler.   This  heuristic  favors  the
           instruction  that has more instructions depending on it.  This is enabled by default when
           scheduling is enabled, i.e.  with -fschedule-insns or  -fschedule-insns2  or  at  -O2  or
           higher.

       -freschedule-modulo-scheduled-loops
           Modulo  scheduling  is  performed  before  traditional  scheduling.   If a loop is modulo
           scheduled, later scheduling passes may change its schedule.  Use this option  to  control
           that behavior.

       -fselective-scheduling
           Schedule  instructions  using  selective scheduling algorithm.  Selective scheduling runs
           instead of the first scheduler pass.

       -fselective-scheduling2
           Schedule instructions using selective scheduling algorithm.   Selective  scheduling  runs
           instead of the second scheduler pass.

       -fsel-sched-pipelining
           Enable  software  pipelining of innermost loops during selective scheduling.  This option
           has no effect unless one of -fselective-scheduling or -fselective-scheduling2  is  turned
           on.

       -fsel-sched-pipelining-outer-loops
           When  pipelining  loops  during  selective  scheduling,  also pipeline outer loops.  This
           option has no effect unless -fsel-sched-pipelining is turned on.

       -fsemantic-interposition
           Some object formats, like ELF, allow interposing of symbols by the dynamic linker.   This
           means that for symbols exported from the DSO, the compiler cannot perform interprocedural
           propagation,  inlining  and  other  optimizations  in  anticipation  that the function or
           variable in question may change. While this feature is useful, for  example,  to  rewrite
           memory  allocation  functions by a debugging implementation, it is expensive in the terms
           of  code  quality.   With  -fno-semantic-interposition  the  compiler  assumes  that   if
           interposition happens for functions the overwriting function will have precisely the same
           semantics  (and  side  effects).   Similarly  if interposition happens for variables, the
           constructor of the variable will be the same.  The  flag  has  no  effect  for  functions
           explicitly  declared  inline  (where  it  is  never  allowed  for interposition to change
           semantics) and for symbols explicitly declared weak.

       -fshrink-wrap
           Emit function prologues only before parts of the function that need it,  rather  than  at
           the top of the function.  This flag is enabled by default at -O and higher.

       -fshrink-wrap-separate
           Shrink-wrap  separate  parts of the prologue and epilogue separately, so that those parts
           are only executed when needed.  This option is on by default, but has  no  effect  unless
           -fshrink-wrap is also turned on and the target supports this.

       -fcaller-saves
           Enable  allocation  of  values  to  registers  that  are  clobbered by function calls, by
           emitting extra instructions to save and restore the registers around  such  calls.   Such
           allocation is done only when it seems to result in better code.

           This option is always enabled by default on certain machines, usually those which have no
           call-preserved registers to use instead.

           Enabled at levels -O2, -O3, -Os.

       -fcombine-stack-adjustments
           Tracks  stack adjustments (pushes and pops) and stack memory references and then tries to
           find ways to combine them.

           Enabled by default at -O1 and higher.

       -fipa-ra
           Use caller save registers for allocation if those registers are not used  by  any  called
           function.   In that case it is not necessary to save and restore them around calls.  This
           is only possible if called functions  are  part  of  same  compilation  unit  as  current
           function and they are compiled before it.

           Enabled at levels -O2, -O3, -Os, however the option is disabled if generated code will be
           instrumented  for  profiling  (-p,  or -pg) or if callee's register usage cannot be known
           exactly (this happens on targets that do not expose prologues and epilogues in RTL).

       -fconserve-stack
           Attempt to minimize stack usage.  The compiler attempts to use less stack space, even  if
           that  makes  the  program  slower.   This  option  implies  setting the large-stack-frame
           parameter to 100 and the large-stack-frame-growth parameter to 400.

       -ftree-reassoc
           Perform reassociation on trees.  This flag is enabled by default at -O and higher.

       -fcode-hoisting
           Perform code hoisting.  Code  hoisting  tries  to  move  the  evaluation  of  expressions
           executed  on  all  paths  to  the function exit as early as possible.  This is especially
           useful as a code size optimization, but it often helps for code speed as well.  This flag
           is enabled by default at -O2 and higher.

       -ftree-pre
           Perform partial redundancy elimination (PRE) on trees.  This flag is enabled  by  default
           at -O2 and -O3.

       -ftree-partial-pre
           Make  partial  redundancy  elimination  (PRE)  more  aggressive.  This flag is enabled by
           default at -O3.

       -ftree-forwprop
           Perform forward propagation on trees.  This flag is enabled by default at -O and higher.

       -ftree-fre
           Perform full redundancy elimination (FRE) on trees.  The difference between FRE  and  PRE
           is  that  FRE  only  considers  expressions that are computed on all paths leading to the
           redundant computation.  This analysis  is  faster  than  PRE,  though  it  exposes  fewer
           redundancies.  This flag is enabled by default at -O and higher.

       -ftree-phiprop
           Perform  hoisting  of  loads from conditional pointers on trees.  This pass is enabled by
           default at -O and higher.

       -fhoist-adjacent-loads
           Speculatively hoist loads from both branches of an if-then-else if  the  loads  are  from
           adjacent  locations  in  the same structure and the target architecture has a conditional
           move instruction.  This flag is enabled by default at -O2 and higher.

       -ftree-copy-prop
           Perform copy propagation on trees.  This pass  eliminates  unnecessary  copy  operations.
           This flag is enabled by default at -O and higher.

       -fipa-pure-const
           Discover which functions are pure or constant.  Enabled by default at -O and higher.

       -fipa-reference
           Discover  which  static variables do not escape the compilation unit.  Enabled by default
           at -O and higher.

       -fipa-reference-addressable
           Discover read-only, write-only and non-addressable static variables.  Enabled by  default
           at -O and higher.

       -fipa-stack-alignment
           Reduce stack alignment on call sites if possible.  Enabled by default.

       -fipa-pta
           Perform  interprocedural  pointer analysis and interprocedural modification and reference
           analysis.  This option can  cause  excessive  memory  and  compile-time  usage  on  large
           compilation units.  It is not enabled by default at any optimization level.

       -fipa-profile
           Perform  interprocedural  profile  propagation.   The  functions  called  only  from cold
           functions are marked as cold. Also functions executed once (such as  "cold",  "noreturn",
           static constructors or destructors) are identified. Cold functions and loop less parts of
           functions  executed  once  are  then  optimized  for  size.  Enabled by default at -O and
           higher.

       -fipa-modref
           Perform interprocedural mod/ref analysis.  This optimization analyzes the side effects of
           functions  (memory  locations  that  are  modified  or  referenced)  and  enables  better
           optimization  across  the  function call boundary.  This flag is enabled by default at -O
           and higher.

       -fipa-cp
           Perform interprocedural constant propagation.  This optimization analyzes the program  to
           determine  when  values passed to functions are constants and then optimizes accordingly.
           This optimization can substantially increase performance if the application has constants
           passed to functions.  This flag is enabled by default at -O2, -Os and -O3.   It  is  also
           enabled by -fprofile-use and -fauto-profile.

       -fipa-cp-clone
           Perform  function  cloning  to  make interprocedural constant propagation stronger.  When
           enabled, interprocedural constant propagation performs function cloning  when  externally
           visible  function  can  be called with constant arguments.  Because this optimization can
           create multiple copies of functions, it may significantly increase code size (see --param
           ipa-cp-unit-growth=value).  This flag is enabled by default at -O3.  It is  also  enabled
           by -fprofile-use and -fauto-profile.

       -fipa-bit-cp
           When  enabled, perform interprocedural bitwise constant propagation. This flag is enabled
           by default at -O2 and by -fprofile-use and -fauto-profile.  It requires that -fipa-cp  is
           enabled.

       -fipa-vrp
           When  enabled,  perform interprocedural propagation of value ranges. This flag is enabled
           by default at -O2. It requires that -fipa-cp is enabled.

       -fipa-icf
           Perform Identical Code Folding for functions and read-only variables.   The  optimization
           reduces code size and may disturb unwind stacks by replacing a function by equivalent one
           with   a   different  name.  The  optimization  works  more  effectively  with  link-time
           optimization enabled.

           Although the behavior is similar to the Gold Linker's ICF optimization, GCC ICF works  on
           different  levels  and  thus the optimizations are not same - there are equivalences that
           are found only by GCC and equivalences found only by Gold.

           This flag is enabled by default at -O2 and -Os.

       -flive-patching=level
           Control GCC's optimizations to produce output suitable for live-patching.

           If the compiler's optimization uses a function's body or information extracted  from  its
           body  to  optimize/change  another function, the latter is called an impacted function of
           the former.  If a function is patched, its impacted functions should be patched too.

           The impacted functions are determined by the  compiler's  interprocedural  optimizations.
           For  example,  a  caller  is impacted when inlining a function into its caller, cloning a
           function and changing its caller to call this  new  clone,  or  extracting  a  function's
           pureness/constness information to optimize its direct or indirect callers, etc.

           Usually,  the more IPA optimizations enabled, the larger the number of impacted functions
           for each function.  In order to control the number of impacted functions and more  easily
           compute  the list of impacted function, IPA optimizations can be partially enabled at two
           different levels.

           The level argument should be one of the following:

           inline-clone
               Only enable inlining and cloning optimizations,  which  includes  inlining,  cloning,
               interprocedural  scalar replacement of aggregates and partial inlining.  As a result,
               when patching a function, all its callers  and  its  clones'  callers  are  impacted,
               therefore need to be patched as well.

               -flive-patching=inline-clone    disables    the    following    optimization   flags:
               -fwhole-program  -fipa-pta  -fipa-reference  -fipa-ra -fipa-icf   -fipa-icf-functions
               -fipa-icf-variables         -fipa-bit-cp          -fipa-vrp          -fipa-pure-const
               -fipa-reference-addressable -fipa-stack-alignment -fipa-modref

           inline-only-static
               Only enable inlining of static functions.   As  a  result,  when  patching  a  static
               function, all its callers are impacted and so need to be patched as well.

               In   addition   to   all   the   flags  that  -flive-patching=inline-clone  disables,
               -flive-patching=inline-only-static disables  the  following  additional  optimization
               flags: -fipa-cp-clone  -fipa-sra  -fpartial-inlining  -fipa-cp

           When -flive-patching is specified without any value, the default value is inline-clone.

           This flag is disabled by default.

           Note that -flive-patching is not supported with link-time optimization (-flto).

       -fisolate-erroneous-paths-dereference
           Detect  paths  that  trigger  erroneous or undefined behavior due to dereferencing a null
           pointer.  Isolate those paths from the main control flow  and  turn  the  statement  with
           erroneous  or undefined behavior into a trap.  This flag is enabled by default at -O2 and
           higher and depends on -fdelete-null-pointer-checks also being enabled.

       -fisolate-erroneous-paths-attribute
           Detect paths that trigger erroneous or undefined behavior due to a null value being  used
           in  a  way  forbidden by a "returns_nonnull" or "nonnull" attribute.  Isolate those paths
           from the main control flow and turn the statement with erroneous  or  undefined  behavior
           into a trap.  This is not currently enabled, but may be enabled by -O2 in the future.

       -ftree-sink
           Perform forward store motion on trees.  This flag is enabled by default at -O and higher.

       -ftree-bit-ccp
           Perform  sparse  conditional  bit  constant  propagation  on  trees and propagate pointer
           alignment information.  This pass only operates on local scalar variables and is  enabled
           by default at -O1 and higher, except for -Og.  It requires that -ftree-ccp is enabled.

       -ftree-ccp
           Perform  sparse conditional constant propagation (CCP) on trees.  This pass only operates
           on local scalar variables and is enabled by default at -O and higher.

       -fssa-backprop
           Propagate information about uses of a value up the definition chain in order to  simplify
           the  definitions.   For  example, this pass strips sign operations if the sign of a value
           never matters.  The flag is enabled by default at -O and higher.

       -fssa-phiopt
           Perform pattern matching on SSA PHI nodes to optimize conditional  code.   This  pass  is
           enabled by default at -O1 and higher, except for -Og.

       -ftree-switch-conversion
           Perform conversion of simple initializations in a switch to initializations from a scalar
           array.  This flag is enabled by default at -O2 and higher.

       -ftree-tail-merge
           Look  for  identical  code  sequences.  When found, replace one with a jump to the other.
           This optimization is known as tail merging or cross jumping.  This  flag  is  enabled  by
           default  at  -O2 and higher.  The compilation time in this pass can be limited using max-
           tail-merge-comparisons parameter and max-tail-merge-iterations parameter.

       -ftree-dce
           Perform dead code elimination (DCE) on trees.  This flag is enabled by default at -O  and
           higher.

       -ftree-builtin-call-dce
           Perform  conditional dead code elimination (DCE) for calls to built-in functions that may
           set "errno" but are otherwise free of side effects.  This flag is enabled by  default  at
           -O2 and higher if -Os is not also specified.

       -ffinite-loops
           Assume  that a loop with an exit will eventually take the exit and not loop indefinitely.
           This allows the compiler to  remove  loops  that  otherwise  have  no  side-effects,  not
           considering eventual endless looping as such.

           This option is enabled by default at -O2 for C++ with -std=c++11 or higher.

       -ftree-dominator-opts
           Perform  a  variety  of  simple  scalar  cleanups  (constant/copy propagation, redundancy
           elimination, range propagation and expression simplification) based on a  dominator  tree
           traversal.   This  also  performs jump threading (to reduce jumps to jumps). This flag is
           enabled by default at -O and higher.

       -ftree-dse
           Perform dead store elimination (DSE) on trees.  A dead store is a  store  into  a  memory
           location  that  is  later overwritten by another store without any intervening loads.  In
           this case the earlier store can be deleted.  This flag is enabled by default  at  -O  and
           higher.

       -ftree-ch
           Perform   loop   header  copying  on  trees.   This  is  beneficial  since  it  increases
           effectiveness of code motion optimizations.  It  also  saves  one  jump.   This  flag  is
           enabled  by  default  at  -O  and  higher.   It  is not enabled for -Os, since it usually
           increases code size.

       -ftree-loop-optimize
           Perform loop optimizations on trees.  This flag is enabled by default at -O and higher.

       -ftree-loop-linear
       -floop-strip-mine
       -floop-block
           Perform loop nest  optimizations.   Same  as  -floop-nest-optimize.   To  use  this  code
           transformation,  GCC  has  to  be  configured with --with-isl to enable the Graphite loop
           transformation infrastructure.

       -fgraphite-identity
           Enable the identity  transformation  for  graphite.   For  every  SCoP  we  generate  the
           polyhedral  representation and transform it back to gimple.  Using -fgraphite-identity we
           can check the costs or benefits of the GIMPLE -> GRAPHITE -> GIMPLE transformation.  Some
           minimal optimizations are also performed by the code generator isl, like index  splitting
           and dead code elimination in loops.

       -floop-nest-optimize
           Enable the isl based loop nest optimizer.  This is a generic loop nest optimizer based on
           the  Pluto  optimization  algorithms.  It calculates a loop structure optimized for data-
           locality and parallelism.  This option is experimental.

       -floop-parallelize-all
           Use the Graphite data dependence analysis to identify loops  that  can  be  parallelized.
           Parallelize  all  the  loops that can be analyzed to not contain loop carried dependences
           without checking that it is profitable to parallelize the loops.

       -ftree-coalesce-vars
           While transforming the program out of the SSA representation, attempt to  reduce  copying
           by  coalescing  versions  of  different  user-defined variables, instead of just compiler
           temporaries.  This may severely limit the ability to debug an optimized program  compiled
           with  -fno-var-tracking-assignments.   In  the  negated  form,  this  flag  prevents  SSA
           coalescing of user variables.  This option is  enabled  by  default  if  optimization  is
           enabled, and it does very little otherwise.

       -ftree-loop-if-convert
           Attempt to transform conditional jumps in the innermost loops to branch-less equivalents.
           The  intent  is  to  remove control-flow from the innermost loops in order to improve the
           ability of the vectorization pass to handle these loops.  This is enabled by  default  if
           vectorization is enabled.

       -ftree-loop-distribution
           Perform  loop  distribution.   This flag can improve cache performance on big loop bodies
           and allow further loop optimizations, like  parallelization  or  vectorization,  to  take
           place.  For example, the loop

                   DO I = 1, N
                     A(I) = B(I) + C
                     D(I) = E(I) * F
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = B(I) + C
                   ENDDO
                   DO I = 1, N
                      D(I) = E(I) * F
                   ENDDO

           This  flag  is  enabled  by  default  at  -O3.   It  is also enabled by -fprofile-use and
           -fauto-profile.

       -ftree-loop-distribute-patterns
           Perform loop distribution of patterns that can be code generated with calls to a library.
           This  flag  is  enabled  by  default  at  -O2  and  higher,  and  by  -fprofile-use   and
           -fauto-profile.

           This  pass distributes the initialization loops and generates a call to memset zero.  For
           example, the loop

                   DO I = 1, N
                     A(I) = 0
                     B(I) = A(I) + I
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = 0
                   ENDDO
                   DO I = 1, N
                      B(I) = A(I) + I
                   ENDDO

           and the initialization loop is transformed into a call to  memset  zero.   This  flag  is
           enabled by default at -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -floop-interchange
           Perform loop interchange outside of graphite.  This flag can improve cache performance on
           loop  nest  and allow further loop optimizations, like vectorization, to take place.  For
           example, the loop

                   for (int i = 0; i < N; i++)
                     for (int j = 0; j < N; j++)
                       for (int k = 0; k < N; k++)
                         c[i][j] = c[i][j] + a[i][k]*b[k][j];

           is transformed to

                   for (int i = 0; i < N; i++)
                     for (int k = 0; k < N; k++)
                       for (int j = 0; j < N; j++)
                         c[i][j] = c[i][j] + a[i][k]*b[k][j];

           This flag is enabled by default  at  -O3.   It  is  also  enabled  by  -fprofile-use  and
           -fauto-profile.

       -floop-unroll-and-jam
           Apply  unroll and jam transformations on feasible loops.  In a loop nest this unrolls the
           outer loop by some factor and fuses the resulting multiple inner  loops.   This  flag  is
           enabled by default at -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -ftree-loop-im
           Perform loop invariant motion on trees.  This pass moves only invariants that are hard to
           handle  at  RTL  level (function calls, operations that expand to nontrivial sequences of
           insns).  With -funswitch-loops it also moves operands of conditions  that  are  invariant
           out  of  the  loop,  so  that  we  can  use  just  trivial invariantness analysis in loop
           unswitching.  The pass also includes store motion.

       -ftree-loop-ivcanon
           Create a canonical counter for number of iterations in loops for which determining number
           of iterations requires complicated analysis.  Later optimizations then may determine  the
           number easily.  Useful especially in connection with unrolling.

       -ftree-scev-cprop
           Perform  final value replacement.  If a variable is modified in a loop in such a way that
           its value when exiting the loop can be determined using only its initial  value  and  the
           number  of  loop  iterations,  replace  uses  of  the  final value by such a computation,
           provided it is sufficiently cheap.  This reduces data dependencies and may allow  further
           simplifications.  Enabled by default at -O and higher.

       -fivopts
           Perform  induction variable optimizations (strength reduction, induction variable merging
           and induction variable elimination) on trees.

       -ftree-parallelize-loops=n
           Parallelize loops, i.e., split their iteration space to run in n threads.  This  is  only
           possible  for  loops  whose  iterations are independent and can be arbitrarily reordered.
           The optimization is only profitable on multiprocessor machines, for loops that  are  CPU-
           intensive,  rather  than  constrained  e.g.  by  memory  bandwidth.   This option implies
           -pthread, and thus is only supported on targets that have support for -pthread.

       -ftree-pta
           Perform function-local points-to analysis on trees.  This flag is enabled by  default  at
           -O1 and higher, except for -Og.

       -ftree-sra
           Perform  scalar  replacement of aggregates.  This pass replaces structure references with
           scalars to prevent committing structures to memory too early.  This flag  is  enabled  by
           default at -O1 and higher, except for -Og.

       -fstore-merging
           Perform  merging  of  narrow  stores  to  consecutive memory addresses.  This pass merges
           contiguous stores of immediate values narrower than a word into  fewer  wider  stores  to
           reduce  the number of instructions.  This is enabled by default at -O2 and higher as well
           as -Os.

       -ftree-ter
           Perform temporary expression replacement during the SSA->normal phase.  Single use/single
           def temporaries are replaced at their use location with their defining expression.   This
           results  in  non-GIMPLE  code, but gives the expanders much more complex trees to work on
           resulting in better RTL generation.  This is enabled by default at -O and higher.

       -ftree-slsr
           Perform straight-line strength reduction on trees.  This recognizes  related  expressions
           involving multiplications and replaces them by less expensive calculations when possible.
           This is enabled by default at -O and higher.

       -ftree-vectorize
           Perform   vectorization   on   trees.   This   flag   enables  -ftree-loop-vectorize  and
           -ftree-slp-vectorize if not explicitly specified.

       -ftree-loop-vectorize
           Perform loop vectorization on trees. This flag is  enabled  by  default  at  -O3  and  by
           -ftree-vectorize, -fprofile-use, and -fauto-profile.

       -ftree-slp-vectorize
           Perform basic block vectorization on trees. This flag is enabled by default at -O3 and by
           -ftree-vectorize, -fprofile-use, and -fauto-profile.

       -fvect-cost-model=model
           Alter  the  cost  model  used  for  vectorization.   The  model argument should be one of
           unlimited, dynamic, cheap or very-cheap.  With the unlimited model the  vectorized  code-
           path  is assumed to be profitable while with the dynamic model a runtime check guards the
           vectorized code-path to enable it only for iteration  counts  that  will  likely  execute
           faster  than  when  executing  the  original  scalar  loop.   The  cheap  model  disables
           vectorization of loops where doing so would  be  cost  prohibitive  for  example  due  to
           required  runtime  checks  for data dependence or alignment but otherwise is equal to the
           dynamic model.  The very-cheap model only allows vectorization if the vector  code  would
           entirely  replace  the  scalar  code  that  is  being  vectorized.   For example, if each
           iteration of a vectorized loop would only be able to handle exactly  four  iterations  of
           the  scalar  loop,  the  very-cheap  model  would  only allow vectorization if the scalar
           iteration count is known to be a multiple of four.

           The default cost model depends on other optimization  flags  and  is  either  dynamic  or
           cheap.

       -fsimd-cost-model=model
           Alter  the  cost  model  used  for  vectorization  of  loops  marked with the OpenMP simd
           directive.  The model argument should be one of unlimited, dynamic, cheap.  All values of
           model have the same meaning as described in -fvect-cost-model and by default a cost model
           defined with -fvect-cost-model is used.

       -ftree-vrp
           Perform Value Range Propagation on trees.  This is similar to  the  constant  propagation
           pass, but instead of values, ranges of values are propagated.  This allows the optimizers
           to remove unnecessary range checks like array bound checks and null pointer checks.  This
           is  enabled by default at -O2 and higher.  Null pointer check elimination is only done if
           -fdelete-null-pointer-checks is enabled.

       -fsplit-paths
           Split paths leading to loop backedges.  This can improve dead code elimination and common
           subexpression elimination.  This is enabled by default at -O3 and above.

       -fsplit-ivs-in-unroller
           Enables expression of values of induction variables in later iterations of  the  unrolled
           loop  using  the  value in the first iteration.  This breaks long dependency chains, thus
           improving efficiency of the scheduling passes.

           A combination of -fweb and CSE is often sufficient to obtain the same  effect.   However,
           that is not reliable in cases where the loop body is more complicated than a single basic
           block.  It also does not work at all on some architectures due to restrictions in the CSE
           pass.

           This optimization is enabled by default.

       -fvariable-expansion-in-unroller
           With  this  option,  the  compiler  creates  multiple copies of some local variables when
           unrolling a loop, which can result in superior code.

           This optimization is enabled by default for PowerPC  targets,  but  disabled  by  default
           otherwise.

       -fpartial-inlining
           Inline  parts  of  functions.   This  option  has any effect only when inlining itself is
           turned on by the -finline-functions or -finline-small-functions options.

           Enabled at levels -O2, -O3, -Os.

       -fpredictive-commoning
           Perform predictive commoning optimization, i.e., reusing computations (especially  memory
           loads and stores) performed in previous iterations of loops.

           This  option  is  enabled  at  level  -O3.   It  is  also  enabled  by  -fprofile-use and
           -fauto-profile.

       -fprefetch-loop-arrays
           If supported by the target machine, generate instructions to prefetch memory  to  improve
           the performance of loops that access large arrays.

           This  option  may  generate  better  or  worse  code; results are highly dependent on the
           structure of loops within the source code.

           Disabled at level -Os.

       -fno-printf-return-value
           Do not substitute constants for known return value of formatted output functions such  as
           "sprintf", "snprintf", "vsprintf", and "vsnprintf" (but not "printf" of "fprintf").  This
           transformation  allows  GCC  to  optimize  or  even eliminate branches based on the known
           return value of these functions called with arguments that are either constant, or  whose
           values are known to be in a range that makes determining the exact return value possible.
           For example, when -fprintf-return-value is in effect, both the branch and the body of the
           "if" statement (but not the call to "snprint") can be optimized away when "i" is a 32-bit
           or smaller integer because the return value is guaranteed to be at most 8.

                   char buf[9];
                   if (snprintf (buf, "%08x", i) >= sizeof buf)
                     ...

           The  -fprintf-return-value  option  relies on other optimizations and yields best results
           with  -O2  and  above.    It   works   in   tandem   with   the   -Wformat-overflow   and
           -Wformat-truncation options.  The -fprintf-return-value option is enabled by default.

       -fno-peephole
       -fno-peephole2
           Disable   any   machine-specific   peephole   optimizations.    The   difference  between
           -fno-peephole and -fno-peephole2 is in how they are implemented  in  the  compiler;  some
           targets use one, some use the other, a few use both.

           -fpeephole is enabled by default.  -fpeephole2 enabled at levels -O2, -O3, -Os.

       -fno-guess-branch-probability
           Do not guess branch probabilities using heuristics.

           GCC  uses  heuristics to guess branch probabilities if they are not provided by profiling
           feedback (-fprofile-arcs).  These heuristics are based on the  control  flow  graph.   If
           some  branch  probabilities  are specified by "__builtin_expect", then the heuristics are
           used to guess branch probabilities for the rest of the control  flow  graph,  taking  the
           "__builtin_expect"  info  into  account.   The  interactions  between  the heuristics and
           "__builtin_expect" can be complex, and in some cases, it may be  useful  to  disable  the
           heuristics so that the effects of "__builtin_expect" are easier to understand.

           It   is   also   possible   to  specify  expected  probability  of  the  expression  with
           "__builtin_expect_with_probability" built-in function.

           The default is -fguess-branch-probability at levels -O, -O2, -O3, -Os.

       -freorder-blocks
           Reorder basic blocks in the compiled function in order to reduce number of taken branches
           and improve code locality.

           Enabled at levels -O, -O2, -O3, -Os.

       -freorder-blocks-algorithm=algorithm
           Use the specified algorithm for basic block reordering.  The algorithm  argument  can  be
           simple, which does not increase code size (except sometimes due to secondary effects like
           alignment),  or  stc,  the "software trace cache" algorithm, which tries to put all often
           executed code together, minimizing the number of branches executed by making extra copies
           of code.

           The default is simple at levels -O, -Os, and stc at levels -O2, -O3.

       -freorder-blocks-and-partition
           In addition to reordering basic blocks in the  compiled  function,  in  order  to  reduce
           number  of taken branches, partitions hot and cold basic blocks into separate sections of
           the assembly and .o files, to improve paging and cache locality performance.

           This optimization is automatically turned off in the presence of  exception  handling  or
           unwind tables (on targets using setjump/longjump or target specific scheme), for linkonce
           sections,  for  functions  with  a user-defined section attribute and on any architecture
           that does not support named sections.  When -fsplit-stack is  used  this  option  is  not
           enabled  by  default  (to avoid linker errors), but may be enabled explicitly (if using a
           working linker).

           Enabled for x86 at levels -O2, -O3, -Os.

       -freorder-functions
           Reorder functions in the object  file  in  order  to  improve  code  locality.   This  is
           implemented  by  using  special  subsections  ".text.hot"  for  most  frequently executed
           functions and ".text.unlikely" for unlikely executed functions.  Reordering  is  done  by
           the  linker  so object file format must support named sections and linker must place them
           in a reasonable way.

           This  option  isn't  effective  unless  you  either   provide   profile   feedback   (see
           -fprofile-arcs  for  details)  or  manually  annotate  functions  with  "hot"  or  "cold"
           attributes.

           Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
           Allow the compiler to assume the strictest aliasing  rules  applicable  to  the  language
           being  compiled.   For  C  (and  C++),  this activates optimizations based on the type of
           expressions.  In particular, an object of one type is assumed never to reside at the same
           address as an object of a different type, unless the types  are  almost  the  same.   For
           example,  an  "unsigned  int"  can  alias  an  "int", but not a "void*" or a "double".  A
           character type may alias any other type.

           Pay special attention to code like this:

                   union a_union {
                     int i;
                     double d;
                   };

                   int f() {
                     union a_union t;
                     t.d = 3.0;
                     return t.i;
                   }

           The practice of reading from a different union member than the one most recently  written
           to  (called  "type-punning")  is  common.   Even  with -fstrict-aliasing, type-punning is
           allowed, provided the memory is accessed through the union  type.   So,  the  code  above
           works as expected.    However, this code might not:

                   int f() {
                     union a_union t;
                     int* ip;
                     t.d = 3.0;
                     ip = &t.i;
                     return *ip;
                   }

           Similarly,  access by taking the address, casting the resulting pointer and dereferencing
           the result has undefined behavior, even if the cast uses a union type, e.g.:

                   int f() {
                     double d = 3.0;
                     return ((union a_union *) &d)->i;
                   }

           The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
       -falign-functions=n:m
       -falign-functions=n:m:n2
       -falign-functions=n:m:n2:m2
           Align the start of functions to the  next  power-of-two  greater  than  or  equal  to  n,
           skipping  up  to m-1 bytes.  This ensures that at least the first m bytes of the function
           can be fetched by the CPU without crossing an n-byte alignment boundary.

           If m is not specified, it defaults to n.

           Examples:  -falign-functions=32  aligns  functions  to   the   next   32-byte   boundary,
           -falign-functions=24  aligns  to  the  next  32-byte boundary only if this can be done by
           skipping 23 bytes or less, -falign-functions=32:7 aligns to  the  next  32-byte  boundary
           only if this can be done by skipping 6 bytes or less.

           The   second  pair  of  n2:m2  values  allows  you  to  specify  a  secondary  alignment:
           -falign-functions=64:7:32:3 aligns to the next 64-byte boundary if this can  be  done  by
           skipping  6  bytes  or less, otherwise aligns to the next 32-byte boundary if this can be
           done by skipping 2 bytes or less.  If m2 is not specified, it defaults to n2.

           Some assemblers only support this flag when n is a power of two;  in  that  case,  it  is
           rounded up.

           -fno-align-functions  and  -falign-functions=1 are equivalent and mean that functions are
           not aligned.

           If n is not specified or is zero, use a machine-dependent default.  The maximum allowed n
           option value is 65536.

           Enabled at levels -O2, -O3.

       -flimit-function-alignment
           If this option is  enabled,  the  compiler  tries  to  avoid  unnecessarily  overaligning
           functions.  It  attempts  to  instruct  the assembler to align by the amount specified by
           -falign-functions, but not to skip more bytes than the size of the function.

       -falign-labels
       -falign-labels=n
       -falign-labels=n:m
       -falign-labels=n:m:n2
       -falign-labels=n:m:n2:m2
           Align all branch targets to a power-of-two boundary.

           Parameters  of   this   option   are   analogous   to   the   -falign-functions   option.
           -fno-align-labels  and  -falign-labels=1  are  equivalent  and  mean  that labels are not
           aligned.

           If -falign-loops or -falign-jumps are applicable and are greater than  this  value,  then
           their values are used instead.

           If n is not specified or is zero, use a machine-dependent default which is very likely to
           be 1, meaning no alignment.  The maximum allowed n option value is 65536.

           Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
       -falign-loops=n:m
       -falign-loops=n:m:n2
       -falign-loops=n:m:n2:m2
           Align loops to a power-of-two boundary.  If the loops are executed many times, this makes
           up for any execution of the dummy padding instructions.

           If -falign-labels is greater than this value, then its value is used instead.

           Parameters   of   this   option   are   analogous   to   the   -falign-functions  option.
           -fno-align-loops and -falign-loops=1 are equivalent and mean that loops are not  aligned.
           The maximum allowed n option value is 65536.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
       -falign-jumps=n:m
       -falign-jumps=n:m:n2
       -falign-jumps=n:m:n2:m2
           Align branch targets to a power-of-two boundary, for branch targets where the targets can
           only be reached by jumping.  In this case, no dummy operations need be executed.

           If -falign-labels is greater than this value, then its value is used instead.

           Parameters   of   this   option   are   analogous   to   the   -falign-functions  option.
           -fno-align-jumps and -falign-jumps=1 are equivalent and mean that loops are not aligned.

           If n is not specified or is zero, use a machine-dependent default.  The maximum allowed n
           option value is 65536.

           Enabled at levels -O2, -O3.

       -fno-allocation-dce
           Do not remove unused C++ allocations in dead code elimination.

       -fallow-store-data-races
           Allow the compiler to perform optimizations that may introduce new data races on  stores,
           without proving that the variable cannot be concurrently accessed by other threads.  Does
           not affect optimization of local data.  It is safe to use this option if it is known that
           global data will not be accessed by multiple threads.

           Examples  of  optimizations  enabled  by -fallow-store-data-races include hoisting or if-
           conversions that may cause a value that was already in memory to be re-written with  that
           same  value.  Such re-writing is safe in a single threaded context but may be unsafe in a
           multi-threaded context.  Note that on some processors, if-conversions may be required  in
           order to enable vectorization.

           Enabled at level -Ofast.

       -funit-at-a-time
           This  option  is  left  for  compatibility reasons. -funit-at-a-time has no effect, while
           -fno-unit-at-a-time implies -fno-toplevel-reorder and -fno-section-anchors.

           Enabled by default.

       -fno-toplevel-reorder
           Do not reorder top-level functions, variables, and "asm" statements.  Output them in  the
           same  order  that  they appear in the input file.  When this option is used, unreferenced
           static variables are not removed.  This option is intended to support existing code  that
           relies  on  a  particular  ordering.   For  new code, it is better to use attributes when
           possible.

           -ftoplevel-reorder is the default at -O1 and higher, and also at -O0 if -fsection-anchors
           is     explicitly     requested.      Additionally     -fno-toplevel-reorder      implies
           -fno-section-anchors.

       -fweb
           Constructs  webs  as  commonly  used for register allocation purposes and assign each web
           individual pseudo register.  This allows the  register  allocation  pass  to  operate  on
           pseudos  directly,  but  also strengthens several other optimization passes, such as CSE,
           loop  optimizer  and  trivial  dead  code  remover.   It  can,  however,  make  debugging
           impossible, since variables no longer stay in a "home register".

           Enabled by default with -funroll-loops.

       -fwhole-program
           Assume  that  the  current  compilation unit represents the whole program being compiled.
           All public functions and variables with the exception  of  "main"  and  those  merged  by
           attribute  "externally_visible"  become static functions and in effect are optimized more
           aggressively by interprocedural optimizers.

           This option should not be used in combination with -flto.  Instead relying  on  a  linker
           plugin should provide safer and more precise information.

       -flto[=n]
           This  option  runs  the  standard link-time optimizer.  When invoked with source code, it
           generates GIMPLE (one of GCC's internal representations) and writes  it  to  special  ELF
           sections in the object file.  When the object files are linked together, all the function
           bodies  are read from these ELF sections and instantiated as if they had been part of the
           same translation unit.

           To use the link-time optimizer, -flto and optimization options  should  be  specified  at
           compile time and during the final link.  It is recommended that you compile all the files
           participating  in  the  same link with the same options and also specify those options at
           link time.  For example:

                   gcc -c -O2 -flto foo.c
                   gcc -c -O2 -flto bar.c
                   gcc -o myprog -flto -O2 foo.o bar.o

           The first two invocations to GCC save a bytecode representation of  GIMPLE  into  special
           ELF sections inside foo.o and bar.o.  The final invocation reads the GIMPLE bytecode from
           foo.o  and  bar.o,  merges  the  two files into a single internal image, and compiles the
           result as usual.  Since both foo.o and bar.o are merged into a single image, this  causes
           all the interprocedural analyses and optimizations in GCC to work across the two files as
           if  they  were a single one.  This means, for example, that the inliner is able to inline
           functions in bar.o into functions in foo.o and vice-versa.

           Another (simpler) way to enable link-time optimization is:

                   gcc -o myprog -flto -O2 foo.c bar.c

           The above generates bytecode for foo.c and bar.c, merges  them  together  into  a  single
           GIMPLE representation and optimizes them as usual to produce myprog.

           The important thing to keep in mind is that to enable link-time optimizations you need to
           use  the  GCC  driver  to  perform  the  link step.  GCC automatically performs link-time
           optimization if any of the objects involved were compiled  with  the  -flto  command-line
           option.   You  can always override the automatic decision to do link-time optimization by
           passing -fno-lto to the link command.

           To make whole program optimization effective, it  is  necessary  to  make  certain  whole
           program  assumptions.   The  compiler  needs  to know what functions and variables can be
           accessed by libraries  and  runtime  outside  of  the  link-time  optimized  unit.   When
           supported  by  the linker, the linker plugin (see -fuse-linker-plugin) passes information
           to the compiler about used and externally visible symbols.  When the linker plugin is not
           available,  -fwhole-program  should  be  used  to  allow  the  compiler  to  make   these
           assumptions, which leads to more aggressive optimization decisions.

           When a file is compiled with -flto without -fuse-linker-plugin, the generated object file
           is  larger  than a regular object file because it contains GIMPLE bytecodes and the usual
           final code (see -ffat-lto-objects).  This means that object files  with  LTO  information
           can  be  linked  as  normal  object  files;  if  -fno-lto  is  passed  to  the linker, no
           interprocedural optimizations  are  applied.   Note  that  when  -fno-fat-lto-objects  is
           enabled  the  compile  stage  is faster but you cannot perform a regular, non-LTO link on
           them.

           When producing the final binary, GCC only applies link-time optimizations to those  files
           that  contain bytecode.  Therefore, you can mix and match object files and libraries with
           GIMPLE bytecodes and final  object  code.   GCC  automatically  selects  which  files  to
           optimize in LTO mode and which files to link without further processing.

           Generally,  options  specified  at  link  time  override those specified at compile time,
           although in some cases GCC attempts to infer link-time options from the settings used  to
           compile the input files.

           If  you  do  not  specify an optimization level option -O at link time, then GCC uses the
           highest optimization level used when  compiling  the  object  files.   Note  that  it  is
           generally  ineffective  to specify an optimization level option only at link time and not
           at compile time, for two  reasons.   First,  compiling  without  optimization  suppresses
           compiler  passes  that gather information needed for effective optimization at link time.
           Second, some early optimization passes can be performed only at compile time and  not  at
           link time.

           There  are some code generation flags preserved by GCC when generating bytecodes, as they
           need to be used during the final  link.   Currently,  the  following  options  and  their
           settings  are  taken from the first object file that explicitly specifies them: -fcommon,
           -fexceptions, -fnon-call-exceptions, -fgnu-tm and all the -m target flags.

           The following options -fPIC, -fpic, -fpie and -fPIE are combined based on  the  following
           scheme:

                   B<-fPIC> + B<-fpic> = B<-fpic>
                   B<-fPIC> + B<-fno-pic> = B<-fno-pic>
                   B<-fpic/-fPIC> + (no option) = (no option)
                   B<-fPIC> + B<-fPIE> = B<-fPIE>
                   B<-fpic> + B<-fPIE> = B<-fpie>
                   B<-fPIC/-fpic> + B<-fpie> = B<-fpie>

           Certain  ABI-changing flags are required to match in all compilation units, and trying to
           override this at link time with a conflicting value is ignored.   This  includes  options
           such as -freg-struct-return and -fpcc-struct-return.

           Other  options  such  as  -ffp-contract,  -fno-strict-overflow,  -fwrapv,  -fno-trapv  or
           -fno-strict-aliasing are passed through to the link stage and merged  conservatively  for
           conflicting translation units.  Specifically -fno-strict-overflow, -fwrapv and -fno-trapv
           take    precedence;   and   for   example   -ffp-contract=off   takes   precedence   over
           -ffp-contract=fast.  You can override them at link time.

           Diagnostic options such as -Wstringop-overflow are passed through to the link  stage  and
           their  setting  matches that of the compile-step at function granularity.  Note that this
           matters only for diagnostics emitted during optimization.  Note that code transforms such
           as inlining can lead to warnings being enabled  or  disabled  for  regions  if  code  not
           consistent with the setting at compile time.

           When you need to pass options to the assembler via -Wa or -Xassembler make sure to either
           compile  such  translation  units  with  -fno-lto  or consistently use the same assembler
           options on all translation units.  You can alternatively also specify  assembler  options
           at LTO link time.

           To  enable  debug  info  generation you need to supply -g at compile time.  If any of the
           input files at link time were built with debug info  generation  enabled  the  link  will
           enable  debug  info generation as well.  Any elaborate debug info settings like the dwarf
           level -gdwarf-5 need to be explicitly repeated at the  linker  command  line  and  mixing
           different settings in different translation units is discouraged.

           If  LTO  encounters  objects  with C linkage declared with incompatible types in separate
           translation units to be linked together (undefined behavior according to ISO C99  6.2.7),
           a  non-fatal  diagnostic  may  be  issued.   The behavior is still undefined at run time.
           Similar diagnostics may be raised for other languages.

           Another feature of LTO is that it is possible to apply interprocedural  optimizations  on
           files written in different languages:

                   gcc -c -flto foo.c
                   g++ -c -flto bar.cc
                   gfortran -c -flto baz.f90
                   g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

           Notice  that  the  final  link  is  done  with  g++  to get the C++ runtime libraries and
           -lgfortran is added to get the  Fortran  runtime  libraries.   In  general,  when  mixing
           languages  in  LTO  mode,  you  should  use  the same link command options as when mixing
           languages in a regular (non-LTO) compilation.

           If object files containing GIMPLE bytecode are stored in a library archive, say libfoo.a,
           it is possible to extract and use them in an LTO link if you  are  using  a  linker  with
           plugin  support.   To create static libraries suitable for LTO, use gcc-ar and gcc-ranlib
           instead of ar and ranlib; to show the symbols of object files with GIMPLE  bytecode,  use
           gcc-nm.   Those  commands  require  that ar, ranlib and nm have been compiled with plugin
           support.  At link time, use the flag  -fuse-linker-plugin  to  ensure  that  the  library
           participates in the LTO optimization process:

                   gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

           With the linker plugin enabled, the linker extracts the needed GIMPLE files from libfoo.a
           and passes them on to the running GCC to make them part of the aggregated GIMPLE image to
           be optimized.

           If you are not using a linker with plugin support and/or do not enable the linker plugin,
           then  the  objects  inside  libfoo.a  are  extracted and linked as usual, but they do not
           participate in the LTO optimization process.  In order to make a static library  suitable
           for  both  LTO  optimization  and  usual  linkage,  compile  its  object files with -flto
           -ffat-lto-objects.

           Link-time optimizations do not require the presence of the whole program to operate.   If
           the  program does not require any symbols to be exported, it is possible to combine -flto
           and -fwhole-program to allow  the  interprocedural  optimizers  to  use  more  aggressive
           assumptions   which   may   lead   to   improved   optimization  opportunities.   Use  of
           -fwhole-program is not needed when linker plugin is active (see -fuse-linker-plugin).

           The current implementation of LTO makes no attempt to generate bytecode that is  portable
           between different types of hosts.  The bytecode files are versioned and there is a strict
           version  check,  so  bytecode  files  generated in one version of GCC do not work with an
           older or newer version of GCC.

           Link-time optimization does not work well with generation  of  debugging  information  on
           systems other than those using a combination of ELF and DWARF.

           If  you specify the optional n, the optimization and code generation done at link time is
           executed in parallel using n parallel jobs by utilizing an installed make  program.   The
           environment variable MAKE may be used to override the program used.

           You  can  also specify -flto=jobserver to use GNU make's job server mode to determine the
           number of parallel jobs. This  is  useful  when  the  Makefile  calling  GCC  is  already
           executing in parallel.  You must prepend a + to the command recipe in the parent Makefile
           for  this  to work.  This option likely only works if MAKE is GNU make.  Even without the
           option value, GCC tries to automatically detect a running GNU make's job server.

           Use -flto=auto to use GNU make's job server, if available,  or  otherwise  fall  back  to
           autodetection of the number of CPU threads present in your system.

       -flto-partition=alg
           Specify  the partitioning algorithm used by the link-time optimizer.  The value is either
           1to1 to specify a partitioning mirroring the original source files or balanced to specify
           partitioning into equally sized chunks (whenever possible) or max to create new partition
           for every symbol where possible.  Specifying none as an algorithm  disables  partitioning
           and  streaming  completely.   The default value is balanced. While 1to1 can be used as an
           workaround for various code  ordering  issues,  the  max  partitioning  is  intended  for
           internal testing only.  The value one specifies that exactly one partition should be used
           while  the  value none bypasses partitioning and executes the link-time optimization step
           directly from the WPA phase.

       -flto-compression-level=n
           This option specifies the level of compression used for intermediate language written  to
           LTO  object  files,  and  is  only  meaningful in conjunction with LTO mode (-flto).  GCC
           currently supports two LTO compression algorithms. For  zstd,  valid  values  are  0  (no
           compression) to 19 (maximum compression), while zlib supports values from 0 to 9.  Values
           outside  this range are clamped to either minimum or maximum of the supported values.  If
           the option is not given, a default balanced compression setting is used.

       -fuse-linker-plugin
           Enables the use of a linker plugin during link-time optimization.  This option relies  on
           plugin support in the linker, which is available in gold or in GNU ld 2.21 or newer.

           This  option  enables  the extraction of object files with GIMPLE bytecode out of library
           archives. This improves the quality of optimization by exposing more code  to  the  link-
           time  optimizer.   This information specifies what symbols can be accessed externally (by
           non-LTO object or during  dynamic  linking).   Resulting  code  quality  improvements  on
           binaries   (and   shared   libraries   that   use   hidden  visibility)  are  similar  to
           -fwhole-program.  See -flto for a description of the effect of this flag and how  to  use
           it.

           This  option  is  enabled  by  default  when  LTO  support  in GCC is enabled and GCC was
           configured for use with a linker supporting plugins (GNU ld 2.21 or newer or gold).

       -ffat-lto-objects
           Fat LTO objects are object files that contain both  the  intermediate  language  and  the
           object  code. This makes them usable for both LTO linking and normal linking. This option
           is effective only when compiling with -flto and is ignored at link time.

           -fno-fat-lto-objects improves compilation time over plain LTO, but requires the  complete
           toolchain  to  be aware of LTO. It requires a linker with linker plugin support for basic
           functionality.  Additionally, nm, ar and ranlib need to support linker plugins to allow a
           full-featured build environment (capable of building static libraries etc).  GCC provides
           the gcc-ar, gcc-nm, gcc-ranlib wrappers to pass the right options to  these  tools.  With
           non fat LTO makefiles need to be modified to use them.

           Note  that  modern  binutils  provide  plugin auto-load mechanism.  Installing the linker
           plugin into $libdir/bfd-plugins has the same effect as  usage  of  the  command  wrappers
           (gcc-ar, gcc-nm and gcc-ranlib).

           The default is -fno-fat-lto-objects on targets with linker plugin support.

       -fcompare-elim
           After  register  allocation  and post-register allocation instruction splitting, identify
           arithmetic instructions that compute processor flags similar to  a  comparison  operation
           based on that arithmetic.  If possible, eliminate the explicit comparison operation.

           This pass only applies to certain targets that cannot explicitly represent the comparison
           operation before register allocation is complete.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcprop-registers
           After  register  allocation and post-register allocation instruction splitting, perform a
           copy-propagation pass to try to reduce scheduling dependencies and occasionally eliminate
           the copy.

           Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
           Profiles collected using an  instrumented  binary  for  multi-threaded  programs  may  be
           inconsistent  due  to  missed  counter  updates.  When this option is specified, GCC uses
           heuristics to correct or smooth out such inconsistencies. By default, GCC emits an  error
           message when an inconsistent profile is detected.

           This option is enabled by -fauto-profile.

       -fprofile-partial-training
           With "-fprofile-use" all portions of programs not executed during train run are optimized
           agressively  for  size rather than speed.  In some cases it is not practical to train all
           possible hot paths in the program. (For example, program may contain  functions  specific
           for  a  given  hardware and trianing may not cover all hardware configurations program is
           run on.)  With "-fprofile-partial-training" profile feedback  will  be  ignored  for  all
           functions  not executed during the train run leading them to be optimized as if they were
           compiled without profile feedback. This leads to better performance when train run is not
           representative but also leads to significantly bigger code.

       -fprofile-use
       -fprofile-use=path
           Enable profile feedback-directed optimizations, and the following optimizations, many  of
           which are generally profitable only with profile feedback available:

           -fbranch-probabilities   -fprofile-values  -funroll-loops   -fpeel-loops  -ftracer  -fvpt
           -finline-functions    -fipa-cp    -fipa-cp-clone    -fipa-bit-cp   -fpredictive-commoning
           -fsplit-loops       -funswitch-loops      -fgcse-after-reload       -ftree-loop-vectorize
           -ftree-slp-vectorize      -fvect-cost-model=dynamic       -ftree-loop-distribute-patterns
           -fprofile-reorder-functions

           Before you can use this option, you must first generate profiling information.

           By  default,  GCC emits an error message if the feedback profiles do not match the source
           code.  This error can be turned into a  warning  by  using  -Wno-error=coverage-mismatch.
           Note  this may result in poorly optimized code.  Additionally, by default, GCC also emits
           a warning message if the feedback profiles do not exist (see -Wmissing-profile).

           If path is specified, GCC looks at the path to find the profile feedback data files.  See
           -fprofile-dir.

       -fauto-profile
       -fauto-profile=path
           Enable  sampling-based  feedback-directed optimizations, and the following optimizations,
           many of which are generally profitable only with profile feedback available:

           -fbranch-probabilities  -fprofile-values -funroll-loops   -fpeel-loops   -ftracer   -fvpt
           -finline-functions    -fipa-cp    -fipa-cp-clone    -fipa-bit-cp   -fpredictive-commoning
           -fsplit-loops       -funswitch-loops      -fgcse-after-reload       -ftree-loop-vectorize
           -ftree-slp-vectorize      -fvect-cost-model=dynamic       -ftree-loop-distribute-patterns
           -fprofile-correction

           path is the name of a file  containing  AutoFDO  profile  information.   If  omitted,  it
           defaults to fbdata.afdo in the current directory.

           Producing  an  AutoFDO  profile  data  file  requires  running your program with the perf
           utility  on  a  supported  GNU/Linux  target   system.    For   more   information,   see
           <https://perf.wiki.kernel.org/>.

           E.g.

                   perf record -e br_inst_retired:near_taken -b -o perf.data \
                       -- your_program

           Then  use  the  create_gcov  tool to convert the raw profile data to a format that can be
           used by GCC.  You must also supply the unstripped binary for your program to  this  tool.
           See <https://github.com/google/autofdo>.

           E.g.

                   create_gcov --binary=your_program.unstripped --profile=perf.data \
                       --gcov=profile.afdo

       The  following  options control compiler behavior regarding floating-point arithmetic.  These
       options trade off between speed and correctness.  All must be specifically enabled.

       -ffloat-store
           Do not store floating-point variables in registers, and inhibit other options that  might
           change whether a floating-point value is taken from a register or memory.

           This option prevents undesirable excess precision on machines such as the 68000 where the
           floating  registers  (of  the  68881)  keep more precision than a "double" is supposed to
           have.  Similarly for the x86 architecture.  For most programs, the excess precision  does
           only good, but a few programs rely on the precise definition of IEEE floating point.  Use
           -ffloat-store for such programs, after modifying them to store all pertinent intermediate
           computations into variables.

       -fexcess-precision=style
           This option allows further control over excess precision on machines where floating-point
           operations  occur  in  a  format  with more precision or range than the IEEE standard and
           interchange floating-point types.  By default, -fexcess-precision=fast is in effect; this
           means that operations may be carried out in a wider precision than the types specified in
           the source if that would result in faster code, and it is unpredictable when rounding  to
           the   types   specified   in   the  source  code  takes  place.   When  compiling  C,  if
           -fexcess-precision=standard  is  specified  then  excess  precision  follows  the   rules
           specified  in  ISO  C99;  in  particular,  both  casts and assignments cause values to be
           rounded to their semantic types (whereas -ffloat-store only affects  assignments).   This
           option  is  enabled  by  default for C if a strict conformance option such as -std=c99 is
           used.  -ffast-math enables -fexcess-precision=fast by default  regardless  of  whether  a
           strict conformance option is used.

           -fexcess-precision=standard  is  not implemented for languages other than C.  On the x86,
           it has no effect if -mfpmath=sse or -mfpmath=sse+387 is specified; in  the  former  case,
           IEEE   semantics  apply  without  excess  precision,  and  in  the  latter,  rounding  is
           unpredictable.

       -ffast-math
           Sets  the  options  -fno-math-errno,   -funsafe-math-optimizations,   -ffinite-math-only,
           -fno-rounding-math, -fno-signaling-nans, -fcx-limited-range and -fexcess-precision=fast.

           This option causes the preprocessor macro "__FAST_MATH__" to be defined.

           This  option  is  not  turned  on  by any -O option besides -Ofast since it can result in
           incorrect output for programs that depend on an  exact  implementation  of  IEEE  or  ISO
           rules/specifications  for math functions. It may, however, yield faster code for programs
           that do not require the guarantees of these specifications.

       -fno-math-errno
           Do not set "errno"  after  calling  math  functions  that  are  executed  with  a  single
           instruction,  e.g.,  "sqrt".   A  program  that  relies on IEEE exceptions for math error
           handling may  want  to  use  this  flag  for  speed  while  maintaining  IEEE  arithmetic
           compatibility.

           This option is not turned on by any -O option since it can result in incorrect output for
           programs  that  depend on an exact implementation of IEEE or ISO rules/specifications for
           math functions. It may, however, yield faster code for programs that do not  require  the
           guarantees of these specifications.

           The default is -fmath-errno.

           On Darwin systems, the math library never sets "errno".  There is therefore no reason for
           the  compiler  to  consider  the  possibility  that  it might, and -fno-math-errno is the
           default.

       -funsafe-math-optimizations
           Allow optimizations for floating-point arithmetic that  (a)  assume  that  arguments  and
           results are valid and (b) may violate IEEE or ANSI standards.  When used at link time, it
           may  include libraries or startup files that change the default FPU control word or other
           similar optimizations.

           This option is not turned on by any -O option since it can result in incorrect output for
           programs that depend on an exact implementation of IEEE or ISO  rules/specifications  for
           math  functions.  It may, however, yield faster code for programs that do not require the
           guarantees  of  these  specifications.   Enables  -fno-signed-zeros,  -fno-trapping-math,
           -fassociative-math and -freciprocal-math.

           The default is -fno-unsafe-math-optimizations.

       -fassociative-math
           Allow  re-association  of operands in series of floating-point operations.  This violates
           the ISO C and C++ language standard by possibly changing computation result.   NOTE:  re-
           ordering  may  change  the  sign  of  zero  as  well as ignore NaNs and inhibit or create
           underflow or overflow (and thus cannot be used on code that relies on  rounding  behavior
           like "(x + 2**52) - 2**52".  May also reorder floating-point comparisons and thus may not
           be  used  when  ordered  comparisons  are  required.   This  option  requires  that  both
           -fno-signed-zeros and -fno-trapping-math be in effect.  Moreover, it  doesn't  make  much
           sense  with  -frounding-math.  For  Fortran the option is automatically enabled when both
           -fno-signed-zeros and -fno-trapping-math are in effect.

           The default is -fno-associative-math.

       -freciprocal-math
           Allow the reciprocal of a value to be used instead of  dividing  by  the  value  if  this
           enables  optimizations.   For  example "x / y" can be replaced with "x * (1/y)", which is
           useful if "(1/y)" is subject to common subexpression elimination.  Note that  this  loses
           precision and increases the number of flops operating on the value.

           The default is -fno-reciprocal-math.

       -ffinite-math-only
           Allow  optimizations for floating-point arithmetic that assume that arguments and results
           are not NaNs or +-Infs.

           This option is not turned on by any -O option since it can result in incorrect output for
           programs that depend on an exact implementation of IEEE or ISO  rules/specifications  for
           math  functions.  It may, however, yield faster code for programs that do not require the
           guarantees of these specifications.

           The default is -fno-finite-math-only.

       -fno-signed-zeros
           Allow optimizations for floating-point arithmetic that ignore  the  signedness  of  zero.
           IEEE  arithmetic  specifies  the  behavior  of  distinct +0.0 and -0.0 values, which then
           prohibits  simplification  of  expressions  such   as   x+0.0   or   0.0*x   (even   with
           -ffinite-math-only).   This  option  implies  that  the  sign  of  a  zero  result  isn't
           significant.

           The default is -fsigned-zeros.

       -fno-trapping-math
           Compile code assuming that floating-point operations cannot generate user-visible  traps.
           These  traps  include  division  by zero, overflow, underflow, inexact result and invalid
           operation.  This option requires that -fno-signaling-nans be  in  effect.   Setting  this
           option may allow faster code if one relies on "non-stop" IEEE arithmetic, for example.

           This  option  should never be turned on by any -O option since it can result in incorrect
           output  for  programs  that  depend  on  an  exact  implementation   of   IEEE   or   ISO
           rules/specifications for math functions.

           The default is -ftrapping-math.

       -frounding-math
           Disable  transformations  and  optimizations  that assume default floating-point rounding
           behavior.  This is round-to-zero for all  floating  point  to  integer  conversions,  and
           round-to-nearest  for  all other arithmetic truncations.  This option should be specified
           for programs that change the FP rounding mode dynamically, or that may be executed with a
           non-default rounding mode.  This  option  disables  constant  folding  of  floating-point
           expressions  at  compile  time  (which  may  be affected by rounding mode) and arithmetic
           transformations that are unsafe in the presence of sign-dependent rounding modes.

           The default is -fno-rounding-math.

           This option is  experimental  and  does  not  currently  guarantee  to  disable  all  GCC
           optimizations  that  are  affected  by rounding mode.  Future versions of GCC may provide
           finer control of this setting using C99's "FENV_ACCESS" pragma.  This command-line option
           will be used to specify the default state for "FENV_ACCESS".

       -fsignaling-nans
           Compile code assuming that IEEE signaling NaNs may  generate  user-visible  traps  during
           floating-point  operations.   Setting  this option disables optimizations that may change
           the  number  of  exceptions  visible  with   signaling   NaNs.    This   option   implies
           -ftrapping-math.

           This option causes the preprocessor macro "__SUPPORT_SNAN__" to be defined.

           The default is -fno-signaling-nans.

           This  option  is  experimental  and  does  not  currently  guarantee  to  disable all GCC
           optimizations that affect signaling NaN behavior.

       -fno-fp-int-builtin-inexact
           Do not allow the built-in functions "ceil",  "floor",  "round"  and  "trunc",  and  their
           "float"  and "long double" variants, to generate code that raises the "inexact" floating-
           point exception for noninteger arguments.  ISO C99 and C11 allow these functions to raise
           the "inexact" exception, but ISO/IEC TS 18661-1:2014, the C bindings to IEEE 754-2008, as
           integrated into ISO C2X, does not allow these functions to do so.

           The default is -ffp-int-builtin-inexact, allowing the exception to be raised, unless  C2X
           or a later C standard is selected.  This option does nothing unless -ftrapping-math is in
           effect.

           Even  if  -fno-fp-int-builtin-inexact  is  used,  if  the  functions generate a call to a
           library function then the "inexact" exception may be raised if the library implementation
           does not follow TS 18661.

       -fsingle-precision-constant
           Treat floating-point constants as single precision instead of implicitly converting  them
           to double-precision constants.

       -fcx-limited-range
           When  enabled,  this  option  states  that  a  range  reduction  step  is not needed when
           performing complex division.  Also, there is no checking whether the result of a  complex
           multiplication  or  division is "NaN + I*NaN", with an attempt to rescue the situation in
           that case.  The default is -fno-cx-limited-range, but is enabled by -ffast-math.

           This option controls the default  setting  of  the  ISO  C99  "CX_LIMITED_RANGE"  pragma.
           Nevertheless, the option applies to all languages.

       -fcx-fortran-rules
           Complex  multiplication  and  division  follow Fortran rules.  Range reduction is done as
           part of complex division, but there is no  checking  whether  the  result  of  a  complex
           multiplication  or  division is "NaN + I*NaN", with an attempt to rescue the situation in
           that case.

           The default is -fno-cx-fortran-rules.

       The following options control optimizations that may improve performance, but are not enabled
       by any -O options.  This section includes experimental options that may produce broken code.

       -fbranch-probabilities
           After running a program compiled with -fprofile-arcs, you can compile it  a  second  time
           using  -fbranch-probabilities, to improve optimizations based on the number of times each
           branch was taken.  When a program  compiled  with  -fprofile-arcs  exits,  it  saves  arc
           execution  counts to a file called sourcename.gcda for each source file.  The information
           in this data file is very dependent on the structure of the generated code, so  you  must
           use the same source code and the same optimization options for both compilations.

           With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each JUMP_INSN and CALL_INSN.
           These  can  be used to improve optimization.  Currently, they are only used in one place:
           in reorg.c, instead of guessing  which  path  a  branch  is  most  likely  to  take,  the
           REG_BR_PROB values are used to exactly determine which path is taken more often.

           Enabled by -fprofile-use and -fauto-profile.

       -fprofile-values
           If  combined  with  -fprofile-arcs,  it  adds  code  so  that  some  data about values of
           expressions in the program is gathered.

           With -fbranch-probabilities, it reads back the data gathered  from  profiling  values  of
           expressions for usage in optimizations.

           Enabled by -fprofile-generate, -fprofile-use, and -fauto-profile.

       -fprofile-reorder-functions
           Function  reordering based on profile instrumentation collects first time of execution of
           a function and orders these functions in ascending order.

           Enabled with -fprofile-use.

       -fvpt
           If combined with -fprofile-arcs, this option instructs the compiler to add code to gather
           information about values of expressions.

           With -fbranch-probabilities, it reads back the data gathered and  actually  performs  the
           optimizations  based  on  them.   Currently  the  optimizations include specialization of
           division operations using the knowledge about the value of the denominator.

           Enabled with -fprofile-use and -fauto-profile.

       -frename-registers
           Attempt to avoid false dependencies in scheduled code by making  use  of  registers  left
           over  after register allocation.  This optimization most benefits processors with lots of
           registers.  Depending on the debug information format adopted by the target, however,  it
           can make debugging impossible, since variables no longer stay in a "home register".

           Enabled by default with -funroll-loops.

       -fschedule-fusion
           Performs  a target dependent pass over the instruction stream to schedule instructions of
           same type together because target machine can execute them more efficiently if  they  are
           adjacent to each other in the instruction flow.

           Enabled at levels -O2, -O3, -Os.

       -ftracer
           Perform  tail duplication to enlarge superblock size.  This transformation simplifies the
           control flow of the function allowing other optimizations to do a better job.

           Enabled by -fprofile-use and -fauto-profile.

       -funroll-loops
           Unroll loops whose number of iterations can be determined at compile time or  upon  entry
           to    the    loop.     -funroll-loops    implies    -frerun-cse-after-loop,   -fweb   and
           -frename-registers.  It also turns on complete loop peeling  (i.e.  complete  removal  of
           loops  with  a  small constant number of iterations).  This option makes code larger, and
           may or may not make it run faster.

           Enabled by -fprofile-use and -fauto-profile.

       -funroll-all-loops
           Unroll all loops, even if their number of  iterations  is  uncertain  when  the  loop  is
           entered.   This  usually  makes programs run more slowly.  -funroll-all-loops implies the
           same options as -funroll-loops.

       -fpeel-loops
           Peels loops for which there is enough information  that  they  do  not  roll  much  (from
           profile  feedback  or  static  analysis).   It  also turns on complete loop peeling (i.e.
           complete removal of loops with small constant number of iterations).

           Enabled by -O3, -fprofile-use, and -fauto-profile.

       -fmove-loop-invariants
           Enables the loop invariant motion pass in the RTL loop optimizer.  Enabled at  level  -O1
           and higher, except for -Og.

       -fsplit-loops
           Split  a  loop into two if it contains a condition that's always true for one side of the
           iteration space and false for the other.

           Enabled by -fprofile-use and -fauto-profile.

       -funswitch-loops
           Move branches with loop invariant conditions out of the loop, with duplicates of the loop
           on both branches (modified according to result of the condition).

           Enabled by -fprofile-use and -fauto-profile.

       -fversion-loops-for-strides
           If a loop iterates over an array with a variable stride, create another  version  of  the
           loop that assumes the stride is always one.  For example:

                   for (int i = 0; i < n; ++i)
                     x[i * stride] = ...;

           becomes:

                   if (stride == 1)
                     for (int i = 0; i < n; ++i)
                       x[i] = ...;
                   else
                     for (int i = 0; i < n; ++i)
                       x[i * stride] = ...;

           This  is  particularly  useful for assumed-shape arrays in Fortran where (for example) it
           allows better vectorization assuming  contiguous  accesses.   This  flag  is  enabled  by
           default at -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -ffunction-sections
       -fdata-sections
           Place  each  function  or data item into its own section in the output file if the target
           supports arbitrary sections.  The name of the function or  the  name  of  the  data  item
           determines the section's name in the output file.

           Use  these  options  on  systems  where  the  linker can perform optimizations to improve
           locality of reference in the instruction space.  Most systems using the ELF object format
           have linkers with such optimizations.  On AIX, the linker  rearranges  sections  (CSECTs)
           based on the call graph.  The performance impact varies.

           Together with a linker garbage collection (linker --gc-sections option) these options may
           lead to smaller statically-linked executables (after stripping).

           On  ELF/DWARF  systems  these  options  do  not  degenerate  the  quality  of  the  debug
           information.  There could be issues with other object files/debug info formats.

           Only use these options when there are significant  benefits  from  doing  so.   When  you
           specify these options, the assembler and linker create larger object and executable files
           and  are  also slower.  These options affect code generation.  They prevent optimizations
           by the compiler and assembler using relative locations inside a  translation  unit  since
           the  locations  are  unknown  until  link  time.   An  example of such an optimization is
           relaxing calls to short call instructions.

       -fstdarg-opt
           Optimize the prologue of variadic argument functions  with  respect  to  usage  of  those
           arguments.

           NOTE:  In Ubuntu 14.10 and later versions, -fstack-protector-strong is enabled by default
           for C, C++, ObjC, ObjC++, if none of -fno-stack-protector, -nostdlib, nor  -ffreestanding
           are found.

       -fsection-anchors
           Try  to  reduce  the  number  of  symbolic  address calculations by using shared "anchor"
           symbols to address nearby objects.  This transformation can help to reduce the number  of
           GOT entries and GOT accesses on some targets.

           For example, the implementation of the following function "foo":

                   static int a, b, c;
                   int foo (void) { return a + b + c; }

           usually  calculates  the  addresses  of  all  three variables, but if you compile it with
           -fsection-anchors, it accesses the variables from a common  anchor  point  instead.   The
           effect is similar to the following pseudocode (which isn't valid C):

                   int foo (void)
                   {
                     register int *xr = &x;
                     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                   }

           Not all targets support this option.

       -fzero-call-used-regs=choice
           Zero  call-used  registers  at  function  return  to  increase program security by either
           mitigating Return-Oriented Programming (ROP) attacks or  preventing  information  leakage
           through registers.

           The  possible  values  of choice are the same as for the "zero_call_used_regs" attribute.
           The default is skip.

           You can control this behavior for a specific function by  using  the  function  attribute
           "zero_call_used_regs".

       --param name=value
           In  some places, GCC uses various constants to control the amount of optimization that is
           done.  For example, GCC does not inline functions that contain more than a certain number
           of instructions.  You can control some of these constants on the command line  using  the
           --param option.

           The  names  of  specific  parameters,  and  the  meaning  of  the values, are tied to the
           internals of the compiler, and are subject to change without notice in future releases.

           In order to get  minimal,  maximal  and  default  value  of  a  parameter,  one  can  use
           --help=param -Q options.

           In  each case, the value is an integer.  The following choices of name are recognized for
           all targets:

           predictable-branch-outcome
               When branch is predicted to be taken with probability lower than this  threshold  (in
               percent), then it is considered well predictable.

           max-rtl-if-conversion-insns
               RTL  if-conversion  tries  to  remove conditional branches around a block and replace
               them with conditionally executed instructions.   This  parameter  gives  the  maximum
               number  of instructions in a block which should be considered for if-conversion.  The
               compiler will also use other heuristics to decide whether if-conversion is likely  to
               be profitable.

           max-rtl-if-conversion-predictable-cost
               RTL  if-conversion will try to remove conditional branches around a block and replace
               them with conditionally executed instructions.  These  parameters  give  the  maximum
               permissible  cost for the sequence that would be generated by if-conversion depending
               on whether the branch is statically determined to be predictable or not.   The  units
               for  this  parameter are the same as those for the GCC internal seq_cost metric.  The
               compiler will try to provide a  reasonable  default  for  this  parameter  using  the
               BRANCH_COST target macro.

           max-crossjump-edges
               The  maximum  number  of incoming edges to consider for cross-jumping.  The algorithm
               used by -fcrossjumping is O(N^2) in the number  of  edges  incoming  to  each  block.
               Increasing  values  mean  more  aggressive  optimization, making the compilation time
               increase with probably small improvement in executable size.

           min-crossjump-insns
               The minimum number of instructions that must be matched at  the  end  of  two  blocks
               before  cross-jumping  is performed on them.  This value is ignored in the case where
               all instructions in the block being cross-jumped from are matched.

           max-grow-copy-bb-insns
               The maximum code size expansion factor when copying basic blocks instead of  jumping.
               The expansion is relative to a jump instruction.

           max-goto-duplication-insns
               The  maximum  number of instructions to duplicate to a block that jumps to a computed
               goto.  To avoid O(N^2) behavior in a number of passes,  GCC  factors  computed  gotos
               early  in  the  compilation  process,  and  unfactors them as late as possible.  Only
               computed jumps at the end of a basic blocks with no more  than  max-goto-duplication-
               insns are unfactored.

           max-delay-slot-insn-search
               The  maximum  number  of  instructions to consider when looking for an instruction to
               fill a delay slot.  If more than this arbitrary number of instructions are  searched,
               the  time  savings  from  filling  the  delay  slot  are  minimal, so stop searching.
               Increasing values mean more aggressive  optimization,  making  the  compilation  time
               increase with probably small improvement in execution time.

           max-delay-slot-live-search
               When  trying to fill delay slots, the maximum number of instructions to consider when
               searching for  a  block  with  valid  live  register  information.   Increasing  this
               arbitrarily   chosen   value  means  more  aggressive  optimization,  increasing  the
               compilation time.  This parameter should be removed  when  the  delay  slot  code  is
               rewritten to maintain the control-flow graph.

           max-gcse-memory
               The  approximate  maximum  amount of memory in "kB" that can be allocated in order to
               perform the global common subexpression elimination  optimization.   If  more  memory
               than specified is required, the optimization is not done.

           max-gcse-insertion-ratio
               If  the ratio of expression insertions to deletions is larger than this value for any
               expression, then RTL PRE inserts or removes the expression and thus leaves  partially
               redundant computations in the instruction stream.

           max-pending-list-length
               The  maximum  number  of  pending  dependencies scheduling allows before flushing the
               current state and starting over.  Large functions with  few  branches  or  calls  can
               create excessively large lists which needlessly consume memory and resources.

           max-modulo-backtrack-attempts
               The  maximum  number  of  backtrack  attempts  the  scheduler should make when modulo
               scheduling a loop.  Larger values can exponentially increase compilation time.

           max-inline-insns-single
               Several parameters control the tree inliner  used  in  GCC.   This  number  sets  the
               maximum number of instructions (counted in GCC's internal representation) in a single
               function  that  the tree inliner considers for inlining.  This only affects functions
               declared inline and methods implemented in a class declaration (C++).

           max-inline-insns-auto
               When you use -finline-functions (included in -O3), a  lot  of  functions  that  would
               otherwise  not be considered for inlining by the compiler are investigated.  To those
               functions, a different (more restrictive) limit compared to functions declared inline
               can be applied (--param max-inline-insns-auto).

           max-inline-insns-small
               This   is   bound   applied   to   calls   which   are   considered   relevant   with
               -finline-small-functions.

           max-inline-insns-size
               This  is  bound  applied  to  calls which are optimized for size. Small growth may be
               desirable to anticipate optimization oppurtunities exposed by inlining.

           uninlined-function-insns
               Number of instructions accounted by inliner for function overhead  such  as  function
               prologue and epilogue.

           uninlined-function-time
               Extra  time accounted by inliner for function overhead such as time needed to execute
               function prologue and epilogue

           inline-heuristics-hint-percent
               The scale  (in  percents)  applied  to  inline-insns-single,  inline-insns-single-O2,
               inline-insns-auto when inline heuristics hints that inlining is very profitable (will
               enable later optimizations).

           uninlined-thunk-insns
           uninlined-thunk-time
               Same  as  --param  uninlined-function-insns  and  --param uninlined-function-time but
               applied to function thunks

           inline-min-speedup
               When estimated performance improvement  of  caller  +  callee  runtime  exceeds  this
               threshold  (in  percent),  the  function  can  be  inlined regardless of the limit on
               --param max-inline-insns-single and --param max-inline-insns-auto.

           large-function-insns
               The limit specifying really large functions.  For functions larger  than  this  limit
               after  inlining,  inlining  is  constrained  by  --param large-function-growth.  This
               parameter is useful primarily to avoid extreme compilation time caused by  non-linear
               algorithms used by the back end.

           large-function-growth
               Specifies  maximal  growth  of  large  function  caused by inlining in percents.  For
               example, parameter value 100 limits large function growth to 2.0 times  the  original
               size.

           large-unit-insns
               The  limit  specifying  large  translation  unit.  Growth caused by inlining of units
               larger than this limit is limited by --param  inline-unit-growth.   For  small  units
               this  might be too tight.  For example, consider a unit consisting of function A that
               is inline and B that just calls A three times.  If B is  small  relative  to  A,  the
               growth  of  unit  is  300\% and yet such inlining is very sane.  For very large units
               consisting of small inlineable functions, however, the overall unit growth  limit  is
               needed to avoid exponential explosion of code size.  Thus for smaller units, the size
               is increased to --param large-unit-insns before applying --param inline-unit-growth.

           lazy-modules
               Maximum number of concurrently open C++ module files when lazy loading.

           inline-unit-growth
               Specifies  maximal  overall  growth  of the compilation unit caused by inlining.  For
               example, parameter value 20 limits unit growth to 1.2 times the original  size.  Cold
               functions  (either  marked  cold  via  an  attribute  or by profile feedback) are not
               accounted into the unit size.

           ipa-cp-unit-growth
               Specifies maximal overall growth of the compilation unit  caused  by  interprocedural
               constant  propagation.   For  example,  parameter  value 10 limits unit growth to 1.1
               times the original size.

           ipa-cp-large-unit-insns
               The size of translation unit that IPA-CP pass considers large.

           large-stack-frame
               The limit specifying large stack frames.  While inlining the algorithm is  trying  to
               not grow past this limit too much.

           large-stack-frame-growth
               Specifies  maximal  growth of large stack frames caused by inlining in percents.  For
               example, parameter value 1000 limits  large  stack  frame  growth  to  11  times  the
               original size.

           max-inline-insns-recursive
           max-inline-insns-recursive-auto
               Specifies  the maximum number of instructions an out-of-line copy of a self-recursive
               inline function can grow into by performing recursive inlining.

               --param  max-inline-insns-recursive  applies  to  functions  declared  inline.    For
               functions    not    declared   inline,   recursive   inlining   happens   only   when
               -finline-functions (included in -O3) is enabled; --param  max-inline-insns-recursive-
               auto applies instead.

           max-inline-recursive-depth
           max-inline-recursive-depth-auto
               Specifies the maximum recursion depth used for recursive inlining.

               --param   max-inline-recursive-depth  applies  to  functions  declared  inline.   For
               functions   not   declared   inline,   recursive   inlining   happens    only    when
               -finline-functions  (included in -O3) is enabled; --param max-inline-recursive-depth-
               auto applies instead.

           min-inline-recursive-probability
               Recursive inlining is profitable only for function having deep recursion  in  average
               and  can  hurt  for function having little recursion depth by increasing the prologue
               size or complexity of function body to other optimizers.

               When profile feedback is available  (see  -fprofile-generate)  the  actual  recursion
               depth  can  be  guessed  from the probability that function recurses via a given call
               expression.   This  parameter  limits  inlining  only  to  call   expressions   whose
               probability exceeds the given threshold (in percents).

           early-inlining-insns
               Specify growth that the early inliner can make.  In effect it increases the amount of
               inlining for code having a large abstraction penalty.

           max-early-inliner-iterations
               Limit of iterations of the early inliner.  This basically bounds the number of nested
               indirect  calls  the  early  inliner can resolve.  Deeper chains are still handled by
               late inlining.

           comdat-sharing-probability
               Probability (in percent) that C++ inline function with comdat visibility  are  shared
               across multiple compilation units.

           modref-max-bases
           modref-max-refs
           modref-max-accesses
               Specifies  the  maximal number of base pointers, references and accesses stored for a
               single function by mod/ref analysis.

           modref-max-tests
               Specifies the maxmal number of tests alias oracle can perform to disambiguate  memory
               locations  using  the  mod/ref  information.   This parameter ought to be bigger than
               --param modref-max-bases and --param modref-max-refs.

           modref-max-depth
               Specifies the maximum depth of DFS walk used by modref escape analysis.  Setting to 0
               disables the analysis completely.

           modref-max-escape-points
               Specifies the maximum number of escape points tracked by modref per SSA-name.

           profile-func-internal-id
               A parameter to control whether to  use  function  internal  id  in  profile  database
               lookup.  If  the  value  is  0,  the  compiler  uses  an id that is based on function
               assembler name and filename, which makes old profile data  more  tolerant  to  source
               changes such as function reordering etc.

           min-vect-loop-bound
               The  minimum  number  of  iterations  under  which  loops  are  not  vectorized  when
               -ftree-vectorize is used.  The number of iterations after vectorization needs  to  be
               greater than the value specified by this option to allow vectorization.

           gcse-cost-distance-ratio
               Scaling  factor in calculation of maximum distance an expression can be moved by GCSE
               optimizations.  This is currently supported only in  the  code  hoisting  pass.   The
               bigger the ratio, the more aggressive code hoisting is with simple expressions, i.e.,
               the  expressions  that  have  cost  less  than  gcse-unrestricted-cost.  Specifying 0
               disables hoisting of simple expressions.

           gcse-unrestricted-cost
               Cost, roughly measured as the cost of a single typical machine instruction, at  which
               GCSE  optimizations  do not constrain the distance an expression can travel.  This is
               currently supported only in the code hoisting pass.  The lesser the  cost,  the  more
               aggressive  code  hoisting  is.   Specifying  0  allows  all  expressions  to  travel
               unrestricted distances.

           max-hoist-depth
               The depth of search in the dominator tree for expressions to hoist.  This is used  to
               avoid quadratic behavior in hoisting algorithm.  The value of 0 does not limit on the
               search, but may slow down compilation of huge functions.

           max-tail-merge-comparisons
               The  maximum  amount  of  similar  bbs  to  compare a bb with.  This is used to avoid
               quadratic behavior in tree tail merging.

           max-tail-merge-iterations
               The maximum amount of iterations of the pass over the  function.   This  is  used  to
               limit compilation time in tree tail merging.

           store-merging-allow-unaligned
               Allow the store merging pass to introduce unaligned stores if it is legal to do so.

           max-stores-to-merge
               The  maximum  number  of  stores  to  attempt to merge into wider stores in the store
               merging pass.

           max-store-chains-to-track
               The maximum number of store chains to track at the same time in the attempt to  merge
               them into wider stores in the store merging pass.

           max-stores-to-track
               The maximum number of stores to track at the same time in the attemt to to merge them
               into wider stores in the store merging pass.

           max-unrolled-insns
               The maximum number of instructions that a loop may have to be unrolled.  If a loop is
               unrolled, this parameter also determines how many times the loop code is unrolled.

           max-average-unrolled-insns
               The  maximum number of instructions biased by probabilities of their execution that a
               loop may have to be unrolled.  If a loop is unrolled, this parameter also  determines
               how many times the loop code is unrolled.

           max-unroll-times
               The maximum number of unrollings of a single loop.

           max-peeled-insns
               The  maximum  number of instructions that a loop may have to be peeled.  If a loop is
               peeled, this parameter also determines how many times the loop code is peeled.

           max-peel-times
               The maximum number of peelings of a single loop.

           max-peel-branches
               The maximum number of branches on the hot path through the peeled sequence.

           max-completely-peeled-insns
               The maximum number of insns of a completely peeled loop.

           max-completely-peel-times
               The maximum number of iterations of a loop to be suitable for complete peeling.

           max-completely-peel-loop-nest-depth
               The maximum depth of a loop nest suitable for complete peeling.

           max-unswitch-insns
               The maximum number of insns of an unswitched loop.

           max-unswitch-level
               The maximum number of branches unswitched in a single loop.

           lim-expensive
               The minimum cost of an expensive expression in the loop invariant motion.

           min-loop-cond-split-prob
               When FDO profile information is available, min-loop-cond-split-prob specifies minimum
               threshold for probability of  semi-invariant  condition  statement  to  trigger  loop
               split.

           iv-consider-all-candidates-bound
               Bound on number of candidates for induction variables, below which all candidates are
               considered  for  each  use  in  induction  variable optimizations.  If there are more
               candidates than this, only the most relevant ones are considered to  avoid  quadratic
               time complexity.

           iv-max-considered-uses
               The  induction  variable  optimizations  give up on loops that contain more induction
               variable uses.

           iv-always-prune-cand-set-bound
               If the number of candidates in the set is smaller than  this  value,  always  try  to
               remove unnecessary ivs from the set when adding a new one.

           avg-loop-niter
               Average number of iterations of a loop.

           dse-max-object-size
               Maximum  size  (in  bytes)  of  objects  tracked  bytewise by dead store elimination.
               Larger values may result in larger compilation times.

           dse-max-alias-queries-per-store
               Maximum number of queries into the alias oracle per store.  Larger values  result  in
               larger compilation times and may result in more removed dead stores.

           scev-max-expr-size
               Bound  on  size  of  expressions  used  in  the  scalar  evolutions  analyzer.  Large
               expressions slow the analyzer.

           scev-max-expr-complexity
               Bound on the complexity  of  the  expressions  in  the  scalar  evolutions  analyzer.
               Complex expressions slow the analyzer.

           max-tree-if-conversion-phi-args
               Maximum  number of arguments in a PHI supported by TREE if conversion unless the loop
               is marked with simd pragma.

           vect-max-version-for-alignment-checks
               The maximum number  of  run-time  checks  that  can  be  performed  when  doing  loop
               versioning for alignment in the vectorizer.

           vect-max-version-for-alias-checks
               The  maximum  number  of  run-time  checks  that  can  be  performed  when doing loop
               versioning for alias in the vectorizer.

           vect-max-peeling-for-alignment
               The maximum number of loop peels to enhance access alignment for vectorizer. Value -1
               means no limit.

           max-iterations-to-track
               The maximum number of iterations of a loop the brute-force algorithm for analysis  of
               the number of iterations of the loop tries to evaluate.

           hot-bb-count-fraction
               The  denominator n of fraction 1/n of the maximal execution count of a basic block in
               the entire program that a basic  block  needs  to  at  least  have  in  order  to  be
               considered  hot.   The default is 10000, which means that a basic block is considered
               hot if its execution count is greater than 1/10000 of the maximal execution count.  0
               means that it is never considered hot.  Used in non-LTO mode.

           hot-bb-count-ws-permille
               The number of most executed permilles, ranging  from  0  to  1000,  of  the  profiled
               execution of the entire program to which the execution count of a basic block must be
               part  of in order to be considered hot.  The default is 990, which means that a basic
               block is considered  hot  if  its  execution  count  contributes  to  the  upper  990
               permilles,  or  99.0%, of the profiled execution of the entire program.  0 means that
               it is never considered hot.  Used in LTO mode.

           hot-bb-frequency-fraction
               The denominator n of fraction 1/n of the execution frequency of the entry block of  a
               function  that  a  basic block of this function needs to at least have in order to be
               considered hot.  The default is 1000, which means that a basic  block  is  considered
               hot  in  a function if it is executed more frequently than 1/1000 of the frequency of
               the entry block of the function.  0 means that it is never considered hot.

           unlikely-bb-count-fraction
               The denominator n of fraction 1/n of the  number  of  profiled  runs  of  the  entire
               program  below  which  the  execution count of a basic block must be in order for the
               basic block to be considered unlikely executed.  The default is 20, which means  that
               a  basic  block is considered unlikely executed if it is executed in fewer than 1/20,
               or 5%, of the runs of the program.  0 means that it  is  always  considered  unlikely
               executed.

           max-predicted-iterations
               The maximum number of loop iterations we predict statically.  This is useful in cases
               where  a  function  contains  a  single  loop  with known bound and another loop with
               unknown bound.  The known number of iterations  is  predicted  correctly,  while  the
               unknown number of iterations average to roughly 10.  This means that the loop without
               bounds appears artificially cold relative to the other one.

           builtin-expect-probability
               Control  the probability of the expression having the specified value. This parameter
               takes a percentage (i.e. 0 ... 100) as input.

           builtin-string-cmp-inline-length
               The maximum length of a constant string for a builtin string cmp  call  eligible  for
               inlining.

           align-threshold
               Select fraction of the maximal frequency of executions of a basic block in a function
               to align the basic block.

           align-loop-iterations
               A loop expected to iterate at least the selected number of iterations is aligned.

           tracer-dynamic-coverage
           tracer-dynamic-coverage-feedback
               This  value  is  used  to  limit  superblock  formation  once the given percentage of
               executed instructions is covered.  This limits unnecessary code size expansion.

               The tracer-dynamic-coverage-feedback parameter is used only when profile feedback  is
               available.  The real profiles (as opposed to statically estimated ones) are much less
               balanced allowing the threshold to be larger value.

           tracer-max-code-growth
               Stop  tail  duplication  once  code  growth  has reached given percentage.  This is a
               rather artificial limit, as most of the duplicates  are  eliminated  later  in  cross
               jumping, so it may be set to much higher values than is the desired code growth.

           tracer-min-branch-ratio
               Stop  reverse  growth  when  the  reverse  probability of best edge is less than this
               threshold (in percent).

           tracer-min-branch-probability
           tracer-min-branch-probability-feedback
               Stop forward growth if the best edge has probability lower than this threshold.

               Similarly to tracer-dynamic-coverage two parameters are provided.  tracer-min-branch-
               probability-feedback is used for compilation with profile  feedback  and  tracer-min-
               branch-probability  compilation  without.   The  value  for  compilation with profile
               feedback needs to be more conservative (higher) in order to make tracer effective.

           stack-clash-protection-guard-size
               Specify the size of the operating system provided stack guard  as  2  raised  to  num
               bytes.   Higher  values  may reduce the number of explicit probes, but a value larger
               than the operating system provided guard will leave code vulnerable  to  stack  clash
               style attacks.

           stack-clash-protection-probe-interval
               Stack  clash  protection involves probing stack space as it is allocated.  This param
               controls the maximum distance between probes into the stack as 2 raised to num bytes.
               Higher values may reduce the number of explicit probes, but a value larger  than  the
               operating  system  provided  guard  will  leave  code vulnerable to stack clash style
               attacks.

           max-cse-path-length
               The maximum number of basic blocks on path that CSE considers.

           max-cse-insns
               The maximum number of instructions CSE processes before flushing.

           ggc-min-expand
               GCC uses a garbage collector to manage its own  memory  allocation.   This  parameter
               specifies  the  minimum  percentage  by  which the garbage collector's heap should be
               allowed to expand between collections.  Tuning this may improve compilation speed; it
               has no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when RAM >= 1GB.  If
               "getrlimit" is available, the notion of "RAM" is  the  smallest  of  actual  RAM  and
               "RLIMIT_DATA"  or  "RLIMIT_AS".   If GCC is not able to calculate RAM on a particular
               platform, the lower bound of 30%  is  used.   Setting  this  parameter  and  ggc-min-
               heapsize  to  zero  causes  a full collection to occur at every opportunity.  This is
               extremely slow, but can be useful for debugging.

           ggc-min-heapsize
               Minimum size of the garbage collector's heap before it begins  bothering  to  collect
               garbage.   The  first  collection  occurs  after  the heap expands by ggc-min-expand%
               beyond ggc-min-heapsize.  Again, tuning this may improve compilation speed,  and  has
               no effect on code generation.

               The default is the smaller of RAM/8, RLIMIT_RSS, or a limit that tries to ensure that
               RLIMIT_DATA  or  RLIMIT_AS  are  not  exceeded,  but with a lower bound of 4096 (four
               megabytes) and an upper bound of 131072 (128 megabytes).   If  GCC  is  not  able  to
               calculate  RAM  on  a  particular  platform,  the  lower bound is used.  Setting this
               parameter very large effectively disables garbage collection.  Setting this parameter
               and ggc-min-expand to zero causes a full collection to occur at every opportunity.

           max-reload-search-insns
               The maximum  number  of  instruction  reload  should  look  backward  for  equivalent
               register.    Increasing   values   mean  more  aggressive  optimization,  making  the
               compilation time increase with probably slightly better performance.

           max-cselib-memory-locations
               The maximum number of memory locations cselib should take into  account.   Increasing
               values  mean  more aggressive optimization, making the compilation time increase with
               probably slightly better performance.

           max-sched-ready-insns
               The maximum number of instructions ready to be issued the scheduler  should  consider
               at  any  given  time  during  the first scheduling pass.  Increasing values mean more
               thorough searches, making the compilation time increase with probably little benefit.

           max-sched-region-blocks
               The maximum number of blocks in a region to be considered for interblock scheduling.

           max-pipeline-region-blocks
               The maximum number of blocks in a region to  be  considered  for  pipelining  in  the
               selective scheduler.

           max-sched-region-insns
               The maximum number of insns in a region to be considered for interblock scheduling.

           max-pipeline-region-insns
               The  maximum  number  of  insns  in  a  region to be considered for pipelining in the
               selective scheduler.

           min-spec-prob
               The minimum probability (in percents) of  reaching  a  source  block  for  interblock
               speculative scheduling.

           max-sched-extend-regions-iters
               The  maximum  number  of  iterations  through  CFG  to  extend regions.  A value of 0
               disables region extensions.

           max-sched-insn-conflict-delay
               The maximum conflict delay for an insn to be considered for speculative motion.

           sched-spec-prob-cutoff
               The minimal probability of speculation success (in  percents),  so  that  speculative
               insns are scheduled.

           sched-state-edge-prob-cutoff
               The  minimum probability an edge must have for the scheduler to save its state across
               it.

           sched-mem-true-dep-cost
               Minimal distance (in CPU  cycles)  between  store  and  load  targeting  same  memory
               locations.

           selsched-max-lookahead
               The  maximum  size of the lookahead window of selective scheduling.  It is a depth of
               search for available instructions.

           selsched-max-sched-times
               The maximum number of  times  that  an  instruction  is  scheduled  during  selective
               scheduling.   This  is  the  limit  on  the  number  of  iterations through which the
               instruction may be pipelined.

           selsched-insns-to-rename
               The maximum number of best instructions in the ready list  that  are  considered  for
               renaming in the selective scheduler.

           sms-min-sc
               The minimum value of stage count that swing modulo scheduler generates.

           max-last-value-rtl
               The  maximum size measured as number of RTLs that can be recorded in an expression in
               combiner for a pseudo register as last known value of that register.

           max-combine-insns
               The maximum number of instructions the RTL combiner tries to combine.

           integer-share-limit
               Small integer constants can use a shared  data  structure,  reducing  the  compiler's
               memory  usage  and  increasing  its  speed.   This sets the maximum value of a shared
               integer constant.

           ssp-buffer-size
               The minimum size of buffers (i.e. arrays) that receive stack smashing protection when
               -fstack-protection is used.

               This default before Ubuntu 10.10 was "8". Currently it is "4", to increase the number
               of functions protected by the stack protector.

           min-size-for-stack-sharing
               The minimum size of variables taking part in stack slot sharing when not optimizing.

           max-jump-thread-duplication-stmts
               Maximum number of statements allowed in a block that  needs  to  be  duplicated  when
               threading jumps.

           max-fields-for-field-sensitive
               Maximum  number  of  fields in a structure treated in a field sensitive manner during
               pointer analysis.

           prefetch-latency
               Estimate on  average  number  of  instructions  that  are  executed  before  prefetch
               finishes.    The   distance  prefetched  ahead  is  proportional  to  this  constant.
               Increasing  this  number  may  also  lead  to  less  streams  being  prefetched  (see
               simultaneous-prefetches).

           simultaneous-prefetches
               Maximum number of prefetches that can run at the same time.

           l1-cache-line-size
               The size of cache line in L1 data cache, in bytes.

           l1-cache-size
               The size of L1 data cache, in kilobytes.

           l2-cache-size
               The size of L2 data cache, in kilobytes.

           prefetch-dynamic-strides
               Whether the loop array prefetch pass should issue software prefetch hints for strides
               that  are  non-constant.   In  some cases this may be beneficial, though the fact the
               stride is non-constant may make it hard to predict when there  is  clear  benefit  to
               issuing these hints.

               Set  to  1 if the prefetch hints should be issued for non-constant strides.  Set to 0
               if prefetch hints should be issued only for strides that are known to be constant and
               below prefetch-minimum-stride.

           prefetch-minimum-stride
               Minimum constant stride, in bytes, to start using prefetch hints for.  If the  stride
               is less than this threshold, prefetch hints will not be issued.

               This  setting  is useful for processors that have hardware prefetchers, in which case
               there may be conflicts between the hardware prefetchers and the software prefetchers.
               If the hardware prefetchers have a maximum stride they can handle, it should be  used
               here to improve the use of software prefetchers.

               A  value  of  -1  means we don't have a threshold and therefore prefetch hints can be
               issued for any constant stride.

               This setting is only useful for strides that are known and constant.

           loop-interchange-max-num-stmts
               The maximum number of stmts in a loop to be interchanged.

           loop-interchange-stride-ratio
               The minimum ratio between stride of two loops for interchange to be profitable.

           min-insn-to-prefetch-ratio
               The minimum ratio between the number of instructions and the number of prefetches  to
               enable prefetching in a loop.

           prefetch-min-insn-to-mem-ratio
               The  minimum  ratio  between  the  number  of  instructions  and the number of memory
               references to enable prefetching in a loop.

           use-canonical-types
               Whether the compiler should use the "canonical" type system.   Should  always  be  1,
               which  uses  a  more  efficient  internal  mechanism  for  comparing types in C++ and
               Objective-C++.  However, if bugs in the canonical type system are causing compilation
               failures, set this value to 0 to disable canonical types.

           switch-conversion-max-branch-ratio
               Switch initialization conversion refuses  to  create  arrays  that  are  bigger  than
               switch-conversion-max-branch-ratio times the number of branches in the switch.

           max-partial-antic-length
               Maximum  length  of the partial antic set computed during the tree partial redundancy
               elimination optimization (-ftree-pre) when optimizing at -O3  and  above.   For  some
               sorts of source code the enhanced partial redundancy elimination optimization can run
               away, consuming all of the memory available on the host machine.  This parameter sets
               a  limit  on  the  length  of  the sets that are computed, which prevents the runaway
               behavior.  Setting a value of 0 for this parameter allows an unlimited set length.

           rpo-vn-max-loop-depth
               Maximum loop depth that is value-numbered optimistically.  When the  limit  hits  the
               innermost  rpo-vn-max-loop-depth  loops  and  the outermost loop in the loop nest are
               value-numbered optimistically and the remaining ones not.

           sccvn-max-alias-queries-per-access
               Maximum number of alias-oracle queries we perform when looking for  redundancies  for
               loads  and  stores.  If this limit is hit the search is aborted and the load or store
               is not considered redundant.  The number of queries is algorithmically limited to the
               number of stores on all paths from the load to the function entry.

           ira-max-loops-num
               IRA uses regional register allocation by default.  If a function contains more  loops
               than  the  number  given by this parameter, only at most the given number of the most
               frequently-executed loops form regions for regional register allocation.

           ira-max-conflict-table-size
               Although IRA uses a sophisticated algorithm to compress the conflict table, the table
               can still require excessive amounts of memory for huge functions.   If  the  conflict
               table  for  a function could be more than the size in MB given by this parameter, the
               register allocator instead uses a faster, simpler, and lower-quality  algorithm  that
               does not require building a pseudo-register conflict table.

           ira-loop-reserved-regs
               IRA can be used to evaluate more accurate register pressure in loops for decisions to
               move  loop invariants (see -O3).  The number of available registers reserved for some
               other purposes is given by this parameter.  Default of  the  parameter  is  the  best
               found from numerous experiments.

           lra-inheritance-ebb-probability-cutoff
               LRA  tries  to  reuse  values  reloaded  in  registers  in  subsequent  insns.   This
               optimization is called inheritance.  EBB is used as a region to do this optimization.
               The parameter defines a minimal fall-through edge probability in percentage  used  to
               add BB to inheritance EBB in LRA.  The default value was chosen from numerous runs of
               SPEC2000 on x86-64.

           loop-invariant-max-bbs-in-loop
               Loop  invariant  motion can be very expensive, both in compilation time and in amount
               of needed compile-time memory, with very large loops.  Loops with more  basic  blocks
               than this parameter won't have loop invariant motion optimization performed on them.

           loop-max-datarefs-for-datadeps
               Building  data dependencies is expensive for very large loops.  This parameter limits
               the number of data references in  loops  that  are  considered  for  data  dependence
               analysis.   These  large  loops  are  no handled by the optimizations using loop data
               dependencies.

           max-vartrack-size
               Sets a maximum number of hash table slots to use during  variable  tracking  dataflow
               analysis  of  any  function.   If  this  limit  is exceeded with variable tracking at
               assignments enabled, analysis for that function is retried without it, after removing
               all debug insns from the function.  If the  limit  is  exceeded  even  without  debug
               insns,  var  tracking  analysis is completely disabled for the function.  Setting the
               parameter to zero makes it unlimited.

           max-vartrack-expr-depth
               Sets a maximum number of recursion levels when attempting to map  variable  names  or
               debug  temporaries  to  value  expressions.   This  trades  compilation time for more
               complete debug information.  If this is set  too  low,  value  expressions  that  are
               available  and  could  be represented in debug information may end up not being used;
               setting this higher may enable the compiler to find more complex  debug  expressions,
               but compile time and memory use may grow.

           max-debug-marker-count
               Sets  a  threshold  on the number of debug markers (e.g. begin stmt markers) to avoid
               complexity explosion at inlining or expanding to RTL.  If a function  has  more  such
               gimple  stmts than the set limit, such stmts will be dropped from the inlined copy of
               a function, and from its RTL expansion.

           min-nondebug-insn-uid
               Use uids starting at  this  parameter  for  nondebug  insns.   The  range  below  the
               parameter     is    reserved    exclusively    for    debug    insns    created    by
               -fvar-tracking-assignments, but debug insns may get (non-overlapping) uids  above  it
               if the reserved range is exhausted.

           ipa-sra-ptr-growth-factor
               IPA-SRA  replaces a pointer to an aggregate with one or more new parameters only when
               their cumulative size is less or equal to ipa-sra-ptr-growth-factor times the size of
               the original pointer parameter.

           ipa-sra-max-replacements
               Maximum pieces of an aggregate that IPA-SRA tracks.  As a consequence, it is also the
               maximum number of replacements of a formal parameter.

           sra-max-scalarization-size-Ospeed
           sra-max-scalarization-size-Osize
               The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA) aim to replace scalar
               parts of aggregates with uses of  independent  scalar  variables.   These  parameters
               control  the  maximum  size,  in  storage units, of aggregate which is considered for
               replacement when compiling  for  speed  (sra-max-scalarization-size-Ospeed)  or  size
               (sra-max-scalarization-size-Osize) respectively.

           sra-max-propagations
               The maximum number of artificial accesses that Scalar Replacement of Aggregates (SRA)
               will track, per one local variable, in order to facilitate copy propagation.

           tm-max-aggregate-size
               When  making  copies  of  thread-local  variables  in  a  transaction, this parameter
               specifies the size in  bytes  after  which  variables  are  saved  with  the  logging
               functions  as  opposed to save/restore code sequence pairs.  This option only applies
               when using -fgnu-tm.

           graphite-max-nb-scop-params
               To avoid  exponential  effects  in  the  Graphite  loop  transforms,  the  number  of
               parameters  in  a Static Control Part (SCoP) is bounded.  A value of zero can be used
               to lift the bound.  A variable whose value is unknown at compilation time and defined
               outside a SCoP is a parameter of the SCoP.

           loop-block-tile-size
               Loop  blocking  or  strip   mining   transforms,   enabled   with   -floop-block   or
               -floop-strip-mine,  strip  mine  each  loop  in  the  loop  nest by a given number of
               iterations.   The  strip  length  can  be  changed  using  the   loop-block-tile-size
               parameter.

           ipa-jump-function-lookups
               Specifies number of statements visited during jump function offset discovery.

           ipa-cp-value-list-size
               IPA-CP  attempts  to  track  all  possible  values  and  types passed to a function's
               parameter in order to propagate them  and  perform  devirtualization.   ipa-cp-value-
               list-size  is  the  maximum  number  of  values  and  types  it stores per one formal
               parameter of a function.

           ipa-cp-eval-threshold
               IPA-CP calculates its own score of  cloning  profitability  heuristics  and  performs
               those cloning opportunities with scores that exceed ipa-cp-eval-threshold.

           ipa-cp-max-recursive-depth
               Maximum depth of recursive cloning for self-recursive function.

           ipa-cp-min-recursive-probability
               Recursive  cloning  only  when  the  probability  of  call being executed exceeds the
               parameter.

           ipa-cp-recursion-penalty
               Percentage penalty the recursive functions will receive when they are  evaluated  for
               cloning.

           ipa-cp-single-call-penalty
               Percentage  penalty  functions  containing  a  single  call  to another function will
               receive when they are evaluated for cloning.

           ipa-max-agg-items
               IPA-CP is also capable to propagate a number of scalar values passed in an aggregate.
               ipa-max-agg-items controls the maximum number of such values per one parameter.

           ipa-cp-loop-hint-bonus
               When IPA-CP determines that a cloning candidate would make the number  of  iterations
               of a loop known, it adds a bonus of ipa-cp-loop-hint-bonus to the profitability score
               of the candidate.

           ipa-max-loop-predicates
               The  maximum  number of different predicates IPA will use to describe when loops in a
               function have known properties.

           ipa-max-aa-steps
               During its analysis of function bodies, IPA-CP employs alias  analysis  in  order  to
               track  values  pointed  to  by function parameters.  In order not spend too much time
               analyzing huge functions, it  gives  up  and  consider  all  memory  clobbered  after
               examining ipa-max-aa-steps statements modifying memory.

           ipa-max-switch-predicate-bounds
               Maximal  number of boundary endpoints of case ranges of switch statement.  For switch
               exceeding this limit, IPA-CP will not construct cloning cost predicate, which is used
               to estimate cloning benefit, for default case of the switch statement.

           ipa-max-param-expr-ops
               IPA-CP will analyze conditional statement that references some function parameter  to
               estimate  benefit  for  cloning  upon  certain  constant  value.   But  if  number of
               operations in a parameter expression exceeds ipa-max-param-expr-ops,  the  expression
               is treated as complicated one, and is not handled by IPA analysis.

           lto-partitions
               Specify  desired  number of partitions produced during WHOPR compilation.  The number
               of partitions should exceed the number of CPUs used for compilation.

           lto-min-partition
               Size of minimal partition for  WHOPR  (in  estimated  instructions).   This  prevents
               expenses of splitting very small programs into too many partitions.

           lto-max-partition
               Size  of  max  partition  for WHOPR (in estimated instructions).  to provide an upper
               bound for individual size  of  partition.   Meant  to  be  used  only  with  balanced
               partitioning.

           lto-max-streaming-parallelism
               Maximal number of parallel processes used for LTO streaming.

           cxx-max-namespaces-for-diagnostic-help
               The  maximum  number  of  namespaces  to consult for suggestions when C++ name lookup
               fails for an identifier.

           sink-frequency-threshold
               The maximum relative execution frequency (in percents) of the target  block  relative
               to  a  statement's  original block to allow statement sinking of a statement.  Larger
               numbers result in more aggressive statement sinking.  A small positive adjustment  is
               applied  for  statements  with  memory  operands as those are even more profitable so
               sink.

           max-stores-to-sink
               The maximum number of conditional store pairs that can be sunk.  Set to 0  if  either
               vectorization   (-ftree-vectorize)   or   if-conversion  (-ftree-loop-if-convert)  is
               disabled.

           case-values-threshold
               The smallest number of different values for which it is  best  to  use  a  jump-table
               instead  of  a  tree of conditional branches.  If the value is 0, use the default for
               the machine.

           jump-table-max-growth-ratio-for-size
               The maximum code size growth ratio when expanding into a  jump  table  (in  percent).
               The parameter is used when optimizing for size.

           jump-table-max-growth-ratio-for-speed
               The  maximum  code  size  growth ratio when expanding into a jump table (in percent).
               The parameter is used when optimizing for speed.

           tree-reassoc-width
               Set the maximum number of instructions executed in  parallel  in  reassociated  tree.
               This  parameter overrides target dependent heuristics used by default if has non zero
               value.

           sched-pressure-algorithm
               Choose between the two available implementations of -fsched-pressure.  Algorithm 1 is
               the original implementation and is the more likely to prevent instructions from being
               reordered.  Algorithm 2 was designed  to  be  a  compromise  between  the  relatively
               conservative  approach  taken by algorithm 1 and the rather aggressive approach taken
               by the default scheduler.  It relies more heavily on having a regular  register  file
               and  accurate  register  pressure  classes.  See haifa-sched.c in the GCC sources for
               more details.

               The default choice depends on the target.

           max-slsr-cand-scan
               Set the maximum number of existing candidates that  are  considered  when  seeking  a
               basis for a new straight-line strength reduction candidate.

           asan-globals
               Enable  buffer  overflow  detection  for  global objects.  This kind of protection is
               enabled by default if you are using -fsanitize=address  option.   To  disable  global
               objects protection use --param asan-globals=0.

           asan-stack
               Enable  buffer  overflow  detection  for  stack  objects.  This kind of protection is
               enabled by default when using -fsanitize=address.  To disable  stack  protection  use
               --param asan-stack=0 option.

           asan-instrument-reads
               Enable  buffer  overflow  detection  for  memory  reads.   This kind of protection is
               enabled by default when using -fsanitize=address.  To disable memory reads protection
               use --param asan-instrument-reads=0.

           asan-instrument-writes
               Enable buffer overflow detection for memory  writes.   This  kind  of  protection  is
               enabled   by  default  when  using  -fsanitize=address.   To  disable  memory  writes
               protection use --param asan-instrument-writes=0 option.

           asan-memintrin
               Enable detection for built-in functions.  This  kind  of  protection  is  enabled  by
               default  when using -fsanitize=address.  To disable built-in functions protection use
               --param asan-memintrin=0.

           asan-use-after-return
               Enable detection of use-after-return.  This kind of protection is enabled by  default
               when   using   the   -fsanitize=address   option.    To   disable   it   use  --param
               asan-use-after-return=0.

               Note:  By  default  the  check  is  disabled  at  run  time.   To  enable   it,   add
               "detect_stack_use_after_return=1" to the environment variable ASAN_OPTIONS.

           asan-instrumentation-with-call-threshold
               If  number  of  memory accesses in function being instrumented is greater or equal to
               this number, use callbacks instead of inline checks.  E.g. to disable inline code use
               --param asan-instrumentation-with-call-threshold=0.

           hwasan-instrument-stack
               Enable hwasan instrumentation of statically sized  stack-allocated  variables.   This
               kind  of  instrumentation  is  enabled by default when using -fsanitize=hwaddress and
               disabled  by  default  when  using  -fsanitize=kernel-hwaddress.   To  disable  stack
               instrumentation  use  --param hwasan-instrument-stack=0, and to enable it use --param
               hwasan-instrument-stack=1.

           hwasan-random-frame-tag
               When  using  stack  instrumentation,  decide  tags  for  stack  variables   using   a
               deterministic sequence beginning at a random tag for each frame.  With this parameter
               unset  tags are chosen using the same sequence but beginning from 1.  This is enabled
               by default for -fsanitize=hwaddress and unavailable for  -fsanitize=kernel-hwaddress.
               To disable it use --param hwasan-random-frame-tag=0.

           hwasan-instrument-allocas
               Enable  hwasan  instrumentation of dynamically sized stack-allocated variables.  This
               kind of instrumentation is enabled by default  when  using  -fsanitize=hwaddress  and
               disabled   by   default   when   using   -fsanitize=kernel-hwaddress.    To   disable
               instrumentation of such variables use  --param  hwasan-instrument-allocas=0,  and  to
               enable it use --param hwasan-instrument-allocas=1.

           hwasan-instrument-reads
               Enable hwasan checks on memory reads.  Instrumentation of reads is enabled by default
               for  both  -fsanitize=hwaddress and -fsanitize=kernel-hwaddress.  To disable checking
               memory reads use --param hwasan-instrument-reads=0.

           hwasan-instrument-writes
               Enable hwasan checks on memory writes.   Instrumentation  of  writes  is  enabled  by
               default  for  both  -fsanitize=hwaddress and -fsanitize=kernel-hwaddress.  To disable
               checking memory writes use --param hwasan-instrument-writes=0.

           hwasan-instrument-mem-intrinsics
               Enable hwasan instrumentation of builtin functions.  Instrumentation of these builtin
               functions   is   enabled   by   default    for    both    -fsanitize=hwaddress    and
               -fsanitize=kernel-hwaddress.   To  disable  instrumentation  of builtin functions use
               --param hwasan-instrument-mem-intrinsics=0.

           use-after-scope-direct-emission-threshold
               If the size of a local variable in bytes is smaller or equal to this number, directly
               poison (or unpoison) shadow memory instead of using run-time callbacks.

           tsan-distinguish-volatile
               Emit special instrumentation for accesses to volatiles.

           tsan-instrument-func-entry-exit
               Emit instrumentation calls to __tsan_func_entry() and __tsan_func_exit().

           max-fsm-thread-path-insns
               Maximum number of instructions to copy when duplicating  blocks  on  a  finite  state
               automaton jump thread path.

           max-fsm-thread-length
               Maximum number of basic blocks on a finite state automaton jump thread path.

           max-fsm-thread-paths
               Maximum number of new jump thread paths to create for a finite state automaton.

           parloops-chunk-size
               Chunk size of omp schedule for loops parallelized by parloops.

           parloops-schedule
               Schedule  type  of  omp schedule for loops parallelized by parloops (static, dynamic,
               guided, auto, runtime).

           parloops-min-per-thread
               The minimum number of iterations per thread of an  innermost  parallelized  loop  for
               which  the parallelized variant is preferred over the single threaded one.  Note that
               for a parallelized loop nest the minimum number of iterations of the  outermost  loop
               per thread is two.

           max-ssa-name-query-depth
               Maximum  depth of recursion when querying properties of SSA names in things like fold
               routines.  One level of recursion corresponds to following a use-def chain.

           max-speculative-devirt-maydefs
               The maximum number of may-defs we analyze when looking for a must-def specifying  the
               dynamic  type of an object that invokes a virtual call we may be able to devirtualize
               speculatively.

           max-vrp-switch-assertions
               The maximum number of assertions to add along the default edge of a switch  statement
               during VRP.

           evrp-mode
               Specifies the mode Early VRP should operate in.

           unroll-jam-min-percent
               The  minimum  percentage  of  memory  references  that must be optimized away for the
               unroll-and-jam transformation to be considered profitable.

           unroll-jam-max-unroll
               The maximum number of times the outer loop should be unrolled by  the  unroll-and-jam
               transformation.

           max-rtl-if-conversion-unpredictable-cost
               Maximum  permissible  cost  for  the  sequence that would be generated by the RTL if-
               conversion pass for a branch that is considered unpredictable.

           max-variable-expansions-in-unroller
               If -fvariable-expansion-in-unroller is used, the maximum  number  of  times  that  an
               individual variable will be expanded during loop unrolling.

           tracer-min-branch-probability-feedback
               Stop  forward  growth if the probability of best edge is less than this threshold (in
               percent). Used when profile feedback is available.

           partial-inlining-entry-probability
               Maximum probability of the entry BB of split region (in percent relative to entry  BB
               of the function) to make partial inlining happen.

           max-tracked-strlens
               Maximum  number  of  strings  for  which  strlen  optimization pass will track string
               lengths.

           gcse-after-reload-partial-fraction
               The threshold ratio for performing partial redundancy elimination after reload.

           gcse-after-reload-critical-fraction
               The threshold  ratio  of  critical  edges  execution  count  that  permit  performing
               redundancy elimination after reload.

           max-loop-header-insns
               The maximum number of insns in loop header duplicated by the copy loop headers pass.

           vect-epilogues-nomask
               Enable loop epilogue vectorization using smaller vector size.

           vect-partial-vector-usage
               Controls  when the loop vectorizer considers using partial vector loads and stores as
               an alternative to falling back to scalar code.  0  stops  the  vectorizer  from  ever
               using  partial  vector loads and stores.  1 allows partial vector loads and stores if
               vectorization removes the need for the code to  iterate.   2  allows  partial  vector
               loads  and  stores  in  all  loops.  The parameter only has an effect on targets that
               support partial vector loads and stores.

           avoid-fma-max-bits
               Maximum number of bits for which we avoid creating FMAs.

           sms-loop-average-count-threshold
               A threshold on the average loop count considered by the swing modulo scheduler.

           sms-dfa-history
               The number of cycles the swing modulo scheduler  considers  when  checking  conflicts
               using DFA.

           max-inline-insns-recursive-auto
               The  maximum  number  of  instructions  non-inline function can grow to via recursive
               inlining.

           graphite-allow-codegen-errors
               Whether codegen errors should be ICEs when -fchecking.

           sms-max-ii-factor
               A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a
               loop.

           lra-max-considered-reload-pseudos
               The max number of reload pseudos which are considered during  spilling  a  non-reload
               pseudo.

           max-pow-sqrt-depth
               Maximum  depth  of  sqrt  chains  to  use  when synthesizing exponentiation by a real
               constant.

           max-dse-active-local-stores
               Maximum number of active local stores in RTL dead store elimination.

           asan-instrument-allocas
               Enable asan allocas/VLAs protection.

           max-iterations-computation-cost
               Bound on the cost of an expression to compute the number of iterations.

           max-isl-operations
               Maximum number of isl operations, 0 means unlimited.

           graphite-max-arrays-per-scop
               Maximum number of arrays per scop.

           max-vartrack-reverse-op-size
               Max. size of loc list for which reverse ops should be added.

           tracer-dynamic-coverage-feedback
               The percentage of function, weighted by execution frequency, that must be covered  by
               trace formation.  Used when profile feedback is available.

           max-inline-recursive-depth-auto
               The maximum depth of recursive inlining for non-inline functions.

           fsm-scale-path-stmts
               Scale  factor to apply to the number of statements in a threading path when comparing
               to the number of (scaled) blocks.

           fsm-maximum-phi-arguments
               Maximum number of arguments a PHI may have before the FSM threader will  not  try  to
               thread through its block.

           uninit-control-dep-attempts
               Maximum   number   of   nested  calls  to  search  for  control  dependencies  during
               uninitialized variable analysis.

           sra-max-scalarization-size-Osize
               Maximum size, in storage units, of  an  aggregate  which  should  be  considered  for
               scalarization when compiling for size.

           fsm-scale-path-blocks
               Scale  factor  to apply to the number of blocks in a threading path when comparing to
               the number of (scaled) statements.

           sched-autopref-queue-depth
               Hardware autoprefetcher scheduler model control flag.  Number of lookahead cycles the
               model looks into; at ' ' only enable instruction sorting heuristic.

           loop-versioning-max-inner-insns
               The maximum number of instructions that an  inner  loop  can  have  before  the  loop
               versioning pass considers it too big to copy.

           loop-versioning-max-outer-insns
               The  maximum  number  of  instructions  that  an  outer loop can have before the loop
               versioning pass considers it too big to copy, discounting any instructions  in  inner
               loops that directly benefit from versioning.

           ssa-name-def-chain-limit
               The  maximum  number of SSA_NAME assignments to follow in determining a property of a
               variable such as its value.  This limits the number of iterations or recursive  calls
               GCC  performs  when  optimizing certain statements or when determining their validity
               prior to issuing diagnostics.

           store-merging-max-size
               Maximum size of a single store merging region in bytes.

           hash-table-verification-limit
               The number of elements for which hash table verification is done  for  each  searched
               element.

           max-find-base-term-values
               Maximum number of VALUEs handled during a single find_base_term call.

           analyzer-max-enodes-per-program-point
               The  maximum  number  of exploded nodes per program point within the analyzer, before
               terminating analysis of that point.

           analyzer-max-constraints
               The maximum number of constraints per state.

           analyzer-min-snodes-for-call-summary
               The minimum number of supernodes within a  function  for  the  analyzer  to  consider
               summarizing its effects at call sites.

           analyzer-max-enodes-for-full-dump
               The maximum depth of exploded nodes that should appear in a dot dump before switching
               to a less verbose format.

           analyzer-max-recursion-depth
               The  maximum  number  of  times  a  callsite  can  appear  in a call stack within the
               analyzer, before terminating analysis of a call that would recurse deeper.

           analyzer-max-svalue-depth
               The maximum depth of a symbolic value, before approximating the value as unknown.

           analyzer-max-infeasible-edges
               The maximum number of infeasible edges to reject before  declaring  a  diagnostic  as
               infeasible.

           gimple-fe-computed-hot-bb-threshold
               The  number of executions of a basic block which is considered hot.  The parameter is
               used only in GIMPLE FE.

           analyzer-bb-explosion-factor
               The maximum number of 'after  supernode'  exploded  nodes  within  the  analyzer  per
               supernode, before terminating analysis.

           ranger-logical-depth
               Maximum  depth  of  logical  expression  evaluation  ranger  will  look  through when
               evaluating outgoing edge ranges.

           openacc-kernels
               Specify    mode    of    OpenACC     `kernels'     constructs     handling.      With
               --param=openacc-kernels=decompose,  OpenACC  `kernels' constructs are decomposed into
               parts, a sequence of compute constructs, each then  handled  individually.   This  is
               work   in   progress.    With   --param=openacc-kernels=parloops,  OpenACC  `kernels'
               constructs are handled by the parloops pass, en bloc.  This is the current default.

           The following choices of name are available on AArch64 targets:

           aarch64-sve-compare-costs
               When vectorizing for SVE, consider using "unpacked" vectors for smaller elements  and
               use  the cost model to pick the cheapest approach.  Also use the cost model to choose
               between SVE and Advanced SIMD vectorization.

               Using unpacked vectors includes storing smaller elements  in  larger  containers  and
               accessing elements with extending loads and truncating stores.

           aarch64-float-recp-precision
               The  number  of Newton iterations for calculating the reciprocal for float type.  The
               precision of division is proportional to this param when  division  approximation  is
               enabled.  The default value is 1.

           aarch64-double-recp-precision
               The  number of Newton iterations for calculating the reciprocal for double type.  The
               precision of division is propotional to this param  when  division  approximation  is
               enabled.  The default value is 2.

           aarch64-autovec-preference
               Force  an ISA selection strategy for auto-vectorization.  Accepts values from 0 to 4,
               inclusive.

               0   Use the default heuristics.

               1   Use only Advanced SIMD for auto-vectorization.

               2   Use only SVE for auto-vectorization.

               3   Use both Advanced SIMD and SVE.  Prefer Advanced SIMD when the costs  are  deemed
                   equal.

               4   Use both Advanced SIMD and SVE.  Prefer SVE when the costs are deemed equal.

               The default value is 0.

           aarch64-loop-vect-issue-rate-niters
               The  tuning  for  some AArch64 CPUs tries to take both latencies and issue rates into
               account when deciding whether a loop should be vectorized using SVE, vectorized using
               Advanced SIMD, or not vectorized at all.  If this parameter is set to n, GCC will not
               use this heuristic for loops that are known to execute in fewer than n Advanced  SIMD
               iterations.

   Program Instrumentation Options
       GCC supports a number of command-line options that control adding run-time instrumentation to
       the  code  it  normally  generates.   For  example, one purpose of instrumentation is collect
       profiling statistics for use in  finding  program  hot  spots,  code  coverage  analysis,  or
       profile-guided  optimizations.   Another  class of program instrumentation is adding run-time
       checking to detect programming errors like  invalid  pointer  dereferences  or  out-of-bounds
       array  accesses, as well as deliberately hostile attacks such as stack smashing or C++ vtable
       hijacking.  There is also a general hook which can  be  used  to  implement  other  forms  of
       tracing or function-level instrumentation for debug or program analysis purposes.

       -p
       -pg Generate  extra  code to write profile information suitable for the analysis program prof
           (for -p) or gprof (for -pg).  You must use this option when compiling  the  source  files
           you want data about, and you must also use it when linking.

           You  can  use  the  function  attribute "no_instrument_function" to suppress profiling of
           individual functions when compiling with these options.

       -fprofile-arcs
           Add code so that program flow  arcs  are  instrumented.   During  execution  the  program
           records how many times each branch and call is executed and how many times it is taken or
           returns.   On targets that support constructors with priority support, profiling properly
           handles constructors, destructors and C++ constructors (and destructors) of classes which
           are used as a type of a global variable.

           When the compiled program exits it saves this data to a file called auxname.gcda for each
           source   file.    The   data   may   be   used   for    profile-directed    optimizations
           (-fbranch-probabilities),  or  for test coverage analysis (-ftest-coverage).  Each object
           file's auxname is generated from the name of the output file, if explicitly specified and
           it is not the final executable, otherwise it is the basename of the source file.  In both
           cases any suffix is removed (e.g. foo.gcda for input file dir/foo.c, or dir/foo.gcda  for
           output file specified as -o dir/foo.o).

       --coverage
           This  option  is  used  to compile and link code instrumented for coverage analysis.  The
           option is a synonym for -fprofile-arcs -ftest-coverage (when compiling) and -lgcov  (when
           linking).  See the documentation for those options for more details.

           *   Compile  the  source  files with -fprofile-arcs plus optimization and code generation
               options.  For test coverage analysis, use the additional -ftest-coverage option.  You
               do not need to profile every source file in a program.

           *   Compile the source files additionally with -fprofile-abs-path to create absolute path
               names in the .gcno files.  This allows gcov to find the correct sources  in  projects
               where compilations occur with different working directories.

           *   Link your object files with -lgcov or -fprofile-arcs (the latter implies the former).

           *   Run the program on a representative workload to generate the arc profile information.
               This  may  be repeated any number of times.  You can run concurrent instances of your
               program, and provided that the file system supports locking, the data files  will  be
               correctly  updated.   Unless a strict ISO C dialect option is in effect, "fork" calls
               are detected and correctly handled without double counting.

           *   For profile-directed optimizations, compile the source  files  again  with  the  same
               optimization and code generation options plus -fbranch-probabilities.

           *   For  test  coverage analysis, use gcov to produce human readable information from the
               .gcno and .gcda files.  Refer to the gcov documentation for further information.

           With -fprofile-arcs, for each function of your program GCC creates a program flow  graph,
           then  finds  a  spanning tree for the graph.  Only arcs that are not on the spanning tree
           have to be instrumented: the compiler adds code to count the number of times  that  these
           arcs  are  executed.   When  an  arc  is  the  only exit or only entrance to a block, the
           instrumentation code can be added to the block; otherwise, a  new  basic  block  must  be
           created to hold the instrumentation code.

       -ftest-coverage
           Produce  a  notes  file  that  the  gcov  code-coverage  utility  can use to show program
           coverage.   Each  source  file's  note  file  is  called  auxname.gcno.   Refer  to   the
           -fprofile-arcs  option  above  for  a  description  of auxname and instructions on how to
           generate test coverage data.  Coverage data matches the source files more closely if  you
           do not optimize.

       -fprofile-abs-path
           Automatically  convert  relative  source  file  names to absolute path names in the .gcno
           files.  This allows gcov to find the correct sources in projects where compilations occur
           with different working directories.

       -fprofile-dir=path
           Set the directory to search for the profile data files in to path.  This  option  affects
           only  the  profile  data generated by -fprofile-generate, -ftest-coverage, -fprofile-arcs
           and used by -fprofile-use and  -fbranch-probabilities  and  its  related  options.   Both
           absolute  and  relative paths can be used.  By default, GCC uses the current directory as
           path, thus the profile data file appears in the same directory as the  object  file.   In
           order to prevent the file name clashing, if the object file name is not an absolute path,
           we  mangle the absolute path of the sourcename.gcda file and use it as the file name of a
           .gcda file.  See similar option -fprofile-note.

           When an executable is run in a massive parallel environment, it is  recommended  to  save
           profile  to different folders.  That can be done with variables in path that are exported
           during run-time:

           %p  process ID.

           %q{VAR}
               value of environment variable VAR

       -fprofile-generate
       -fprofile-generate=path
           Enable options usually used for instrumenting application to produce profile  useful  for
           later   recompilation   with   profile   feedback   based  optimization.   You  must  use
           -fprofile-generate both when compiling and when linking your program.

           The following options are enabled: -fprofile-arcs, -fprofile-values,  -finline-functions,
           and -fipa-bit-cp.

           If  path is specified, GCC looks at the path to find the profile feedback data files. See
           -fprofile-dir.

           To optimize the program based on the collected profile information, use -fprofile-use.

       -fprofile-info-section
       -fprofile-info-section=name
           Register  the  profile  information  in  the  specified  section  instead  of   using   a
           constructor/destructor.   The  section  name  is  name  if it is specified, otherwise the
           section name defaults to ".gcov_info".  A pointer to the profile information generated by
           -fprofile-arcs or -ftest-coverage is placed in the specified section for each translation
           unit.  This option disables the profile information registration  through  a  constructor
           and  it disables the profile information processing through a destructor.  This option is
           not intended to be used in hosted environments such as  GNU/Linux.   It  targets  systems
           with  limited  resources  which  do not support constructors and destructors.  The linker
           could collect the input sections in a continuous memory block and define  start  and  end
           symbols.   The  runtime  support  could dump the profiling information registered in this
           linker set during program termination to a serial line for example.  A GNU linker  script
           example which defines a linker output section follows:

                     .gcov_info      :
                     {
                       PROVIDE (__gcov_info_start = .);
                       KEEP (*(.gcov_info))
                       PROVIDE (__gcov_info_end = .);
                     }

       -fprofile-note=path
           If path is specified, GCC saves .gcno file into path location.  If you combine the option
           with multiple source files, the .gcno file will be overwritten.

       -fprofile-prefix-path=path
           This   option   can   be   used  in  combination  with  profile-generate=profile_dir  and
           profile-use=profile_dir to inform GCC where is the base directory of built  source  tree.
           By default profile_dir will contain files with mangled absolute paths of all object files
           in  the  built  project.   This  is  not  desirable  when  directory  used  to  build the
           instrumented binary differs from the directory used to build the  binary  optimized  with
           profile  feedback  because the profile data will not be found during the optimized build.
           In such setups -fprofile-prefix-path=path with path pointing to the base directory of the
           build can be used to strip the irrelevant part of  the  path  and  keep  all  file  names
           relative to the main build directory.

       -fprofile-update=method
           Alter  the  update  method  for  an  application  instrumented for profile feedback based
           optimization.  The method argument should be one of single, atomic or prefer-atomic.  The
           first one is useful for single-threaded  applications,  while  the  second  one  prevents
           profile corruption by emitting thread-safe code.

           Warning:  When  an application does not properly join all threads (or creates an detached
           thread), a profile file can be still corrupted.

           Using prefer-atomic would be transformed either to atomic, when supported by a target, or
           to single otherwise.  The GCC driver automatically selects prefer-atomic when -pthread is
           present in the command line.

       -fprofile-filter-files=regex
           Instrument only functions from files whose name matches any of  the  regular  expressions
           (separated by semi-colons).

           For  example,  -fprofile-filter-files=main\.c;module.*\.c will instrument only main.c and
           all C files starting with 'module'.

       -fprofile-exclude-files=regex
           Instrument only functions from files whose  name  does  not  match  any  of  the  regular
           expressions (separated by semi-colons).

           For  example,  -fprofile-exclude-files=/usr/.*  will prevent instrumentation of all files
           that are located in the /usr/ folder.

       -fprofile-reproducible=[multithreaded|parallel-runs|serial]
           Control level of reproducibility of profile gathered by "-fprofile-generate".  This makes
           it possible to rebuild program with same  outcome  which  is  useful,  for  example,  for
           distribution packages.

           With   -fprofile-reproducible=serial   the  profile  gathered  by  -fprofile-generate  is
           reproducible provided the trained program behaves the same  at  each  invocation  of  the
           train run, it is not multi-threaded and profile data streaming is always done in the same
           order.   Note  that  profile  streaming happens at the end of program run but also before
           "fork" function is invoked.

           Note that it is quite common that execution counts of some part of programs depends,  for
           example, on length of temporary file names or memory space randomization (that may affect
           hash-table  collision  rate).  Such non-reproducible part of programs may be annotated by
           "no_instrument_function" function attribute. gcov-dump  with  -l  can  be  used  to  dump
           gathered data and verify that they are indeed reproducible.

           With -fprofile-reproducible=parallel-runs collected profile stays reproducible regardless
           the  order  of  streaming of the data into gcda files.  This setting makes it possible to
           run multiple instances of instrumented program in parallel (such as with "make -j"). This
           reduces quality of gathered data, in particular of indirect call profiling.

       -fsanitize=address
           Enable AddressSanitizer, a fast memory error detector.  Memory  access  instructions  are
           instrumented  to  detect  out-of-bounds  and  use-after-free  bugs.   The  option enables
           -fsanitize-address-use-after-scope.                                                   See
           <https://github.com/google/sanitizers/wiki/AddressSanitizer>  for more details.  The run-
           time behavior can be influenced using the ASAN_OPTIONS environment variable.  When set to
           "help=1", the available options are shown at startup of the  instrumented  program.   See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags>   for  a
           list of supported options.  The option  cannot  be  combined  with  -fsanitize=thread  or
           -fsanitize=hwaddress.   Note  that  the  only  target  -fsanitize=hwaddress  is currently
           supported on is AArch64.

       -fsanitize=kernel-address
           Enable AddressSanitizer for Linux kernel.  See <https://github.com/google/kasan> for more
           details.

       -fsanitize=hwaddress
           Enable Hardware-assisted AddressSanitizer, which uses a hardware ability  to  ignore  the
           top byte of a pointer to allow the detection of memory errors with a low memory overhead.
           Memory  access  instructions  are instrumented to detect out-of-bounds and use-after-free
           bugs.      The     option      enables      -fsanitize-address-use-after-scope.       See
           <https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html>     for    more
           details.  The run-time behavior can be influenced using  the  HWASAN_OPTIONS  environment
           variable.   When  set  to  "help=1",  the  available  options are shown at startup of the
           instrumented  program.   The  option  cannot  be  combined  with   -fsanitize=thread   or
           -fsanitize=address, and is currently only available on AArch64.

       -fsanitize=kernel-hwaddress
           Enable  Hardware-assisted  AddressSanitizer for compilation of the Linux kernel.  Similar
           to -fsanitize=kernel-address but using an alternate instrumentation method,  and  similar
           to  -fsanitize=hwaddress but with instrumentation differences necessary for compiling the
           Linux kernel.  These differences are to avoid hwasan library initialization calls and  to
           account for the stack pointer having a different value in its top byte.

           Note:  This option has different defaults to the -fsanitize=hwaddress.  Instrumenting the
           stack and alloca calls are not on by default but are still  possible  by  specifying  the
           command-line      options      --param      hwasan-instrument-stack=1     and     --param
           hwasan-instrument-allocas=1 respectively. Using a random frame tag is not implemented for
           kernel instrumentation.

       -fsanitize=pointer-compare
           Instrument comparison operation (<, <=, >, >=) with pointer operands.  The option must be
           combined with either -fsanitize=kernel-address or -fsanitize=address The option cannot be
           combined with -fsanitize=thread.  Note: By default the check is disabled at run time.  To
           enable it, add "detect_invalid_pointer_pairs=2" to the environment variable ASAN_OPTIONS.
           Using "detect_invalid_pointer_pairs=1" detects invalid operation only when both  pointers
           are non-null.

       -fsanitize=pointer-subtract
           Instrument  subtraction  with  pointer operands.  The option must be combined with either
           -fsanitize=kernel-address or  -fsanitize=address  The  option  cannot  be  combined  with
           -fsanitize=thread.   Note:  By  default the check is disabled at run time.  To enable it,
           add "detect_invalid_pointer_pairs=2" to  the  environment  variable  ASAN_OPTIONS.  Using
           "detect_invalid_pointer_pairs=1"  detects  invalid  operation only when both pointers are
           non-null.

       -fsanitize=thread
           Enable ThreadSanitizer, a fast  data  race  detector.   Memory  access  instructions  are
           instrumented         to         detect         data         race        bugs.         See
           <https://github.com/google/sanitizers/wiki#threadsanitizer> for more  details.  The  run-
           time  behavior  can  be  influenced  using  the  TSAN_OPTIONS  environment  variable; see
           <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags> for a list of  supported
           options.  The option cannot be combined with -fsanitize=address, -fsanitize=leak.

           Note  that  sanitized  atomic  builtins cannot throw exceptions when operating on invalid
           memory addresses with non-call exceptions (-fnon-call-exceptions).

       -fsanitize=leak
           Enable LeakSanitizer, a memory leak detector.  This option only matters  for  linking  of
           executables  and  the  executable is linked against a library that overrides "malloc" and
           other                    allocator                    functions.                      See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer>     for    more
           details.  The run-time behavior can be  influenced  using  the  LSAN_OPTIONS  environment
           variable.  The option cannot be combined with -fsanitize=thread.

       -fsanitize=undefined
           Enable   UndefinedBehaviorSanitizer,   a   fast  undefined  behavior  detector.   Various
           computations  are  instrumented  to  detect   undefined   behavior   at   runtime.    See
           <https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html>  for  more  details.    The
           run-time behavior  can  be  influenced  using  the  UBSAN_OPTIONS  environment  variable.
           Current suboptions are:

           -fsanitize=shift
               This  option  enables checking that the result of a shift operation is not undefined.
               Note that what exactly is considered undefined differs slightly between C and C++, as
               well  as  between  ISO  C90  and  C99,  etc.   This  option   has   two   suboptions,
               -fsanitize=shift-base and -fsanitize=shift-exponent.

           -fsanitize=shift-exponent
               This  option  enables  checking  that the second argument of a shift operation is not
               negative and is smaller than the precision of the promoted first argument.

           -fsanitize=shift-base
               If the second argument of a shift operation is within range, check that the result of
               a shift operation is not undefined.  Note that what exactly is  considered  undefined
               differs slightly between C and C++, as well as between ISO C90 and C99, etc.

           -fsanitize=integer-divide-by-zero
               Detect integer division by zero as well as "INT_MIN / -1" division.

           -fsanitize=unreachable
               With  this  option,  the  compiler  turns  the  "__builtin_unreachable"  call  into a
               diagnostics message call instead.  When reaching  the  "__builtin_unreachable"  call,
               the behavior is undefined.

           -fsanitize=vla-bound
               This  option instructs the compiler to check that the size of a variable length array
               is positive.

           -fsanitize=null
               This option enables pointer checking.  Particularly, the application built with  this
               option  turned  on  will  issue  an error message when it tries to dereference a NULL
               pointer, or if a reference (possibly an rvalue reference) is bound to a NULL pointer,
               or if a method is invoked on an object pointed by a NULL pointer.

           -fsanitize=return
               This option enables return statement  checking.   Programs  built  with  this  option
               turned  on will issue an error message when the end of a non-void function is reached
               without actually returning a value.  This option works in C++ only.

           -fsanitize=signed-integer-overflow
               This option enables signed integer overflow checking.  We check that  the  result  of
               "+",  "*", and both unary and binary "-" does not overflow in the signed arithmetics.
               Note, integer promotion rules must be taken into account.  That is, the following  is
               not an overflow:

                       signed char a = SCHAR_MAX;
                       a++;

           -fsanitize=bounds
               This  option enables instrumentation of array bounds.  Various out of bounds accesses
               are detected.   Flexible  array  members,  flexible  array  member-like  arrays,  and
               initializers of variables with static storage are not instrumented.

           -fsanitize=bounds-strict
               This  option  enables  strict  instrumentation  of  array bounds.  Most out of bounds
               accesses are detected, including flexible array members and  flexible  array  member-
               like arrays.  Initializers of variables with static storage are not instrumented.

           -fsanitize=alignment
               This  option enables checking of alignment of pointers when they are dereferenced, or
               when a reference is bound to insufficiently aligned  target,  or  when  a  method  or
               constructor is invoked on insufficiently aligned object.

           -fsanitize=object-size
               This    option    enables    instrumentation   of   memory   references   using   the
               "__builtin_object_size"  function.   Various  out  of  bounds  pointer  accesses  are
               detected.

           -fsanitize=float-divide-by-zero
               Detect   floating-point   division   by   zero.    Unlike   other   similar  options,
               -fsanitize=float-divide-by-zero  is  not  enabled  by   -fsanitize=undefined,   since
               floating-point  division  by zero can be a legitimate way of obtaining infinities and
               NaNs.

           -fsanitize=float-cast-overflow
               This option enables floating-point type to integer  conversion  checking.   We  check
               that  the  result of the conversion does not overflow.  Unlike other similar options,
               -fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined.   This  option
               does not work well with "FE_INVALID" exceptions enabled.

           -fsanitize=nonnull-attribute
               This  option  enables  instrumentation of calls, checking whether null values are not
               passed to arguments marked as requiring a non-null value by  the  "nonnull"  function
               attribute.

           -fsanitize=returns-nonnull-attribute
               This  option  enables  instrumentation  of return statements in functions marked with
               "returns_nonnull" function attribute, to detect returning of null  values  from  such
               functions.

           -fsanitize=bool
               This option enables instrumentation of loads from bool.  If a value other than 0/1 is
               loaded, a run-time error is issued.

           -fsanitize=enum
               This  option  enables instrumentation of loads from an enum type.  If a value outside
               the range of values for the enum type is loaded, a run-time error is issued.

           -fsanitize=vptr
               This option enables instrumentation of C++ member function calls, member accesses and
               some conversions between  pointers  to  base  and  derived  classes,  to  verify  the
               referenced object has the correct dynamic type.

           -fsanitize=pointer-overflow
               This   option  enables  instrumentation  of  pointer  arithmetics.   If  the  pointer
               arithmetics overflows, a run-time error is issued.

           -fsanitize=builtin
               This option enables instrumentation of arguments to selected builtin  functions.   If
               an  invalid  value  is  passed  to  such arguments, a run-time error is issued.  E.g.
               passing 0 as the argument to "__builtin_ctz"  or  "__builtin_clz"  invokes  undefined
               behavior and is diagnosed by this option.

           While -ftrapv causes traps for signed overflows to be emitted, -fsanitize=undefined gives
           a diagnostic message.  This currently works only for the C family of languages.

       -fno-sanitize=all
           This  option  disables all previously enabled sanitizers.  -fsanitize=all is not allowed,
           as some sanitizers cannot be used together.

       -fasan-shadow-offset=number
           This option forces GCC to use custom shadow offset in  AddressSanitizer  checks.   It  is
           useful for experimenting with different shadow memory layouts in Kernel AddressSanitizer.

       -fsanitize-sections=s1,s2,...
           Sanitize global variables in selected user-defined sections.  si may contain wildcards.

       -fsanitize-recover[=opts]
           -fsanitize-recover=  controls  error  recovery  mode  for  sanitizers mentioned in comma-
           separated list of opts.  Enabling this option for a  sanitizer  component  causes  it  to
           attempt  to  continue  running  the program as if no error happened.  This means multiple
           runtime errors can be reported in a single program run, and the exit code of the  program
           may  indicate  success  even  when errors have been reported.  The -fno-sanitize-recover=
           option can be used to alter this behavior: only the first detected error is reported  and
           program then exits with a non-zero exit code.

           Currently this feature only works for -fsanitize=undefined (and its suboptions except for
           -fsanitize=unreachable     and     -fsanitize=return),    -fsanitize=float-cast-overflow,
           -fsanitize=float-divide-by-zero, -fsanitize=bounds-strict, -fsanitize=kernel-address  and
           -fsanitize=address.   For these sanitizers error recovery is turned on by default, except
           -fsanitize=address, for which this feature is experimental.   -fsanitize-recover=all  and
           -fno-sanitize-recover=all   is  also  accepted,  the  former  enables  recovery  for  all
           sanitizers that support it, the latter disables recovery for all sanitizers that  support
           it.

           Even  if  a  recovery mode is turned on the compiler side, it needs to be also enabled on
           the runtime library side, otherwise the failures are still fatal.   The  runtime  library
           defaults  to  "halt_on_error=0" for ThreadSanitizer and UndefinedBehaviorSanitizer, while
           default value for AddressSanitizer is "halt_on_error=1". This can be  overridden  through
           setting the "halt_on_error" flag in the corresponding environment variable.

           Syntax  without an explicit opts parameter is deprecated.  It is equivalent to specifying
           an opts list of:

                   undefined,float-cast-overflow,float-divide-by-zero,bounds-strict

       -fsanitize-address-use-after-scope
           Enable sanitization of local variables to detect use-after-scope bugs.  The  option  sets
           -fstack-reuse to none.

       -fsanitize-undefined-trap-on-error
           The  -fsanitize-undefined-trap-on-error option instructs the compiler to report undefined
           behavior using "__builtin_trap" rather than a "libubsan" library routine.  The  advantage
           of  this  is  that  the "libubsan" library is not needed and is not linked in, so this is
           usable even in freestanding environments.

       -fsanitize-coverage=trace-pc
           Enable   coverage-guided   fuzzing   code   instrumentation.    Inserts   a    call    to
           "__sanitizer_cov_trace_pc" into every basic block.

       -fsanitize-coverage=trace-cmp
           Enable   dataflow   guided   fuzzing   code   instrumentation.    Inserts   a   call   to
           "__sanitizer_cov_trace_cmp1", "__sanitizer_cov_trace_cmp2",  "__sanitizer_cov_trace_cmp4"
           or  "__sanitizer_cov_trace_cmp8"  for  integral comparison with both operands variable or
           "__sanitizer_cov_trace_const_cmp1",                   "__sanitizer_cov_trace_const_cmp2",
           "__sanitizer_cov_trace_const_cmp4"  or  "__sanitizer_cov_trace_const_cmp8"  for  integral
           comparison    with    one    operand    constant,     "__sanitizer_cov_trace_cmpf"     or
           "__sanitizer_cov_trace_cmpd"      for     float     or     double     comparisons     and
           "__sanitizer_cov_trace_switch" for switch statements.

       -fcf-protection=[full|branch|return|none|check]
           Enable code instrumentation of control-flow transfers to  increase  program  security  by
           checking  that  target  addresses of control-flow transfer instructions (such as indirect
           function call, function return, indirect jump) are valid.  This  prevents  diverting  the
           flow  of  control  to  an  unexpected  target.   This is intended to protect against such
           threats as Return-oriented Programming (ROP), and similarly call/jmp-oriented programming
           (COP/JOP).

           The value "branch" tells the compiler to implement checking of validity  of  control-flow
           transfer  at  the point of indirect branch instructions, i.e. call/jmp instructions.  The
           value "return" implements checking of validity at the point of returning from a function.
           The value "full" is an alias for specifying both "branch" and "return". The value  "none"
           turns off instrumentation.

           The value "check" is used for the final link with link-time optimization (LTO).  An error
           is  issued  if  LTO object files are compiled with different -fcf-protection values.  The
           value "check" is ignored at the compile time.

           The macro "__CET__" is defined when -fcf-protection is used.  The first bit of  "__CET__"
           is  set  to  1 for the value "branch" and the second bit of "__CET__" is set to 1 for the
           "return".

           You can also use the "nocf_check" attribute to identify which functions and calls  should
           be skipped from instrumentation.

           Currently the x86 GNU/Linux target provides an implementation based on Intel Control-flow
           Enforcement Technology (CET) which works for i686 processor or newer.

           NOTE:  In  Ubuntu  19.10 and later versions, -fcf-protection is enabled by default for C,
           C++, ObjC, ObjC++, if none of -fno-cf-protection nor -fcf-protection=* are found.

       -fstack-protector
           Emit extra code to check for buffer overflows, such as stack smashing attacks.   This  is
           done  by  adding  a  guard  variable to functions with vulnerable objects.  This includes
           functions that call "alloca", and functions with buffers larger than or equal to 8 bytes.
           The guards are initialized when a function is entered and then checked when the  function
           exits.   If a guard check fails, an error message is printed and the program exits.  Only
           variables that are actually  allocated  on  the  stack  are  considered,  optimized  away
           variables or variables allocated in registers don't count.

       -fstack-protector-all
           Like -fstack-protector except that all functions are protected.

       -fstack-protector-strong
           Like  -fstack-protector  but includes additional functions to be protected --- those that
           have local array  definitions,  or  have  references  to  local  frame  addresses.   Only
           variables  that  are  actually  allocated  on  the  stack  are considered, optimized away
           variables or variables allocated in registers don't count.

       -fstack-protector-explicit
           Like -fstack-protector but only protects those functions which have  the  "stack_protect"
           attribute.

       -fstack-check
           Generate  code to verify that you do not go beyond the boundary of the stack.  You should
           specify this flag if you are running in an environment with  multiple  threads,  but  you
           only  rarely  need to specify it in a single-threaded environment since stack overflow is
           automatically detected on nearly all systems if there is only one stack.

           Note that this switch does not actually cause checking to be done; the  operating  system
           or  the  language  runtime  must do that.  The switch causes generation of code to ensure
           that they see the stack being extended.

           You can additionally specify a string parameter: no  means  no  checking,  generic  means
           force  the  use of old-style checking, specific means use the best checking method and is
           equivalent to bare -fstack-check.

           Old-style checking is a generic mechanism that requires no specific target support in the
           compiler but comes with the following drawbacks:

           1.  Modified allocation strategy for large objects: they are always allocated dynamically
               if their size exceeds a fixed threshold.  Note this may change the semantics of  some
               code.

           2.  Fixed  limit  on  the  size  of the static frame of functions: when it is topped by a
               particular function, stack checking is not reliable and a warning is  issued  by  the
               compiler.

           3.  Inefficiency:  because  of  both  the  modified  allocation  strategy and the generic
               implementation, code performance is hampered.

           Note that old-style stack checking is also the fallback method for specific if no  target
           support has been added in the compiler.

           -fstack-check=  is  designed  for  Ada's  needs  to  detect  infinite recursion and stack
           overflows.  specific is an excellent choice when compiling Ada code.  It is not generally
           sufficient to protect against stack-clash attacks.  To protect  against  those  you  want
           -fstack-clash-protection.

       -fstack-clash-protection
           Generate  code  to  prevent  stack clash style attacks.  When this option is enabled, the
           compiler will only allocate one page of stack space at a time and each page  is  accessed
           immediately  after allocation.  Thus, it prevents allocations from jumping over any stack
           guard page provided by the operating system.

           Most targets do not fully support stack clash  protection.   However,  on  those  targets
           -fstack-clash-protection      will      protect      dynamic      stack      allocations.
           -fstack-clash-protection may also provide limited protection for static stack allocations
           if the target supports -fstack-check=specific.

           NOTE: In Ubuntu 19.10 and later versions, -fstack-clash-protection is enabled by  default
           for C, C++, ObjC, ObjC++, unless -fno-stack-clash-protection is found.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
           Generate  code  to ensure that the stack does not grow beyond a certain value, either the
           value of a register or the address of a symbol.  If a larger stack is required, a  signal
           is  raised at run time.  For most targets, the signal is raised before the stack overruns
           the boundary, so it is possible to catch the signal without taking special precautions.

           For instance, if the stack starts at absolute address 0x80000000 and grows downwards, you
           can       use       the        flags        -fstack-limit-symbol=__stack_limit        and
           -Wl,--defsym,__stack_limit=0x7ffe0000  to enforce a stack limit of 128KB.  Note that this
           may only work with the GNU linker.

           You can locally override stack limit checking  by  using  the  "no_stack_limit"  function
           attribute.

       -fsplit-stack
           Generate  code  to  automatically  split  the  stack  before it overflows.  The resulting
           program has a discontiguous stack which can only overflow if the  program  is  unable  to
           allocate  any  more memory.  This is most useful when running threaded programs, as it is
           no longer necessary to calculate a good stack size to  use  for  each  thread.   This  is
           currently only implemented for the x86 targets running GNU/Linux.

           When  code  compiled  with -fsplit-stack calls code compiled without -fsplit-stack, there
           may not be much stack space available for the latter code to run.  If compiling all code,
           including library code, with -fsplit-stack is not an option, then the linker can  fix  up
           these  calls  so  that  the code compiled without -fsplit-stack always has a large stack.
           Support for this is implemented in the gold linker  in  GNU  binutils  release  2.21  and
           later.

       -fvtable-verify=[std|preinit|none]
           This  option  is  only  available when compiling C++ code.  It turns on (or off, if using
           -fvtable-verify=none) the security feature that verifies at run time, for  every  virtual
           call, that the vtable pointer through which the call is made is valid for the type of the
           object,  and  has  not  been  corrupted  or overwritten.  If an invalid vtable pointer is
           detected at run time, an error is reported and execution of the  program  is  immediately
           halted.

           This  option  causes  run-time  data structures to be built at program startup, which are
           used for verifying the vtable pointers.  The options std and preinit control  the  timing
           of  when  these  data  structures are built.  In both cases the data structures are built
           before execution reaches "main".  Using -fvtable-verify=std causes the data structures to
           be   built   after   shared    libraries    have    been    loaded    and    initialized.
           -fvtable-verify=preinit  causes them to be built before shared libraries have been loaded
           and initialized.

           If this option  appears  multiple  times  in  the  command  line  with  different  values
           specified,  none takes highest priority over both std and preinit; preinit takes priority
           over std.

       -fvtv-debug
           When used in conjunction  with  -fvtable-verify=std  or  -fvtable-verify=preinit,  causes
           debug versions of the runtime functions for the vtable verification feature to be called.
           This  flag  also  causes  the  compiler to log information about which vtable pointers it
           finds for each class.  This information is written to a file  named  vtv_set_ptr_data.log
           in the directory named by the environment variable VTV_LOGS_DIR if that is defined or the
           current working directory otherwise.

           Note:   This  feature appends data to the log file. If you want a fresh log file, be sure
           to delete any existing one.

       -fvtv-counts
           This is  a  debugging  flag.   When  used  in  conjunction  with  -fvtable-verify=std  or
           -fvtable-verify=preinit,  this  causes  the compiler to keep track of the total number of
           virtual calls it encounters and the number of verifications it inserts.  It  also  counts
           the  number  of calls to certain run-time library functions that it inserts and logs this
           information for each compilation unit.  The compiler writes this information  to  a  file
           named  vtv_count_data.log in the directory named by the environment variable VTV_LOGS_DIR
           if that is defined or the current working directory otherwise.  It also counts  the  size
           of   the   vtable   pointer   sets  for  each  class,  and  writes  this  information  to
           vtv_class_set_sizes.log in the same directory.

           Note:  This feature appends data to the log files.  To get fresh log files,  be  sure  to
           delete any existing ones.

       -finstrument-functions
           Generate  instrumentation  calls  for  entry  and exit to functions.  Just after function
           entry and just before function exit, the following profiling functions  are  called  with
           the   address   of  the  current  function  and  its  call  site.   (On  some  platforms,
           "__builtin_return_address" does not work beyond the current function, so  the  call  site
           information may not be available to the profiling functions otherwise.)

                   void __cyg_profile_func_enter (void *this_fn,
                                                  void *call_site);
                   void __cyg_profile_func_exit  (void *this_fn,
                                                  void *call_site);

           The  first  argument  is  the  address of the start of the current function, which may be
           looked up exactly in the symbol table.

           This instrumentation is also done for functions expanded inline in other functions.   The
           profiling  calls indicate where, conceptually, the inline function is entered and exited.
           This means that addressable versions of such functions must be available.   If  all  your
           uses  of  a  function  are expanded inline, this may mean an additional expansion of code
           size.  If you use "extern inline"  in  your  C  code,  an  addressable  version  of  such
           functions  must be provided.  (This is normally the case anyway, but if you get lucky and
           the optimizer always expands the functions inline, you might  have  gotten  away  without
           providing static copies.)

           A  function  may  be  given  the  attribute  "no_instrument_function", in which case this
           instrumentation is not done.  This can be used, for example, for the profiling  functions
           listed  above,  high-priority  interrupt  routines,  and  any  functions  from  which the
           profiling functions cannot safely be called (perhaps signal handlers,  if  the  profiling
           routines generate output or allocate memory).

       -finstrument-functions-exclude-file-list=file,file,...
           Set  the list of functions that are excluded from instrumentation (see the description of
           -finstrument-functions).  If the file that contains a function  definition  matches  with
           one of file, then that function is not instrumented.  The match is done on substrings: if
           the file parameter is a substring of the file name, it is considered to be a match.

           For example:

                   -finstrument-functions-exclude-file-list=/bits/stl,include/sys

           excludes  any  inline  function  defined  in  files  whose pathnames contain /bits/stl or
           include/sys.

           If, for some reason, you want to include letter , in one of sym, write  ,.  For  example,
           -finstrument-functions-exclude-file-list=',,tmp'  (note  the single quote surrounding the
           option).

       -finstrument-functions-exclude-function-list=sym,sym,...
           This is similar to -finstrument-functions-exclude-file-list, but  this  option  sets  the
           list  of  function  names  to  be excluded from instrumentation.  The function name to be
           matched is its user-visible name, such as "vector<int> blah(const  vector<int>  &)",  not
           the  internal  mangled  name  (e.g.,  "_Z4blahRSt6vectorIiSaIiEE").  The match is done on
           substrings: if the sym parameter is a substring of the function name, it is considered to
           be a match.  For C99 and C++ extended identifiers, the function name  must  be  given  in
           UTF-8, not using universal character names.

       -fpatchable-function-entry=N[,M]
           Generate  N  NOPs  right at the beginning of each function, with the function entry point
           before the Mth NOP.  If M is omitted, it defaults to 0 so the function  entry  points  to
           the address just at the first NOP.  The NOP instructions reserve extra space which can be
           used  to patch in any desired instrumentation at run time, provided that the code segment
           is writable.  The amount of space is controllable indirectly via the number of NOPs;  the
           NOP  instruction used corresponds to the instruction emitted by the internal GCC back-end
           interface "gen_nop".  This behavior  is  target-specific  and  may  also  depend  on  the
           architecture variant and/or other compilation options.

           For  run-time  identification, the starting addresses of these areas, which correspond to
           their  respective  function  entries  minus  M,  are  additionally   collected   in   the
           "__patchable_function_entries" section of the resulting binary.

           Note   that   the  value  of  "__attribute__  ((patchable_function_entry  (N,M)))"  takes
           precedence over command-line option -fpatchable-function-entry=N,M.  This can be used  to
           increase the area size or to remove it completely on a single function.  If "N=0", no pad
           location is recorded.

           The  NOP  instructions  are inserted at---and maybe before, depending on M---the function
           entry address, even before the prologue.

           The maximum value of N and M is 65535.

   Options Controlling the Preprocessor
       These options control the C preprocessor, which is run on each C source  file  before  actual
       compilation.

       If  you  use the -E option, nothing is done except preprocessing.  Some of these options make
       sense only together with -E because they cause the preprocessor output to be  unsuitable  for
       actual compilation.

       In addition to the options listed here, there are a number of options to control search paths
       for  include  files  documented  in  Directory  Options.   Options  to  control  preprocessor
       diagnostics are listed in Warning Options.

       -D name
           Predefine name as a macro, with definition 1.

       -D name=definition
           The contents of definition are  tokenized  and  processed  as  if  they  appeared  during
           translation  phase  three  in  a  #define  directive.   In  particular, the definition is
           truncated by embedded newline characters.

           If you are invoking the preprocessor from a shell or shell-like program you may  need  to
           use  the  shell's quoting syntax to protect characters such as spaces that have a meaning
           in the shell syntax.

           If you wish to define a function-like macro on the command line, write its argument  list
           with surrounding parentheses before the equals sign (if any).  Parentheses are meaningful
           to   most   shells,   so   you   should   quote   the   option.    With   sh   and   csh,
           -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are given on  the  command  line.   All
           -imacros file and -include file options are processed after all -D and -U options.

       -U name
           Cancel any previous definition of name, either built in or provided with a -D option.

       -include file
           Process  file  as  if  "#include "file"" appeared as the first line of the primary source
           file.  However, the first directory searched  for  file  is  the  preprocessor's  working
           directory  instead of the directory containing the main source file.  If not found there,
           it is searched for in the remainder of the "#include "..."" search chain as normal.

           If multiple -include options are given, the files are included in the order  they  appear
           on the command line.

       -imacros file
           Exactly  like  -include, except that any output produced by scanning file is thrown away.
           Macros it defines remain defined.  This allows you to  acquire  all  the  macros  from  a
           header without also processing its declarations.

           All files specified by -imacros are processed before all files specified by -include.

       -undef
           Do  not  predefine  any  system-specific or GCC-specific macros.  The standard predefined
           macros remain defined.

       -pthread
           Define additional macros required for using the POSIX threads library.   You  should  use
           this  option  consistently for both compilation and linking.  This option is supported on
           GNU/Linux targets, most other Unix derivatives, and also on x86 Cygwin and MinGW targets.

       -M  Instead of outputting the result of  preprocessing,  output  a  rule  suitable  for  make
           describing  the  dependencies of the main source file.  The preprocessor outputs one make
           rule containing the object file name for that source file, a colon, and the names of  all
           the  included  files,  including  those  coming  from  -include  or -imacros command-line
           options.

           Unless specified explicitly (with -MT or -MQ), the object file name consists of the  name
           of  the source file with any suffix replaced with object file suffix and with any leading
           directory parts removed.  If there are many included files then the rule  is  split  into
           several lines using \-newline.  The rule has no commands.

           This  option  does  not  suppress the preprocessor's debug output, such as -dM.  To avoid
           mixing such debug output with the dependency rules  you  should  explicitly  specify  the
           dependency output file with -MF, or use an environment variable like DEPENDENCIES_OUTPUT.
           Debug output is still sent to the regular output stream as normal.

           Passing -M to the driver implies -E, and suppresses warnings with an implicit -w.

       -MM Like  -M but do not mention header files that are found in system header directories, nor
           header files that are included, directly or indirectly, from such a header.

           This implies that the choice of angle brackets or double quotes in an #include  directive
           does not in itself determine whether that header appears in -MM dependency output.

       -MF file
           When  used  with  -M  or  -MM,  specifies a file to write the dependencies to.  If no -MF
           switch is given the preprocessor sends  the  rules  to  the  same  place  it  would  send
           preprocessed output.

           When  used  with  the  driver  options  -MD or -MMD, -MF overrides the default dependency
           output file.

           If file is -, then the dependencies are written to stdout.

       -MG In conjunction with an option such as -M requesting dependency  generation,  -MG  assumes
           missing  header  files  are  generated files and adds them to the dependency list without
           raising an error.   The  dependency  filename  is  taken  directly  from  the  "#include"
           directive  without  prepending  any  path.  -MG also suppresses preprocessed output, as a
           missing header file renders this useless.

           This feature is used in automatic updating of makefiles.

       -Mno-modules
           Disable dependency generation for compiled module interfaces.

       -MP This option instructs CPP to add a phony target for each dependency other than  the  main
           file, causing each to depend on nothing.  These dummy rules work around errors make gives
           if you remove header files without updating the Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency generation.  By default CPP takes the
           name of the main input file, deletes any directory components and any file suffix such as
           .c, and appends the platform's usual object suffix.  The result is the target.

           An -MT option sets the target to be exactly the string you specify.  If you want multiple
           targets, you can specify them as a single argument to -MT, or use multiple -MT options.

           For example, -MT '$(objpfx)foo.o' might give

                   $(objpfx)foo.o: foo.c

       -MQ target
           Same   as   -MT,   but   it   quotes   any   characters   which   are  special  to  Make.
           -MQ '$(objpfx)foo.o' gives

                   $$(objpfx)foo.o: foo.c

           The default target is automatically quoted, as if it were given with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.  The  driver  determines
           file  based on whether an -o option is given.  If it is, the driver uses its argument but
           with a suffix of .d, otherwise it takes the name of the input file, removes any directory
           components and suffix, and applies a .d suffix.

           If -MD is used in conjunction with -E,  any  -o  switch  is  understood  to  specify  the
           dependency output file, but if used without -E, each -o is understood to specify a target
           object file.

           Since  -E  is not implied, -MD can be used to generate a dependency output file as a side
           effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system header files.

       -fpreprocessed
           Indicate to the preprocessor that the input file has  already  been  preprocessed.   This
           suppresses  things  like  macro expansion, trigraph conversion, escaped newline splicing,
           and processing of  most  directives.   The  preprocessor  still  recognizes  and  removes
           comments,  so  that  you  can  pass  a  file preprocessed with -C to the compiler without
           problems.  In this mode the integrated preprocessor is little more than a  tokenizer  for
           the front ends.

           -fpreprocessed  is  implicit  if the input file has one of the extensions .i, .ii or .mi.
           These are the extensions that GCC uses for preprocessed files created by -save-temps.

       -fdirectives-only
           When preprocessing, handle directives, but do not expand macros.

           The option's behavior depends on the -E and -fpreprocessed options.

           With -E, preprocessing is limited to  the  handling  of  directives  such  as  "#define",
           "#ifdef",  and  "#error".   Other  preprocessor  operations,  such as macro expansion and
           trigraph conversion are not  performed.   In  addition,  the  -dD  option  is  implicitly
           enabled.

           With  -fpreprocessed,  predefinition of command line and most builtin macros is disabled.
           Macros such as "__LINE__", which are contextually dependent, are handled normally.   This
           enables compilation of files previously preprocessed with "-E -fdirectives-only".

           With  both  -E  and  -fpreprocessed,  the rules for -fpreprocessed take precedence.  This
           enables full preprocessing of files previously preprocessed with "-E -fdirectives-only".

       -fdollars-in-identifiers
           Accept $ in identifiers.

       -fextended-identifiers
           Accept universal character names and extended characters in identifiers.  This option  is
           enabled by default for C99 (and later C standard versions) and C++.

       -fno-canonical-system-headers
           When preprocessing, do not shorten system header paths with canonicalization.

       -fmax-include-depth=depth
           Set the maximum depth of the nested #include. The default is 200.

       -ftabstop=width
           Set  the  distance  between tab stops.  This helps the preprocessor report correct column
           numbers in warnings or errors, even if tabs appear on the line.  If  the  value  is  less
           than 1 or greater than 100, the option is ignored.  The default is 8.

       -ftrack-macro-expansion[=level]
           Track  locations  of  tokens  across  macro  expansions. This allows the compiler to emit
           diagnostic about the current macro expansion stack when a compilation error occurs  in  a
           macro  expansion.  Using this option makes the preprocessor and the compiler consume more
           memory. The level parameter can be used  to  choose  the  level  of  precision  of  token
           location  tracking  thus decreasing the memory consumption if necessary. Value 0 of level
           de-activates this option. Value 1 tracks tokens locations in a degraded mode for the sake
           of minimal memory overhead. In this mode all tokens resulting from the  expansion  of  an
           argument of a function-like macro have the same location. Value 2 tracks tokens locations
           completely. This value is the most memory hungry.  When this option is given no argument,
           the default parameter value is 2.

           Note that "-ftrack-macro-expansion=2" is activated by default.

       -fmacro-prefix-map=old=new
           When   preprocessing   files  residing  in  directory  old,  expand  the  "__FILE__"  and
           "__BASE_FILE__" macros as if the files resided in directory new  instead.   This  can  be
           used to change an absolute path to a relative path by using . for new which can result in
           more  reproducible  builds  that  are  location  independent.   This  option also affects
           "__builtin_FILE()" during compilation.  See also -ffile-prefix-map.

       -fexec-charset=charset
           Set the execution character set, used for string and character constants.  The default is
           UTF-8.  charset can be any encoding supported by the system's "iconv" library routine.

       -fwide-exec-charset=charset
           Set the wide execution character set, used for wide string and character constants.   The
           default is one of UTF-32BE, UTF-32LE, UTF-16BE, or UTF-16LE, whichever corresponds to the
           width  of  "wchar_t"  and  the big-endian or little-endian byte order being used for code
           generation.  As with -fexec-charset,  charset  can  be  any  encoding  supported  by  the
           system's  "iconv" library routine; however, you will have problems with encodings that do
           not fit exactly in "wchar_t".

       -finput-charset=charset
           Set the input character set, used for translation from the character  set  of  the  input
           file  to  the  source  character set used by GCC.  If the locale does not specify, or GCC
           cannot get this information  from  the  locale,  the  default  is  UTF-8.   This  can  be
           overridden  by either the locale or this command-line option.  Currently the command-line
           option takes precedence if there's a conflict.  charset can be any encoding supported  by
           the system's "iconv" library routine.

       -fpch-deps
           When using precompiled headers, this flag causes the dependency-output flags to also list
           the  files  from  the  precompiled  header's  dependencies.   If  not specified, only the
           precompiled header are listed and not the files that were  used  to  create  it,  because
           those files are not consulted when a precompiled header is used.

       -fpch-preprocess
           This  option  allows  use of a precompiled header together with -E.  It inserts a special
           "#pragma", "#pragma GCC pch_preprocess "filename"" in the output to mark the place  where
           the  precompiled  header was found, and its filename.  When -fpreprocessed is in use, GCC
           recognizes this "#pragma" and loads the PCH.

           This option is off by default, because the resulting preprocessed output is  only  really
           suitable as input to GCC.  It is switched on by -save-temps.

           You should not write this "#pragma" in your own code, but it is safe to edit the filename
           if the PCH file is available in a different location.  The filename may be absolute or it
           may be relative to GCC's current directory.

       -fworking-directory
           Enable  generation  of  linemarkers in the preprocessor output that let the compiler know
           the current working directory at the time of preprocessing.  When this option is enabled,
           the preprocessor emits, after the  initial  linemarker,  a  second  linemarker  with  the
           current  working  directory  followed by two slashes.  GCC uses this directory, when it's
           present in the preprocessed input, as  the  directory  emitted  as  the  current  working
           directory  in  some  debugging information formats.  This option is implicitly enabled if
           debugging information is enabled, but  this  can  be  inhibited  with  the  negated  form
           -fno-working-directory.   If  the -P flag is present in the command line, this option has
           no effect, since no "#line" directives are emitted whatsoever.

       -A predicate=answer
           Make an assertion with the predicate predicate and answer answer.  This form is preferred
           to the older form -A predicate(answer), which is still supported, because it does not use
           shell special characters.

       -A -predicate=answer
           Cancel an assertion with the predicate predicate and answer answer.

       -C  Do not discard comments.  All comments are passed through to the output file, except  for
           comments in processed directives, which are deleted along with the directive.

           You  should  be  prepared  for  side effects when using -C; it causes the preprocessor to
           treat comments as tokens in their own right.  For  example,  comments  appearing  at  the
           start  of  what  would  be  a directive line have the effect of turning that line into an
           ordinary source line, since the first token on the line is no longer a #.

       -CC Do not discard comments, including during macro expansion.  This is like -C, except  that
           comments  contained  within  macros  are also passed through to the output file where the
           macro is expanded.

           In addition to the side effects of the -C option, the -CC  option  causes  all  C++-style
           comments  inside  a  macro to be converted to C-style comments.  This is to prevent later
           use of that macro from inadvertently commenting out the remainder of the source line.

           The -CC option is generally used to support lint comments.

       -P  Inhibit generation of linemarkers in the output from the  preprocessor.   This  might  be
           useful when running the preprocessor on something that is not C code, and will be sent to
           a program which might be confused by the linemarkers.

       -traditional
       -traditional-cpp
           Try  to  imitate  the  behavior  of  pre-standard  C  preprocessors,  as opposed to ISO C
           preprocessors.  See the GNU CPP manual for details.

           Note that GCC does not otherwise attempt to emulate a pre-standard C compiler, and  these
           options are only supported with the -E switch, or when invoking CPP explicitly.

       -trigraphs
           Support ISO C trigraphs.  These are three-character sequences, all starting with ??, that
           are  defined  by ISO C to stand for single characters.  For example, ??/ stands for \, so
           '??/n' is a character constant for a newline.

           The nine trigraphs and their replacements are

                   Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                   Replacement:      [    ]    {    }    #    \    ^    |    ~

           By default, GCC ignores trigraphs, but in standard-conforming  modes  it  converts  them.
           See the -std and -ansi options.

       -remap
           Enable  special code to work around file systems which only permit very short file names,
           such as MS-DOS.

       -H  Print the name of each header file used, in addition to other  normal  activities.   Each
           name  is indented to show how deep in the #include stack it is.  Precompiled header files
           are also printed, even if they are found to be invalid;  an  invalid  precompiled  header
           file is printed with ...x and a valid one with ...! .

       -dletters
           Says  to  make  debugging  dumps  during  compilation as specified by letters.  The flags
           documented here are those relevant to the preprocessor.  Other letters are interpreted by
           the compiler proper, or reserved for future versions of GCC, and so are silently ignored.
           If you specify letters whose behavior conflicts, the result is undefined.

           -dM Instead of the normal output, generate a list  of  #define  directives  for  all  the
               macros defined during the execution of the preprocessor, including predefined macros.
               This  gives  you  a  way  of  finding  out  what is predefined in your version of the
               preprocessor.  Assuming you have no file foo.h, the command

                       touch foo.h; cpp -dM foo.h

               shows all the predefined macros.

               If you use  -dM  without  the  -E  option,  -dM  is  interpreted  as  a  synonym  for
               -fdump-rtl-mach.

           -dD Like  -dM  except  in two respects: it does not include the predefined macros, and it
               outputs both the #define directives and the result of preprocessing.  Both  kinds  of
               output go to the standard output file.

           -dN Like -dD, but emit only the macro names, not their expansions.

           -dI Output #include directives in addition to the result of preprocessing.

           -dU Like -dD except that only macros that are expanded, or whose definedness is tested in
               preprocessor  directives,  are output; the output is delayed until the use or test of
               the macro; and #undef directives are also output for macros tested but  undefined  at
               the time.

       -fdebug-cpp
           This  option  is  only useful for debugging GCC.  When used from CPP or with -E, it dumps
           debugging information about location maps.  Every token in the output is preceded by  the
           dump of the map its location belongs to.

           When used from GCC without -E, this option has no effect.

       -Wp,option
           You  can use -Wp,option to bypass the compiler driver and pass option directly through to
           the preprocessor.  If option contains commas, it is split into multiple  options  at  the
           commas.   However,  many  options are modified, translated or interpreted by the compiler
           driver before being passed to the preprocessor, and -Wp  forcibly  bypasses  this  phase.
           The  preprocessor's  direct  interface is undocumented and subject to change, so whenever
           possible you should avoid using -Wp and let the driver handle the options instead.

       -Xpreprocessor option
           Pass option as an option to the preprocessor.  You can use this to supply system-specific
           preprocessor options that GCC does not recognize.

           If you want to pass an option that takes an argument, you must use -Xpreprocessor  twice,
           once for the option and once for the argument.

       -no-integrated-cpp
           Perform  preprocessing  as  a separate pass before compilation.  By default, GCC performs
           preprocessing as an integrated part of input tokenization and parsing.  If this option is
           provided, the appropriate language front end (cc1, cc1plus, or cc1obj  for  C,  C++,  and
           Objective-C, respectively) is instead invoked twice, once for preprocessing only and once
           for  actual  compilation  of  the  preprocessed  input.   This  option  may  be useful in
           conjunction with the -B or -wrapper options  to  specify  an  alternate  preprocessor  or
           perform  additional  processing  of  the  program source between normal preprocessing and
           compilation.

       -flarge-source-files
           Adjust GCC to expect large source files, at the expense of slower compilation and  higher
           memory usage.

           Specifically,  GCC  normally  tracks  both  column numbers and line numbers within source
           files and it normally prints both of these numbers in diagnostics.  However, once it  has
           processed  a  certain  number  of source lines, it stops tracking column numbers and only
           tracks line numbers.  This means that diagnostics for later lines do not  include  column
           numbers.   It also means that options like -Wmisleading-indentation cease to work at that
           point, although the compiler prints a note if this happens.  Passing -flarge-source-files
           significantly increases the number of source lines that GCC can process before  it  stops
           tracking columns.

   Passing Options to the Assembler
       You can pass options to the assembler.

       -Wa,option
           Pass  option  as an option to the assembler.  If option contains commas, it is split into
           multiple options at the commas.

       -Xassembler option
           Pass option as an option to the assembler.  You can use this  to  supply  system-specific
           assembler options that GCC does not recognize.

           If  you  want  to  pass an option that takes an argument, you must use -Xassembler twice,
           once for the option and once for the argument.

   Options for Linking
       These options come into play when the compiler links object files into an  executable  output
       file.  They are meaningless if the compiler is not doing a link step.

       object-file-name
           A  file  name  that  does not end in a special recognized suffix is considered to name an
           object file or library.  (Object files are distinguished from  libraries  by  the  linker
           according  to  the  file  contents.)   If linking is done, these object files are used as
           input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and object file names should
           not be used as arguments.

       -flinker-output=type
           This option controls code generation of the link-time optimizer.  By default  the  linker
           output  is automatically determined by the linker plugin.  For debugging the compiler and
           if incremental linking with a non-LTO object file is desired, it may be useful to control
           the type manually.

           If type is exec, code generation produces a static binary. In this case -fpic  and  -fpie
           are both disabled.

           If  type  is dyn, code generation produces a shared library.  In this case -fpic or -fPIC
           is preserved, but not enabled automatically.   This  allows  to  build  shared  libraries
           without position-independent code on architectures where this is possible, i.e. on x86.

           If  type  is  pie,  code generation produces an -fpie executable. This results in similar
           optimizations as exec except that -fpie is not disabled if specified at compilation time.

           If type is rel, the compiler assumes that incremental  linking  is  done.   The  sections
           containing  intermediate  code  for link-time optimization are merged, pre-optimized, and
           output to the resulting object file. In  addition,  if  -ffat-lto-objects  is  specified,
           binary  code  is  produced  for  future  non-LTO  linking.  The  object  file produced by
           incremental linking is smaller than a static library produced from the same object files.
           At link time the result of incremental linking also loads faster than  a  static  library
           assuming that the majority of objects in the library are used.

           Finally  nolto-rel  configures the compiler for incremental linking where code generation
           is forced, a final binary is produced, and the  intermediate  code  for  later  link-time
           optimization  is  stripped.  When multiple object files are linked together the resulting
           code is better optimized than with link-time optimizations disabled (for example,  cross-
           module inlining happens), but most of benefits of whole program optimizations are lost.

           During  the  incremental  link  (by  -r)  the linker plugin defaults to rel. With current
           interfaces to GNU Binutils it is however not possible to incrementally link  LTO  objects
           and  non-LTO  objects  into  a  single  mixed  object  file.   If  any of object files in
           incremental link cannot be used for link-time optimization, the linker  plugin  issues  a
           warning  and uses nolto-rel. To maintain whole program optimization, it is recommended to
           link such objects into static library instead. Alternatively it is possible to  use  H.J.
           Lu's binutils with support for mixed objects.

       -fuse-ld=bfd
           Use the bfd linker instead of the default linker.

       -fuse-ld=gold
           Use the gold linker instead of the default linker.

       -fuse-ld=lld
           Use the LLVM lld linker instead of the default linker.

       -fuse-ld=mold
           Use the Modern Linker (mold) instead of the default linker.

       -llibrary
       -l library
           Search  the library named library when linking.  (The second alternative with the library
           as a separate argument is only for POSIX compliance and is not recommended.)

           The -l  option  is  passed  directly  to  the  linker  by  GCC.   Refer  to  your  linker
           documentation  for  exact  details.   The  general  description  below applies to the GNU
           linker.

           The linker searches a standard list of directories  for  the  library.   The  directories
           searched include several standard system directories plus any that you specify with -L.

           Static  libraries  are  archives  of object files, and have file names like liblibrary.a.
           Some  targets  also  support  shared  libraries,  which   typically   have   names   like
           liblibrary.so.   If  both  static  and  shared  libraries  are  found,  the  linker gives
           preference to linking with the shared library unless the -static option is used.

           It makes a difference where in the command you write this option; the linker searches and
           processes libraries and object files in the order they are specified.   Thus,  foo.o  -lz
           bar.o searches library z after file foo.o but before bar.o.  If bar.o refers to functions
           in z, those functions may not be loaded.

       -lobjc
           You  need  this  special  case  of  the  -l  option  in  order  to link an Objective-C or
           Objective-C++ program.

       -nostartfiles
           Do not use the standard system startup files when linking.  The standard system libraries
           are used normally, unless -nostdlib, -nolibc, or -nodefaultlibs is used.

       -nodefaultlibs
           Do not use the standard system libraries when linking.  Only the  libraries  you  specify
           are passed to the linker, and options specifying linkage of the system libraries, such as
           -static-libgcc  or  -shared-libgcc,  are  ignored.   The  standard startup files are used
           normally, unless -nostartfiles is used.

           The compiler may generate calls to "memcmp", "memset",  "memcpy"  and  "memmove".   These
           entries  are  usually resolved by entries in libc.  These entry points should be supplied
           through some other mechanism when this option is specified.

       -nolibc
           Do not use the C library or system libraries tightly coupled with it when linking.  Still
           link with the startup files, libgcc or toolchain provided language support libraries such
           as libgnat, libgfortran or libstdc++ unless options preventing their inclusion  are  used
           as  well.   This  typically  removes  -lc  from  the link command line, as well as system
           libraries that normally go with it and become meaningless when absence of a C library  is
           assumed, for example -lpthread or -lm in some configurations.  This is intended for bare-
           board targets when there is indeed no C library available.

       -nostdlib
           Do not use the standard system startup files or libraries when linking.  No startup files
           and  only  the  libraries  you  specify  are passed to the linker, and options specifying
           linkage of the system libraries, such as -static-libgcc or -shared-libgcc, are ignored.

           The compiler may generate calls to "memcmp", "memset",  "memcpy"  and  "memmove".   These
           entries  are  usually resolved by entries in libc.  These entry points should be supplied
           through some other mechanism when this option is specified.

           One of the standard libraries bypassed by -nostdlib and  -nodefaultlibs  is  libgcc.a,  a
           library  of  internal  subroutines  which GCC uses to overcome shortcomings of particular
           machines, or special needs for some languages.

           In most cases, you need libgcc.a even when you want to avoid  other  standard  libraries.
           In  other  words, when you specify -nostdlib or -nodefaultlibs you should usually specify
           -lgcc as well.  This ensures that you have  no  unresolved  references  to  internal  GCC
           library  subroutines.   (An  example  of such an internal subroutine is "__main", used to
           ensure C++ constructors are called.)

       -e entry
       --entry=entry
           Specify that the program entry point is  entry.   The  argument  is  interpreted  by  the
           linker; the GNU linker accepts either a symbol name or an address.

       -pie
           Produce  a dynamically linked position independent executable on targets that support it.
           For predictable results, you  must  also  specify  the  same  set  of  options  used  for
           compilation (-fpie, -fPIE, or model suboptions) when you specify this linker option.

       -no-pie
           Don't produce a dynamically linked position independent executable.

       -static-pie
           Produce  a  static  position independent executable on targets that support it.  A static
           position independent executable is similar to a static executable, but can be  loaded  at
           any address without a dynamic linker.  For predictable results, you must also specify the
           same  set  of  options  used for compilation (-fpie, -fPIE, or model suboptions) when you
           specify this linker option.

       -pthread
           Link with the POSIX threads library.  This option is supported on GNU/Linux targets, most
           other Unix derivatives, and also on x86 Cygwin and MinGW targets.  On some  targets  this
           option  also  sets flags for the preprocessor, so it should be used consistently for both
           compilation and linking.

       -r  Produce a relocatable object as output.  This is also known as partial linking.

       -rdynamic
           Pass the flag -export-dynamic to the  ELF  linker,  on  targets  that  support  it.  This
           instructs the linker to add all symbols, not only used ones, to the dynamic symbol table.
           This  option  is  needed  for some uses of "dlopen" or to allow obtaining backtraces from
           within a program.

       -s  Remove all symbol table and relocation information from the executable.

       -static
           On systems that support dynamic linking, this overrides -pie and  prevents  linking  with
           the shared libraries.  On other systems, this option has no effect.

       -shared
           Produce  a  shared  object  which  can  then  be  linked  with  other  objects to form an
           executable.  Not all systems support this option.  For predictable results, you must also
           specify the same set of options used for compilation (-fpic, -fPIC, or model  suboptions)
           when you specify this linker option.[1]

       -shared-libgcc
       -static-libgcc
           On systems that provide libgcc as a shared library, these options force the use of either
           the  shared  or  static  version, respectively.  If no shared version of libgcc was built
           when the compiler was configured, these options have no effect.

           There are several situations in which an application should use the shared libgcc instead
           of the static version.  The most common of these is when the application wishes to  throw
           and  catch  exceptions  across  different  shared  libraries.   In that case, each of the
           libraries as well as the application itself should use the shared libgcc.

           Therefore, the G++ driver automatically adds -shared-libgcc whenever you build  a  shared
           library  or  a main executable, because C++ programs typically use exceptions, so this is
           the right thing to do.

           If, instead, you use the GCC driver to create shared libraries, you may  find  that  they
           are  not  always linked with the shared libgcc.  If GCC finds, at its configuration time,
           that  you  have  a  non-GNU  linker  or  a  GNU  linker  that  does  not  support  option
           --eh-frame-hdr,  it  links the shared version of libgcc into shared libraries by default.
           Otherwise, it takes advantage of the linker and  optimizes  away  the  linking  with  the
           shared  version  of  libgcc,  linking with the static version of libgcc by default.  This
           allows  exceptions  to  propagate  through  such  shared  libraries,  without   incurring
           relocation costs at library load time.

           However,  if  a  library or main executable is supposed to throw or catch exceptions, you
           must link it using the G++ driver, or using the option -shared-libgcc, such  that  it  is
           linked with the shared libgcc.

       -static-libasan
           When   the  -fsanitize=address  option  is  used  to  link  a  program,  the  GCC  driver
           automatically links against libasan.  If libasan is available as a  shared  library,  and
           the  -static  option  is not used, then this links against the shared version of libasan.
           The -static-libasan option directs the GCC driver to  link  libasan  statically,  without
           necessarily linking other libraries statically.

       -static-libtsan
           When the -fsanitize=thread option is used to link a program, the GCC driver automatically
           links  against  libtsan.   If  libtsan  is available as a shared library, and the -static
           option is not used,  then  this  links  against  the  shared  version  of  libtsan.   The
           -static-libtsan  option  directs  the  GCC  driver  to  link  libtsan statically, without
           necessarily linking other libraries statically.

       -static-liblsan
           When the -fsanitize=leak option is used to link a program, the GCC  driver  automatically
           links  against  liblsan.   If  liblsan  is available as a shared library, and the -static
           option is not used,  then  this  links  against  the  shared  version  of  liblsan.   The
           -static-liblsan  option  directs  the  GCC  driver  to  link  liblsan statically, without
           necessarily linking other libraries statically.

       -static-libubsan
           When the  -fsanitize=undefined  option  is  used  to  link  a  program,  the  GCC  driver
           automatically  links against libubsan.  If libubsan is available as a shared library, and
           the -static option is not used, then this links against the shared version  of  libubsan.
           The  -static-libubsan  option directs the GCC driver to link libubsan statically, without
           necessarily linking other libraries statically.

       -static-libstdc++
           When the g++ program is used to link a  C++  program,  it  normally  automatically  links
           against libstdc++.  If libstdc++ is available as a shared library, and the -static option
           is  not  used, then this links against the shared version of libstdc++.  That is normally
           fine.  However, it is sometimes useful to freeze the version of  libstdc++  used  by  the
           program  without  going all the way to a fully static link.  The -static-libstdc++ option
           directs the g++ driver to link libstdc++ statically, without  necessarily  linking  other
           libraries statically.

       -symbolic
           Bind  references  to  global  symbols  when  building  a  shared  object.  Warn about any
           unresolved references (unless overridden by the link editor option -Xlinker  -z  -Xlinker
           defs).  Only a few systems support this option.

       -T script
           Use  script as the linker script.  This option is supported by most systems using the GNU
           linker.  On some targets, such as bare-board targets without an operating system, the  -T
           option may be required when linking to avoid references to undefined symbols.

       -Xlinker option
           Pass  option  as  an  option  to  the linker.  You can use this to supply system-specific
           linker options that GCC does not recognize.

           If you want to pass an option that takes a  separate  argument,  you  must  use  -Xlinker
           twice,  once  for  the  option  and  once for the argument.  For example, to pass -assert
           definitions, you must write -Xlinker -assert -Xlinker definitions.  It does not  work  to
           write  -Xlinker  "-assert definitions", because this passes the entire string as a single
           argument, which is not what the linker expects.

           When using the GNU linker, it is usually more convenient  to  pass  arguments  to  linker
           options  using  the option=value syntax than as separate arguments.  For example, you can
           specify -Xlinker -Map=output.map rather than -Xlinker -Map  -Xlinker  output.map.   Other
           linkers may not support this syntax for command-line options.

       -Wl,option
           Pass  option  as  an  option  to the linker.  If option contains commas, it is split into
           multiple options at the commas.  You can use this syntax  to  pass  an  argument  to  the
           option.   For  example,  -Wl,-Map,output.map  passes -Map output.map to the linker.  When
           using the GNU linker, you can also get the same effect with -Wl,-Map=output.map.

           NOTE: In Ubuntu 8.10 and later versions, for LDFLAGS, the option  -Wl,-z,relro  is  used.
           To disable, use -Wl,-z,norelro.

       -u symbol
           Pretend the symbol symbol is undefined, to force linking of library modules to define it.
           You  can  use  -u  multiple  times  with different symbols to force loading of additional
           library modules.

       -z keyword
           -z is passed directly on to the linker along with the keyword keyword. See the section in
           the documentation of your linker for permitted values and their meanings.

   Options for Directory Search
       These options specify directories to search for header files, for libraries and for parts  of
       the compiler:

       -I dir
       -iquote dir
       -isystem dir
       -idirafter dir
           Add  the  directory dir to the list of directories to be searched for header files during
           preprocessing.  If dir begins with = or $SYSROOT, then the = or $SYSROOT is  replaced  by
           the sysroot prefix; see --sysroot and -isysroot.

           Directories  specified  with  -iquote  apply  only  to  the  quote form of the directive,
           "#include "file"".  Directories specified with  -I,  -isystem,  or  -idirafter  apply  to
           lookup for both the "#include "file"" and "#include <file>" directives.

           You  can specify any number or combination of these options on the command line to search
           for header files in several directories.  The lookup order is as follows:

           1.  For the quote form of the include directive, the directory of  the  current  file  is
               searched first.

           2.  For  the  quote  form  of the include directive, the directories specified by -iquote
               options are searched in left-to-right order, as they appear on the command line.

           3.  Directories specified with -I options are scanned in left-to-right order.

           4.  Directories specified with -isystem options are scanned in left-to-right order.

           5.  Standard system directories are scanned.

           6.  Directories specified with -idirafter options are scanned in left-to-right order.

           You can use -I to override a system header file, substituting  your  own  version,  since
           these  directories  are  searched  before  the  standard  system header file directories.
           However, you should not use this option to add directories that  contain  vendor-supplied
           system header files; use -isystem for that.

           The  -isystem  and  -idirafter  options also mark the directory as a system directory, so
           that it gets  the  same  special  treatment  that  is  applied  to  the  standard  system
           directories.

           If  a  standard system include directory, or a directory specified with -isystem, is also
           specified with -I, the -I option is ignored.  The directory is still searched  but  as  a
           system  directory  at its normal position in the system include chain.  This is to ensure
           that GCC's procedure to fix buggy system headers and the ordering for the "#include_next"
           directive are not inadvertently changed.  If you really need to change the  search  order
           for system directories, use the -nostdinc and/or -isystem options.

       -I- Split the include path.  This option has been deprecated.  Please use -iquote instead for
           -I directories before the -I- and remove the -I- option.

           Any  directories  specified  with  -I  options  before  -I- are searched only for headers
           requested with "#include "file"";  they  are  not  searched  for  "#include <file>".   If
           additional directories are specified with -I options after the -I-, those directories are
           searched for all #include directives.

           In  addition,  -I- inhibits the use of the directory of the current file directory as the
           first search directory for "#include "file"".  There is no way to override this effect of
           -I-.

       -iprefix prefix
           Specify prefix as  the  prefix  for  subsequent  -iwithprefix  options.   If  the  prefix
           represents a directory, you should include the final /.

       -iwithprefix dir
       -iwithprefixbefore dir
           Append  dir  to  the  prefix  specified  previously  with -iprefix, and add the resulting
           directory to the include search path.  -iwithprefixbefore puts it in the  same  place  -I
           would; -iwithprefix puts it where -idirafter would.

       -isysroot dir
           This  option  is  like the --sysroot option, but applies only to header files (except for
           Darwin targets, where it applies to both header files and libraries).  See the  --sysroot
           option for more information.

       -imultilib dir
           Use dir as a subdirectory of the directory containing target-specific C++ headers.

       -nostdinc
           Do  not  search  the  standard system directories for header files.  Only the directories
           explicitly specified with -I, -iquote,  -isystem,  and/or  -idirafter  options  (and  the
           directory of the current file, if appropriate) are searched.

       -nostdinc++
           Do  not  search  for  header files in the C++-specific standard directories, but do still
           search the other standard directories.  (This  option  is  used  when  building  the  C++
           library.)

       -iplugindir=dir
           Set  the  directory  to  search  for  plugins that are passed by -fplugin=name instead of
           -fplugin=path/name.so.  This option is not meant to be used by the user, but only  passed
           by the driver.

       -Ldir
           Add directory dir to the list of directories to be searched for -l.

       -Bprefix
           This  option  specifies where to find the executables, libraries, include files, and data
           files of the compiler itself.

           The compiler driver program runs one or more of the subprograms cpp, cc1, as and ld.   It
           tries  prefix  as  a  prefix  for  each  program  it  tries to run, both with and without
           machine/version/ for the corresponding target machine and compiler version.

           For each subprogram to be run, the compiler driver first tries the -B prefix, if any.  If
           that name is not found, or if  -B  is  not  specified,  the  driver  tries  two  standard
           prefixes,  /usr/lib/gcc/  and /usr/local/lib/gcc/.  If neither of those results in a file
           name that is found, the unmodified program name is searched  for  using  the  directories
           specified in your PATH environment variable.

           The  compiler  checks  to  see  if  the path provided by -B refers to a directory, and if
           necessary it adds a directory separator character at the end of the path.

           -B prefixes that effectively specify directory names  also  apply  to  libraries  in  the
           linker,  because  the  compiler  translates these options into -L options for the linker.
           They also apply to include files in the preprocessor,  because  the  compiler  translates
           these  options  into  -isystem  options for the preprocessor.  In this case, the compiler
           appends include to the prefix.

           The runtime support file libgcc.a can also be  searched  for  using  the  -B  prefix,  if
           needed.  If it is not found there, the two standard prefixes above are tried, and that is
           all.  The file is left out of the link if it is not found by those means.

           Another  way  to  specify  a  prefix  much  like  the -B prefix is to use the environment
           variable GCC_EXEC_PREFIX.

           As a special kludge, if the path provided by -B is [dir/]stageN/, where N is a number  in
           the  range  0  to  9,  then  it is replaced by [dir/]include.  This is to help with boot-
           strapping the compiler.

       -no-canonical-prefixes
           Do not expand any symbolic links, resolve references to /../ or /./,  or  make  the  path
           absolute when generating a relative prefix.

       --sysroot=dir
           Use  dir  as  the  logical root directory for headers and libraries.  For example, if the
           compiler normally searches for headers in /usr/include  and  libraries  in  /usr/lib,  it
           instead searches dir/usr/include and dir/usr/lib.

           If  you  use both this option and the -isysroot option, then the --sysroot option applies
           to libraries, but the -isysroot option applies to header files.

           The GNU linker (beginning with version 2.16) has the necessary support for  this  option.
           If  your  linker  does not support this option, the header file aspect of --sysroot still
           works, but the library aspect does not.

       --no-sysroot-suffix
           For some targets, a suffix is added to  the  root  directory  specified  with  --sysroot,
           depending  on  the  other  options  used,  so  that  headers  may for example be found in
           dir/suffix/usr/include instead of dir/usr/include.  This option disables the addition  of
           such a suffix.

   Options for Code Generation Conventions
       These machine-independent options control the interface conventions used in code generation.

       Most  of  them have both positive and negative forms; the negative form of -ffoo is -fno-foo.
       In the table below, only one of the forms is listed---the one that is not the  default.   You
       can figure out the other form by either removing no- or adding it.

       -fstack-reuse=reuse-level
           This  option  controls  stack  space  reuse  for  user  declared local/auto variables and
           compiler generated temporaries.  reuse_level can be all, named_vars, or none. all enables
           stack reuse for all local variables and temporaries, named_vars enables  the  reuse  only
           for  user  defined  local variables with names, and none disables stack reuse completely.
           The default value is all. The option is needed when the program extends the lifetime of a
           scoped local variable or a compiler generated temporary beyond the end point  defined  by
           the  language.   When a lifetime of a variable ends, and if the variable lives in memory,
           the optimizing compiler has the freedom to reuse its stack space with  other  temporaries
           or  scoped  local  variables  whose  live  range  does  not  overlap with it. Legacy code
           extending local lifetime is likely to break with the stack reuse optimization.

           For example,

                      int *p;
                      {
                        int local1;

                        p = &local1;
                        local1 = 10;
                        ....
                      }
                      {
                         int local2;
                         local2 = 20;
                         ...
                      }

                      if (*p == 10)  // out of scope use of local1
                        {

                        }

           Another example:

                      struct A
                      {
                          A(int k) : i(k), j(k) { }
                          int i;
                          int j;
                      };

                      A *ap;

                      void foo(const A& ar)
                      {
                         ap = &ar;
                      }

                      void bar()
                      {
                         foo(A(10)); // temp object's lifetime ends when foo returns

                         {
                           A a(20);
                           ....
                         }
                         ap->i+= 10;  // ap references out of scope temp whose space
                                      // is reused with a. What is the value of ap->i?
                      }

           The lifetime of a compiler generated temporary is well defined by the C++ standard.  When
           a  lifetime  of  a  temporary  ends, and if the temporary lives in memory, the optimizing
           compiler has the freedom to reuse its stack space with other temporaries or scoped  local
           variables  whose  live  range  does  not overlap with it. However some of the legacy code
           relies on the behavior of older compilers  in  which  temporaries'  stack  space  is  not
           reused,  the  aggressive  stack  reuse can lead to runtime errors. This option is used to
           control the temporary stack reuse optimization.

       -ftrapv
           This option generates traps for signed overflow on addition, subtraction,  multiplication
           operations.   The  options  -ftrapv  and  -fwrapv  override  each other, so using -ftrapv
           -fwrapv on the command-line results in -fwrapv being effective.  Note  that  only  active
           options  override,  so  using  -ftrapv  -fwrapv -fno-wrapv on the command-line results in
           -ftrapv being effective.

       -fwrapv
           This option instructs the compiler to assume that signed arithmetic overflow of addition,
           subtraction and multiplication wraps around using twos-complement  representation.   This
           flag  enables  some  optimizations  and disables others.  The options -ftrapv and -fwrapv
           override each other, so using -ftrapv -fwrapv on  the  command-line  results  in  -fwrapv
           being  effective.   Note  that  only  active  options  override, so using -ftrapv -fwrapv
           -fno-wrapv on the command-line results in -ftrapv being effective.

       -fwrapv-pointer
           This option instructs the compiler to assume that pointer arithmetic overflow on addition
           and subtraction wraps around using twos-complement representation.   This  flag  disables
           some optimizations which assume pointer overflow is invalid.

       -fstrict-overflow
           This  option  implies  -fno-wrapv  -fno-wrapv-pointer  and  when  negated implies -fwrapv
           -fwrapv-pointer.

       -fexceptions
           Enable exception handling.  Generates extra code needed  to  propagate  exceptions.   For
           some  targets,  this  implies  GCC  generates frame unwind information for all functions,
           which can produce significant data size overhead, although it does not affect  execution.
           If  you do not specify this option, GCC enables it by default for languages like C++ that
           normally require exception handling, and disables it for languages like  C  that  do  not
           normally  require  it.  However, you may need to enable this option when compiling C code
           that needs to interoperate properly with exception handlers written in C++.  You may also
           wish to disable this option if you are  compiling  older  C++  programs  that  don't  use
           exception handling.

       -fnon-call-exceptions
           Generate  code  that  allows  trapping  instructions to throw exceptions.  Note that this
           requires platform-specific runtime support that does not exist everywhere.  Moreover,  it
           only  allows  trapping  instructions  to  throw  exceptions,  i.e.  memory  references or
           floating-point instructions.  It does not allow exceptions to be  thrown  from  arbitrary
           signal handlers such as "SIGALRM".

       -fdelete-dead-exceptions
           Consider  that  instructions  that may throw exceptions but don't otherwise contribute to
           the execution of the program can be optimized away.  This option is  enabled  by  default
           for  the  Ada  compiler,  as  permitted  by the Ada language specification.  Optimization
           passes that cause dead exceptions to be removed are enabled  independently  at  different
           optimization levels.

       -funwind-tables
           Similar  to  -fexceptions, except that it just generates any needed static data, but does
           not affect the generated code in any other way.  You normally do not need to enable  this
           option; instead, a language processor that needs this handling enables it on your behalf.

       -fasynchronous-unwind-tables
           Generate  unwind  table  in  DWARF  format, if supported by target machine.  The table is
           exact at each  instruction  boundary,  so  it  can  be  used  for  stack  unwinding  from
           asynchronous events (such as debugger or garbage collector).

       -fno-gnu-unique
           On  systems  with  recent  GNU  assembler  and  C  library,  the  C++  compiler  uses the
           "STB_GNU_UNIQUE" binding to make sure that definitions of template  static  data  members
           and  static  local  variables  in  inline  functions  are  unique even in the presence of
           "RTLD_LOCAL"; this is necessary to avoid problems with a library used  by  two  different
           "RTLD_LOCAL"  plugins  depending on a definition in one of them and therefore disagreeing
           with the other one about the binding of the symbol.  But  this  causes  "dlclose"  to  be
           ignored  for  affected  DSOs;  if  your  program  relies on reinitialization of a DSO via
           "dlclose" and "dlopen", you can use -fno-gnu-unique.

       -fpcc-struct-return
           Return "short" "struct" and "union" values in memory like longer  ones,  rather  than  in
           registers.   This  convention  is  less  efficient,  but it has the advantage of allowing
           intercallability between GCC-compiled files and  files  compiled  with  other  compilers,
           particularly the Portable C Compiler (pcc).

           The  precise  convention  for  returning  structures  in  memory  depends  on  the target
           configuration macros.

           Short structures and unions are those whose size and alignment match that of some integer
           type.

           Warning: code compiled with the -fpcc-struct-return switch is not binary compatible  with
           code  compiled  with  the -freg-struct-return switch.  Use it to conform to a non-default
           application binary interface.

       -freg-struct-return
           Return "struct" and "union" values in registers when possible.  This  is  more  efficient
           for small structures than -fpcc-struct-return.

           If  you  specify  neither  -fpcc-struct-return  nor  -freg-struct-return, GCC defaults to
           whichever convention is standard for the target.  If there is no standard convention, GCC
           defaults to -fpcc-struct-return, except on targets where GCC is the  principal  compiler.
           In  those  cases,  we  can  choose the standard, and we chose the more efficient register
           return alternative.

           Warning: code compiled with the -freg-struct-return switch is not binary compatible  with
           code  compiled  with  the -fpcc-struct-return switch.  Use it to conform to a non-default
           application binary interface.

       -fshort-enums
           Allocate to an "enum" type only as many bytes as it  needs  for  the  declared  range  of
           possible  values.   Specifically,  the  "enum" type is equivalent to the smallest integer
           type that has enough room.

           Warning: the -fshort-enums switch  causes  GCC  to  generate  code  that  is  not  binary
           compatible  with  code generated without that switch.  Use it to conform to a non-default
           application binary interface.

       -fshort-wchar
           Override the underlying type for "wchar_t" to be "short  unsigned  int"  instead  of  the
           default for the target.  This option is useful for building programs to run under WINE.

           Warning:  the  -fshort-wchar  switch  causes  GCC  to  generate  code  that is not binary
           compatible with code generated without that switch.  Use it to conform to  a  non-default
           application binary interface.

       -fcommon
           In  C  code,  this  option  controls the placement of global variables defined without an
           initializer, known as tentative definitions in the C standard.  Tentative definitions are
           distinct from declarations of a variable with the "extern" keyword, which do not allocate
           storage.

           The default is -fno-common, which specifies that the compiler places uninitialized global
           variables in the BSS section of the object file.  This inhibits the merging of  tentative
           definitions  by the linker so you get a multiple-definition error if the same variable is
           accidentally defined in more than one compilation unit.

           The -fcommon places uninitialized global variables in a common block.   This  allows  the
           linker to resolve all tentative definitions of the same variable in different compilation
           units  to  the  same  object,  or  to  a  non-tentative  definition.   This  behavior  is
           inconsistent with C++, and on many targets implies a  speed  and  code  size  penalty  on
           global  variable  references.   It is mainly useful to enable legacy code to link without
           errors.

       -fno-ident
           Ignore the "#ident" directive.

       -finhibit-size-directive
           Don't output a ".size" assembler directive, or anything else that would cause trouble  if
           the function is split in the middle, and the two halves are placed at locations far apart
           in  memory.  This option is used when compiling crtstuff.c; you should not need to use it
           for anything else.

       -fverbose-asm
           Put extra commentary information in the generated assembly code to make it more readable.
           This option is generally only of use to those who actually need  to  read  the  generated
           assembly code (perhaps while debugging the compiler itself).

           -fno-verbose-asm,  the  default, causes the extra information to be omitted and is useful
           when comparing two assembler files.

           The added comments include:

           *   information on the compiler version and command-line options,

           *   the source code  lines  associated  with  the  assembly  instructions,  in  the  form
               FILENAME:LINENUMBER:CONTENT OF LINE,

           *   hints  on which high-level expressions correspond to the various assembly instruction
               operands.

           For example, given this C source file:

                   int test (int n)
                   {
                     int i;
                     int total = 0;

                     for (i = 0; i < n; i++)
                       total += i * i;

                     return total;
                   }

           compiling to (x86_64) assembly via -S and emitting the result direct to stdout via -o -

                   gcc -S test.c -fverbose-asm -Os -o -

           gives output similar to this:

                           .file   "test.c"
                   # GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu)
                     [...snip...]
                   # options passed:
                     [...snip...]

                           .text
                           .globl  test
                           .type   test, @function
                   test:
                   .LFB0:
                           .cfi_startproc
                   # test.c:4:   int total = 0;
                           xorl    %eax, %eax      # <retval>
                   # test.c:6:   for (i = 0; i < n; i++)
                           xorl    %edx, %edx      # i
                   .L2:
                   # test.c:6:   for (i = 0; i < n; i++)
                           cmpl    %edi, %edx      # n, i
                           jge     .L5     #,
                   # test.c:7:     total += i * i;
                           movl    %edx, %ecx      # i, tmp92
                           imull   %edx, %ecx      # i, tmp92
                   # test.c:6:   for (i = 0; i < n; i++)
                           incl    %edx    # i
                   # test.c:7:     total += i * i;
                           addl    %ecx, %eax      # tmp92, <retval>
                           jmp     .L2     #
                   .L5:
                   # test.c:10: }
                           ret
                           .cfi_endproc
                   .LFE0:
                           .size   test, .-test
                           .ident  "GCC: (GNU) 7.0.0 20160809 (experimental)"
                           .section        .note.GNU-stack,"",@progbits

           The comments are intended for humans rather than machines and hence the precise format of
           the comments is subject to change.

       -frecord-gcc-switches
           This switch causes the command line used to invoke the compiler to be recorded  into  the
           object  file  that is being created.  This switch is only implemented on some targets and
           the exact format of the recording is target and binary  file  format  dependent,  but  it
           usually takes the form of a section containing ASCII text.  This switch is related to the
           -fverbose-asm  switch,  but  that switch only records information in the assembler output
           file as comments, so it never reaches the object file.   See  also  -grecord-gcc-switches
           for another way of storing compiler options into the object file.

       -fpic
           Generate  position-independent  code  (PIC)  suitable  for  use  in  a shared library, if
           supported for the target machine.  Such code accesses all constant  addresses  through  a
           global  offset table (GOT).  The dynamic loader resolves the GOT entries when the program
           starts (the dynamic loader is not part of GCC; it is part of the operating  system).   If
           the  GOT  size for the linked executable exceeds a machine-specific maximum size, you get
           an error message from the linker indicating that -fpic  does  not  work;  in  that  case,
           recompile  with  -fPIC  instead.  (These maximums are 8k on the SPARC, 28k on AArch64 and
           32k on the m68k and RS/6000.  The x86 has no such limit.)

           Position-independent code requires special support, and therefore works only  on  certain
           machines.   For  the  x86,  GCC supports PIC for System V but not for the Sun 386i.  Code
           generated for the IBM RS/6000 is always position-independent.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 1.

       -fPIC
           If supported for the target machine, emit position-independent code, suitable for dynamic
           linking and avoiding any limit on the size of the global offset table.  This option makes
           a difference on AArch64, m68k, PowerPC and SPARC.

           Position-independent code requires special support, and therefore works only  on  certain
           machines.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 2.

       -fpie
       -fPIE
           These options are similar to -fpic and -fPIC, but the generated position-independent code
           can be only linked into executables.  Usually these options are used to compile code that
           will be linked using the -pie GCC option.

           -fpie  and  -fPIE  both  define  the macros "__pie__" and "__PIE__".  The macros have the
           value 1 for -fpie and 2 for -fPIE.

       -fno-plt
           Do not use the PLT for external function calls in  position-independent  code.   Instead,
           load  the callee address at call sites from the GOT and branch to it.  This leads to more
           efficient code by eliminating PLT stubs and exposing  GOT  loads  to  optimizations.   On
           architectures  such  as  32-bit  x86 where PLT stubs expect the GOT pointer in a specific
           register, this gives more register allocation freedom  to  the  compiler.   Lazy  binding
           requires use of the PLT; with -fno-plt all external symbols are resolved at load time.

           Alternatively,  the function attribute "noplt" can be used to avoid calls through the PLT
           for specific external functions.

           In position-dependent code, a few targets also convert calls to functions that are marked
           to not use the PLT to use the GOT instead.

       -fno-jump-tables
           Do not use jump tables for switch statements even where it would be more  efficient  than
           other  code  generation  strategies.   This option is of use in conjunction with -fpic or
           -fPIC for building code that forms part of a dynamic  linker  and  cannot  reference  the
           address  of  a  jump  table.   On some targets, jump tables do not require a GOT and this
           option is not needed.

       -fno-bit-tests
           Do not use bit tests for switch statements even where it would  be  more  efficient  than
           other code generation strategies.

       -ffixed-reg
           Treat the register named reg as a fixed register; generated code should never refer to it
           (except perhaps as a stack pointer, frame pointer or in some other fixed role).

           reg must be the name of a register.  The register names accepted are machine-specific and
           are defined in the "REGISTER_NAMES" macro in the machine description macro file.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-used-reg
           Treat  the  register  named  reg  as  an allocable register that is clobbered by function
           calls.  It may be allocated for temporaries or variables that do not live across a  call.
           Functions compiled this way do not save and restore the register reg.

           It  is  an  error  to use this flag with the frame pointer or stack pointer.  Use of this
           flag for other registers that have fixed pervasive roles in the machine's execution model
           produces disastrous results.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-saved-reg
           Treat the register named reg as an allocable register saved  by  functions.   It  may  be
           allocated  even for temporaries or variables that live across a call.  Functions compiled
           this way save and restore the register reg if they use it.

           It is an error to use this flag with the frame pointer or stack  pointer.   Use  of  this
           flag for other registers that have fixed pervasive roles in the machine's execution model
           produces disastrous results.

           A  different  sort  of disaster results from the use of this flag for a register in which
           function values may be returned.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fpack-struct[=n]
           Without a value specified, pack all structure members together  without  holes.   When  a
           value is specified (which must be a small power of two), pack structure members according
           to  this  value,  representing  the  maximum  alignment  (that  is,  objects with default
           alignment requirements larger than this are output  potentially  unaligned  at  the  next
           fitting location.

           Warning:  the  -fpack-struct  switch  causes  GCC  to  generate  code  that is not binary
           compatible with code generated without that switch.   Additionally,  it  makes  the  code
           suboptimal.  Use it to conform to a non-default application binary interface.

       -fleading-underscore
           This  option  and  its  counterpart,  -fno-leading-underscore,  forcibly change the way C
           symbols are represented in the object file.  One use is to help link with legacy assembly
           code.

           Warning: the -fleading-underscore switch causes GCC to generate code that is  not  binary
           compatible  with  code generated without that switch.  Use it to conform to a non-default
           application binary interface.  Not all targets provide complete support for this switch.

       -ftls-model=model
           Alter the thread-local storage model to be used.  The model argument  should  be  one  of
           global-dynamic,  local-dynamic,  initial-exec  or  local-exec.   Note  that the choice is
           subject to optimization: the compiler may use a more  efficient  model  for  symbols  not
           visible outside of the translation unit, or if -fpic is not given on the command line.

           The default without -fpic is initial-exec; with -fpic the default is global-dynamic.

       -ftrampolines
           For  targets  that  normally  need trampolines for nested functions, always generate them
           instead of using descriptors.  Otherwise, for targets that do not  need  them,  like  for
           example HP-PA or IA-64, do nothing.

           A  trampoline  is a small piece of code that is created at run time on the stack when the
           address of a nested  function  is  taken,  and  is  used  to  call  the  nested  function
           indirectly.   Therefore,  it  requires  the  stack to be made executable in order for the
           program to work properly.

           -fno-trampolines is enabled by default on  a  language  by  language  basis  to  let  the
           compiler  avoid  generating them, if it computes that this is safe, and replace them with
           descriptors.  Descriptors are made up of data  only,  but  the  generated  code  must  be
           prepared  to  deal with them.  As of this writing, -fno-trampolines is enabled by default
           only for Ada.

           Moreover, code compiled with -ftrampolines and code compiled  with  -fno-trampolines  are
           not  binary  compatible  if  nested functions are present.  This option must therefore be
           used on a program-wide basis and be manipulated with extreme care.

       -fvisibility=[default|internal|hidden|protected]
           Set the default ELF image symbol visibility to the  specified  option---all  symbols  are
           marked  with  this  unless  overridden  within  the  code.   Using  this feature can very
           substantially improve linking and load times of shared  object  libraries,  produce  more
           optimized  code,  provide  near-perfect  API  export  and  prevent symbol clashes.  It is
           strongly recommended that you use this in any shared objects you distribute.

           Despite the nomenclature, default always means  public;  i.e.,  available  to  be  linked
           against  from  outside  the  shared object.  protected and internal are pretty useless in
           real-world usage so the only other commonly  used  option  is  hidden.   The  default  if
           -fvisibility isn't specified is default, i.e., make every symbol public.

           A  good  explanation  of  the  benefits  offered by ensuring ELF symbols have the correct
           visibility is given by "How To Write Shared Libraries" by Ulrich Drepper  (which  can  be
           found  at <https://www.akkadia.org/drepper/>)---however a superior solution made possible
           by this option to marking things hidden when the default is public is to make the default
           hidden and mark things  public.   This  is  the  norm  with  DLLs  on  Windows  and  with
           -fvisibility=hidden    and    "__attribute__    ((visibility("default")))"   instead   of
           "__declspec(dllexport)" you get almost identical semantics with identical  syntax.   This
           is a great boon to those working with cross-platform projects.

           For  those  adding  visibility  support  to  existing  code,  you  may  find "#pragma GCC
           visibility" of use.  This works by  you  enclosing  the  declarations  you  wish  to  set
           visibility  for with (for example) "#pragma GCC visibility push(hidden)" and "#pragma GCC
           visibility pop".  Bear in mind that symbol visibility should be viewed as part of the API
           interface contract and thus all new code should always specify visibility when it is  not
           the default; i.e., declarations only for use within the local DSO should always be marked
           explicitly  as  hidden  as so to avoid PLT indirection overheads---making this abundantly
           clear also aids readability and self-documentation of the code.  Note that due to ISO C++
           specification requirements, "operator new"  and  "operator  delete"  must  always  be  of
           default visibility.

           Be aware that headers from outside your project, in particular system headers and headers
           from any other library you use, may not be expecting to be compiled with visibility other
           than  the default.  You may need to explicitly say "#pragma GCC visibility push(default)"
           before including any such headers.

           "extern" declarations are not  affected  by  -fvisibility,  so  a  lot  of  code  can  be
           recompiled  with  -fvisibility=hidden  with  no  modifications.  However, this means that
           calls to "extern" functions with no explicit visibility  use  the  PLT,  so  it  is  more
           effective to use "__attribute ((visibility))" and/or "#pragma GCC visibility" to tell the
           compiler which "extern" declarations should be treated as hidden.

           Note  that  -fvisibility  does  affect  C++  vague linkage entities. This means that, for
           instance, an exception class that is be thrown between DSOs  must  be  explicitly  marked
           with default visibility so that the type_info nodes are unified between the DSOs.

           An   overview   of   these  techniques,  their  benefits  and  how  to  use  them  is  at
           <http://gcc.gnu.org/wiki/Visibility>.

       -fstrict-volatile-bitfields
           This option should be used if accesses to volatile bit-fields (or other structure fields,
           although the compiler usually honors those types anyway) should use a  single  access  of
           the  width of the field's type, aligned to a natural alignment if possible.  For example,
           targets with memory-mapped peripheral registers might require all such accesses to be  16
           bits  wide;  with this flag you can declare all peripheral bit-fields as "unsigned short"
           (assuming short is 16 bits on these targets) to force GCC to use 16-bit accesses  instead
           of, perhaps, a more efficient 32-bit access.

           If  this  option  is  disabled, the compiler uses the most efficient instruction.  In the
           previous example, that might be a 32-bit load  instruction,  even  though  that  accesses
           bytes  that  do  not  contain  any  portion  of the bit-field, or memory-mapped registers
           unrelated to the one being updated.

           In some cases, such as when the "packed" attribute is applied to a  structure  field,  it
           may  not  be  possible  to access the field with a single read or write that is correctly
           aligned for the target machine.  In this case  GCC  falls  back  to  generating  multiple
           accesses rather than code that will fault or truncate the result at run time.

           Note:  Due to restrictions of the C/C++11 memory model, write accesses are not allowed to
           touch  non  bit-field  members.   It  is  therefore recommended to define all bits of the
           field's type as bit-field members.

           The default value of this option is determined by the application  binary  interface  for
           the target processor.

       -fsync-libcalls
           This option controls whether any out-of-line instance of the "__sync" family of functions
           may be used to implement the C++11 "__atomic" family of functions.

           The  default  value of this option is enabled, thus the only useful form of the option is
           -fno-sync-libcalls.  This option is used in the implementation of the  libatomic  runtime
           library.

   GCC Developer Options
       This section describes command-line options that are primarily of interest to GCC developers,
       including options to support compiler testing and investigation of compiler bugs and compile-
       time  performance problems.  This includes options that produce debug dumps at various points
       in the compilation; that print statistics such as memory use and  execution  time;  and  that
       print  information  about  GCC's configuration, such as where it searches for libraries.  You
       should rarely need to use any of these options for ordinary compilation and linking tasks.

       Many developer options that cause GCC to dump output to a file  take  an  optional  =filename
       suffix.  You  can  specify  stdout  or  - to dump to standard output, and stderr for standard
       error.

       If =filename is omitted, a default dump file name is constructed by  concatenating  the  base
       dump  file  name, a pass number, phase letter, and pass name.  The base dump file name is the
       name of output file produced by the compiler if explicitly specified and not  an  executable;
       otherwise  it is the source file name.  The pass number is determined by the order passes are
       registered with the compiler's pass manager.  This is generally the  same  as  the  order  of
       execution,  but  passes  registered  by  plugins,  target-specific passes, or passes that are
       otherwise registered late are numbered higher than the pass named final,  even  if  they  are
       executed  earlier.   The  phase  letter is one of i (inter-procedural analysis), l (language-
       specific), r (RTL), or t (tree).  The files are created in the directory of the output file.

       -fcallgraph-info
       -fcallgraph-info=MARKERS
           Makes the compiler output callgraph information for the  program,  on  a  per-object-file
           basis.   The information is generated in the common VCG format.  It can be decorated with
           additional, per-node and/or per-edge information, if a list of comma-separated markers is
           additionally specified.  When the "su" marker is specified, the  callgraph  is  decorated
           with stack usage information; it is equivalent to -fstack-usage.  When the "da" marker is
           specified,  the  callgraph  is  decorated  with  information  about dynamically allocated
           objects.

           When compiling with -flto, no callgraph information is output along with the object file.
           At LTO link time, -fcallgraph-info may generate multiple callgraph information files next
           to intermediate LTO output files.

       -dletters
       -fdump-rtl-pass
       -fdump-rtl-pass=filename
           Says to make debugging dumps during compilation at times specified by letters.   This  is
           used for debugging the RTL-based passes of the compiler.

           Some -dletters switches have different meaning when -E is used for preprocessing.

           Debug  dumps can be enabled with a -fdump-rtl switch or some -d option letters.  Here are
           the possible letters for use in pass and letters, and their meanings:

           -fdump-rtl-alignments
               Dump after branch alignments have been computed.

           -fdump-rtl-asmcons
               Dump after fixing rtl statements that have unsatisfied in/out constraints.

           -fdump-rtl-auto_inc_dec
               Dump after auto-inc-dec discovery.  This pass is only run on architectures that  have
               auto inc or auto dec instructions.

           -fdump-rtl-barriers
               Dump after cleaning up the barrier instructions.

           -fdump-rtl-bbpart
               Dump after partitioning hot and cold basic blocks.

           -fdump-rtl-bbro
               Dump after block reordering.

           -fdump-rtl-btl1
           -fdump-rtl-btl2
               -fdump-rtl-btl1  and  -fdump-rtl-btl2 enable dumping after the two branch target load
               optimization passes.

           -fdump-rtl-bypass
               Dump after jump bypassing and control flow optimizations.

           -fdump-rtl-combine
               Dump after the RTL instruction combination pass.

           -fdump-rtl-compgotos
               Dump after duplicating the computed gotos.

           -fdump-rtl-ce1
           -fdump-rtl-ce2
           -fdump-rtl-ce3
               -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable dumping after the three  if
               conversion passes.

           -fdump-rtl-cprop_hardreg
               Dump after hard register copy propagation.

           -fdump-rtl-csa
               Dump after combining stack adjustments.

           -fdump-rtl-cse1
           -fdump-rtl-cse2
               -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the two common subexpression
               elimination passes.

           -fdump-rtl-dce
               Dump after the standalone dead code elimination passes.

           -fdump-rtl-dbr
               Dump after delayed branch scheduling.

           -fdump-rtl-dce1
           -fdump-rtl-dce2
               -fdump-rtl-dce1   and  -fdump-rtl-dce2  enable  dumping  after  the  two  dead  store
               elimination passes.

           -fdump-rtl-eh
               Dump after finalization of EH handling code.

           -fdump-rtl-eh_ranges
               Dump after conversion of EH handling range regions.

           -fdump-rtl-expand
               Dump after RTL generation.

           -fdump-rtl-fwprop1
           -fdump-rtl-fwprop2
               -fdump-rtl-fwprop1 and  -fdump-rtl-fwprop2  enable  dumping  after  the  two  forward
               propagation passes.

           -fdump-rtl-gcse1
           -fdump-rtl-gcse2
               -fdump-rtl-gcse1   and   -fdump-rtl-gcse2   enable   dumping   after   global  common
               subexpression elimination.

           -fdump-rtl-init-regs
               Dump after the initialization of the registers.

           -fdump-rtl-initvals
               Dump after the computation of the initial value sets.

           -fdump-rtl-into_cfglayout
               Dump after converting to cfglayout mode.

           -fdump-rtl-ira
               Dump after iterated register allocation.

           -fdump-rtl-jump
               Dump after the second jump optimization.

           -fdump-rtl-loop2
               -fdump-rtl-loop2 enables dumping after the rtl loop optimization passes.

           -fdump-rtl-mach
               Dump after performing the machine dependent reorganization pass, if that pass exists.

           -fdump-rtl-mode_sw
               Dump after removing redundant mode switches.

           -fdump-rtl-rnreg
               Dump after register renumbering.

           -fdump-rtl-outof_cfglayout
               Dump after converting from cfglayout mode.

           -fdump-rtl-peephole2
               Dump after the peephole pass.

           -fdump-rtl-postreload
               Dump after post-reload optimizations.

           -fdump-rtl-pro_and_epilogue
               Dump after generating the function prologues and epilogues.

           -fdump-rtl-sched1
           -fdump-rtl-sched2
               -fdump-rtl-sched1  and  -fdump-rtl-sched2  enable  dumping  after  the  basic   block
               scheduling passes.

           -fdump-rtl-ree
               Dump after sign/zero extension elimination.

           -fdump-rtl-seqabstr
               Dump after common sequence discovery.

           -fdump-rtl-shorten
               Dump after shortening branches.

           -fdump-rtl-sibling
               Dump after sibling call optimizations.

           -fdump-rtl-split1
           -fdump-rtl-split2
           -fdump-rtl-split3
           -fdump-rtl-split4
           -fdump-rtl-split5
               These options enable dumping after five rounds of instruction splitting.

           -fdump-rtl-sms
               Dump after modulo scheduling.  This pass is only run on some architectures.

           -fdump-rtl-stack
               Dump  after  conversion from GCC's "flat register file" registers to the x87's stack-
               like registers.  This pass is only run on x86 variants.

           -fdump-rtl-subreg1
           -fdump-rtl-subreg2
               -fdump-rtl-subreg1  and  -fdump-rtl-subreg2  enable  dumping  after  the  two  subreg
               expansion passes.

           -fdump-rtl-unshare
               Dump after all rtl has been unshared.

           -fdump-rtl-vartrack
               Dump after variable tracking.

           -fdump-rtl-vregs
               Dump after converting virtual registers to hard registers.

           -fdump-rtl-web
               Dump after live range splitting.

           -fdump-rtl-regclass
           -fdump-rtl-subregs_of_mode_init
           -fdump-rtl-subregs_of_mode_finish
           -fdump-rtl-dfinit
           -fdump-rtl-dfinish
               These dumps are defined but always produce empty files.

           -da
           -fdump-rtl-all
               Produce all the dumps listed above.

           -dA Annotate the assembler output with miscellaneous debugging information.

           -dD Dump  all  macro  definitions,  at  the  end  of preprocessing, in addition to normal
               output.

           -dH Produce a core dump whenever an error occurs.

           -dp Annotate the assembler output with a comment indicating which pattern and alternative
               is used.  The length and cost of each instruction are also printed.

           -dP Dump the RTL in the assembler output as a  comment  before  each  instruction.   Also
               turns on -dp annotation.

           -dx Just  generate  RTL  for  a  function  instead  of  compiling  it.  Usually used with
               -fdump-rtl-expand.

       -fdump-debug
           Dump debugging information generated during the debug generation phase.

       -fdump-earlydebug
           Dump debugging information generated during the early debug generation phase.

       -fdump-noaddr
           When doing debugging dumps, suppress address output.  This makes it more feasible to  use
           diff  on debugging dumps for compiler invocations with different compiler binaries and/or
           different text / bss / data / heap / stack / dso start locations.

       -freport-bug
           Collect and dump debug information into a temporary file if an  internal  compiler  error
           (ICE) occurs.

       -fdump-unnumbered
           When  doing debugging dumps, suppress instruction numbers and address output.  This makes
           it more feasible to use diff on debugging dumps for compiler invocations  with  different
           options, in particular with and without -g.

       -fdump-unnumbered-links
           When  doing  debugging  dumps (see -d option above), suppress instruction numbers for the
           links to the previous and next instructions in a sequence.

       -fdump-ipa-switch
       -fdump-ipa-switch-options
           Control the dumping at various stages of inter-procedural analysis  language  tree  to  a
           file.   The  file  name  is generated by appending a switch specific suffix to the source
           file name, and the file is created in  the  same  directory  as  the  output  file.   The
           following dumps are possible:

           all Enables all inter-procedural analysis dumps.

           cgraph
               Dumps  information  about  call-graph  optimization,  unused  function  removal,  and
               inlining decisions.

           inline
               Dump after function inlining.

           Additionally, the options -optimized, -missed, -note, and -all can be provided, with  the
           same meaning as for -fopt-info, defaulting to -optimized.

           For  example,  -fdump-ipa-inline-optimized-missed will emit information on callsites that
           were inlined, along with callsites that were not inlined.

           By default, the dump will contain messages about successful optimizations (equivalent  to
           -optimized) together with low-level details about the analysis.

       -fdump-lang
           Dump  language-specific  information.   The  file  name is made by appending .lang to the
           source file name.

       -fdump-lang-all
       -fdump-lang-switch
       -fdump-lang-switch-options
       -fdump-lang-switch-options=filename
           Control the dumping of language-specific information.  The options and filename  portions
           behave as described in the -fdump-tree option.  The following switch values are accepted:

           all Enable all language-specific dumps.

           class
               Dump class hierarchy information.  Virtual table information is emitted unless 'slim'
               is specified.  This option is applicable to C++ only.

           module
               Dump  module  information.   Options lineno (locations), graph (reachability), blocks
               (clusters), uid (serialization), alias (mergeable), asmname (Elrond), eh  (mapper)  &
               vops  (macros)  may provide additional information.  This option is applicable to C++
               only.

           raw Dump the raw internal tree data.  This option is applicable to C++ only.

       -fdump-passes
           Print on stderr the list of optimization passes that are turned on and off by the current
           command-line options.

       -fdump-statistics-option
           Enable and control dumping of pass statistics in a  separate  file.   The  file  name  is
           generated  by  appending  a suffix ending in .statistics to the source file name, and the
           file is created in the same directory as the output file.  If the -option form  is  used,
           -stats  causes counters to be summed over the whole compilation unit while -details dumps
           every event as the passes generate them.  The default with no option is to  sum  counters
           for each function compiled.

       -fdump-tree-all
       -fdump-tree-switch
       -fdump-tree-switch-options
       -fdump-tree-switch-options=filename
           Control  the  dumping at various stages of processing the intermediate language tree to a
           file.  If the -options form is used, options is a  list  of  -  separated  options  which
           control the details of the dump.  Not all options are applicable to all dumps; those that
           are not meaningful are ignored.  The following options are available

           address
               Print  the  address  of  each  node.   Usually  this  is not meaningful as it changes
               according to the environment and source file.  Its primary use is for tying up a dump
               file with a debug environment.

           asmname
               If "DECL_ASSEMBLER_NAME" has been set for a given decl, use that in the dump  instead
               of  "DECL_NAME".   Its primary use is ease of use working backward from mangled names
               in the assembly file.

           slim
               When dumping front-end intermediate representations, inhibit dumping of members of  a
               scope  or  body  of a function merely because that scope has been reached.  Only dump
               such items when they are directly reachable by some other path.

               When dumping pretty-printed trees, this option inhibits dumping the bodies of control
               structures.

               When dumping RTL, print the RTL in slim (condensed) form instead of the default LISP-
               like representation.

           raw Print a raw representation of the tree.  By default, trees are pretty-printed into  a
               C-like representation.

           details
               Enable  more  detailed  dumps  (not  honored  by  every  dump  option).  Also include
               information from the optimization passes.

           stats
               Enable dumping various statistics about the pass (not honored by every dump option).

           blocks
               Enable showing basic block boundaries (disabled in raw dumps).

           graph
               For each of the other indicated dump files (-fdump-rtl-pass), dump  a  representation
               of the control flow graph suitable for viewing with GraphViz to file.passid.pass.dot.
               Each  function  in  the  file  is  pretty-printed as a subgraph, so that GraphViz can
               render them all in a single plot.

               This option currently only works for RTL dumps, and the RTL is always dumped in  slim
               form.

           vops
               Enable showing virtual operands for every statement.

           lineno
               Enable showing line numbers for statements.

           uid Enable showing the unique ID ("DECL_UID") for each variable.

           verbose
               Enable showing the tree dump for each statement.

           eh  Enable showing the EH region number holding each statement.

           scev
               Enable showing scalar evolution analysis details.

           optimized
               Enable showing optimization information (only available in certain passes).

           missed
               Enable showing missed optimization information (only available in certain passes).

           note
               Enable other detailed optimization information (only available in certain passes).

           all Turn on all options, except raw, slim, verbose and lineno.

           optall
               Turn on all optimization options, i.e., optimized, missed, and note.

           To determine what tree dumps are available or find the dump for a pass of interest follow
           the steps below.

           1.  Invoke  GCC  with  -fdump-passes  and  in  the  stderr  output  look  for a code that
               corresponds to the pass you are interested in.  For example, the  codes  "tree-evrp",
               "tree-vrp1",  and "tree-vrp2" correspond to the three Value Range Propagation passes.
               The number at the end distinguishes distinct invocations of the same pass.

           2.  To enable the creation of the dump file, append the pass code to the  -fdump-  option
               prefix  and invoke GCC with it.  For example, to enable the dump from the Early Value
               Range Propagation pass, invoke GCC with the -fdump-tree-evrp option.  Optionally, you
               may specify the name of the dump file.  If you don't  specify  one,  GCC  creates  as
               described below.

           3.  Find  the pass dump in a file whose name is composed of three components separated by
               a period: the name of the source file GCC was invoked to compile,  a  numeric  suffix
               indicating the pass number followed by the letter t for tree passes (and the letter r
               for  RTL  passes),  and  finally the pass code.  For example, the Early VRP pass dump
               might be in a file named myfile.c.038t.evrp in the current working  directory.   Note
               that  the  numeric  codes  are  not  stable and may change from one version of GCC to
               another.

       -fopt-info
       -fopt-info-options
       -fopt-info-options=filename
           Controls optimization dumps from various optimization passes. If  the  -options  form  is
           used,  options  is  a  list of - separated option keywords to select the dump details and
           optimizations.

           The options can be divided into three groups:

           1.  options describing what kinds of messages should be emitted,

           2.  options describing the verbosity of the dump, and

           3.  options describing which optimizations should be included.

           The options from each group can be freely mixed as they are non-overlapping. However,  in
           case  of  any  conflicts,  the  later options override the earlier options on the command
           line.

           The following options control which kinds of messages should be emitted:

           optimized
               Print information when an optimization is successfully applied. It is up to a pass to
               decide which information is relevant. For example, the vectorizer  passes  print  the
               source location of loops which are successfully vectorized.

           missed
               Print  information  about  missed  optimizations.  Individual  passes  control  which
               information to include in the output.

           note
               Print verbose information about optimizations, such as certain transformations,  more
               detailed messages about decisions etc.

           all Print detailed optimization information. This includes optimized, missed, and note.

           The following option controls the dump verbosity:

           internals
               By  default,  only "high-level" messages are emitted. This option enables additional,
               more detailed, messages, which are likely to only be of interest to GCC developers.

           One or more of the following  option  keywords  can  be  used  to  describe  a  group  of
           optimizations:

           ipa Enable dumps from all interprocedural optimizations.

           loop
               Enable dumps from all loop optimizations.

           inline
               Enable dumps from all inlining optimizations.

           omp Enable dumps from all OMP (Offloading and Multi Processing) optimizations.

           vec Enable dumps from all vectorization optimizations.

           optall
               Enable  dumps  from  all optimizations. This is a superset of the optimization groups
               listed above.

           If options is omitted, it defaults to optimized-optall,  which  means  to  dump  messages
           about successful optimizations from all the passes, omitting messages that are treated as
           "internals".

           If  the  filename  is  provided, then the dumps from all the applicable optimizations are
           concatenated into the filename.   Otherwise  the  dump  is  output  onto  stderr.  Though
           multiple  -fopt-info  options  are  accepted, only one of them can include a filename. If
           other filenames are provided then all but the first such option are ignored.

           Note that the output filename is overwritten in case of multiple translation units. If  a
           combined  output  from  multiple  translation  units  is  desired,  stderr should be used
           instead.

           In the following example, the optimization info is output to stderr:

                   gcc -O3 -fopt-info

           This example:

                   gcc -O3 -fopt-info-missed=missed.all

           outputs missed optimization report from all the passes into missed.all, and this one:

                   gcc -O2 -ftree-vectorize -fopt-info-vec-missed

           prints information about missed optimization opportunities from vectorization  passes  on
           stderr.   Note  that  -fopt-info-vec-missed  is equivalent to -fopt-info-missed-vec.  The
           order of the optimization group names and message types listed after -fopt-info does  not
           matter.

           As another example,

                   gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

           outputs  information  about  missed optimizations as well as optimized locations from all
           the inlining passes into inline.txt.

           Finally, consider:

                   gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

           Here the two output filenames vec.miss and loop.opt are in conflict since only one output
           file is allowed. In this case, only the first option  takes  effect  and  the  subsequent
           options  are  ignored.  Thus  only  vec.miss  is  produced  which contains dumps from the
           vectorizer about missed opportunities.

       -fsave-optimization-record
           Write a SRCFILE.opt-record.json.gz file detailing what optimizations were performed,  for
           those optimizations that support -fopt-info.

           This option is experimental and the format of the data within the compressed JSON file is
           subject to change.

           It is roughly equivalent to a machine-readable version of -fopt-info-all, as a collection
           of  messages  with  source  file,  line  number  and  column  number,  with the following
           additional data for each message:

           *   the execution count of the code being optimized, along with  metadata  about  whether
               this  was  from  actual  profile  data,  or  just  an estimate, allowing consumers to
               prioritize messages by code hotness,

           *   the function name of the code being optimized, where applicable,

           *   the "inlining chain" for the code being optimized, so that when a function is inlined
               into several different places (which might themselves be  inlined),  the  reader  can
               distinguish between the copies,

           *   objects  identifying those parts of the message that refer to expressions, statements
               or symbol-table nodes, which of these categories they are, and, when available, their
               source code location,

           *   the GCC pass that emitted the message, and

           *   the location in GCC's own code from which the message was emitted

           Additionally, some messages  are  logically  nested  within  other  messages,  reflecting
           implementation details of the optimization passes.

       -fsched-verbose=n
           On  targets that use instruction scheduling, this option controls the amount of debugging
           output the scheduler prints to the dump files.

           For  n  greater  than   zero,   -fsched-verbose   outputs   the   same   information   as
           -fdump-rtl-sched1  and  -fdump-rtl-sched2.   For n greater than one, it also output basic
           block probabilities, detailed ready list information and unit/insn info.  For  n  greater
           than  two, it includes RTL at abort point, control-flow and regions info.  And for n over
           four, -fsched-verbose also includes dependence info.

       -fenable-kind-pass
       -fdisable-kind-pass=range-list
           This is a set of options that are used to explicitly disable/enable optimization  passes.
           These  options are intended for use for debugging GCC.  Compiler users should use regular
           options for enabling/disabling passes instead.

           -fdisable-ipa-pass
               Disable IPA pass pass. pass is the pass name.  If the same pass is statically invoked
               in the compiler multiple times, the pass name should be appended  with  a  sequential
               number starting from 1.

           -fdisable-rtl-pass
           -fdisable-rtl-pass=range-list
               Disable  RTL  pass  pass.   pass  is  the  pass name.  If the same pass is statically
               invoked in the compiler multiple times, the pass  name  should  be  appended  with  a
               sequential  number starting from 1.  range-list is a comma-separated list of function
               ranges or assembler names.  Each range is a number pair separated by  a  colon.   The
               range  is  inclusive  in  both ends.  If the range is trivial, the number pair can be
               simplified as a single number.  If the function's call graph node's uid falls  within
               one  of  the  specified  ranges,  the pass is disabled for that function.  The uid is
               shown in the function header of a dump file, and the pass  names  can  be  dumped  by
               using option -fdump-passes.

           -fdisable-tree-pass
           -fdisable-tree-pass=range-list
               Disable tree pass pass.  See -fdisable-rtl for the description of option arguments.

           -fenable-ipa-pass
               Enable IPA pass pass.  pass is the pass name.  If the same pass is statically invoked
               in  the  compiler  multiple times, the pass name should be appended with a sequential
               number starting from 1.

           -fenable-rtl-pass
           -fenable-rtl-pass=range-list
               Enable RTL  pass  pass.   See  -fdisable-rtl  for  option  argument  description  and
               examples.

           -fenable-tree-pass
           -fenable-tree-pass=range-list
               Enable tree pass pass.  See -fdisable-rtl for the description of option arguments.

           Here are some examples showing uses of these options.

                   # disable ccp1 for all functions
                      -fdisable-tree-ccp1
                   # disable complete unroll for function whose cgraph node uid is 1
                      -fenable-tree-cunroll=1
                   # disable gcse2 for functions at the following ranges [1,1],
                   # [300,400], and [400,1000]
                   # disable gcse2 for functions foo and foo2
                      -fdisable-rtl-gcse2=foo,foo2
                   # disable early inlining
                      -fdisable-tree-einline
                   # disable ipa inlining
                      -fdisable-ipa-inline
                   # enable tree full unroll
                      -fenable-tree-unroll

       -fchecking
       -fchecking=n
           Enable internal consistency checking.  The default depends on the compiler configuration.
           -fchecking=2  enables  further  internal  consistency  checking  that  might  affect code
           generation.

       -frandom-seed=string
           This option provides a seed that GCC uses  in  place  of  random  numbers  in  generating
           certain  symbol  names that have to be different in every compiled file.  It is also used
           to place unique stamps in coverage data files and the object  files  that  produce  them.
           You can use the -frandom-seed option to produce reproducibly identical object files.

           The  string  can  either  be  a number (decimal, octal or hex) or an arbitrary string (in
           which case it's converted to a number by computing CRC32).

           The string should be different for every file you compile.

       -save-temps
           Store the usual "temporary" intermediate files permanently; name them as auxiliary output
           files, as specified described under -dumpbase and -dumpdir.

           When used in combination with the -x command-line option, -save-temps is sensible  enough
           to  avoid  overwriting  an  input  source file with the same extension as an intermediate
           file.  The corresponding intermediate file may be obtained by renaming  the  source  file
           before using -save-temps.

       -save-temps=cwd
           Equivalent to -save-temps -dumpdir ./.

       -save-temps=obj
           Equivalent  to -save-temps -dumpdir outdir/, where outdir/ is the directory of the output
           file specified after the -o option, including any directory separators.  If the -o option
           is not used, the -save-temps=obj switch behaves like -save-temps=cwd.

       -time[=file]
           Report the CPU time taken by each subprocess in the compilation sequence.  For  C  source
           files, this is the compiler proper and assembler (plus the linker if linking is done).

           Without the specification of an output file, the output looks like this:

                   # cc1 0.12 0.01
                   # as 0.00 0.01

           The  first  number  on  each  line  is  the "user time", that is time spent executing the
           program itself.  The second number is  "system  time",  time  spent  executing  operating
           system routines on behalf of the program.  Both numbers are in seconds.

           With  the  specification of an output file, the output is appended to the named file, and
           it looks like this:

                   0.12 0.01 cc1 <options>
                   0.00 0.01 as <options>

           The "user time" and the "system time" are moved before the program name, and the  options
           passed  to  the  program  are  displayed,  so that one can later tell what file was being
           compiled, and with which options.

       -fdump-final-insns[=file]
           Dump the final internal representation (RTL)  to  file.   If  the  optional  argument  is
           omitted  (or if file is "."), the name of the dump file is determined by appending ".gkd"
           to the dump base name, see -dumpbase.

       -fcompare-debug[=opts]
           If no error occurs during compilation, run the compiler a second time,  adding  opts  and
           -fcompare-debug-second to the arguments passed to the second compilation.  Dump the final
           internal representation in both compilations, and print an error if they differ.

           If the equal sign is omitted, the default -gtoggle is used.

           The environment variable GCC_COMPARE_DEBUG, if defined, non-empty and nonzero, implicitly
           enables  -fcompare-debug.   If  GCC_COMPARE_DEBUG  is defined to a string starting with a
           dash, then it is used for opts, otherwise the default -gtoggle is used.

           -fcompare-debug=,  with  the  equal   sign   but   without   opts,   is   equivalent   to
           -fno-compare-debug, which disables the dumping of the final representation and the second
           compilation, preventing even GCC_COMPARE_DEBUG from taking effect.

           To  verify  full  coverage  during  -fcompare-debug testing, set GCC_COMPARE_DEBUG to say
           -fcompare-debug-not-overridden, which GCC rejects as an  invalid  option  in  any  actual
           compilation  (rather  than  preprocessing,  assembly or linking).  To get just a warning,
           setting GCC_COMPARE_DEBUG to -w%n-fcompare-debug not overridden will do.

       -fcompare-debug-second
           This option is implicitly passed to the compiler for the second compilation requested  by
           -fcompare-debug,  along with options to silence warnings, and omitting other options that
           would cause the compiler to produce output to files or  to  standard  output  as  a  side
           effect.   Dump files and preserved temporary files are renamed so as to contain the ".gk"
           additional extension during the second compilation, to avoid overwriting those  generated
           by the first.

           When  this option is passed to the compiler driver, it causes the first compilation to be
           skipped, which makes it useful for little other than debugging the compiler proper.

       -gtoggle
           Turn off generation of debug info, if leaving out this option generates it, or turn it on
           at level 2 otherwise.  The position of this argument in the command line does not matter;
           it takes effect after all other options are processed, and  it  does  so  only  once,  no
           matter  how  many  times  it  is  given.   This  is  mainly  intended  to  be  used  with
           -fcompare-debug.

       -fvar-tracking-assignments-toggle
           Toggle -fvar-tracking-assignments, in the same way that -gtoggle toggles -g.

       -Q  Makes the compiler print out each function  name  as  it  is  compiled,  and  print  some
           statistics about each pass when it finishes.

       -ftime-report
           Makes  the  compiler  print  some statistics about the time consumed by each pass when it
           finishes.

       -ftime-report-details
           Record the time consumed by infrastructure parts separately for each pass.

       -fira-verbose=n
           Control the verbosity of the dump  file  for  the  integrated  register  allocator.   The
           default value is 5.  If the value n is greater or equal to 10, the dump output is sent to
           stderr using the same format as n minus 10.

       -flto-report
           Prints  a  report  with internal details on the workings of the link-time optimizer.  The
           contents of this report vary from version to version.  It is meant to be  useful  to  GCC
           developers when processing object files in LTO mode (via -flto).

           Disabled by default.

       -flto-report-wpa
           Like -flto-report, but only print for the WPA phase of link-time optimization.

       -fmem-report
           Makes  the  compiler  print  some  statistics  about  permanent memory allocation when it
           finishes.

       -fmem-report-wpa
           Makes the compiler print some statistics about permanent memory allocation  for  the  WPA
           phase only.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
           Makes  the  compiler  print  some  statistics about permanent memory allocation before or
           after interprocedural optimization.

       -fprofile-report
           Makes the compiler print some statistics about consistency of the (estimated) profile and
           effect of individual passes.

       -fstack-usage
           Makes the compiler output stack usage information for  the  program,  on  a  per-function
           basis.   The  filename  for the dump is made by appending .su to the auxname.  auxname is
           generated from the name of the output file, if explicitly specified  and  it  is  not  an
           executable,  otherwise  it  is  the  basename of the source file.  An entry is made up of
           three fields:

           *   The name of the function.

           *   A number of bytes.

           *   One or more qualifiers: "static", "dynamic", "bounded".

           The qualifier "static" means that the function manipulates the stack statically: a  fixed
           number  of  bytes  are allocated for the frame on function entry and released on function
           exit; no stack adjustments are otherwise made in the function.  The second field is  this
           fixed number of bytes.

           The  qualifier  "dynamic"  means  that the function manipulates the stack dynamically: in
           addition to the static allocation described above, stack adjustments are made in the body
           of the function, for example  to  push/pop  arguments  around  function  calls.   If  the
           qualifier  "bounded"  is  also  present,  the  amount  of these adjustments is bounded at
           compile time and the second field is an upper bound of the total amount of stack used  by
           the  function.   If  it is not present, the amount of these adjustments is not bounded at
           compile time and the second field only represents the bounded part.

       -fstats
           Emit statistics about front-end processing at the end of the compilation.  This option is
           supported only by the C++ front end, and the information is generally only useful to  the
           G++ development team.

       -fdbg-cnt-list
           Print the name and the counter upper bound for all debug counters.

       -fdbg-cnt=counter-value-list
           Set  the  internal  debug  counter lower and upper bound.  counter-value-list is a comma-
           separated list of name:lower_bound1-upper_bound1  [:lower_bound2-upper_bound2...]  tuples
           which  sets  the  name  of  the counter and list of closed intervals.  The lower_bound is
           optional   and   is   zero   initialized    if    not    set.     For    example,    with
           -fdbg-cnt=dce:2-4:10-11,tail_call:10,  dbg_cnt(dce)  returns true only for second, third,
           fourth, tenth and eleventh invocation.  For dbg_cnt(tail_call) true is returned for first
           10 invocations.

       -print-file-name=library
           Print the full absolute name of  the  library  file  library  that  would  be  used  when
           linking---and  don't  do  anything  else.  With this option, GCC does not compile or link
           anything; it just prints the file name.

       -print-multi-directory
           Print the directory name corresponding to the multilib selected  by  any  other  switches
           present in the command line.  This directory is supposed to exist in GCC_EXEC_PREFIX.

       -print-multi-lib
           Print  the  mapping  from multilib directory names to compiler switches that enable them.
           The directory name is separated from the switches by ;, and each switch starts with an  @
           instead  of  the  -,  without spaces between multiple switches.  This is supposed to ease
           shell processing.

       -print-multi-os-directory
           Print the path  to  OS  libraries  for  the  selected  multilib,  relative  to  some  lib
           subdirectory.   If  OS libraries are present in the lib subdirectory and no multilibs are
           used, this is  usually  just  .,  if  OS  libraries  are  present  in  libsuffix  sibling
           directories this prints e.g. ../lib64, ../lib or ../lib32, or if OS libraries are present
           in lib/subdir subdirectories it prints e.g. amd64, sparcv9 or ev6.

       -print-multiarch
           Print  the  path  to  OS  libraries  for  the  selected  multiarch,  relative to some lib
           subdirectory.

       -print-prog-name=program
           Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
           Same as -print-file-name=libgcc.a.

           This is useful when you use -nostdlib or -nodefaultlibs but you  do  want  to  link  with
           libgcc.a.  You can do:

                   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
           Print the name of the configured installation directory and a list of program and library
           directories gcc searches---and don't do anything else.

           This  is useful when gcc prints the error message installation problem, cannot exec cpp0:
           No such file or directory.  To resolve this you either need to put  cpp0  and  the  other
           compiler  components  where  gcc  expects  to  find  them, or you can set the environment
           variable GCC_EXEC_PREFIX to the directory where you installed  them.   Don't  forget  the
           trailing /.

       -print-sysroot
           Print  the  target sysroot directory that is used during compilation.  This is the target
           sysroot specified either at configure time or using the --sysroot option,  possibly  with
           an  extra suffix that depends on compilation options.  If no target sysroot is specified,
           the option prints nothing.

       -print-sysroot-headers-suffix
           Print the suffix added to the target sysroot when searching for headers, or give an error
           if the compiler is not configured with such a suffix---and don't do anything else.

       -dumpmachine
           Print the compiler's target  machine  (for  example,  i686-pc-linux-gnu)---and  don't  do
           anything else.

       -dumpversion
           Print  the  compiler version (for example, 3.0, 6.3.0 or 7)---and don't do anything else.
           This is the compiler version used in filesystem paths and specs.  Depending  on  how  the
           compiler  has been configured it can be just a single number (major version), two numbers
           separated by a dot (major and minor version) or three numbers separated by  dots  (major,
           minor and patchlevel version).

       -dumpfullversion
           Print  the full compiler version---and don't do anything else. The output is always three
           numbers separated by dots, major, minor and patchlevel version.

       -dumpspecs
           Print the compiler's built-in specs---and don't do anything else.  (This is used when GCC
           itself is being built.)

   Machine-Dependent Options
       Each target machine supported by GCC can have its own options---for example, to allow you  to
       compile  for  a  particular processor variant or ABI, or to control optimizations specific to
       that machine.  By convention, the names of machine-specific options start with -m.

       Some configurations of the compiler also support additional target-specific options,  usually
       for compatibility with other compilers on the same platform.

       AArch64 Options

       These options are defined for AArch64 implementations:

       -mabi=name
           Generate  code  for the specified data model.  Permissible values are ilp32 for SysV-like
           data model where int, long int and pointers are 32 bits,  and  lp64  for  SysV-like  data
           model where int is 32 bits, but long int and pointers are 64 bits.

           The  default  depends on the specific target configuration.  Note that the LP64 and ILP32
           ABIs are not link-compatible; you must compile your entire program with the same ABI, and
           link with a compatible set of libraries.

       -mbig-endian
           Generate  big-endian  code.   This  is  the  default  when  GCC  is  configured  for   an
           aarch64_be-*-* target.

       -mgeneral-regs-only
           Generate  code  which  uses  only  the  general-purpose registers.  This will prevent the
           compiler from using floating-point and Advanced SIMD registers but will  not  impose  any
           restrictions on the assembler.

       -mlittle-endian
           Generate  little-endian  code.   This  is  the  default  when  GCC  is  configured for an
           aarch64-*-* but not an aarch64_be-*-* target.

       -mcmodel=tiny
           Generate code for the tiny code model.  The program and its  statically  defined  symbols
           must be within 1MB of each other.  Programs can be statically or dynamically linked.

       -mcmodel=small
           Generate  code  for the small code model.  The program and its statically defined symbols
           must be within 4GB of each other.  Programs can  be  statically  or  dynamically  linked.
           This is the default code model.

       -mcmodel=large
           Generate  code  for  the large code model.  This makes no assumptions about addresses and
           sizes of sections.  Programs can be statically linked only.  The -mcmodel=large option is
           incompatible with -mabi=ilp32, -fpic and -fPIC.

       -mstrict-align
       -mno-strict-align
           Avoid or allow generating memory accesses that may not be aligned  on  a  natural  object
           boundary as described in the architecture specification.

       -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer
           Omit or keep the frame pointer in leaf functions.  The former behavior is the default.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
           Generate stack protection code using canary at guard.  Supported locations are global for
           a global canary or sysreg for a canary in an appropriate system register.

           With    the    latter    choice    the    options   -mstack-protector-guard-reg=reg   and
           -mstack-protector-guard-offset=offset furthermore specify which system register to use as
           base register for reading the canary, and from what offset from that base register. There
           is no default register or offset as this is entirely for use within the Linux kernel.

       -mtls-dialect=desc
           Use TLS descriptors as the thread-local storage mechanism for  dynamic  accesses  of  TLS
           variables.  This is the default.

       -mtls-dialect=traditional
           Use  traditional  TLS  as  the thread-local storage mechanism for dynamic accesses of TLS
           variables.

       -mtls-size=size
           Specify bit size of immediate TLS offsets.  Valid values are 12, 24, 32, 48.  This option
           requires binutils 2.26 or newer.

       -mfix-cortex-a53-835769
       -mno-fix-cortex-a53-835769
           Enable or disable the workaround for the ARM  Cortex-A53  erratum  number  835769.   This
           involves  inserting  a  NOP  instruction  between  memory instructions and 64-bit integer
           multiply-accumulate instructions.

       -mfix-cortex-a53-843419
       -mno-fix-cortex-a53-843419
           Enable or disable the workaround for the ARM  Cortex-A53  erratum  number  843419.   This
           erratum workaround is made at link time and this will only pass the corresponding flag to
           the linker.

       -mlow-precision-recip-sqrt
       -mno-low-precision-recip-sqrt
           Enable  or  disable  the  reciprocal  square root approximation.  This option only has an
           effect if -ffast-math or -funsafe-math-optimizations is  used  as  well.   Enabling  this
           reduces precision of reciprocal square root results to about 16 bits for single precision
           and to 32 bits for double precision.

       -mlow-precision-sqrt
       -mno-low-precision-sqrt
           Enable  or  disable  the  square  root  approximation.  This option only has an effect if
           -ffast-math or -funsafe-math-optimizations  is  used  as  well.   Enabling  this  reduces
           precision of square root results to about 16 bits for single precision and to 32 bits for
           double precision.  If enabled, it implies -mlow-precision-recip-sqrt.

       -mlow-precision-div
       -mno-low-precision-div
           Enable  or  disable  the  division  approximation.   This  option  only  has an effect if
           -ffast-math or -funsafe-math-optimizations  is  used  as  well.   Enabling  this  reduces
           precision  of  division  results to about 16 bits for single precision and to 32 bits for
           double precision.

       -mtrack-speculation
       -mno-track-speculation
           Enable or disable generation of additional code to track  speculative  execution  through
           conditional branches.  The tracking state can then be used by the compiler when expanding
           calls to "__builtin_speculation_safe_copy" to permit a more efficient code sequence to be
           generated.

       -moutline-atomics
       -mno-outline-atomics
           Enable  or  disable  calls  to out-of-line helpers to implement atomic operations.  These
           helpers will, at runtime, determine if the LSE instructions from ARMv8.1-A can  be  used;
           if  not, they will use the load/store-exclusive instructions that are present in the base
           ARMv8.0 ISA.

           This option is only applicable when compiling for the base ARMv8.0 instruction  set.   If
           using  a later revision, e.g. -march=armv8.1-a or -march=armv8-a+lse, the ARMv8.1-Atomics
           instructions will be used directly.  The same applies when using -mcpu= when the selected
           cpu supports the lse feature.  This option is on by default.

       -march=name
           Specify the name of  the  target  architecture  and,  optionally,  one  or  more  feature
           modifiers.  This option has the form -march=arch{+[no]feature}*.

           The  table  below  summarizes  the permissible values for arch and the features that they
           enable by default:

           arch value : Architecture : Includes by default
           armv8-a : Armv8-A : +fp, +simd
           armv8.1-a : Armv8.1-A : armv8-a, +crc, +lse, +rdma
           armv8.2-a : Armv8.2-A : armv8.1-a
           armv8.3-a : Armv8.3-A : armv8.2-a, +pauth
           armv8.4-a : Armv8.4-A : armv8.3-a, +flagm, +fp16fml, +dotprod
           armv8.5-a : Armv8.5-A : armv8.4-a, +sb, +ssbs, +predres
           armv8.6-a : Armv8.6-A : armv8.5-a, +bf16, +i8mm
           armv8-r : Armv8-R : armv8-r

           The value native is available on native AArch64 GNU/Linux and causes the compiler to pick
           the architecture of the host system.  This option has no effect if the compiler is unable
           to recognize the architecture of the host system,

           The   permissible   values   for   feature   are   listed   in   the    sub-section    on
           aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.  Where conflicting feature
           modifiers are specified, the right-most feature is used.

           GCC uses name to determine what kind of instructions it can emit when generating assembly
           code.  If -march is specified without either of -mtune or -mcpu also being specified, the
           code is tuned to perform well across a range of target processors implementing the target
           architecture.

       -mtune=name
           Specify the name of the target processor for which GCC should tune the performance of the
           code.    Permissible  values  for  this  option  are:  generic,  cortex-a35,  cortex-a53,
           cortex-a55, cortex-a57, cortex-a72,  cortex-a73,  cortex-a75,  cortex-a76,  cortex-a76ae,
           cortex-a77,  cortex-a65, cortex-a65ae, cortex-a34, cortex-a78, cortex-a78ae, cortex-a78c,
           ares, exynos-m1, emag, falkor, neoverse-512tvb,  neoverse-e1,  neoverse-n1,  neoverse-n2,
           neoverse-v1,neoverse-v2,  grace,  qdf24xx,  saphira,  phecda,  xgene1,  vulcan, octeontx,
           octeontx81,    octeontx83,   octeontx2,    octeontx2t98,    octeontx2t96    octeontx2t93,
           octeontx2f95, octeontx2f95n, octeontx2f95mm, a64fx, thunderx, thunderxt88, thunderxt88p1,
           thunderxt81,      tsv110,     thunderxt83,     thunderx2t99,     thunderx3t110,     zeus,
           cortex-a57.cortex-a53,           cortex-a72.cortex-a53,            cortex-a73.cortex-a35,
           cortex-a73.cortex-a53,    cortex-a75.cortex-a55,    cortex-a76.cortex-a55,    cortex-r82,
           cortex-x1, ampere1, ampere1a, cobalt-100 and native.

           The   values   cortex-a57.cortex-a53,    cortex-a72.cortex-a53,    cortex-a73.cortex-a35,
           cortex-a73.cortex-a53,  cortex-a75.cortex-a55,  cortex-a76.cortex-a55  specify  that  GCC
           should tune for a big.LITTLE system.

           The value neoverse-512tvb specifies that GCC should tune  for  Neoverse  cores  that  (a)
           implement  SVE  and  (b)  have  a total vector bandwidth of 512 bits per cycle.  In other
           words, the option tells GCC to tune  for  Neoverse  cores  that  can  execute  4  128-bit
           Advanced  SIMD  arithmetic instructions a cycle and that can execute an equivalent number
           of SVE arithmetic instructions per cycle (2 for 256-bit SVE, 4 for 128-bit SVE).  This is
           more general than tuning for a specific core like Neoverse V1 but is more  specific  than
           the default tuning described below.

           Additionally  on  native  AArch64 GNU/Linux systems the value native tunes performance to
           the host system.  This option has no effect if the compiler is unable  to  recognize  the
           processor of the host system.

           Where none of -mtune=, -mcpu= or -march= are specified, the code is tuned to perform well
           across a range of target processors.

           This option cannot be suffixed by feature modifiers.

       -mcpu=name
           Specify  the  name  of  the  target processor, optionally suffixed by one or more feature
           modifiers.  This option has the  form  -mcpu=cpu{+[no]feature}*,  where  the  permissible
           values  for  cpu  are the same as those available for -mtune.  The permissible values for
           feature are documented in the sub-section on aarch64-feature-modifiers,,-march and  -mcpu
           Feature  Modifiers.   Where  conflicting  feature modifiers are specified, the right-most
           feature is used.

           GCC uses name to determine what kind of instructions it can emit when generating assembly
           code (as if by -march) and to determine the  target  processor  for  which  to  tune  for
           performance  (as  if by -mtune).  Where this option is used in conjunction with -march or
           -mtune, those options take precedence over the appropriate part of this option.

           -mcpu=neoverse-512tvb is special in that it does  not  refer  to  a  specific  core,  but
           instead  refers  to all Neoverse cores that (a) implement SVE and (b) have a total vector
           bandwidth of 512 bits  a  cycle.   Unless  overridden  by  -march,  -mcpu=neoverse-512tvb
           generates  code  that  can  run  on  a  Neoverse  V1 core, since Neoverse V1 is the first
           Neoverse core with these properties.  Unless overridden by -mtune,  -mcpu=neoverse-512tvb
           tunes code in the same way as for -mtune=neoverse-512tvb.

       -moverride=string
           Override  tuning  decisions  made  by  the back-end in response to a -mtune= switch.  The
           syntax, semantics, and accepted values for string in this option are not guaranteed to be
           consistent across releases.

           This option is only intended to be useful when developing GCC.

       -mverbose-cost-dump
           Enable verbose cost model dumping in the debug dump files.  This option is  provided  for
           use in debugging the compiler.

       -mpc-relative-literal-loads
       -mno-pc-relative-literal-loads
           Enable or disable PC-relative literal loads.  With this option literal pools are accessed
           using a single instruction and emitted after each function.  This limits the maximum size
           of functions to 1MB.  This is enabled by default for -mcmodel=tiny.

       -msign-return-address=scope
           Select  the  function scope on which return address signing will be applied.  Permissible
           values are none, which disables return address signing, non-leaf, which  enables  pointer
           signing  for  functions  which  are  not  leaf  functions, and all, which enables pointer
           signing for all functions.  The default value is none. This option has been deprecated by
           -mbranch-protection.

       -mbranch-protection=none|standard|pac-ret[+leaf+b-key]|bti
           Select the branch protection features to use.  none is the  default  and  turns  off  all
           types  of  branch protection.  standard turns on all types of branch protection features.
           If a feature has additional tuning options, then standard sets it to its standard  level.
           pac-ret[+leaf]  turns  on return address signing to its standard level: signing functions
           that save the return address to memory (non-leaf functions  will  practically  always  do
           this)  using  the a-key.  The optional argument leaf can be used to extend the signing to
           include leaf functions.  The optional argument b-key can be used to  sign  the  functions
           with  the  B-key  instead  of  the  A-key.   bti  turns  on  branch target identification
           mechanism.

       -mharden-sls=opts
           Enable compiler hardening against straight line speculation  (SLS).   opts  is  a  comma-
           separated list of the following options:

           retbr
           blr

           In  addition, -mharden-sls=all enables all SLS hardening while -mharden-sls=none disables
           all SLS hardening.

       -msve-vector-bits=bits
           Specify the number of bits in an SVE vector register.  This option  only  has  an  effect
           when SVE is enabled.

           GCC supports two forms of SVE code generation: "vector-length agnostic" output that works
           with  any  size of vector register and "vector-length specific" output that allows GCC to
           make assumptions about the vector length when it is useful for optimization reasons.  The
           possible values of bits are: scalable, 128, 256, 512, 1024 and 2048.  Specifying scalable
           selects vector-length agnostic output.  At present -msve-vector-bits=128  also  generates
           vector-length  agnostic output for big-endian targets.  All other values generate vector-
           length specific code.  The behavior of these values may change in future releases and  no
           value  except  scalable  should  be  relied on for producing code that is portable across
           different hardware SVE vector lengths.

           The default is -msve-vector-bits=scalable, which produces vector-length agnostic code.

       -march and -mcpu Feature Modifiers

       Feature modifiers used with -march and -mcpu can be any of the following and  their  inverses
       nofeature:

       crc Enable CRC extension.  This is on by default for -march=armv8.1-a.

       crypto
           Enable   Crypto   extension.    This   also  enables  Advanced  SIMD  and  floating-point
           instructions.

       fp  Enable floating-point instructions.  This is on by default for all  possible  values  for
           options -march and -mcpu.

       simd
           Enable  Advanced SIMD instructions.  This also enables floating-point instructions.  This
           is on by default for all possible values for options -march and -mcpu.

       sve Enable Scalable Vector Extension instructions.   This  also  enables  Advanced  SIMD  and
           floating-point instructions.

       lse Enable Large System Extension instructions.  This is on by default for -march=armv8.1-a.

       rdma
           Enable  Round  Double  Multiply  Accumulate  instructions.   This  is  on  by default for
           -march=armv8.1-a.

       fp16
           Enable FP16 extension.  This also enables floating-point instructions.

       fp16fml
           Enable FP16 fmla  extension.   This  also  enables  FP16  extensions  and  floating-point
           instructions.  This option is enabled by default for -march=armv8.4-a. Use of this option
           with architectures prior to Armv8.2-A is not supported.

       rcpc
           Enable the RcPc extension.  This does not change code generation from GCC, but is  passed
           on  to  the  assembler,  enabling inline asm statements to use instructions from the RcPc
           extension.

       dotprod
           Enable the Dot Product extension.  This also enables Advanced SIMD instructions.

       aes Enable the Armv8-a aes and pmull crypto  extension.   This  also  enables  Advanced  SIMD
           instructions.

       sha2
           Enable the Armv8-a sha2 crypto extension.  This also enables Advanced SIMD instructions.

       sha3
           Enable   the  sha512  and  sha3  crypto  extension.   This  also  enables  Advanced  SIMD
           instructions. Use of this option with architectures prior to Armv8.2-A is not supported.

       sm4 Enable the sm3 and sm4 crypto extension.  This also enables Advanced  SIMD  instructions.
           Use of this option with architectures prior to Armv8.2-A is not supported.

       profile
           Enable  the Statistical Profiling extension.  This option is only to enable the extension
           at the assembler level and does not affect code generation.

       rng Enable the Armv8.5-a Random Number instructions.  This  option  is  only  to  enable  the
           extension at the assembler level and does not affect code generation.

       memtag
           Enable  the  Armv8.5-a  Memory Tagging Extensions.  Use of this option with architectures
           prior to Armv8.5-A is not supported.

       sb  Enable the Armv8-a Speculation Barrier instruction.  This option is only  to  enable  the
           extension  at  the  assembler  level and does not affect code generation.  This option is
           enabled by default for -march=armv8.5-a.

       ssbs
           Enable the Armv8-a Speculative Store Bypass Safe instruction.  This  option  is  only  to
           enable  the  extension  at the assembler level and does not affect code generation.  This
           option is enabled by default for -march=armv8.5-a.

       predres
           Enable the Armv8-a Execution and Data Prediction Restriction instructions.   This  option
           is  only  to  enable  the  extension  at  the  assembler  level  and does not affect code
           generation.  This option is enabled by default for -march=armv8.5-a.

       sve2
           Enable the Armv8-a Scalable Vector Extension 2.  This also enables SVE instructions.

       sve2-bitperm
           Enable SVE2 bitperm instructions.  This also enables SVE2 instructions.

       sve2-sm4
           Enable SVE2 sm4 instructions.  This also enables SVE2 instructions.

       sve2-aes
           Enable SVE2 aes instructions.  This also enables SVE2 instructions.

       sve2-sha3
           Enable SVE2 sha3 instructions.  This also enables SVE2 instructions.

       tme Enable the Transactional Memory Extension.

       i8mm
           Enable 8-bit Integer Matrix Multiply instructions.  This also enables Advanced  SIMD  and
           floating-point  instructions.   This  option  is enabled by default for -march=armv8.6-a.
           Use of this option with architectures prior to Armv8.2-A is not supported.

       f32mm
           Enable 32-bit Floating  point  Matrix  Multiply  instructions.   This  also  enables  SVE
           instructions.  Use of this option with architectures prior to Armv8.2-A is not supported.

       f64mm
           Enable  64-bit  Floating  point  Matrix  Multiply  instructions.   This  also enables SVE
           instructions.  Use of this option with architectures prior to Armv8.2-A is not supported.

       bf16
           Enable brain half-precision floating-point instructions.  This also enables Advanced SIMD
           and floating-point instructions.  This option is enabled by default for -march=armv8.6-a.
           Use of this option with architectures prior to Armv8.2-A is not supported.

       flagm
           Enable the Flag Manipulation instructions Extension.

       pauth
           Enable the Pointer Authentication Extension.

       Feature crypto implies aes, sha2, and simd,  which  implies  fp.   Conversely,  nofp  implies
       nosimd, which implies nocrypto, noaes and nosha2.

       Adapteva Epiphany Options

       These -m options are defined for Adapteva Epiphany:

       -mhalf-reg-file
           Don't  allocate  any  register  in  the  range "r32"..."r63".  That allows code to run on
           hardware variants that lack these registers.

       -mprefer-short-insn-regs
           Preferentially allocate registers that allow  short  instruction  generation.   This  can
           result in increased instruction count, so this may either reduce or increase overall code
           size.

       -mbranch-cost=num
           Set  the  cost  of  branches  to  roughly num "simple" instructions.  This cost is only a
           heuristic and is not guaranteed to produce consistent results across releases.

       -mcmove
           Enable the generation of conditional moves.

       -mnops=num
           Emit num NOPs before every other generated instruction.

       -mno-soft-cmpsf
           For single-precision floating-point comparisons, emit an "fsub" instruction and test  the
           flags.   This  is faster than a software comparison, but can get incorrect results in the
           presence of NaNs, or when two different  small  numbers  are  compared  such  that  their
           difference  is  calculated  as zero.  The default is -msoft-cmpsf, which uses slower, but
           IEEE-compliant, software comparisons.

       -mstack-offset=num
           Set the offset between the top of the stack and the stack pointer.  E.g., a  value  of  8
           means  that  the  eight  bytes  in  the range "sp+0...sp+7" can be used by leaf functions
           without stack allocation.  Values other than 8 or 16 are untested and unlikely  to  work.
           Note  also  that  this option changes the ABI; compiling a program with a different stack
           offset than the libraries have been compiled with generally does not work.   This  option
           can  be  useful if you want to evaluate if a different stack offset would give you better
           code, but to actually use a different stack offset  to  build  working  programs,  it  is
           recommended  to  configure  the  toolchain  with  the appropriate --with-stack-offset=num
           option.

       -mno-round-nearest
           Make the scheduler assume that the rounding mode has been set to truncating.  The default
           is -mround-nearest.

       -mlong-calls
           If not otherwise specified by an attribute, assume all calls might be beyond  the  offset
           range  of  the  "b"  /  "bl" instructions, and therefore load the function address into a
           register before performing a (otherwise direct) call.  This is the default.

       -mshort-calls
           If not otherwise specified by an attribute, assume all direct calls are in the  range  of
           the  "b" / "bl" instructions, so use these instructions for direct calls.  The default is
           -mlong-calls.

       -msmall16
           Assume addresses can be loaded as  16-bit  unsigned  values.   This  does  not  apply  to
           function addresses for which -mlong-calls semantics are in effect.

       -mfp-mode=mode
           Set  the  prevailing mode of the floating-point unit.  This determines the floating-point
           mode that is provided and expected at function call and return time.   Making  this  mode
           match  the  mode  you predominantly need at function start can make your programs smaller
           and faster by avoiding unnecessary mode switches.

           mode can be set to one the following values:

           caller
               Any mode at function entry is valid, and  retained  or  restored  when  the  function
               returns,  and  when  it  calls  other  functions.   This mode is useful for compiling
               libraries or other compilation units you might want  to  incorporate  into  different
               programs  with  different  prevailing FPU modes, and the convenience of being able to
               use a single object file outweighs the size and speed overhead  for  any  extra  mode
               switching  that  might  be  needed,  compared  with  what would be needed with a more
               specific choice of prevailing FPU mode.

           truncate
               This is the mode used for floating-point calculations  with  truncating  (i.e.  round
               towards  zero)  rounding  mode.   That  includes  conversion  from  floating point to
               integer.

           round-nearest
               This is the mode used for floating-point calculations  with  round-to-nearest-or-even
               rounding mode.

           int This  is  the  mode  used  to  perform integer calculations in the FPU, e.g.  integer
               multiply, or integer multiply-and-accumulate.

           The default is -mfp-mode=caller

       -mno-split-lohi
       -mno-postinc
       -mno-postmodify
           Code generation tweaks that disable, respectively, splitting of 32-bit loads,  generation
           of  post-increment  addresses, and generation of post-modify addresses.  The defaults are
           msplit-lohi, -mpost-inc, and -mpost-modify.

       -mnovect-double
           Change the preferred SIMD mode to SImode.   The  default  is  -mvect-double,  which  uses
           DImode as preferred SIMD mode.

       -max-vect-align=num
           The  maximum alignment for SIMD vector mode types.  num may be 4 or 8.  The default is 8.
           Note that this is an ABI  change,  even  though  many  library  function  interfaces  are
           unaffected  if  they  don't  use  SIMD  vector  modes  in  places that affect size and/or
           alignment of relevant types.

       -msplit-vecmove-early
           Split vector moves into single word moves before reload.  In theory this can give  better
           register allocation, but so far the reverse seems to be generally the case.

       -m1reg-reg
           Specify  a register to hold the constant -1, which makes loading small negative constants
           and certain bitmasks faster.  Allowable values for reg are r43 and r63, which specify use
           of that register as a fixed register, and none, which means that no register is used  for
           this purpose.  The default is -m1reg-none.

       AMD GCN Options

       These options are defined specifically for the AMD GCN port.

       -march=gpu
       -mtune=gpu
           Set architecture type or tuning for gpu. Supported values for gpu are

           fiji
               Compile for GCN3 Fiji devices (gfx803).

           gfx900
               Compile for GCN5 Vega 10 devices (gfx900).

           gfx906
               Compile for GCN5 Vega 20 devices (gfx906).

       -msram-ecc=on
       -msram-ecc=off
       -msram-ecc=any
           Compile  binaries  suitable  for  devices with the SRAM-ECC feature enabled, disabled, or
           either mode.  This feature can be enabled per-process on some devices.  The compiled code
           must match the device mode. The default is any, for devices that support it.

       -mstack-size=bytes
           Specify how many bytes of stack space will be requested for each GPU thread (wave-front).
           Beware that there may be many threads and limited memory  available.   The  size  of  the
           stack  allocation  may  also have an impact on run-time performance.  The default is 32KB
           when using OpenACC or OpenMP, and 1MB otherwise.

       -mxnack
           Compile binaries suitable for devices with  the  XNACK  feature  enabled.   Some  devices
           always  require XNACK and some allow the user to configure XNACK.  The compiled code must
           match the device mode.   The  default  is  -mno-xnack.   At  present  this  option  is  a
           placeholder for support that is not yet implemented.

       ARC Options

       The following options control the architecture variant for which code is being compiled:

       -mbarrel-shifter
           Generate   instructions  supported  by  barrel  shifter.   This  is  the  default  unless
           -mcpu=ARC601 or -mcpu=ARCEM is in effect.

       -mjli-always
           Force to call a function using jli_s instruction.  This option is valid  only  for  ARCv2
           architecture.

       -mcpu=cpu
           Set  architecture  type,  register  usage, and instruction scheduling parameters for cpu.
           There  are  also  shortcut  alias  options  available  for  backward  compatibility   and
           convenience.  Supported values for cpu are

           arc600
               Compile for ARC600.  Aliases: -mA6, -mARC600.

           arc601
               Compile for ARC601.  Alias: -mARC601.

           arc700
               Compile  for  ARC700.   Aliases: -mA7, -mARC700.  This is the default when configured
               with --with-cpu=arc700.

           arcem
               Compile for ARC EM.

           archs
               Compile for ARC HS.

           em  Compile for ARC EM CPU with no hardware extensions.

           em4 Compile for ARC EM4 CPU.

           em4_dmips
               Compile for ARC EM4 DMIPS CPU.

           em4_fpus
               Compile for ARC EM4 DMIPS CPU with the single-precision floating-point extension.

           em4_fpuda
               Compile for ARC EM4 DMIPS CPU with single-precision floating-point and double  assist
               instructions.

           hs  Compile for ARC HS CPU with no hardware extensions except the atomic instructions.

           hs34
               Compile for ARC HS34 CPU.

           hs38
               Compile for ARC HS38 CPU.

           hs38_linux
               Compile for ARC HS38 CPU with all hardware extensions on.

           arc600_norm
               Compile for ARC 600 CPU with "norm" instructions enabled.

           arc600_mul32x16
               Compile for ARC 600 CPU with "norm" and 32x16-bit multiply instructions enabled.

           arc600_mul64
               Compile for ARC 600 CPU with "norm" and "mul64"-family instructions enabled.

           arc601_norm
               Compile for ARC 601 CPU with "norm" instructions enabled.

           arc601_mul32x16
               Compile for ARC 601 CPU with "norm" and 32x16-bit multiply instructions enabled.

           arc601_mul64
               Compile for ARC 601 CPU with "norm" and "mul64"-family instructions enabled.

           nps400
               Compile for ARC 700 on NPS400 chip.

           em_mini
               Compile for ARC EM minimalist configuration featuring reduced register set.

       -mdpfp
       -mdpfp-compact
           Generate double-precision FPX instructions, tuned for the compact implementation.

       -mdpfp-fast
           Generate double-precision FPX instructions, tuned for the fast implementation.

       -mno-dpfp-lrsr
           Disable "lr" and "sr" instructions from using FPX extension aux registers.

       -mea
           Generate  extended  arithmetic instructions.  Currently only "divaw", "adds", "subs", and
           "sat16" are supported.  Only valid for -mcpu=ARC700.

       -mno-mpy
           Do not generate "mpy"-family instructions for ARC700.  This option is deprecated.

       -mmul32x16
           Generate 32x16-bit multiply and multiply-accumulate instructions.

       -mmul64
           Generate "mul64" and "mulu64" instructions.  Only valid for -mcpu=ARC600.

       -mnorm
           Generate "norm" instructions.  This is the default if -mcpu=ARC700 is in effect.

       -mspfp
       -mspfp-compact
           Generate single-precision FPX instructions, tuned for the compact implementation.

       -mspfp-fast
           Generate single-precision FPX instructions, tuned for the fast implementation.

       -msimd
           Enable generation of ARC SIMD instructions via target-specific builtins.  Only valid  for
           -mcpu=ARC700.

       -msoft-float
           This  option ignored; it is provided for compatibility purposes only.  Software floating-
           point code is emitted by default, and this default can overridden by FPX options; -mspfp,
           -mspfp-compact, or -mspfp-fast for  single  precision,  and  -mdpfp,  -mdpfp-compact,  or
           -mdpfp-fast for double precision.

       -mswap
           Generate "swap" instructions.

       -matomic
           This  enables  use  of  the  locked  load/store conditional extension to implement atomic
           memory built-in functions.  Not available for ARC 6xx or ARC EM cores.

       -mdiv-rem
           Enable "div" and "rem" instructions for ARCv2 cores.

       -mcode-density
           Enable code density instructions for ARC EM.  This option is on by default for ARC HS.

       -mll64
           Enable double load/store operations for ARC HS cores.

       -mtp-regno=regno
           Specify thread pointer register number.

       -mmpy-option=multo
           Compile ARCv2 code with a multiplier design option.  You can  specify  the  option  using
           either  a  string or numeric value for multo.  wlh1 is the default value.  The recognized
           values are:

           0
           none
               No multiplier available.

           1
           w   16x16 multiplier, fully pipelined.  The following instructions  are  enabled:  "mpyw"
               and "mpyuw".

           2
           wlh1
               32x32  multiplier,  fully  pipelined  (1  stage).   The  following  instructions  are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           3
           wlh2
               32x32 multiplier,  fully  pipelined  (2  stages).   The  following  instructions  are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           4
           wlh3
               Two   16x16  multipliers,  blocking,  sequential.   The  following  instructions  are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           5
           wlh4
               One  16x16  multiplier,  blocking,  sequential.   The  following   instructions   are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           6
           wlh5
               One   32x4   multiplier,   blocking,  sequential.   The  following  instructions  are
               additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s".

           7
           plus_dmpy
               ARC HS SIMD support.

           8
           plus_macd
               ARC HS SIMD support.

           9
           plus_qmacw
               ARC HS SIMD support.

           This option is only available for ARCv2 cores.

       -mfpu=fpu
           Enables  support  for  specific  floating-point  hardware  extensions  for  ARCv2  cores.
           Supported values for fpu are:

           fpus
               Enables support for single-precision floating-point hardware extensions.

           fpud
               Enables support for double-precision floating-point hardware extensions.  The single-
               precision floating-point extension is also enabled.  Not available for ARC EM.

           fpuda
               Enables support for double-precision floating-point hardware extensions using double-
               precision assist instructions.  The single-precision floating-point extension is also
               enabled.  This option is only available for ARC EM.

           fpuda_div
               Enables support for double-precision floating-point hardware extensions using double-
               precision assist instructions.  The single-precision floating-point, square-root, and
               divide extensions are also enabled.  This option is only available for ARC EM.

           fpuda_fma
               Enables support for double-precision floating-point hardware extensions using double-
               precision   assist  instructions.   The  single-precision  floating-point  and  fused
               multiply and add hardware extensions are also enabled.  This option is only available
               for ARC EM.

           fpuda_all
               Enables support for double-precision floating-point hardware extensions using double-
               precision  assist  instructions.   All   single-precision   floating-point   hardware
               extensions are also enabled.  This option is only available for ARC EM.

           fpus_div
               Enables  support for single-precision floating-point, square-root and divide hardware
               extensions.

           fpud_div
               Enables support for double-precision floating-point, square-root and divide  hardware
               extensions.  This option includes option fpus_div. Not available for ARC EM.

           fpus_fma
               Enables  support  for  single-precision  floating-point  and  fused  multiply and add
               hardware extensions.

           fpud_fma
               Enables support for  double-precision  floating-point  and  fused  multiply  and  add
               hardware  extensions.   This  option includes option fpus_fma.  Not available for ARC
               EM.

           fpus_all
               Enables support for all single-precision floating-point hardware extensions.

           fpud_all
               Enables  support  for  all  single-  and  double-precision  floating-point   hardware
               extensions.  Not available for ARC EM.

       -mirq-ctrl-saved=register-range, blink, lp_count
           Specifies  general-purposes  registers that the processor automatically saves/restores on
           interrupt entry and exit.  register-range is specified as two registers  separated  by  a
           dash.   The  register  range  always  starts with "r0", the upper limit is "fp" register.
           blink and lp_count are optional.  This option is only valid for ARC EM and ARC HS cores.

       -mrgf-banked-regs=number
           Specifies the number of registers replicated in second register bank  on  entry  to  fast
           interrupt.   Fast  interrupts  are  interrupts with the highest priority level P0.  These
           interrupts save only PC and  STATUS32  registers  to  avoid  memory  transactions  during
           interrupt  entry  and exit sequences.  Use this option when you are using fast interrupts
           in an ARC V2 family processor.  Permitted values are 4, 8, 16, and 32.

       -mlpc-width=width
           Specify the width of the "lp_count" register.  Valid values for width are 8, 16, 20,  24,
           28  and  32  bits.  The default width is fixed to 32 bits.  If the width is less than 32,
           the compiler does not attempt to transform loops in your program to  use  the  zero-delay
           loop  mechanism  unless  it  is  known that the "lp_count" register can hold the required
           loop-counter value.  Depending on the width specified, the compiler and run-time  library
           might  continue  to  use the loop mechanism for various needs.  This option defines macro
           "__ARC_LPC_WIDTH__" with the value of width.

       -mrf16
           This option instructs the compiler to generate code for a 16-entry register  file.   This
           option defines the "__ARC_RF16__" preprocessor macro.

       -mbranch-index
           Enable use of "bi" or "bih" instructions to implement jump tables.

       The following options are passed through to the assembler, and also define preprocessor macro
       symbols.

       -mdsp-packa
           Passed  down  to  the  assembler  to  enable  the  DSP  Pack A extensions.  Also sets the
           preprocessor symbol "__Xdsp_packa".  This option is deprecated.

       -mdvbf
           Passed down to the assembler to enable the dual Viterbi butterfly extension.   Also  sets
           the preprocessor symbol "__Xdvbf".  This option is deprecated.

       -mlock
           Passed down to the assembler to enable the locked load/store conditional extension.  Also
           sets the preprocessor symbol "__Xlock".

       -mmac-d16
           Passed  down  to  the  assembler.  Also sets the preprocessor symbol "__Xxmac_d16".  This
           option is deprecated.

       -mmac-24
           Passed down to the assembler.  Also sets  the  preprocessor  symbol  "__Xxmac_24".   This
           option is deprecated.

       -mrtsc
           Passed  down  to  the  assembler  to  enable  the  64-bit  time-stamp  counter  extension
           instruction.  Also sets the preprocessor symbol "__Xrtsc".  This option is deprecated.

       -mswape
           Passed down to the assembler to enable the  swap  byte  ordering  extension  instruction.
           Also sets the preprocessor symbol "__Xswape".

       -mtelephony
           Passed  down  to  the  assembler  to  enable  dual-  and  single-operand instructions for
           telephony.  Also sets the preprocessor symbol "__Xtelephony".  This option is deprecated.

       -mxy
           Passed down to  the  assembler  to  enable  the  XY  memory  extension.   Also  sets  the
           preprocessor symbol "__Xxy".

       The following options control how the assembly code is annotated:

       -misize
           Annotate assembler instructions with estimated addresses.

       -mannotate-align
           Explain  what  alignment considerations lead to the decision to make an instruction short
           or long.

       The following options are passed through to the linker:

       -marclinux
           Passed through to the linker, to specify use of the "arclinux" emulation.  This option is
           enabled by default in tool chains built for "arc-linux-uclibc"  and  "arceb-linux-uclibc"
           targets when profiling is not requested.

       -marclinux_prof
           Passed  through  to  the  linker,  to specify use of the "arclinux_prof" emulation.  This
           option  is  enabled  by  default  in  tool  chains  built  for   "arc-linux-uclibc"   and
           "arceb-linux-uclibc" targets when profiling is requested.

       The following options control the semantics of generated code:

       -mlong-calls
           Generate  calls  as  register  indirect  calls,  thus providing access to the full 32-bit
           address range.

       -mmedium-calls
           Don't use less than 25-bit addressing range for calls, which is the offset available  for
           an unconditional branch-and-link instruction.  Conditional execution of function calls is
           suppressed,  to  allow  use  of  the  25-bit  range,  rather  than  the 21-bit range with
           conditional  branch-and-link.   This  is  the  default  for   tool   chains   built   for
           "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -G num
           Put  definitions  of  externally-visible  data in a small data section if that data is no
           bigger than num bytes.  The default value of num is 4 for any  ARC  configuration,  or  8
           when we have double load/store operations.

       -mno-sdata
           Do  not  generate  sdata  references.   This  is  the  default  for tool chains built for
           "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -mvolatile-cache
           Use ordinarily cached memory accesses for volatile references.  This is the default.

       -mno-volatile-cache
           Enable cache bypass for volatile references.

       The following options fine tune code generation:

       -malign-call
           Do alignment optimizations for call instructions.

       -mauto-modify-reg
           Enable the use of pre/post modify with register displacement.

       -mbbit-peephole
           Enable bbit peephole2.

       -mno-brcc
           This option disables a target-specific pass in arc_reorg to  generate  compare-and-branch
           ("brcc")  instructions.   It  has no effect on generation of these instructions driven by
           the combiner pass.

       -mcase-vector-pcrel
           Use PC-relative switch case tables to enable case table shortening.  This is the  default
           for -Os.

       -mcompact-casesi
           Enable  compact  "casesi"  pattern.   This is the default for -Os, and only available for
           ARCv1 cores.  This option is deprecated.

       -mno-cond-exec
           Disable the ARCompact-specific pass to generate conditional execution instructions.

           Due to delay slot scheduling and interactions between  operand  numbers,  literal  sizes,
           instruction  lengths,  and  the support for conditional execution, the target-independent
           pass to generate conditional execution is often lacking, so  the  ARC  port  has  kept  a
           special   pass   around   that  tries  to  find  more  conditional  execution  generation
           opportunities after register allocation, branch shortening,  and  delay  slot  scheduling
           have been done.  This pass generally, but not always, improves performance and code size,
           at  the cost of extra compilation time, which is why there is an option to switch it off.
           If you have a problem with call  instructions  exceeding  their  allowable  offset  range
           because they are conditionalized, you should consider using -mmedium-calls instead.

       -mearly-cbranchsi
           Enable pre-reload use of the "cbranchsi" pattern.

       -mexpand-adddi
           Expand "adddi3" and "subdi3" at RTL generation time into "add.f", "adc" etc.  This option
           is deprecated.

       -mindexed-loads
           Enable  the  use  of indexed loads.  This can be problematic because some optimizers then
           assume that indexed stores exist, which is not the case.

       -mlra
           Enable Local Register Allocation.  This is still experimental for ARC, so by default  the
           compiler uses standard reload (i.e. -mno-lra).

       -mlra-priority-none
           Don't indicate any priority for target registers.

       -mlra-priority-compact
           Indicate target register priority for r0..r3 / r12..r15.

       -mlra-priority-noncompact
           Reduce target register priority for r0..r3 / r12..r15.

       -mmillicode
           When  optimizing  for  size  (using  -Os),  prologues  and epilogues that have to save or
           restore a large number of registers are often  shortened  by  using  call  to  a  special
           function  in  libgcc;  this  is referred to as a millicode call.  As these calls can pose
           performance issues, and/or cause linking issues when linking in a nonstandard  way,  this
           option is provided to turn on or off millicode call generation.

       -mcode-density-frame
           This  option  enable  the  compiler  to  emit  "enter"  and  "leave" instructions.  These
           instructions are only valid for CPUs with code-density feature.

       -mmixed-code
           Tweak register allocation to help 16-bit instruction generation.  This generally has  the
           effect of decreasing the average instruction size while increasing the instruction count.

       -mq-class
           Ths  option  is  deprecated.  Enable q instruction alternatives.  This is the default for
           -Os.

       -mRcq
           Enable Rcq constraint handling.  Most short code generation depends on this.  This is the
           default.

       -mRcw
           Enable Rcw constraint handling.  Most ccfsm condexec mostly depends on this.  This is the
           default.

       -msize-level=level
           Fine-tune size optimization with regards  to  instruction  lengths  and  alignment.   The
           recognized values for level are:

           0   No size optimization.  This level is deprecated and treated like 1.

           1   Short instructions are used opportunistically.

           2   In addition, alignment of loops and of code after barriers are dropped.

           3   In addition, optional data alignment is dropped, and the option Os is enabled.

           This  defaults  to 3 when -Os is in effect.  Otherwise, the behavior when this is not set
           is equivalent to level 1.

       -mtune=cpu
           Set instruction scheduling parameters for cpu, overriding any implied by -mcpu=.

           Supported values for cpu are

           ARC600
               Tune for ARC600 CPU.

           ARC601
               Tune for ARC601 CPU.

           ARC700
               Tune for ARC700 CPU with standard multiplier block.

           ARC700-xmac
               Tune for ARC700 CPU with XMAC block.

           ARC725D
               Tune for ARC725D CPU.

           ARC750D
               Tune for ARC750D CPU.

       -mmultcost=num
           Cost to assume for a multiply instruction, with 4 being equal to a normal instruction.

       -munalign-prob-threshold=probability
           Set probability threshold for unaligning branches.  When tuning for ARC700 and optimizing
           for speed, branches without filled delay slot are preferably emitted unaligned and  long,
           unless  profiling  indicates  that  the  probability  for the branch to be taken is below
           probability.  The default is (REG_BR_PROB_BASE/2), i.e. 5000.

       The following options are maintained for backward compatibility, but are now  deprecated  and
       will be removed in a future release:

       -margonaut
           Obsolete FPX.

       -mbig-endian
       -EB Compile code for big-endian targets.  Use of these options is now deprecated.  Big-endian
           code  is  supported  by  configuring  GCC to build "arceb-elf32" and "arceb-linux-uclibc"
           targets, for which big endian is the default.

       -mlittle-endian
       -EL Compile code for little-endian targets.  Use of these options is now deprecated.  Little-
           endian code is supported by configuring GCC to build "arc-elf32"  and  "arc-linux-uclibc"
           targets, for which little endian is the default.

       -mbarrel_shifter
           Replaced by -mbarrel-shifter.

       -mdpfp_compact
           Replaced by -mdpfp-compact.

       -mdpfp_fast
           Replaced by -mdpfp-fast.

       -mdsp_packa
           Replaced by -mdsp-packa.

       -mEA
           Replaced by -mea.

       -mmac_24
           Replaced by -mmac-24.

       -mmac_d16
           Replaced by -mmac-d16.

       -mspfp_compact
           Replaced by -mspfp-compact.

       -mspfp_fast
           Replaced by -mspfp-fast.

       -mtune=cpu
           Values  arc600,  arc601,  arc700  and arc700-xmac for cpu are replaced by ARC600, ARC601,
           ARC700 and ARC700-xmac respectively.

       -multcost=num
           Replaced by -mmultcost.

       ARM Options

       These -m options are defined for the ARM port:

       -mabi=name
           Generate code for the specified ABI.  Permissible values  are:  apcs-gnu,  atpcs,  aapcs,
           aapcs-linux and iwmmxt.

       -mapcs-frame
           Generate  a  stack  frame  that is compliant with the ARM Procedure Call Standard for all
           functions, even if this is not strictly necessary for  correct  execution  of  the  code.
           Specifying  -fomit-frame-pointer  with  this  option  causes  the  stack frames not to be
           generated  for  leaf  functions.   The  default  is  -mno-apcs-frame.   This  option   is
           deprecated.

       -mapcs
           This is a synonym for -mapcs-frame and is deprecated.

       -mthumb-interwork
           Generate  code that supports calling between the ARM and Thumb instruction sets.  Without
           this option, on pre-v5 architectures, the two instruction sets cannot  be  reliably  used
           inside  one  program.  The default is -mno-thumb-interwork, since slightly larger code is
           generated when -mthumb-interwork is specified.  In AAPCS configurations  this  option  is
           meaningless.

       -mno-sched-prolog
           Prevent  the reordering of instructions in the function prologue, or the merging of those
           instruction with the instructions in the function's body.  This means that all  functions
           start  with  a  recognizable set of instructions (or in fact one of a choice from a small
           set of different function prologues), and this information can  be  used  to  locate  the
           start of functions inside an executable piece of code.  The default is -msched-prolog.

       -mfloat-abi=name
           Specifies  which  floating-point  ABI  to  use.  Permissible values are: soft, softfp and
           hard.

           Specifying soft causes GCC to generate output containing library calls for floating-point
           operations.   softfp  allows  the  generation  of  code  using  hardware   floating-point
           instructions,  but still uses the soft-float calling conventions.  hard allows generation
           of floating-point instructions and uses FPU-specific calling conventions.

           The default depends on the specific target configuration.  Note that the  hard-float  and
           soft-float  ABIs  are  not link-compatible; you must compile your entire program with the
           same ABI, and link with a compatible set of libraries.

       -mgeneral-regs-only
           Generate code which uses only the  general-purpose  registers.   This  will  prevent  the
           compiler  from  using  floating-point and Advanced SIMD registers but will not impose any
           restrictions on the assembler.

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  This is the default for all
           standard configurations.

       -mbig-endian
           Generate code for a processor running in big-endian mode; the default is to compile  code
           for a little-endian processor.

       -mbe8
       -mbe32
           When  linking  a big-endian image select between BE8 and BE32 formats.  The option has no
           effect for little-endian images and is ignored.  The default is dependent on the selected
           target architecture.  For ARMv6 and later architectures the default  is  BE8,  for  older
           architectures the default is BE32.  BE32 format has been deprecated by ARM.

       -march=name[+extension...]
           This  specifies the name of the target ARM architecture.  GCC uses this name to determine
           what kind of instructions it can emit when generating assembly code.  This option can  be
           used in conjunction with or instead of the -mcpu= option.

           Permissible  names are: armv4t, armv5t, armv5te, armv6, armv6j, armv6k, armv6kz, armv6t2,
           armv6z, armv6zk, armv7,  armv7-a,  armv7ve,  armv8-a,  armv8.1-a,  armv8.2-a,  armv8.3-a,
           armv8.4-a,  armv8.5-a, armv8.6-a, armv7-r, armv8-r, armv6-m, armv6s-m, armv7-m, armv7e-m,
           armv8-m.base, armv8-m.main, armv8.1-m.main, iwmmxt and iwmmxt2.

           Additionally, the following architectures, which lack support  for  the  Thumb  execution
           state, are recognized but support is deprecated: armv4.

           Many of the architectures support extensions.  These can be added by appending +extension
           to  the  architecture  name.   Extension  options are processed in order and capabilities
           accumulate.  An extension will also enable any necessary base extensions  upon  which  it
           depends.  For example, the +crypto extension will always enable the +simd extension.  The
           exception  to  the additive construction is for extensions that are prefixed with +no...:
           these extensions disable the specified option and any other extensions that may depend on
           the presence of that extension.

           For example, -march=armv7-a+simd+nofp+vfpv4 is equivalent to writing -march=armv7-a+vfpv4
           since the +simd option is entirely disabled by the +nofp option that follows it.

           Most extension names are generically named, but have an effect that is dependent upon the
           architecture to which it is applied.  For example, the +simd option  can  be  applied  to
           both  armv7-a  and  armv8-a  architectures, but will enable the original ARMv7-A Advanced
           SIMD (Neon) extensions for armv7-a and the ARMv8-A variant for armv8-a.

           The table below lists the supported extensions for each architecture.  Architectures  not
           mentioned do not support any extensions.

           armv5te
           armv6
           armv6j
           armv6k
           armv6kz
           armv6t2
           armv6z
           armv6zk
               +fp The  VFPv2  floating-point  instructions.  The extension +vfpv2 can be used as an
                   alias for this extension.

               +nofp
                   Disable the floating-point instructions.

           armv7
               The common subset of the ARMv7-A, ARMv7-R and ARMv7-M architectures.

               +fp The VFPv3 floating-point instructions, with 16 double-precision  registers.   The
                   extension  +vfpv3-d16  can  be  used  as  an alias for this extension.  Note that
                   floating-point is  not  supported  by  the  base  ARMv7-M  architecture,  but  is
                   compatible with both the ARMv7-A and ARMv7-R architectures.

               +nofp
                   Disable the floating-point instructions.

           armv7-a
               +mp The multiprocessing extension.

               +sec
                   The security extension.

               +fp The  VFPv3  floating-point instructions, with 16 double-precision registers.  The
                   extension +vfpv3-d16 can be used as an alias for this extension.

               +simd
                   The Advanced SIMD (Neon) v1  and  the  VFPv3  floating-point  instructions.   The
                   extensions +neon and +neon-vfpv3 can be used as aliases for this extension.

               +vfpv3
                   The VFPv3 floating-point instructions, with 32 double-precision registers.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions, with 16 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv3-fp16
                   The VFPv3 floating-point instructions, with 32 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv4-d16
                   The VFPv4 floating-point instructions, with 16 double-precision registers.

               +vfpv4
                   The VFPv4 floating-point instructions, with 32 double-precision registers.

               +neon-fp16
                   The  Advanced  SIMD (Neon) v1 and the VFPv3 floating-point instructions, with the
                   half-precision floating-point conversion operations.

               +neon-vfpv4
                   The Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions.

               +nosimd
                   Disable the Advanced SIMD instructions (does not disable floating point).

               +nofp
                   Disable the floating-point and Advanced SIMD instructions.

           armv7ve
               The extended version of the ARMv7-A architecture with support for virtualization.

               +fp The VFPv4 floating-point instructions, with 16 double-precision  registers.   The
                   extension +vfpv4-d16 can be used as an alias for this extension.

               +simd
                   The  Advanced  SIMD  (Neon)  v2  and  the VFPv4 floating-point instructions.  The
                   extension +neon-vfpv4 can be used as an alias for this extension.

               +vfpv3-d16
                   The VFPv3 floating-point instructions, with 16 double-precision registers.

               +vfpv3
                   The VFPv3 floating-point instructions, with 32 double-precision registers.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions, with 16 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv3-fp16
                   The VFPv3 floating-point instructions, with 32 double-precision registers and the
                   half-precision floating-point conversion operations.

               +vfpv4-d16
                   The VFPv4 floating-point instructions, with 16 double-precision registers.

               +vfpv4
                   The VFPv4 floating-point instructions, with 32 double-precision registers.

               +neon
                   The Advanced SIMD (Neon) v1  and  the  VFPv3  floating-point  instructions.   The
                   extension +neon-vfpv3 can be used as an alias for this extension.

               +neon-fp16
                   The  Advanced  SIMD (Neon) v1 and the VFPv3 floating-point instructions, with the
                   half-precision floating-point conversion operations.

               +nosimd
                   Disable the Advanced SIMD instructions (does not disable floating point).

               +nofp
                   Disable the floating-point and Advanced SIMD instructions.

           armv8-a
               +crc
                   The Cyclic Redundancy Check (CRC) instructions.

               +simd
                   The ARMv8-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

           armv8.1-a
               +simd
                   The ARMv8.1-A Advanced SIMD and floating-point instructions.

               +crypto
                   The  cryptographic  instructions.   This  also  enables  the  Advanced  SIMD  and
                   floating-point instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

           armv8.2-a
           armv8.3-a
               +fp16
                   The  half-precision  floating-point  data  processing  instructions.   This  also
                   enables the Advanced SIMD and floating-point instructions.

               +fp16fml
                   The half-precision floating-point fmla extension.  This also  enables  the  half-
                   precision   floating-point   extension   and  Advanced  SIMD  and  floating-point
                   instructions.

               +simd
                   The ARMv8.1-A Advanced SIMD and floating-point instructions.

               +crypto
                   The  cryptographic  instructions.   This  also  enables  the  Advanced  SIMD  and
                   floating-point instructions.

               +dotprod
                   Enable the Dot Product extension.  This also enables Advanced SIMD instructions.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

               +i8mm
                   8-bit  Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.   This  also  enables  Advanced
                   SIMD and floating-point instructions.

           armv8.4-a
               +fp16
                   The  half-precision  floating-point  data  processing  instructions.   This  also
                   enables the Advanced SIMD and floating-point instructions  as  well  as  the  Dot
                   Product extension and the half-precision floating-point fmla extension.

               +simd
                   The  ARMv8.3-A  Advanced  SIMD and floating-point instructions as well as the Dot
                   Product extension.

               +crypto
                   The  cryptographic  instructions.   This  also  enables  the  Advanced  SIMD  and
                   floating-point instructions as well as the Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

               +i8mm
                   8-bit  Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.   This  also  enables  Advanced
                   SIMD and floating-point instructions.

           armv8.5-a
               +fp16
                   The  half-precision  floating-point  data  processing  instructions.   This  also
                   enables the Advanced SIMD and floating-point instructions  as  well  as  the  Dot
                   Product extension and the half-precision floating-point fmla extension.

               +simd
                   The  ARMv8.3-A  Advanced  SIMD and floating-point instructions as well as the Dot
                   Product extension.

               +crypto
                   The  cryptographic  instructions.   This  also  enables  the  Advanced  SIMD  and
                   floating-point instructions as well as the Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +i8mm
                   8-bit  Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.   This  also  enables  Advanced
                   SIMD and floating-point instructions.

           armv8.6-a
               +fp16
                   The  half-precision  floating-point  data  processing  instructions.   This  also
                   enables the Advanced SIMD and floating-point instructions  as  well  as  the  Dot
                   Product extension and the half-precision floating-point fmla extension.

               +simd
                   The  ARMv8.3-A  Advanced  SIMD and floating-point instructions as well as the Dot
                   Product extension.

               +crypto
                   The  cryptographic  instructions.   This  also  enables  the  Advanced  SIMD  and
                   floating-point instructions as well as the Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

               +i8mm
                   8-bit  Integer Matrix Multiply instructions.  This also enables Advanced SIMD and
                   floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.   This  also  enables  Advanced
                   SIMD and floating-point instructions.

           armv7-r
               +fp.sp
                   The  single-precision  VFPv3 floating-point instructions.  The extension +vfpv3xd
                   can be used as an alias for this extension.

               +fp The VFPv3 floating-point instructions with 16  double-precision  registers.   The
                   extension +vfpv3-d16 can be used as an alias for this extension.

               +vfpv3xd-d16-fp16
                   The  single-precision  VFPv3 floating-point instructions with 16 double-precision
                   registers and the half-precision floating-point conversion operations.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions with 16 double-precision registers and  the
                   half-precision floating-point conversion operations.

               +nofp
                   Disable the floating-point extension.

               +idiv
                   The ARM-state integer division instructions.

               +noidiv
                   Disable the ARM-state integer division extension.

           armv7e-m
               +fp The single-precision VFPv4 floating-point instructions.

               +fpv5
                   The single-precision FPv5 floating-point instructions.

               +fp.dp
                   The single- and double-precision FPv5 floating-point instructions.

               +nofp
                   Disable the floating-point extensions.

           armv8.1-m.main
               +dsp
                   The DSP instructions.

               +mve
                   The M-Profile Vector Extension (MVE) integer instructions.

               +mve.fp
                   The  M-Profile Vector Extension (MVE) integer and single precision floating-point
                   instructions.

               +fp The single-precision floating-point instructions.

               +fp.dp
                   The single- and double-precision floating-point instructions.

               +nofp
                   Disable the floating-point extension.

               +cdecp0, +cdecp1, ... , +cdecp7
                   Enable the Custom Datapath Extension (CDE) on selected coprocessors according  to
                   the numbers given in the options in the range 0 to 7.

           armv8-m.main
               +dsp
                   The DSP instructions.

               +nodsp
                   Disable the DSP extension.

               +fp The single-precision floating-point instructions.

               +fp.dp
                   The single- and double-precision floating-point instructions.

               +nofp
                   Disable the floating-point extension.

               +cdecp0, +cdecp1, ... , +cdecp7
                   Enable  the Custom Datapath Extension (CDE) on selected coprocessors according to
                   the numbers given in the options in the range 0 to 7.

           armv8-r
               +crc
                   The Cyclic Redundancy Check (CRC) instructions.

               +fp.sp
                   The single-precision FPv5 floating-point instructions.

               +simd
                   The ARMv8-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic instructions.

           -march=native causes the compiler to auto-detect the architecture of the build  computer.
           At  present,  this  feature is only supported on GNU/Linux, and not all architectures are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mtune=name
           This option specifies the name of the target ARM processor for which GCC should tune  the
           performance of the code.  For some ARM implementations better performance can be obtained
           by  using  this  option.   Permissible names are: arm7tdmi, arm7tdmi-s, arm710t, arm720t,
           arm740t, strongarm, strongarm110,  strongarm1100,  0strongarm1110,  arm8,  arm810,  arm9,
           arm9e,  arm920,  arm920t,  arm922t, arm946e-s, arm966e-s, arm968e-s, arm926ej-s, arm940t,
           arm9tdmi, arm10tdmi,  arm1020t,  arm1026ej-s,  arm10e,  arm1020e,  arm1022e,  arm1136j-s,
           arm1136jf-s,  mpcore,  mpcorenovfp, arm1156t2-s, arm1156t2f-s, arm1176jz-s, arm1176jzf-s,
           generic-armv7-a, cortex-a5,  cortex-a7,  cortex-a8,  cortex-a9,  cortex-a12,  cortex-a15,
           cortex-a17,  cortex-a32,  cortex-a35,  cortex-a53,  cortex-a55,  cortex-a57,  cortex-a72,
           cortex-a73, cortex-a75, cortex-a76, cortex-a76ae, cortex-a77,  cortex-a78,  cortex-a78ae,
           cortex-a78c,  ares,  cortex-r4,  cortex-r4f, cortex-r5, cortex-r7, cortex-r8, cortex-r52,
           cortex-m0,  cortex-m0plus,  cortex-m1,  cortex-m3,  cortex-m4,   cortex-m7,   cortex-m23,
           cortex-m33,     cortex-m35p,     cortex-m55,     cortex-x1,     cortex-m1.small-multiply,
           cortex-m0.small-multiply,    cortex-m0plus.small-multiply,    exynos-m1,     marvell-pj4,
           neoverse-n1,  neoverse-n2,  neoverse-v1,  xscale,  iwmmxt, iwmmxt2, ep9312, fa526, fa626,
           fa606te, fa626te, fmp626, fa726te, xgene1.

           Additionally, this option can specify that GCC should tune the performance  of  the  code
           for    a    big.LITTLE    system.     Permissible    names   are:   cortex-a15.cortex-a7,
           cortex-a17.cortex-a7,            cortex-a57.cortex-a53,            cortex-a72.cortex-a53,
           cortex-a72.cortex-a35,            cortex-a73.cortex-a53,           cortex-a75.cortex-a55,
           cortex-a76.cortex-a55.

           -mtune=generic-arch specifies that GCC  should  tune  the  performance  for  a  blend  of
           processors  within  architecture  arch.  The aim is to generate code that run well on the
           current most popular processors, balancing between optimizations that benefit  some  CPUs
           in  the  range,  and  avoiding  performance  pitfalls of other CPUs.  The effects of this
           option may change in future GCC versions as CPU models come and go.

           -mtune permits the same extension options as -mcpu, but  the  extension  options  do  not
           affect the tuning of the generated code.

           -mtune=native  causes  the  compiler  to  auto-detect  the CPU of the build computer.  At
           present, this feature is only supported on  GNU/Linux,  and  not  all  architectures  are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mcpu=name[+extension...]
           This  specifies  the  name of the target ARM processor.  GCC uses this name to derive the
           name of the target ARM architecture (as if specified by -march)  and  the  ARM  processor
           type for which to tune for performance (as if specified by -mtune).  Where this option is
           used  in  conjunction  with  -march  or  -mtune,  those  options take precedence over the
           appropriate part of this option.

           Many of the supported CPUs implement optional architectural extensions.  Where this is so
           the architectural extensions are normally enabled by default.   If  implementations  that
           lack  the  extension  exist,  then  the  extension  syntax  can  be used to disable those
           extensions  that  have  been  omitted.   For  floating-point  and  Advanced  SIMD  (Neon)
           instructions,  the settings of the options -mfloat-abi and -mfpu must also be considered:
           floating-point and Advanced SIMD instructions will only be used if -mfloat-abi is not set
           to soft; and any setting of -mfpu other than auto will override the  available  floating-
           point and SIMD extension instructions.

           For  example,  cortex-a9  can  be found in three major configurations: integer only, with
           just a floating-point unit or with floating-point and Advanced SIMD.  The default  is  to
           enable  all the instructions, but the extensions +nosimd and +nofp can be used to disable
           just the SIMD or both the SIMD and floating-point instructions respectively.

           Permissible names for this option are the same as those for -mtune.

           The following extension options are common to the listed CPUs:

           +nodsp
               Disable the DSP instructions on cortex-m33, cortex-m35p.

           +nofp
               Disables the floating-point instructions on arm9e, arm946e-s,  arm966e-s,  arm968e-s,
               arm10e, arm1020e, arm1022e, arm926ej-s, arm1026ej-s, cortex-r5, cortex-r7, cortex-r8,
               cortex-m4,  cortex-m7,  cortex-m33  and cortex-m35p.  Disables the floating-point and
               SIMD instructions on generic-armv7-a,  cortex-a5,  cortex-a7,  cortex-a8,  cortex-a9,
               cortex-a12,   cortex-a15,   cortex-a17,  cortex-a15.cortex-a7,  cortex-a17.cortex-a7,
               cortex-a32, cortex-a35, cortex-a53 and cortex-a55.

           +nofp.dp
               Disables  the  double-precision  component  of  the  floating-point  instructions  on
               cortex-r5, cortex-r7, cortex-r8, cortex-r52 and cortex-m7.

           +nosimd
               Disables   the   SIMD  (but  not  floating-point)  instructions  on  generic-armv7-a,
               cortex-a5, cortex-a7 and cortex-a9.

           +crypto
               Enables  the  cryptographic  instructions  on  cortex-a32,  cortex-a35,   cortex-a53,
               cortex-a55,   cortex-a57,  cortex-a72,  cortex-a73,  cortex-a75,  exynos-m1,  xgene1,
               cortex-a57.cortex-a53,         cortex-a72.cortex-a53,          cortex-a73.cortex-a35,
               cortex-a73.cortex-a53 and cortex-a75.cortex-a55.

           Additionally the generic-armv7-a pseudo target defaults to VFPv3 with 16 double-precision
           registers.   It  supports  the  following  extension  options: mp, sec, vfpv3-d16, vfpv3,
           vfpv3-d16-fp16, vfpv3-fp16, vfpv4-d16, vfpv4, neon,  neon-vfpv3,  neon-fp16,  neon-vfpv4.
           The meanings are the same as for the extensions to -march=armv7-a.

           -mcpu=generic-arch    is   also   permissible,   and   is   equivalent   to   -march=arch
           -mtune=generic-arch.  See -mtune for more information.

           -mcpu=native causes the compiler to auto-detect  the  CPU  of  the  build  computer.   At
           present,  this  feature  is  only  supported  on GNU/Linux, and not all architectures are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mfpu=name
           This specifies what floating-point hardware (or hardware emulation) is available  on  the
           target.    Permissible   names   are:   auto,   vfpv2,   vfpv3,   vfpv3-fp16,  vfpv3-d16,
           vfpv3-d16-fp16,  vfpv3xd,  vfpv3xd-fp16,   neon-vfpv3,   neon-fp16,   vfpv4,   vfpv4-d16,
           fpv4-sp-d16,    neon-vfpv4,    fpv5-d16,   fpv5-sp-d16,   fp-armv8,   neon-fp-armv8   and
           crypto-neon-fp-armv8.  Note that neon is an alias for neon-vfpv3 and vfp is an alias  for
           vfpv2.

           The  setting  auto  is  the default and is special.  It causes the compiler to select the
           floating-point and Advanced SIMD instructions based on the settings of -mcpu and -march.

           If the selected floating-point hardware includes the NEON  extension  (e.g.  -mfpu=neon),
           note  that  floating-point  operations are not generated by GCC's auto-vectorization pass
           unless -funsafe-math-optimizations is also specified.  This is because NEON hardware does
           not fully implement the IEEE 754 standard for floating-point  arithmetic  (in  particular
           denormal  values are treated as zero), so the use of NEON instructions may lead to a loss
           of precision.

           You can also set the fpu name at function level  by  using  the  target("fpu=")  function
           attributes or pragmas.

       -mfp16-format=name
           Specify the format of the "__fp16" half-precision floating-point type.  Permissible names
           are  none, ieee, and alternative; the default is none, in which case the "__fp16" type is
           not defined.

       -mstructure-size-boundary=n
           The sizes of all structures and unions are rounded up to a multiple of the number of bits
           set by this option.  Permissible values are 8, 32 and 64.  The default value  varies  for
           different  toolchains.   For the COFF targeted toolchain the default value is 8.  A value
           of 64 is only allowed if the underlying ABI supports it.

           Specifying a larger number can produce faster, more efficient code, but can also increase
           the size of the program.  Different values are potentially incompatible.   Code  compiled
           with  one  value  cannot  necessarily expect to work with code or libraries compiled with
           another value, if they exchange information using structures or unions.

           This option is deprecated.

       -mabort-on-noreturn
           Generate a call to the function "abort" at the end  of  a  "noreturn"  function.   It  is
           executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of the function
           into  a  register and then performing a subroutine call on this register.  This switch is
           needed if the target function lies outside of the 64-megabyte  addressing  range  of  the
           offset-based version of subroutine call instruction.

           Even  if  this switch is enabled, not all function calls are turned into long calls.  The
           heuristic is that static functions,  functions  that  have  the  "short_call"  attribute,
           functions that are inside the scope of a "#pragma no_long_calls" directive, and functions
           whose  definitions have already been compiled within the current compilation unit are not
           turned into long calls.  The exceptions to this rule are that weak function  definitions,
           functions  with  the "long_call" attribute or the "section" attribute, and functions that
           are within the scope of a "#pragma long_calls" directive  are  always  turned  into  long
           calls.

           This  feature is not enabled by default.  Specifying -mno-long-calls restores the default
           behavior,  as  does  placing  the  function  calls  within  the  scope  of   a   "#pragma
           long_calls_off"  directive.   Note  these  switches  have  no  effect on how the compiler
           generates code to handle function calls via function pointers.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than loading  it  in  the
           prologue  for  each  function.   The  runtime system is responsible for initializing this
           register with an appropriate value before execution begins.

       -mpic-register=reg
           Specify the register to be used for PIC addressing.  For  standard  PIC  base  case,  the
           default  is  any suitable register determined by compiler.  For single PIC base case, the
           default is R9 if target is EABI based or stack-checking is enabled, otherwise the default
           is R10.

       -mpic-data-is-text-relative
           Assume that the displacement between the text and data segments is fixed at  static  link
           time.  This permits using PC-relative addressing operations to access data known to be in
           the  data segment.  For non-VxWorks RTP targets, this option is enabled by default.  When
           disabled on such targets, it will enable -msingle-pic-base by default.

       -mpoke-function-name
           Write the name of each function into the text section, directly  preceding  the  function
           prologue.  The generated code is similar to this:

                        t0
                            .ascii "arm_poke_function_name", 0
                            .align
                        t1
                            .word 0xff000000 + (t1 - t0)
                        arm_poke_function_name
                            mov     ip, sp
                            stmfd   sp!, {fp, ip, lr, pc}
                            sub     fp, ip, #4

           When performing a stack backtrace, code can inspect the value of "pc" stored at "fp + 0".
           If  the  trace function then looks at location "pc - 12" and the top 8 bits are set, then
           we know that there is a function name embedded immediately preceding  this  location  and
           has length "((pc[-3]) & 0xff000000)".

       -mthumb
       -marm
           Select  between  generating  code that executes in ARM and Thumb states.  The default for
           most configurations is to generate code that executes in ARM state, but the  default  can
           be changed by configuring GCC with the --with-mode=state configure option.

           You  can  also  override  the  ARM  and  Thumb  mode  for  each  function  by  using  the
           target("thumb") and target("arm") function attributes or pragmas.

       -mflip-thumb
           Switch ARM/Thumb modes on alternating functions.  This option is provided for  regression
           testing  of  mixed  Thumb/ARM  code  generation,  and is not intended for ordinary use in
           compiling code.

       -mtpcs-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard  for  all
           non-leaf  functions.   (A  leaf  function is one that does not call any other functions.)
           The default is -mno-tpcs-frame.

       -mtpcs-leaf-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard  for  all
           leaf  functions.   (A  leaf function is one that does not call any other functions.)  The
           default is -mno-apcs-leaf-frame.

       -mcallee-super-interworking
           Gives all externally visible functions in the file being compiled an ARM instruction  set
           header  which  switches  to  Thumb  mode before executing the rest of the function.  This
           allows these functions to be called from non-interworking code.  This option is not valid
           in AAPCS configurations because interworking is enabled by default.

       -mcaller-super-interworking
           Allows calls via function pointers (including virtual  functions)  to  execute  correctly
           regardless  of  whether the target code has been compiled for interworking or not.  There
           is a small overhead in the cost of  executing  a  function  pointer  if  this  option  is
           enabled.   This  option  is  not  valid  in  AAPCS configurations because interworking is
           enabled by default.

       -mtp=name
           Specify the access model for the thread local storage  pointer.   The  valid  models  are
           soft,  which generates calls to "__aeabi_read_tp", cp15, which fetches the thread pointer
           from "cp15" directly (supported in the arm6k architecture), and auto, which uses the best
           available method for the selected processor.  The default setting is auto.

       -mtls-dialect=dialect
           Specify the dialect to  use  for  accessing  thread  local  storage.   Two  dialects  are
           supported---gnu and gnu2.  The gnu dialect selects the original GNU scheme for supporting
           local and global dynamic TLS models.  The gnu2 dialect selects the GNU descriptor scheme,
           which  provides  better  performance  for shared libraries.  The GNU descriptor scheme is
           compatible with the original scheme, but does require new assembler, linker  and  library
           support.   Initial and local exec TLS models are unaffected by this option and always use
           the original scheme.

       -mword-relocations
           Only generate absolute relocations on word-sized  values  (i.e.  R_ARM_ABS32).   This  is
           enabled  by default on targets (uClinux, SymbianOS) where the runtime loader imposes this
           restriction,  and  when  -fpic  or  -fPIC  is  specified.  This  option  conflicts   with
           -mslow-flash-data.

       -mfix-cortex-m3-ldrd
           Some  Cortex-M3 cores can cause data corruption when "ldrd" instructions with overlapping
           destination  and  base  registers  are  used.   This  option  avoids   generating   these
           instructions.  This option is enabled by default when -mcpu=cortex-m3 is specified.

       -munaligned-access
       -mno-unaligned-access
           Enables  (or  disables) reading and writing of 16- and 32- bit values from addresses that
           are not 16- or 32- bit  aligned.   By  default  unaligned  access  is  disabled  for  all
           pre-ARMv6,  all ARMv6-M and for ARMv8-M Baseline architectures, and enabled for all other
           architectures.  If unaligned access is not enabled then words in packed  data  structures
           are accessed a byte at a time.

           The  ARM  attribute  "Tag_CPU_unaligned_access"  is  set  in the generated object file to
           either true or false, depending upon the setting of this option.  If unaligned access  is
           enabled then the preprocessor symbol "__ARM_FEATURE_UNALIGNED" is also defined.

       -mneon-for-64bits
           This option is deprecated and has no effect.

       -mslow-flash-data
           Assume  loading  data  from flash is slower than fetching instruction.  Therefore literal
           load is minimized for better performance.  This option is only supported  when  compiling
           for ARMv7 M-profile and off by default. It conflicts with -mword-relocations.

       -masm-syntax-unified
           Assume  inline assembler is using unified asm syntax.  The default is currently off which
           implies divided syntax.  This option has no impact on Thumb2. However, this may change in
           future releases of GCC.  Divided syntax should be considered deprecated.

       -mrestrict-it
           Restricts generation of IT blocks to conform to the rules of ARMv8-A.  IT blocks can only
           contain a single 16-bit instruction from a select set of instructions. This option is  on
           by default for ARMv8-A Thumb mode.

       -mprint-tune-info
           Print  CPU  tuning information as comment in assembler file.  This is an option used only
           for regression testing of the compiler and not intended for  ordinary  use  in  compiling
           code.  This option is disabled by default.

       -mverbose-cost-dump
           Enable  verbose  cost model dumping in the debug dump files.  This option is provided for
           use in debugging the compiler.

       -mpure-code
           Do not allow constant data to be placed in code sections.  Additionally,  when  compiling
           for ELF object format give all text sections the ELF processor-specific section attribute
           "SHF_ARM_PURECODE".   This  option  is  only  available  when generating non-pic code for
           M-profile targets.

       -mcmse
           Generate secure code as per the "ARMv8-M Security Extensions: Requirements on Development
           Tools     Engineering      Specification",      which      can      be      found      on
           <https://developer.arm.com/documentation/ecm0359818/latest/>.

       -mfix-cmse-cve-2021-35465
           Mitigate  against  a  potential  security  issue  with  the  "VLLDM"  instruction in some
           M-profile devices when using CMSE (CVE-2021-365465).  This option is enabled  by  default
           when  the  option  -mcpu=  is used with "cortex-m33", "cortex-m35p" or "cortex-m55".  The
           option -mno-fix-cmse-cve-2021-35465 can be used to disable the mitigation.

       -mfdpic
       -mno-fdpic
           Select the FDPIC ABI, which uses 64-bit function descriptors  to  represent  pointers  to
           functions.   When  the  compiler is configured for "arm-*-uclinuxfdpiceabi" targets, this
           option is on by default and implies -fPIE if  none  of  the  PIC/PIE-related  options  is
           provided.  On other targets, it only enables the FDPIC-specific code generation features,
           and the user should explicitly provide the PIC/PIE-related options as needed.

           Note  that  static  linking  is  not supported because it would still involve the dynamic
           linker when the program self-relocates.  If such behavior is acceptable, use -static  and
           -Wl,-dynamic-linker options.

           The  opposite  -mno-fdpic option is useful (and required) to build the Linux kernel using
           the same ("arm-*-uclinuxfdpiceabi") toolchain as the  one  used  to  build  the  userland
           programs.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
           Specify Atmel AVR instruction set architectures (ISA) or MCU type.

           The default for this option is avr2.

           GCC supports the following AVR devices and ISAs:

           "avr2"
               "Classic"  devices with up to 8 KiB of program memory.  mcu = "attiny22", "attiny26",
               "at90s2313",  "at90s2323",  "at90s2333",   "at90s2343",   "at90s4414",   "at90s4433",
               "at90s4434", "at90c8534", "at90s8515", "at90s8535".

           "avr25"
               "Classic" devices with up to 8 KiB of program memory and with the "MOVW" instruction.
               mcu  =  "attiny13",  "attiny13a",  "attiny24",  "attiny24a", "attiny25", "attiny261",
               "attiny261a",  "attiny2313",  "attiny2313a",  "attiny43u",  "attiny44",  "attiny44a",
               "attiny45",   "attiny48",   "attiny441",   "attiny461",  "attiny461a",  "attiny4313",
               "attiny84",   "attiny84a",   "attiny85",   "attiny87",    "attiny88",    "attiny828",
               "attiny841", "attiny861", "attiny861a", "ata5272", "ata6616c", "at86rf401".

           "avr3"
               "Classic"  devices  with  16  KiB  up to 64 KiB of program memory.  mcu = "at76c711",
               "at43usb355".

           "avr31"
               "Classic" devices with 128 KiB of program memory.  mcu = "atmega103", "at43usb320".

           "avr35"
               "Classic" devices with 16 KiB up to 64 KiB of program  memory  and  with  the  "MOVW"
               instruction.    mcu   =   "attiny167",   "attiny1634",   "atmega8u2",   "atmega16u2",
               "atmega32u2", "ata5505", "ata6617c", "ata664251", "at90usb82", "at90usb162".

           "avr4"
               "Enhanced"  devices  with  up  to  8  KiB  of  program  memory.   mcu  =  "atmega48",
               "atmega48a",   "atmega48p",   "atmega48pa",   "atmega48pb",   "atmega8",  "atmega8a",
               "atmega8hva",  "atmega88",  "atmega88a",  "atmega88p",  "atmega88pa",   "atmega88pb",
               "atmega8515",  "atmega8535", "ata6285", "ata6286", "ata6289", "ata6612c", "at90pwm1",
               "at90pwm2", "at90pwm2b", "at90pwm3", "at90pwm3b", "at90pwm81".

           "avr5"
               "Enhanced" devices with 16 KiB up to 64 KiB of program  memory.   mcu  =  "atmega16",
               "atmega16a",   "atmega16hva",   "atmega16hva2",   "atmega16hvb",   "atmega16hvbrevb",
               "atmega16m1",  "atmega16u4",  "atmega161",  "atmega162",  "atmega163",  "atmega164a",
               "atmega164p",  "atmega164pa", "atmega165", "atmega165a", "atmega165p", "atmega165pa",
               "atmega168", "atmega168a", "atmega168p", "atmega168pa",  "atmega168pb",  "atmega169",
               "atmega169a",  "atmega169p",  "atmega169pa",  "atmega32",  "atmega32a", "atmega32c1",
               "atmega32hvb",   "atmega32hvbrevb",   "atmega32m1",    "atmega32u4",    "atmega32u6",
               "atmega323",  "atmega324a",  "atmega324p",  "atmega324pa", "atmega325", "atmega325a",
               "atmega325p", "atmega325pa", "atmega328", "atmega328p",  "atmega328pb",  "atmega329",
               "atmega329a",     "atmega329p",     "atmega329pa",    "atmega3250",    "atmega3250a",
               "atmega3250p",   "atmega3250pa",    "atmega3290",    "atmega3290a",    "atmega3290p",
               "atmega3290pa",  "atmega406",  "atmega64",  "atmega64a", "atmega64c1", "atmega64hve",
               "atmega64hve2", "atmega64m1", "atmega64rfr2", "atmega640", "atmega644", "atmega644a",
               "atmega644p",    "atmega644pa",    "atmega644rfr2",    "atmega645",     "atmega645a",
               "atmega645p",  "atmega649",  "atmega649a", "atmega649p", "atmega6450", "atmega6450a",
               "atmega6450p",  "atmega6490",  "atmega6490a",  "atmega6490p",  "ata5795",  "ata5790",
               "ata5790n",  "ata5791",  "ata6613c",  "ata6614q",  "ata5782",  "ata5831",  "ata8210",
               "ata8510",  "ata5702m322",  "at90pwm161",  "at90pwm216",  "at90pwm316",  "at90can32",
               "at90can64", "at90scr100", "at90usb646", "at90usb647", "at94k", "m3000".

           "avr51"
               "Enhanced"  devices with 128 KiB of program memory.  mcu = "atmega128", "atmega128a",
               "atmega128rfa1",   "atmega128rfr2",   "atmega1280",    "atmega1281",    "atmega1284",
               "atmega1284p", "atmega1284rfr2", "at90can128", "at90usb1286", "at90usb1287".

           "avr6"
               "Enhanced"  devices  with  3-byte  PC, i.e. with more than 128 KiB of program memory.
               mcu = "atmega256rfr2", "atmega2560", "atmega2561", "atmega2564rfr2".

           "avrxmega2"
               "XMEGA" devices with more than 8 KiB and up to 64  KiB  of  program  memory.   mcu  =
               "atxmega8e5",    "atxmega16a4",    "atxmega16a4u",    "atxmega16c4",   "atxmega16d4",
               "atxmega16e5",   "atxmega32a4",   "atxmega32a4u",    "atxmega32c3",    "atxmega32c4",
               "atxmega32d3", "atxmega32d4", "atxmega32e5".

           "avrxmega3"
               "XMEGA"  devices  with  up  to  64  KiB  of combined program memory and RAM, and with
               program memory visible in the RAM address space.   mcu  =  "attiny202",  "attiny204",
               "attiny212",   "attiny214",   "attiny402",   "attiny404",  "attiny406",  "attiny412",
               "attiny414",  "attiny416",  "attiny417",   "attiny804",   "attiny806",   "attiny807",
               "attiny814",  "attiny816",  "attiny817",  "attiny1604",  "attiny1606",  "attiny1607",
               "attiny1614", "attiny1616", "attiny1617", "attiny3214",  "attiny3216",  "attiny3217",
               "atmega808",  "atmega809",  "atmega1608",  "atmega1609",  "atmega3208", "atmega3209",
               "atmega4808", "atmega4809".

           "avrxmega4"
               "XMEGA" devices with more than 64 KiB and up to 128 KiB of  program  memory.   mcu  =
               "atxmega64a3",    "atxmega64a3u",   "atxmega64a4u",   "atxmega64b1",   "atxmega64b3",
               "atxmega64c3", "atxmega64d3", "atxmega64d4".

           "avrxmega5"
               "XMEGA" devices with more than 64 KiB and up to 128 KiB of program  memory  and  more
               than 64 KiB of RAM.  mcu = "atxmega64a1", "atxmega64a1u".

           "avrxmega6"
               "XMEGA"  devices  with  more  than  128 KiB of program memory.  mcu = "atxmega128a3",
               "atxmega128a3u",  "atxmega128b1",  "atxmega128b3",  "atxmega128c3",   "atxmega128d3",
               "atxmega128d4",   "atxmega192a3",  "atxmega192a3u",  "atxmega192c3",  "atxmega192d3",
               "atxmega256a3", "atxmega256a3b", "atxmega256a3bu",  "atxmega256a3u",  "atxmega256c3",
               "atxmega256d3", "atxmega384c3", "atxmega384d3".

           "avrxmega7"
               "XMEGA" devices with more than 128 KiB of program memory and more than 64 KiB of RAM.
               mcu = "atxmega128a1", "atxmega128a1u", "atxmega128a4u".

           "avrtiny"
               "TINY"  Tiny core devices with 512 B up to 4 KiB of program memory.  mcu = "attiny4",
               "attiny5", "attiny9", "attiny10", "attiny20", "attiny40".

           "avr1"
               This ISA is implemented by the minimal AVR core and  supported  for  assembler  only.
               mcu = "attiny11", "attiny12", "attiny15", "attiny28", "at90s1200".

       -mabsdata
           Assume  that  all data in static storage can be accessed by LDS / STS instructions.  This
           option has only an effect on reduced Tiny devices like ATtiny40.  See also the  "absdata"
           AVR Variable Attributes,variable attribute.

       -maccumulate-args
           Accumulate  outgoing  function  arguments  and acquire/release the needed stack space for
           outgoing function arguments once in function  prologue/epilogue.   Without  this  option,
           outgoing arguments are pushed before calling a function and popped afterwards.

           Popping  the  arguments  after  the  function  call  can  be  expensive  on  AVR  so that
           accumulating the stack space might lead to smaller executables because arguments need not
           be removed from the stack after such a function call.

           This option can lead to reduced code size for functions that  perform  several  calls  to
           functions that get their arguments on the stack like calls to printf-like functions.

       -mbranch-cost=cost
           Set  the branch costs for conditional branch instructions to cost.  Reasonable values for
           cost are small, non-negative integers. The default branch cost is 0.

       -mcall-prologues
           Functions prologues/epilogues are expanded as calls  to  appropriate  subroutines.   Code
           size is smaller.

       -mdouble=bits
       -mlong-double=bits
           Set  the  size  (in  bits) of the "double" or "long double" type, respectively.  Possible
           values for bits are 32 and 64.  Whether or not a  specific  value  for  bits  is  allowed
           depends    on    the   "--with-double="   and   "--with-long-double="   configure options
           ("https://gcc.gnu.org/install/configure.html#avr"), and the same applies for the  default
           values of the options.

       -mgas-isr-prologues
           Interrupt service routines (ISRs) may use the "__gcc_isr" pseudo instruction supported by
           GNU  Binutils.   If  this  option is on, the feature can still be disabled for individual
           ISRs by means of the  AVR  Function  Attributes,,"no_gccisr"  function  attribute.   This
           feature is activated per default if optimization is on (but not with -Og, @pxref{Optimize
           Options}), and if GNU Binutils support PR21683 ("https://sourceware.org/PR21683").

       -mint8
           Assume  "int"  to  be  8-bit integer.  This affects the sizes of all types: a "char" is 1
           byte, an "int" is 1 byte, a "long" is 2 bytes, and "long long" is 4 bytes.   Please  note
           that  this  option  does  not  conform to the C standards, but it results in smaller code
           size.

       -mmain-is-OS_task
           Do not save registers in "main".  The effect is the same  like  attaching  attribute  AVR
           Function  Attributes,,"OS_task" to "main". It is activated per default if optimization is
           on.

       -mn-flash=num
           Assume that the flash memory has a size of num times 64 KiB.

       -mno-interrupts
           Generated code is not compatible with hardware interrupts.  Code size is smaller.

       -mrelax
           Try to replace "CALL" resp.  "JMP"  instruction  by  the  shorter  "RCALL"  resp.  "RJMP"
           instruction  if  applicable.   Setting  -mrelax just adds the --mlink-relax option to the
           assembler's command line and the --relax option to the linker's command line.

           Jump relaxing is performed by the linker because jump offsets are not known  before  code
           is  located. Therefore, the assembler code generated by the compiler is the same, but the
           instructions in the executable may differ from instructions in the assembler code.

           Relaxing must be turned on if linker stubs are needed, see  the  section  on  "EIND"  and
           linker stubs below.

       -mrmw
           Assume  that  the  device supports the Read-Modify-Write instructions "XCH", "LAC", "LAS"
           and "LAT".

       -mshort-calls
           Assume that "RJMP" and "RCALL" can target the whole program memory.

           This option is used internally for multilib selection.  It is not an optimization option,
           and you don't need to set it by hand.

       -msp8
           Treat the stack pointer register as an 8-bit register, i.e. assume the high byte  of  the
           stack pointer is zero.  In general, you don't need to set this option by hand.

           This  option  is  used  internally  by  the  compiler  to  select and build multilibs for
           architectures "avr2" and "avr25".  These  architectures  mix  devices  with  and  without
           "SPH".   For any setting other than -mmcu=avr2 or -mmcu=avr25 the compiler driver adds or
           removes this option from the compiler proper's command line, because  the  compiler  then
           knows if the device or architecture has an 8-bit stack pointer and thus no "SPH" register
           or not.

       -mstrict-X
           Use  address register "X" in a way proposed by the hardware.  This means that "X" is only
           used in indirect, post-increment or pre-decrement addressing.

           Without this option, the "X" register may be used in the same way as  "Y"  or  "Z"  which
           then is emulated by additional instructions.  For example, loading a value with "X+const"
           addressing with a small non-negative "const < 64" to a register Rn is performed as

                   adiw r26, const   ; X += const
                   ld   <Rn>, X        ; <Rn> = *X
                   sbiw r26, const   ; X -= const

       -mtiny-stack
           Only change the lower 8 bits of the stack pointer.

       -mfract-convert-truncate
           Allow  to  use  truncation  instead  of  rounding towards zero for fractional fixed-point
           types.

       -nodevicelib
           Don't link against AVR-LibC's device specific library "lib<mcu>.a".

       -nodevicespecs
           Don't add -specs=device-specs/specs-mcu to the compiler driver's command line.  The  user
           takes  responsibility for supplying the sub-processes like compiler proper, assembler and
           linker with appropriate command line options.  This means that the user has to supply her
           private device specs file by means of -specs=path-to-specs-file.  There is no  more  need
           for option -mmcu=mcu.

           This  option  can  also  serve  as  a  replacement for the older way of specifying custom
           device-specs files that needed -B some-path to point to  a  directory  which  contains  a
           folder  named "device-specs" which contains a specs file named "specs-mcu", where mcu was
           specified by -mmcu=mcu.

       -Waddr-space-convert
           Warn about conversions between address spaces in the case  where  the  resulting  address
           space is not contained in the incoming address space.

       -Wmisspelled-isr
           Warn if the ISR is misspelled, i.e. without __vector prefix.  Enabled by default.

       "EIND" and Devices with More Than 128 Ki Bytes of Flash

       Pointers  in  the  implementation  are  16  bits wide.  The address of a function or label is
       represented as word address so that indirect jumps and calls can target any code  address  in
       the range of 64 Ki words.

       In order to facilitate indirect jump on devices with more than 128 Ki bytes of program memory
       space,  there  is  a  special function register called "EIND" that serves as most significant
       part of the target address when "EICALL" or "EIJMP" instructions are used.

       Indirect jumps and calls on these devices are handled as follows  by  the  compiler  and  are
       subject to some limitations:

       *   The compiler never sets "EIND".

       *   The compiler uses "EIND" implicitly in "EICALL"/"EIJMP" instructions or might read "EIND"
           directly in order to emulate an indirect call/jump by means of a "RET" instruction.

       *   The  compiler  assumes  that  "EIND"  never changes during the startup code or during the
           application. In particular, "EIND" is not saved/restored in function or interrupt service
           routine prologue/epilogue.

       *   For indirect calls to functions and computed goto, the linker generates stubs. Stubs  are
           jump pads sometimes also called trampolines. Thus, the indirect call/jump jumps to such a
           stub.  The stub contains a direct jump to the desired address.

       *   Linker  relaxation  must be turned on so that the linker generates the stubs correctly in
           all situations. See the compiler option -mrelax and the linker option --relax.  There are
           corner cases where the linker is supposed to generate stubs but aborts without relaxation
           and without a helpful error message.

       *   The default linker script is arranged for code with "EIND = 0".  If code is  supposed  to
           work  for  a  setup  with  "EIND != 0", a custom linker script has to be used in order to
           place the sections whose name start with ".trampolines" into  the  segment  where  "EIND"
           points to.

       *   The  startup  code from libgcc never sets "EIND".  Notice that startup code is a blend of
           code from libgcc and AVR-LibC.  For the impact  of  AVR-LibC  on  "EIND",  see  the  AVR-
           LibC user manual ("http://nongnu.org/avr-libc/user-manual/").

       *   It  is  legitimate  for user-specific startup code to set up "EIND" early, for example by
           means of initialization code located in section ".init3". Such code runs prior to general
           startup code that initializes RAM and calls constructors, but after the  bit  of  startup
           code from AVR-LibC that sets "EIND" to the segment where the vector table is located.

                   #include <avr/io.h>

                   static void
                   __attribute__((section(".init3"),naked,used,no_instrument_function))
                   init3_set_eind (void)
                   {
                     __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                     "out %i0,r24" :: "n" (&EIND) : "r24","memory");
                   }

           The "__trampolines_start" symbol is defined in the linker script.

       *   Stubs are generated automatically by the linker if the following two conditions are met:

           -<The address of a label is taken by means of the "gs" modifier>
               (short for generate stubs) like so:

                       LDI r24, lo8(gs(<func>))
                       LDI r25, hi8(gs(<func>))

           -<The final location of that label is in a code segment>
               outside the segment where the stubs are located.

       *   The compiler emits such "gs" modifiers for code labels in the following situations:

           -<Taking address of a function or code label.>
           -<Computed goto.>
           -<If prologue-save function is used, see -mcall-prologues>
               command-line option.

           -<Switch/case dispatch tables. If you do not want such dispatch>
               tables you can specify the -fno-jump-tables command-line option.

           -<C and C++ constructors/destructors called during startup/shutdown.>
           -<If the tools hit a gs() modifier explained above.>
       *   Jumping to non-symbolic addresses like so is not supported:

                   int main (void)
                   {
                       /* Call function at word address 0x2 */
                       return ((int(*)(void)) 0x2)();
                   }

           Instead,  a  stub  has  to be set up, i.e. the function has to be called through a symbol
           ("func_4" in the example):

                   int main (void)
                   {
                       extern int func_4 (void);

                       /* Call function at byte address 0x4 */
                       return func_4();
                   }

           and the application be linked with -Wl,--defsym,func_4=0x4.  Alternatively, "func_4"  can
           be defined in the linker script.

       Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function Registers

       Some  AVR  devices  support  memories  larger than the 64 KiB range that can be accessed with
       16-bit pointers.  To access memory locations outside this 64 KiB  range,  the  content  of  a
       "RAMP"  register  is  used as high part of the address: The "X", "Y", "Z" address register is
       concatenated with the "RAMPX", "RAMPY", "RAMPZ" special function register,  respectively,  to
       get a wide address. Similarly, "RAMPD" is used together with direct addressing.

       *   The startup code initializes the "RAMP" special function registers with zero.

       *   If  a  AVR  Named  Address  Spaces,named address space other than generic or "__flash" is
           used, then "RAMPZ" is set as needed before the operation.

       *   If the device supports RAM larger than 64 KiB and the compiler needs to change "RAMPZ" to
           accomplish an operation, "RAMPZ" is reset to zero after the operation.

       *   If  the  device  comes  with  a  specific  "RAMP"  register,  the  ISR  prologue/epilogue
           saves/restores  that  SFR  and  initializes  it  with  zero  in  case  the ISR code might
           (implicitly) use it.

       *   RAM larger than 64 KiB is not supported by GCC  for  AVR  targets.   If  you  use  inline
           assembler  to  read from locations outside the 16-bit address range and change one of the
           "RAMP" registers, you must reset it to zero after the access.

       AVR Built-in Macros

       GCC defines several built-in macros so that the user  code  can  test  for  the  presence  or
       absence  of  features.   Almost  any of the following built-in macros are deduced from device
       capabilities and thus triggered by the -mmcu= command-line option.

       For even more AVR-specific built-in macros see AVR Named  Address  Spaces  and  AVR  Built-in
       Functions.

       "__AVR_ARCH__"
           Build-in  macro  that  resolves  to a decimal number that identifies the architecture and
           depends on the -mmcu=mcu option.  Possible values are:

           2, 25, 3, 31, 35, 4, 5, 51, 6

           for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5", "avr51", "avr6",

           respectively and

           100, 102, 103, 104, 105, 106, 107

           for  mcu="avrtiny",  "avrxmega2",  "avrxmega3",  "avrxmega4",  "avrxmega5",  "avrxmega6",
           "avrxmega7",  respectively.   If  mcu  specifies  a  device,  this  built-in macro is set
           accordingly. For example, with -mmcu=atmega8 the macro is defined to 4.

       "__AVR_Device__"
           Setting -mmcu=device defines this built-in macro which reflects the  device's  name.  For
           example,  -mmcu=atmega8  defines  the  built-in macro "__AVR_ATmega8__", -mmcu=attiny261a
           defines "__AVR_ATtiny261A__", etc.

           The built-in macros' names follow the scheme "__AVR_Device__" where Device is the  device
           name as from the AVR user manual. The difference between Device in the built-in macro and
           device in -mmcu=device is that the latter is always lowercase.

           If  device  is  not  a  device but only a core architecture like avr51, this macro is not
           defined.

       "__AVR_DEVICE_NAME__"
           Setting -mmcu=device defines this built-in macro to the device's name. For example,  with
           -mmcu=atmega8 the macro is defined to "atmega8".

           If  device  is  not  a  device but only a core architecture like avr51, this macro is not
           defined.

       "__AVR_XMEGA__"
           The device / architecture belongs to the XMEGA family of devices.

       "__AVR_HAVE_ELPM__"
           The device has the "ELPM" instruction.

       "__AVR_HAVE_ELPMX__"
           The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

       "__AVR_HAVE_MOVW__"
           The device has the "MOVW" instruction to perform 16-bit register-register moves.

       "__AVR_HAVE_LPMX__"
           The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

       "__AVR_HAVE_MUL__"
           The device has a hardware multiplier.

       "__AVR_HAVE_JMP_CALL__"
           The device has the "JMP" and "CALL" instructions.  This is the case for devices with more
           than 8 KiB of program memory.

       "__AVR_HAVE_EIJMP_EICALL__"
       "__AVR_3_BYTE_PC__"
           The device has the "EIJMP" and "EICALL" instructions.  This is the case for devices  with
           more  than 128 KiB of program memory.  This also means that the program counter (PC) is 3
           bytes wide.

       "__AVR_2_BYTE_PC__"
           The program counter (PC) is 2 bytes wide. This is the case for devices with up to 128 KiB
           of program memory.

       "__AVR_HAVE_8BIT_SP__"
       "__AVR_HAVE_16BIT_SP__"
           The stack pointer (SP) register is treated as 8-bit respectively 16-bit register  by  the
           compiler.  The definition of these macros is affected by -mtiny-stack.

       "__AVR_HAVE_SPH__"
       "__AVR_SP8__"
           The  device  has the SPH (high part of stack pointer) special function register or has an
           8-bit stack pointer, respectively.  The definition of these macros is affected by  -mmcu=
           and in the cases of -mmcu=avr2 and -mmcu=avr25 also by -msp8.

       "__AVR_HAVE_RAMPD__"
       "__AVR_HAVE_RAMPX__"
       "__AVR_HAVE_RAMPY__"
       "__AVR_HAVE_RAMPZ__"
           The  device  has  the  "RAMPD",  "RAMPX",  "RAMPY",  "RAMPZ"  special  function register,
           respectively.

       "__NO_INTERRUPTS__"
           This macro reflects the -mno-interrupts command-line option.

       "__AVR_ERRATA_SKIP__"
       "__AVR_ERRATA_SKIP_JMP_CALL__"
           Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit instructions  because  of  a
           hardware  erratum.  Skip instructions are "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".  The
           second macro is only defined if "__AVR_HAVE_JMP_CALL__" is also set.

       "__AVR_ISA_RMW__"
           The device has Read-Modify-Write instructions (XCH, LAC, LAS and LAT).

       "__AVR_SFR_OFFSET__=offset"
           Instructions that can address I/O special function registers directly like  "IN",  "OUT",
           "SBI",  etc.  may use a different address as if addressed by an instruction to access RAM
           like "LD" or "STS". This offset  depends  on  the  device  architecture  and  has  to  be
           subtracted from the RAM address in order to get the respective I/O address.

       "__AVR_SHORT_CALLS__"
           The -mshort-calls command line option is set.

       "__AVR_PM_BASE_ADDRESS__=addr"
           Some devices support reading from flash memory by means of "LD*" instructions.  The flash
           memory  is  seen in the data address space at an offset of "__AVR_PM_BASE_ADDRESS__".  If
           this macro is not defined, this feature is not available.  If defined, the address  space
           is linear and there is no need to put ".rodata" into RAM.  This is handled by the default
           linker  description file, and is currently available for "avrtiny" and "avrxmega3".  Even
           more convenient, there is no need to use address spaces like "__flash" or  features  like
           attribute "progmem" and "pgm_read_*".

       "__WITH_AVRLIBC__"
           The  compiler  is  configured  to be used together with AVR-Libc.  See the --with-avrlibc
           configure option.

       "__HAVE_DOUBLE_MULTILIB__"
           Defined if -mdouble= acts as a multilib option.

       "__HAVE_DOUBLE32__"
       "__HAVE_DOUBLE64__"
           Defined if the compiler supports 32-bit double resp. 64-bit double.  The actual layout is
           specified by option -mdouble=.

       "__DEFAULT_DOUBLE__"
           The size in bits of "double" if -mdouble= is not set.  To test the layout of "double"  in
           a program, use the built-in macro "__SIZEOF_DOUBLE__".

       "__HAVE_LONG_DOUBLE32__"
       "__HAVE_LONG_DOUBLE64__"
       "__HAVE_LONG_DOUBLE_MULTILIB__"
       "__DEFAULT_LONG_DOUBLE__"
           Same as above, but for "long double" instead of "double".

       "__WITH_DOUBLE_COMPARISON__"
           Reflects     the     "--with-double-comparison={tristate|bool|libf7}"    configure option
           ("https://gcc.gnu.org/install/configure.html#avr") and is defined to 2 or 3.

       "__WITH_LIBF7_LIBGCC__"
       "__WITH_LIBF7_MATH__"
       "__WITH_LIBF7_MATH_SYMBOLS__"
           Reflects       the       "--with-libf7={libgcc|math|math-symbols}"       configure option
           ("https://gcc.gnu.org/install/configure.html#avr").

       Blackfin Options

       -mcpu=cpu[-sirevision]
           Specifies the name of the target Blackfin processor.  Currently, cpu can be one of bf512,
           bf514,  bf516,  bf518,  bf522,  bf523,  bf524,  bf525, bf526, bf527, bf531, bf532, bf533,
           bf534, bf536, bf537, bf538, bf539, bf542, bf544, bf547,  bf548,  bf549,  bf542m,  bf544m,
           bf547m, bf548m, bf549m, bf561, bf592.

           The  optional sirevision specifies the silicon revision of the target Blackfin processor.
           Any workarounds available for the targeted silicon revision are enabled.   If  sirevision
           is  none,  no  workarounds  are  enabled.   If sirevision is any, all workarounds for the
           targeted processor are enabled.  The  "__SILICON_REVISION__"  macro  is  defined  to  two
           hexadecimal  digits representing the major and minor numbers in the silicon revision.  If
           sirevision is none, the "__SILICON_REVISION__" is not defined.  If sirevision is any, the
           "__SILICON_REVISION__" is defined to be 0xffff.  If this optional sirevision is not used,
           GCC assumes the latest known silicon revision of the targeted Blackfin processor.

           GCC defines a preprocessor macro for the specified cpu.  For the bfin-elf toolchain, this
           option causes the hardware BSP provided by libgloss to be  linked  in  if  -msim  is  not
           given.

           Without this option, bf532 is used as the processor by default.

           Note  that  support  for  bf561 is incomplete.  For bf561, only the preprocessor macro is
           defined.

       -msim
           Specifies that the program will be run on the simulator.  This causes the  simulator  BSP
           provided  by  libgloss  to  be  linked  in.   This  option  has  effect only for bfin-elf
           toolchain.  Certain other options, such as -mid-shared-library and -mfdpic, imply -msim.

       -momit-leaf-frame-pointer
           Don't keep the frame  pointer  in  a  register  for  leaf  functions.   This  avoids  the
           instructions  to  save,  set  up  and  restore frame pointers and makes an extra register
           available in leaf functions.

       -mspecld-anomaly
           When enabled, the compiler ensures that the generated code does not  contain  speculative
           loads  after  jump instructions. If this option is used, "__WORKAROUND_SPECULATIVE_LOADS"
           is defined.

       -mno-specld-anomaly
           Don't generate extra code to prevent speculative loads from occurring.

       -mcsync-anomaly
           When enabled, the compiler ensures that the generated code  does  not  contain  CSYNC  or
           SSYNC  instructions  too  soon  after  conditional  branches.   If  this  option is used,
           "__WORKAROUND_SPECULATIVE_SYNCS" is defined.

       -mno-csync-anomaly
           Don't generate extra code to prevent CSYNC or SSYNC instructions from occurring too  soon
           after a conditional branch.

       -mlow64k
           When  enabled,  the  compiler  is free to take advantage of the knowledge that the entire
           program fits into the low 64k of memory.

       -mno-low64k
           Assume that the program is arbitrarily large.  This is the default.

       -mstack-check-l1
           Do stack checking using information placed into  L1  scratchpad  memory  by  the  uClinux
           kernel.

       -mid-shared-library
           Generate  code that supports shared libraries via the library ID method.  This allows for
           execute  in  place  and  shared  libraries  in  an  environment  without  virtual  memory
           management.   This  option  implies  -fPIC.   With a bfin-elf target, this option implies
           -msim.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are being used.  This is  the
           default.

       -mleaf-id-shared-library
           Generate  code that supports shared libraries via the library ID method, but assumes that
           this library or executable won't link against any other ID shared libraries.  That allows
           the compiler to use faster code for jumps and calls.

       -mno-leaf-id-shared-library
           Do not assume that the code being compiled won't link against any  ID  shared  libraries.
           Slower code is generated for jump and call insns.

       -mshared-library-id=n
           Specifies  the  identification  number  of  the  ID-based  shared library being compiled.
           Specifying a value of 0 generates more compact code; specifying other values  forces  the
           allocation  of that number to the current library but is no more space- or time-efficient
           than omitting this option.

       -msep-data
           Generate code that allows the data segment to be located in a different  area  of  memory
           from  the  text  segment.   This  allows  for  execute in place in an environment without
           virtual memory management by eliminating relocations against the text section.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text segment.  This  is  the
           default.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of the function
           into  a  register and then performing a subroutine call on this register.  This switch is
           needed if the target function lies outside of the 24-bit addressing range of the  offset-
           based version of subroutine call instruction.

           This  feature is not enabled by default.  Specifying -mno-long-calls restores the default
           behavior.  Note these switches have no effect on  how  the  compiler  generates  code  to
           handle function calls via function pointers.

       -mfast-fp
           Link  with  the  fast  floating-point  library.  This  library  relaxes  some of the IEEE
           floating-point standard's rules for checking inputs against Not-a-Number  (NAN),  in  the
           interest of performance.

       -minline-plt
           Enable  inlining of PLT entries in function calls to functions that are not known to bind
           locally.  It has no effect without -mfdpic.

       -mmulticore
           Build a standalone application for multicore Blackfin  processors.   This  option  causes
           proper  start  files  and  link  scripts supporting multicore to be used, and defines the
           macro "__BFIN_MULTICORE".  It can only be used with -mcpu=bf561[-sirevision].

           This option can be used with -mcorea or -mcoreb, which selects  the  one-application-per-
           core  programming  model.   Without  -mcorea or -mcoreb, the single-application/dual-core
           programming model is used. In this model, the main function of Core B should be named  as
           "coreb_main".

           If this option is not used, the single-core application programming model is used.

       -mcorea
           Build  a  standalone  application for Core A of BF561 when using the one-application-per-
           core programming model. Proper start files and link scripts are used to support  Core  A,
           and  the  macro  "__BFIN_COREA"  is defined.  This option can only be used in conjunction
           with -mmulticore.

       -mcoreb
           Build a standalone application for Core B of BF561 when  using  the  one-application-per-
           core  programming  model. Proper start files and link scripts are used to support Core B,
           and the macro "__BFIN_COREB" is defined. When this option is used, "coreb_main" should be
           used instead of "main".  This option can only be used in conjunction with -mmulticore.

       -msdram
           Build a standalone application for SDRAM. Proper start files and link scripts are used to
           put the application into SDRAM, and the macro  "__BFIN_SDRAM"  is  defined.   The  loader
           should initialize SDRAM before loading the application.

       -micplb
           Assume  that  ICPLBs  are  enabled  at  run  time.  This has an effect on certain anomaly
           workarounds.  For Linux targets, the  default  is  to  assume  ICPLBs  are  enabled;  for
           standalone applications the default is off.

       C6X Options

       -march=name
           This specifies the name of the target architecture.  GCC uses this name to determine what
           kind  of  instructions it can emit when generating assembly code.  Permissible names are:
           c62x, c64x, c64x+, c67x, c67x+, c674x.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -msim
           Choose startup files and linker script suitable for the simulator.

       -msdata=default
           Put small global and static data in the ".neardata"  section,  which  is  pointed  to  by
           register  "B14".   Put  small uninitialized global and static data in the ".bss" section,
           which is adjacent to  the  ".neardata"  section.   Put  small  read-only  data  into  the
           ".rodata"  section.   The  corresponding  sections  used  for  large  pieces  of data are
           ".fardata", ".far" and ".const".

       -msdata=all
           Put all data, not just small objects, into the sections reserved for small data, and  use
           addressing relative to the "B14" register to access them.

       -msdata=none
           Make no use of the sections reserved for small data, and use absolute addresses to access
           all  data.  Put all initialized global and static data in the ".fardata" section, and all
           uninitialized data in the ".far" section.   Put  all  constant  data  into  the  ".const"
           section.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
           Generate  code for the specified architecture.  The choices for architecture-type are v3,
           v8 and v10 for respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.  Default is v0.

       -mtune=architecture-type
           Tune to architecture-type everything applicable about the generated code, except for  the
           ABI  and  the  set  of available instructions.  The choices for architecture-type are the
           same as for -march=architecture-type.

       -mmax-stack-frame=n
           Warn when the stack frame of a function exceeds n bytes.

       -metrax4
       -metrax100
           The  options  -metrax4  and  -metrax100  are  synonyms  for   -march=v3   and   -march=v8
           respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
           Work  around a bug in the "muls" and "mulu" instructions for CPU models where it applies.
           This option is active by default.

       -mpdebug
           Enable CRIS-specific verbose debug-related information in the assembly code.  This option
           also has the effect of turning off the #NO_APP formatted-code indicator to the  assembler
           at the beginning of the assembly file.

       -mcc-init
           Do not use condition-code results from previous instruction; always emit compare and test
           instructions before use of condition codes.

       -mno-side-effects
           Do not emit instructions with side effects in addressing modes other than post-increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
           These  options  (no-  options)  arrange  (eliminate  arrangements)  for  the stack frame,
           individual data and constants to be aligned for the maximum single data access  size  for
           the  chosen CPU model.  The default is to arrange for 32-bit alignment.  ABI details such
           as structure layout are not affected by these options.

       -m32-bit
       -m16-bit
       -m8-bit
           Similar to the stack- data- and const-align options  above,  these  options  arrange  for
           stack  frame, writable data and constants to all be 32-bit, 16-bit or 8-bit aligned.  The
           default is 32-bit alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
           With -mno-prologue-epilogue, the normal function prologue and epilogue which set  up  the
           stack  frame  are omitted and no return instructions or return sequences are generated in
           the code.  Use this option only together with visual inspection of the compiled code:  no
           warnings  or errors are generated when call-saved registers must be saved, or storage for
           local variables needs to be allocated.

       -melf
           Legacy no-op option.

       -sim
           This option arranges to link with input-output functions from a simulator library.  Code,
           initialized data and zero-initialized data are allocated consecutively.

       -sim2
           Like -sim, but pass linker options to locate initialized data  at  0x40000000  and  zero-
           initialized data at 0x80000000.

       CR16 Options

       These options are defined specifically for the CR16 ports.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mcr16cplus
       -mcr16c
           Generate code for CR16C or CR16C+ architecture. CR16C+ architecture is default.

       -msim
           Links  the  library  libsim.a  which  is  in compatible with simulator. Applicable to ELF
           compiler only.

       -mint32
           Choose integer type as 32-bit wide.

       -mbit-ops
           Generates "sbit"/"cbit" instructions for bit manipulations.

       -mdata-model=model
           Choose a data model. The choices for model are near, far or medium.  medium  is  default.
           However,  far  is  not valid with -mcr16c, as the CR16C architecture does not support the
           far data model.

       C-SKY Options

       GCC supports these options when compiling for C-SKY V2 processors.

       -march=arch
           Specify the C-SKY target architecture.  Valid values for arch are: ck801,  ck802,  ck803,
           ck807, and ck810.  The default is ck810.

       -mcpu=cpu
           Specify  the  C-SKY  target  processor.   Valid values for cpu are: ck801, ck801t, ck802,
           ck802t, ck802j,  ck803,  ck803h,  ck803t,  ck803ht,  ck803f,  ck803fh,  ck803e,  ck803eh,
           ck803et,  ck803eht,  ck803ef,  ck803efh, ck803ft, ck803eft, ck803efht, ck803r1, ck803hr1,
           ck803tr1, ck803htr1, ck803fr1, ck803fhr1,  ck803er1,  ck803ehr1,  ck803etr1,  ck803ehtr1,
           ck803efr1,  ck803efhr1,  ck803ftr1,  ck803eftr1,  ck803efhtr1,  ck803s, ck803st, ck803se,
           ck803sf, ck803sef, ck803seft, ck807e, ck807ef, ck807, ck807f, ck810e,  ck810et,  ck810ef,
           ck810eft, ck810, ck810v, ck810f, ck810t, ck810fv, ck810tv, ck810ft, and ck810ftv.

       -mbig-endian
       -EB
       -mlittle-endian
       -EL Select big- or little-endian code.  The default is little-endian.

       -mfloat-abi=name
           Specifies  which  floating-point  ABI  to  use.  Permissible values are: soft, softfp and
           hard.

           Specifying soft causes GCC to generate output containing library calls for floating-point
           operations.   softfp  allows  the  generation  of  code  using  hardware   floating-point
           instructions,  but still uses the soft-float calling conventions.  hard allows generation
           of floating-point instructions and uses FPU-specific calling conventions.

           The default depends on the specific target configuration.  Note that the  hard-float  and
           soft-float  ABIs  are  not link-compatible; you must compile your entire program with the
           same ABI, and link with a compatible set of libraries.

       -mhard-float
       -msoft-float
           Select hardware or software floating-point implementations.  The default is soft float.

       -mdouble-float
       -mno-double-float
           When -mhard-float is in effect, enable generation of double-precision float instructions.
           This is the default except when compiling for CK803.

       -mfdivdu
       -mno-fdivdu
           When -mhard-float is in effect, enable generation of  "frecipd",  "fsqrtd",  and  "fdivd"
           instructions.  This is the default except when compiling for CK803.

       -mfpu=fpu
           Select  the  floating-point  processor.   This option can only be used with -mhard-float.
           Values  for  fpu  are  fpv2_sf  (equivalent  to  -mno-double-float   -mno-fdivdu),   fpv2
           (-mdouble-float -mno-divdu), and fpv2_divd (-mdouble-float -mdivdu).

       -melrw
       -mno-elrw
           Enable  the  extended  "lrw"  instruction.   This option defaults to on for CK801 and off
           otherwise.

       -mistack
       -mno-istack
           Enable interrupt stack instructions; the default is off.

           The -mistack option is required to handle the "interrupt" and "isr" function attributes.

       -mmp
           Enable multiprocessor instructions; the default is off.

       -mcp
           Enable coprocessor instructions; the default is off.

       -mcache
           Enable coprocessor instructions; the default is off.

       -msecurity
           Enable C-SKY security instructions; the default is off.

       -mtrust
           Enable C-SKY trust instructions; the default is off.

       -mdsp
       -medsp
       -mvdsp
           Enable C-SKY DSP, Enhanced DSP, or Vector DSP instructions, respectively.  All  of  these
           options default to off.

       -mdiv
       -mno-div
           Generate divide instructions.  Default is off.

       -msmart
       -mno-smart
           Generate  code  for  Smart Mode, using only registers numbered 0-7 to allow use of 16-bit
           instructions.  This option is ignored for CK801 where this is the required behavior,  and
           it defaults to on for CK802.  For other targets, the default is off.

       -mhigh-registers
       -mno-high-registers
           Generate  code  using the high registers numbered 16-31.  This option is not supported on
           CK801, CK802, or CK803, and is enabled by default for other processors.

       -manchor
       -mno-anchor
           Generate code using global anchor symbol addresses.

       -mpushpop
       -mno-pushpop
           Generate code using "push" and "pop" instructions.  This option defaults to on.

       -mmultiple-stld
       -mstm
       -mno-multiple-stld
       -mno-stm
           Generate code using "stm" and "ldm" instructions.  This option isn't supported  on  CK801
           but is enabled by default on other processors.

       -mconstpool
       -mno-constpool
           Create  constant  pools  in  the compiler instead of deferring it to the assembler.  This
           option is the default and required for correct code generation on CK801 and CK802, and is
           optional on other processors.

       -mstack-size
       -mno-stack-size
           Emit ".stack_size" directives for each function in  the  assembly  output.   This  option
           defaults to off.

       -mccrt
       -mno-ccrt
           Generate  code for the C-SKY compiler runtime instead of libgcc.  This option defaults to
           off.

       -mbranch-cost=n
           Set the branch costs to roughly "n" instructions.  The default is 1.

       -msched-prolog
       -mno-sched-prolog
           Permit scheduling of function prologue and epilogue sequences.   Using  this  option  can
           result in code that is not compliant with the C-SKY V2 ABI prologue requirements and that
           cannot be debugged or backtraced.  It is disabled by default.

       -msim
           Links  the  library  libsemi.a  which  is in compatible with simulator. Applicable to ELF
           compiler only.

       Darwin Options

       These options are defined for all architectures running the Darwin operating system.

       FSF GCC on Darwin does not create "fat" object files; it  creates  an  object  file  for  the
       single  architecture  that  GCC was built to target.  Apple's GCC on Darwin does create "fat"
       files if multiple -arch options are used; it does  so  by  running  the  compiler  or  linker
       multiple times and joining the results together with lipo.

       The  subtype  of the file created (like ppc7400 or ppc970 or i686) is determined by the flags
       that specify the ISA that GCC is targeting, like -mcpu or -march.  The  -force_cpusubtype_ALL
       option can be used to override this.

       The  Darwin tools vary in their behavior when presented with an ISA mismatch.  The assembler,
       as, only permits instructions to be used that are valid for the subtype of  the  file  it  is
       generating,  so  you  cannot put 64-bit instructions in a ppc750 object file.  The linker for
       shared libraries, /usr/bin/libtool, fails and prints an error if asked  to  create  a  shared
       library  with  a less restrictive subtype than its input files (for instance, trying to put a
       ppc970 object file in a ppc7400 library).  The linker for executables, ld, quietly gives  the
       executable the most restrictive subtype of any of its input files.

       -Fdir
           Add the framework directory dir to the head of the list of directories to be searched for
           header  files.   These directories are interleaved with those specified by -I options and
           are scanned in a left-to-right order.

           A framework directory is a directory with frameworks in it.  A framework is  a  directory
           with  a  Headers  and/or  PrivateHeaders  directory contained directly in it that ends in
           .framework.  The name of a  framework  is  the  name  of  this  directory  excluding  the
           .framework.   Headers  associated  with  the  framework  are  found  in  one of those two
           directories, with Headers being searched first.  A subframework is a framework  directory
           that is in a framework's Frameworks directory.  Includes of subframework headers can only
           appear  in  a  header  of  a  framework  that  contains the subframework, or in a sibling
           subframework header.  Two subframeworks are siblings if they occur in the same framework.
           A subframework should not have the same name as a framework; a warning is issued if  this
           is  violated.   Currently  a  subframework  cannot have subframeworks; in the future, the
           mechanism may be extended to support this.  The  standard  frameworks  can  be  found  in
           /System/Library/Frameworks  and  /Library/Frameworks.   An  example  include  looks  like
           "#include <Framework/header.h>", where Framework denotes the name of  the  framework  and
           header.h is found in the PrivateHeaders or Headers directory.

       -iframeworkdir
           Like  -F  except  the  directory is a treated as a system directory.  The main difference
           between this -iframework and -F is that with -iframework the compiler does not warn about
           constructs contained within header files found via dir.  This option is  valid  only  for
           the C family of languages.

       -gused
           Emit  debugging  information for symbols that are used.  For stabs debugging format, this
           enables -feliminate-unused-debug-symbols.  This is by default ON.

       -gfull
           Emit debugging information for all symbols and types.

       -fconstant-cfstrings
           The -fconstant-cfstrings is an alias for -mconstant-cfstrings.

       -mconstant-cfstrings
           When the NeXT runtime is  being  used  (the  default  on  these  systems),  override  any
           -fconstant-string-class  setting  and cause "@"...""  literals to be laid out as constant
           CoreFoundation strings.

       -mmacosx-version-min=version
           The earliest version of MacOS X that this executable will run  on  is  version.   Typical
           values supported for version include 12, 10.12, and 10.5.8.

           If  the  compiler  was built to use the system's headers by default, then the default for
           this option is the system version on which the compiler is running, otherwise the default
           is to make choices that are compatible with as many systems and code bases as possible.

       -mkernel
           Enable  kernel  development  mode.   The  -mkernel  option  sets  -static,   -fno-common,
           -fno-use-cxa-atexit,  -fno-exceptions,  -fno-non-call-exceptions, -fapple-kext, -fno-weak
           and  -fno-rtti  where  applicable.   This  mode  also  sets  -mno-altivec,  -msoft-float,
           -fno-builtin and -mlong-branch for PowerPC targets.

       -mone-byte-bool
           Override the defaults for "bool" so that "sizeof(bool)==1".  By default sizeof(bool) is 4
           when compiling for Darwin/PowerPC and 1 when compiling for Darwin/x86, so this option has
           no effect on x86.

           Warning:  The  -mone-byte-bool  switch  causes  GCC  to  generate code that is not binary
           compatible with code generated without  that  switch.   Using  this  switch  may  require
           recompiling  all other modules in a program, including system libraries.  Use this switch
           to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
           Generate code suitable  for  fast  turnaround  development,  such  as  to  allow  GDB  to
           dynamically   load   .o   files   into  already-running  programs.   -findirect-data  and
           -ffix-and-continue are provided for backwards compatibility.

       -all_load
           Loads all members of static archive libraries.  See man ld(1) for more information.

       -arch_errors_fatal
           Cause the errors having to do with files that have the wrong architecture to be fatal.

       -bind_at_load
           Causes the output file to be marked such that the dynamic linker will bind all  undefined
           references when the file is loaded or launched.

       -bundle
           Produce a Mach-o bundle format file.  See man ld(1) for more information.

       -bundle_loader executable
           This  option  specifies the executable that will load the build output file being linked.
           See man ld(1) for more information.

       -dynamiclib
           When passed this option, GCC produces a dynamic library instead  of  an  executable  when
           linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
           This  causes  GCC's output file to have the ALL subtype, instead of one controlled by the
           -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
           These options are passed to the Darwin linker.  The Darwin linker man page describes them
           in detail.

       DEC Alpha Options

       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions for floating-point  operations.
           When  -msoft-float is specified, functions in libgcc.a are used to perform floating-point
           operations.  Unless they  are  replaced  by  routines  that  emulate  the  floating-point
           operations, or compiled in such a way as to call such emulations routines, these routines
           issue  floating-point  operations.    If you are compiling for an Alpha without floating-
           point operations, you must ensure that the library is built so as not to call them.

           Note that Alpha implementations without floating-point operations are  required  to  have
           floating-point registers.

       -mfp-reg
       -mno-fp-regs
           Generate  code  that  uses  (does not use) the floating-point register set.  -mno-fp-regs
           implies -msoft-float.  If the floating-point register set  is  not  used,  floating-point
           operands  are  passed  in  integer  registers as if they were integers and floating-point
           results are passed in $0 instead of $f0.  This is a non-standard calling sequence, so any
           function with a floating-point argument or return value  called  by  code  compiled  with
           -mno-fp-regs must also be compiled with that option.

           A  typical  use of this option is building a kernel that does not use, and hence need not
           save and restore, any floating-point registers.

       -mieee
           The  Alpha  architecture  implements  floating-point  hardware  optimized   for   maximum
           performance.  It is mostly compliant with the IEEE floating-point standard.  However, for
           full compliance, software assistance is required.  This option generates code fully IEEE-
           compliant  code  except  that  the  inexact-flag  is not maintained (see below).  If this
           option is turned on, the preprocessor macro "_IEEE_FP"  is  defined  during  compilation.
           The  resulting  code  is  less  efficient  but  is able to correctly support denormalized
           numbers and exceptional IEEE values such as not-a-number and plus/minus infinity.   Other
           Alpha compilers call this option -ieee_with_no_inexact.

       -mieee-with-inexact
           This  is  like  -mieee  except  the  generated code also maintains the IEEE inexact-flag.
           Turning on this option causes the generated code to implement fully-compliant IEEE  math.
           In  addition to "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.  On some
           Alpha implementations the resulting code may execute significantly slower than  the  code
           generated  by default.  Since there is very little code that depends on the inexact-flag,
           you should normally not specify this option.  Other  Alpha  compilers  call  this  option
           -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
           This  option  controls  what  floating-point  related  traps  are  enabled.   Other Alpha
           compilers call this option -fptm trap-mode.  The trap mode can be  set  to  one  of  four
           values:

           n   This  is  the default (normal) setting.  The only traps that are enabled are the ones
               that cannot be disabled in software (e.g., division by zero trap).

           u   In addition to the traps enabled by n, underflow traps are enabled as well.

           su  Like u, but the instructions are marked to be safe for software completion (see Alpha
               architecture manual for details).

           sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
           Selects the IEEE rounding mode.  Other Alpha compilers call this option  -fprm  rounding-
           mode.  The rounding-mode can be one of:

           n   Normal  IEEE  rounding  mode.  Floating-point numbers are rounded towards the nearest
               machine number or towards the even machine number in case of a tie.

           m   Round towards minus infinity.

           c   Chopped rounding mode.  Floating-point numbers are rounded towards zero.

           d   Dynamic rounding mode.  A field in the floating-point  control  register  (fpcr,  see
               Alpha  architecture  reference  manual)  controls the rounding mode in effect.  The C
               library initializes this register for rounding towards plus infinity.   Thus,  unless
               your program modifies the fpcr, d corresponds to round towards plus infinity.

       -mtrap-precision=trap-precision
           In  the  Alpha  architecture,  floating-point  traps  are  imprecise.  This means without
           software assistance it is  impossible  to  recover  from  a  floating  trap  and  program
           execution  normally  needs  to  be  terminated.   GCC  can  generate code that can assist
           operating system trap handlers in determining the exact location that caused a  floating-
           point  trap.   Depending  on  the  requirements  of  an  application, different levels of
           precisions can be selected:

           p   Program precision.  This option is the default and means  a  trap  handler  can  only
               identify which program caused a floating-point exception.

           f   Function  precision.   The  trap  handler  can  determine  the function that caused a
               floating-point exception.

           i   Instruction precision.  The trap handler can determine  the  exact  instruction  that
               caused a floating-point exception.

           Other   Alpha   compilers   provide   the   equivalent  options  called  -scope_safe  and
           -resumption_safe.

       -mieee-conformant
           This option marks the generated code as IEEE conformant.  You must not  use  this  option
           unless   you   also   specify   -mtrap-precision=i   and   either   -mfp-trap-mode=su  or
           -mfp-trap-mode=sui.  Its only effect is to emit  the  line  .eflag  48  in  the  function
           prologue of the generated assembly file.

       -mbuild-constants
           Normally GCC examines a 32- or 64-bit integer constant to see if it can construct it from
           smaller constants in two or three instructions.  If it cannot, it outputs the constant as
           a literal and generates code to load it from the data segment at run time.

           Use  this option to require GCC to construct all integer constants using code, even if it
           takes more instructions (the maximum is six).

           You typically use this option to build a shared library dynamic loader.  Itself a  shared
           library, it must relocate itself in memory before it can find the variables and constants
           in its own data segment.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
           Indicate  whether  GCC  should  generate  code  to use the optional BWX, CIX, FIX and MAX
           instruction sets.  The default is to use the instruction sets supported by the  CPU  type
           specified  via  -mcpu=  option  or  that  of  the  CPU  on which GCC was built if none is
           specified.

       -mfloat-vax
       -mfloat-ieee
           Generate code that uses (does not use) VAX F and G floating-point arithmetic  instead  of
           IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
           Older  Alpha  assemblers  provided  no  way  to  generate  symbol  relocations except via
           assembler macros.  Use of these macros does not  allow  optimal  instruction  scheduling.
           GNU  binutils  as  of  version  2.12  supports  a  new syntax that allows the compiler to
           explicitly mark which relocations should apply to which  instructions.   This  option  is
           mostly  useful for debugging, as GCC detects the capabilities of the assembler when it is
           built and sets the default accordingly.

       -msmall-data
       -mlarge-data
           When -mexplicit-relocs is in effect, static data is accessed via gp-relative relocations.
           When -msmall-data is used, objects 8 bytes long or smaller are placed  in  a  small  data
           area  (the  ".sdata" and ".sbss" sections) and are accessed via 16-bit relocations off of
           the $gp register.  This limits the size of the small data area to 64KB,  but  allows  the
           variables to be directly accessed via a single instruction.

           The  default  is  -mlarge-data.   With this option the data area is limited to just below
           2GB.  Programs that require more than 2GB of data must use "malloc" or "mmap" to allocate
           the data in the heap instead of in the program's data segment.

           When generating code for shared libraries, -fpic implies -msmall-data and  -fPIC  implies
           -mlarge-data.

       -msmall-text
       -mlarge-text
           When  -msmall-text  is used, the compiler assumes that the code of the entire program (or
           shared library) fits in 4MB, and is thus  reachable  with  a  branch  instruction.   When
           -msmall-data  is  used, the compiler can assume that all local symbols share the same $gp
           value, and thus reduce the number of instructions required for a function call from 4  to
           1.

           The default is -mlarge-text.

       -mcpu=cpu_type
           Set  the instruction set and instruction scheduling parameters for machine type cpu_type.
           You can specify either the EV style name or the corresponding chip number.  GCC  supports
           scheduling  parameters  for  the  EV4,  EV5  and EV6 family of processors and chooses the
           default values for the instruction set from the processor you specify.   If  you  do  not
           specify a processor type, GCC defaults to the processor on which the compiler was built.

           Supported values for cpu_type are

           ev4
           ev45
           21064
               Schedules as an EV4 and has no instruction set extensions.

           ev5
           21164
               Schedules as an EV5 and has no instruction set extensions.

           ev56
           21164a
               Schedules as an EV5 and supports the BWX extension.

           pca56
           21164pc
           21164PC
               Schedules as an EV5 and supports the BWX and MAX extensions.

           ev6
           21264
               Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.

           ev67
           21264a
               Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.

           Native  toolchains  also  support  the  value native, which selects the best architecture
           option for the host processor.  -mcpu=native has no effect if GCC does not recognize  the
           processor.

       -mtune=cpu_type
           Set   only  the  instruction  scheduling  parameters  for  machine  type  cpu_type.   The
           instruction set is not changed.

           Native toolchains also support the value native,  which  selects  the  best  architecture
           option for the host processor.  -mtune=native has no effect if GCC does not recognize the
           processor.

       -mmemory-latency=time
           Sets the latency the scheduler should assume for typical memory references as seen by the
           application.   This  number is highly dependent on the memory access patterns used by the
           application and the size of the external cache on the machine.

           Valid options for time are

           number
               A decimal number representing clock cycles.

           L1
           L2
           L3
           main
               The compiler contains estimates of the number of clock cycles for "typical" EV4 & EV5
               hardware for the Level 1, 2 & 3 caches (also called Dcache, Scache, and  Bcache),  as
               well as to main memory.  Note that L3 is only valid for EV5.

       eBPF Options

       -mframe-limit=bytes
           This  specifies  the hard limit for frame sizes, in bytes.  Currently, the value that can
           be specified should be less than or equal  to  32767.   Defaults  to  whatever  limit  is
           imposed by the version of the Linux kernel targeted.

       -mkernel=version
           This specifies the minimum version of the kernel that will run the compiled program.  GCC
           uses  this  version to determine which instructions to use, what kernel helpers to allow,
           etc.  Currently, version can be one of 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8,  4.9,
           4.10,  4.11,  4.12, 4.13, 4.14, 4.15, 4.16, 4.17, 4.18, 4.19, 4.20, 5.0, 5.1, 5.2, latest
           and native.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -mxbpf
           Generate code for an expanded version of BPF, which  relaxes  some  of  the  restrictions
           imposed by the BPF architecture:

           -<Save and restore callee-saved registers at function entry and>
               exit, respectively.

       FR30 Options

       These options are defined specifically for the FR30 port.

       -msmall-model
           Use  the  small  address  space model.  This can produce smaller code, but it does assume
           that all symbolic values and addresses fit into a 20-bit range.

       -mno-lsim
           Assume that runtime support has been provided and so there is  no  need  to  include  the
           simulator library (libsim.a) on the linker command line.

       FT32 Options

       These options are defined specifically for the FT32 port.

       -msim
           Specifies  that  the  program  will  be  run  on the simulator.  This causes an alternate
           runtime startup and library to be linked.  You must not use this option  when  generating
           programs  that  will  run on real hardware; you must provide your own runtime library for
           whatever I/O functions are needed.

       -mlra
           Enable Local Register Allocation.  This is still experimental for FT32, so by default the
           compiler uses standard reload.

       -mnodiv
           Do not use div and mod instructions.

       -mft32b
           Enable use of the extended instructions of the FT32B processor.

       -mcompress
           Compress all code using the Ft32B code compression scheme.

       -mnopm
           Do not generate code that reads program memory.

       FRV Options

       -mgpr-32
           Only use the first 32 general-purpose registers.

       -mgpr-64
           Use all 64 general-purpose registers.

       -mfpr-32
           Use only the first 32 floating-point registers.

       -mfpr-64
           Use all 64 floating-point registers.

       -mhard-float
           Use hardware instructions for floating-point operations.

       -msoft-float
           Use library routines for floating-point operations.

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
           Do not try to dynamically allocate condition code registers, only use "icc0" and "fcc0".

       -mdword
           Change ABI to use double word insns.

       -mno-dword
           Do not use double word instructions.

       -mdouble
           Use floating-point double instructions.

       -mno-double
           Do not use floating-point double instructions.

       -mmedia
           Use media instructions.

       -mno-media
           Do not use media instructions.

       -mmuladd
           Use multiply and add/subtract instructions.

       -mno-muladd
           Do not use multiply and add/subtract instructions.

       -mfdpic
           Select the FDPIC ABI, which uses function descriptors to represent pointers to functions.
           Without any PIC/PIE-related options, it implies -fPIE.  With -fpic or -fpie,  it  assumes
           GOT  entries  and  small  data  are within a 12-bit range from the GOT base address; with
           -fPIC or -fPIE, GOT offsets are computed with 32 bits.   With  a  bfin-elf  target,  this
           option implies -msim.

       -minline-plt
           Enable  inlining of PLT entries in function calls to functions that are not known to bind
           locally.  It has no effect without -mfdpic.  It's enabled by default  if  optimizing  for
           speed  and compiling for shared libraries (i.e., -fPIC or -fpic), or when an optimization
           option such as -O3 or above is present in the command line.

       -mTLS
           Assume a large TLS segment when generating thread-local code.

       -mtls
           Do not assume a large TLS segment when generating thread-local code.

       -mgprel-ro
           Enable the use of "GPREL" relocations in the FDPIC ABI for data that is known  to  be  in
           read-only  sections.   It's enabled by default, except for -fpic or -fpie: even though it
           may help make the global offset table smaller, it trades 1 instruction for 4.  With -fPIC
           or -fPIE, it trades 3 instructions for 4, one of which may be shared by multiple symbols,
           and it avoids the need for a GOT entry for the referenced symbol, so it's more likely  to
           be a win.  If it is not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
           Link with the (library, not FD) pic libraries.  It's implied by -mlibrary-pic, as well as
           by -fPIC and -fpic without -mfdpic.  You should never have to use it explicitly.

       -mlinked-fp
           Follow  the EABI requirement of always creating a frame pointer whenever a stack frame is
           allocated.  This option is enabled by default and can be disabled with -mno-linked-fp.

       -mlong-calls
           Use indirect addressing to call functions outside the  current  compilation  unit.   This
           allows the functions to be placed anywhere within the 32-bit address space.

       -malign-labels
           Try  to  align  labels  to an 8-byte boundary by inserting NOPs into the previous packet.
           This option only has an effect when VLIW packing  is  enabled.   It  doesn't  create  new
           packets; it merely adds NOPs to existing ones.

       -mlibrary-pic
           Generate position-independent EABI code.

       -macc-4
           Use only the first four media accumulator registers.

       -macc-8
           Use all eight media accumulator registers.

       -mpack
           Pack VLIW instructions.

       -mno-pack
           Do not pack VLIW instructions.

       -mno-eflags
           Do not mark ABI switches in e_flags.

       -mcond-move
           Enable the use of conditional-move instructions (default).

           This  switch  is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-cond-move
           Disable the use of conditional-move instructions.

           This switch is mainly for debugging the compiler and will likely be removed in  a  future
           version.

       -mscc
           Enable the use of conditional set instructions (default).

           This  switch  is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-scc
           Disable the use of conditional set instructions.

           This switch is mainly for debugging the compiler and will likely be removed in  a  future
           version.

       -mcond-exec
           Enable the use of conditional execution (default).

           This  switch  is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-cond-exec
           Disable the use of conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in  a  future
           version.

       -mvliw-branch
           Run a pass to pack branches into VLIW instructions (default).

           This  switch  is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-vliw-branch
           Do not run a pass to pack branches into VLIW instructions.

           This switch is mainly for debugging the compiler and will likely be removed in  a  future
           version.

       -mmulti-cond-exec
           Enable optimization of "&&" and "||" in conditional execution (default).

           This  switch  is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-multi-cond-exec
           Disable optimization of "&&" and "||" in conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in  a  future
           version.

       -mnested-cond-exec
           Enable nested conditional execution optimizations (default).

           This  switch  is mainly for debugging the compiler and will likely be removed in a future
           version.

       -mno-nested-cond-exec
           Disable nested conditional execution optimizations.

           This switch is mainly for debugging the compiler and will likely be removed in  a  future
           version.

       -moptimize-membar
           This switch removes redundant "membar" instructions from the compiler-generated code.  It
           is enabled by default.

       -mno-optimize-membar
           This  switch  disables  the automatic removal of redundant "membar" instructions from the
           generated code.

       -mtomcat-stats
           Cause gas to print out tomcat statistics.

       -mcpu=cpu
           Select the processor type for which to generate code.  Possible values  are  frv,  fr550,
           tomcat, fr500, fr450, fr405, fr400, fr300 and simple.

       GNU/Linux Options

       These -m options are defined for GNU/Linux targets:

       -mglibc
           Use   the   GNU   C   library.    This  is  the  default  except  on  *-*-linux-*uclibc*,
           *-*-linux-*musl* and *-*-linux-*android* targets.

       -muclibc
           Use uClibc C library.  This is the default on *-*-linux-*uclibc* targets.

       -mmusl
           Use the musl C library.  This is the default on *-*-linux-*musl* targets.

       -mbionic
           Use Bionic C library.  This is the default on *-*-linux-*android* targets.

       -mandroid
           Compile  code   compatible   with   Android   platform.    This   is   the   default   on
           *-*-linux-*android* targets.

           When  compiling,  this  option  enables -mbionic, -fPIC, -fno-exceptions and -fno-rtti by
           default.  When linking, this option makes the GCC driver pass Android-specific options to
           the linker.  Finally, this option causes  the  preprocessor  macro  "__ANDROID__"  to  be
           defined.

       -tno-android-cc
           Disable   compilation  effects  of  -mandroid,  i.e.,  do  not  enable  -mbionic,  -fPIC,
           -fno-exceptions and -fno-rtti by default.

       -tno-android-ld
           Disable linking effects of -mandroid, i.e., pass standard Linux linking  options  to  the
           linker.

       H8/300 Options

       These -m options are defined for the H8/300 implementations:

       -mrelax
           Shorten  some  address  references  at  link  time, when possible; uses the linker option
           -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the normal  mode.   This  switch  must  be  used
           either with -mh or -ms.

       -ms2600
           Generate code for the H8S/2600.  This switch must be used with -ms.

       -mexr
           Extended  registers  are  stored  on  stack  before  execution  of  function with monitor
           attribute. Default option is -mexr.  This option is valid only for H8S targets.

       -mno-exr
           Extended registers are not stored on stack before  execution  of  function  with  monitor
           attribute. Default option is -mno-exr.  This option is valid only for H8S targets.

       -mint32
           Make "int" data 32 bits by default.

       -malign-300
           On  the H8/300H and H8S, use the same alignment rules as for the H8/300.  The default for
           the H8/300H and H8S is to align longs  and  floats  on  4-byte  boundaries.   -malign-300
           causes them to be aligned on 2-byte boundaries.  This option has no effect on the H8/300.

       HPPA Options

       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
           Generate  code for the specified architecture.  The choices for architecture-type are 1.0
           for  PA  1.0,  1.1  for  PA  1.1,  and   2.0   for   PA   2.0   processors.    Refer   to
           /usr/lib/sched.models  on an HP-UX system to determine the proper architecture option for
           your machine.  Code compiled for lower numbered architectures  runs  on  higher  numbered
           architectures, but not the other way around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
           Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mcaller-copies
           The  caller  copies function arguments passed by hidden reference.  This option should be
           used with care as it is not compatible with the default 32-bit  runtime.   However,  only
           aggregates larger than eight bytes are passed by hidden reference and the option provides
           better compatibility with OpenMP.

       -mjump-in-delay
           This option is ignored and provided for compatibility purposes only.

       -mdisable-fpregs
           Prevent  floating-point  registers  from being used in any manner.  This is necessary for
           compiling kernels that perform lazy context switching of  floating-point  registers.   If
           you  use  this  option  and  attempt  to  perform floating-point operations, the compiler
           aborts.

       -mdisable-indexing
           Prevent the compiler from using indexing address modes.  This avoids some rather  obscure
           problems when compiling MIG generated code under MACH.

       -mno-space-regs
           Generate  code  that  assumes  the  target  has  no  space registers.  This allows GCC to
           generate faster indirect calls and use unscaled index address modes.

           Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
           Generate code that assumes calls never cross space boundaries.  This allows GCC  to  emit
           code that performs faster indirect calls.

           This option does not work in the presence of shared libraries or nested functions.

       -mfixed-range=register-range
           Generate  code treating the given register range as fixed registers.  A fixed register is
           one that the register allocator cannot use.  This is useful when compiling  kernel  code.
           A  register  range  is specified as two registers separated by a dash.  Multiple register
           ranges can be specified separated by a comma.

       -mlong-load-store
           Generate 3-instruction load and store sequences as sometimes required  by  the  HP-UX  10
           linker.  This is equivalent to the +k option to the HP compilers.

       -mportable-runtime
           Use the portable calling conventions proposed by HP for ELF systems.

       -mgas
           Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
           Schedule  code  according  to the constraints for the machine type cpu-type.  The choices
           for cpu-type are 700 7100, 7100LC, 7200, 7300 and 8000.  Refer  to  /usr/lib/sched.models
           on  an  HP-UX  system  to  determine  the proper scheduling option for your machine.  The
           default scheduling is 8000.

       -mlinker-opt
           Enable the optimization pass in the HP-UX linker.  Note  this  makes  symbolic  debugging
           impossible.  It also triggers a bug in the HP-UX 8 and HP-UX 9 linkers in which they give
           bogus error messages when linking some programs.

       -msoft-float
           Generate  output  containing  library  calls  for floating point.  Warning: the requisite
           libraries are not available for  all  HPPA  targets.   Normally  the  facilities  of  the
           machine's  usual  C  compiler  are  used,  but  this  cannot  be  done directly in cross-
           compilation.  You must make your own arrangements to provide suitable  library  functions
           for cross-compilation.

           -msoft-float  changes  the  calling  convention in the output file; therefore, it is only
           useful if you compile all of a program with this option.   In  particular,  you  need  to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to
           work.

       -msio
           Generate  the  predefine,  "_SIO", for server IO.  The default is -mwsio.  This generates
           the predefines, "__hp9000s700", "__hp9000s700__" and "_WSIO", for workstation IO.   These
           options are available under HP-UX and HI-UX.

       -mgnu-ld
           Use  options  specific  to  GNU  ld.   This  passes  -shared to ld when building a shared
           library.  It is the default when GCC is configured, explicitly or  implicitly,  with  the
           GNU  linker.   This  option  does  not  affect  which  ld is called; it only changes what
           parameters are passed to that ld.  The ld that is called is determined by  the  --with-ld
           configure  option, GCC's program search path, and finally by the user's PATH.  The linker
           used by GCC can be printed using which `gcc -print-prog-name=ld`.  This  option  is  only
           available on the 64-bit HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

       -mhp-ld
           Use  options  specific to HP ld.  This passes -b to ld when building a shared library and
           passes +Accept TypeMismatch to  ld  on  all  links.   It  is  the  default  when  GCC  is
           configured,  explicitly  or  implicitly, with the HP linker.  This option does not affect
           which ld is called; it only changes what parameters are passed to that ld.  The  ld  that
           is called is determined by the --with-ld configure option, GCC's program search path, and
           finally  by  the  user's  PATH.   The  linker used by GCC can be printed using which `gcc
           -print-prog-name=ld`.  This option is only  available  on  the  64-bit  HP-UX  GCC,  i.e.
           configured with hppa*64*-*-hpux*.

       -mlong-calls
           Generate  code that uses long call sequences.  This ensures that a call is always able to
           reach linker generated stubs.  The default is  to  generate  long  calls  only  when  the
           distance  from the call site to the beginning of the function or translation unit, as the
           case may be, exceeds a predefined limit set by the branch type being  used.   The  limits
           for  normal calls are 7,600,000 and 240,000 bytes, respectively for the PA 2.0 and PA 1.X
           architectures.  Sibcalls are always limited at 240,000 bytes.

           Distances are measured from the beginning of functions when using the -ffunction-sections
           option, or when using the -mgas and -mno-portable-runtime options  together  under  HP-UX
           with the SOM linker.

           It  is normally not desirable to use this option as it degrades performance.  However, it
           may be useful in large applications, particularly when partial linking is used  to  build
           the application.

           The types of long calls used depends on the capabilities of the assembler and linker, and
           the  type  of  code  being  generated.   The impact on systems that support long absolute
           calls, and long pic symbol-difference or pc-relative calls should  be  relatively  small.
           However, an indirect call is used on 32-bit ELF systems in pic code and it is quite long.

       -munix=unix-std
           Generate compiler predefines and select a startfile for the specified UNIX standard.  The
           choices  for  unix-std  are 93, 95 and 98.  93 is supported on all HP-UX versions.  95 is
           available on HP-UX 10.10 and later.  98 is available  on  HP-UX  11.11  and  later.   The
           default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to 11.00, and 98 for HP-
           UX 11.11 and later.

           -munix=93 provides the same predefines as GCC 3.3 and 3.4.  -munix=95 provides additional
           predefines  for  "XOPEN_UNIX"  and  "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.
           -munix=98 provides additional  predefines  for  "_XOPEN_UNIX",  "_XOPEN_SOURCE_EXTENDED",
           "_INCLUDE__STDC_A1_SOURCE" and "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

           It  is  important  to  note  that  this option changes the interfaces for various library
           routines.  It also affects the operational behavior of the C library.  Thus, extreme care
           is needed in using this option.

           Library code that is intended to operate with more than one UNIX standard must test,  set
           and  restore  the  variable  "__xpg4_extended_mask"  as  appropriate.   Most GNU software
           doesn't provide this capability.

       -nolibdld
           Suppress the generation of link options to search libdld.sl when the  -static  option  is
           specified on HP-UX 10 and later.

       -static
           The HP-UX implementation of setlocale in libc has a dependency on libdld.sl.  There isn't
           an  archive  version  of  libdld.sl.  Thus, when the -static option is specified, special
           link options are needed to resolve this dependency.

           On HP-UX 10 and later, the GCC driver adds the necessary options to link  with  libdld.sl
           when  the  -static  option is specified.  This causes the resulting binary to be dynamic.
           On the 64-bit port, the linkers generate dynamic binaries by default in  any  case.   The
           -nolibdld option can be used to prevent the GCC driver from adding these link options.

       -threads
           Add support for multithreading with the dce thread library under HP-UX.  This option sets
           flags for both the preprocessor and linker.

       IA-64 Options

       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
           Generate code for a big-endian target.  This is the default for HP-UX.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default for AIX5 and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
           Generate (or don't) code for the GNU assembler.  This is the default.

       -mgnu-ld
       -mno-gnu-ld
           Generate (or don't) code for the GNU linker.  This is the default.

       -mno-pic
           Generate  code  that  does not use a global pointer register.  The result is not position
           independent code, and violates the IA-64 ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
           Generate (or don't) a stop bit immediately before and after volatile asm statements.

       -mregister-names
       -mno-register-names
           Generate (or don't) in, loc, and out register names for the stacked registers.  This  may
           make assembler output more readable.

       -mno-sdata
       -msdata
           Disable  (or  enable)  optimizations that use the small data section.  This may be useful
           for working around optimizer bugs.

       -mconstant-gp
           Generate code that uses a single constant global pointer  value.   This  is  useful  when
           compiling kernel code.

       -mauto-pic
           Generate code that is self-relocatable.  This implies -mconstant-gp.  This is useful when
           compiling firmware code.

       -minline-float-divide-min-latency
           Generate  code  for  inline  divides  of  floating-point values using the minimum latency
           algorithm.

       -minline-float-divide-max-throughput
           Generate code for inline divides of floating-point values using  the  maximum  throughput
           algorithm.

       -mno-inline-float-divide
           Do not generate inline code for divides of floating-point values.

       -minline-int-divide-min-latency
           Generate code for inline divides of integer values using the minimum latency algorithm.

       -minline-int-divide-max-throughput
           Generate  code  for  inline  divides  of  integer  values  using  the  maximum throughput
           algorithm.

       -mno-inline-int-divide
           Do not generate inline code for divides of integer values.

       -minline-sqrt-min-latency
           Generate code for inline square roots using the minimum latency algorithm.

       -minline-sqrt-max-throughput
           Generate code for inline square roots using the maximum throughput algorithm.

       -mno-inline-sqrt
           Do not generate inline code for "sqrt".

       -mfused-madd
       -mno-fused-madd
           Do  (don't)  generate  code  that  uses  the  fused  multiply/add  or   multiply/subtract
           instructions.  The default is to use these instructions.

       -mno-dwarf2-asm
       -mdwarf2-asm
           Don't (or do) generate assembler code for the DWARF line number debugging info.  This may
           be useful when not using the GNU assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
           Allow  stop  bits  to  be  placed earlier than immediately preceding the instruction that
           triggered the stop bit.  This can improve instruction scheduling, but does not always  do
           so.

       -mfixed-range=register-range
           Generate  code treating the given register range as fixed registers.  A fixed register is
           one that the register allocator cannot use.  This is useful when compiling  kernel  code.
           A  register  range  is specified as two registers separated by a dash.  Multiple register
           ranges can be specified separated by a comma.

       -mtls-size=tls-size
           Specify bit size of immediate TLS offsets.  Valid values are 14, 22, and 64.

       -mtune=cpu-type
           Tune the instruction scheduling for a particular CPU, Valid values are itanium, itanium1,
           merced, itanium2, and mckinley.

       -milp32
       -mlp64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int,  long
           and  pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and pointer
           to 64 bits.  These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
           (Dis/En)able data speculative scheduling before reload.  This results  in  generation  of
           "ld.a"  instructions  and  the  corresponding check instructions ("ld.c" / "chk.a").  The
           default setting is disabled.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
           (En/Dis)able data speculative scheduling after reload.  This  results  in  generation  of
           "ld.a"  instructions  and  the  corresponding check instructions ("ld.c" / "chk.a").  The
           default setting is enabled.

       -mno-sched-control-spec
       -msched-control-spec
           (Dis/En)able control speculative scheduling.   This  feature  is  available  only  during
           region  scheduling  (i.e.  before  reload).   This  results  in  generation of the "ld.s"
           instructions and the corresponding check instructions "chk.s".  The  default  setting  is
           disabled.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
           (En/Dis)able  speculative  scheduling  of the instructions that are dependent on the data
           speculative loads before  reload.   This  is  effective  only  with  -msched-br-data-spec
           enabled.  The default setting is enabled.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
           (En/Dis)able  speculative  scheduling  of the instructions that are dependent on the data
           speculative loads  after  reload.   This  is  effective  only  with  -msched-ar-data-spec
           enabled.  The default setting is enabled.

       -msched-in-control-spec
       -mno-sched-in-control-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on the control
           speculative  loads.   This  is  effective  only  with  -msched-control-spec enabled.  The
           default setting is enabled.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
           If enabled, data-speculative instructions are chosen for schedule only if  there  are  no
           other  choices  at  the  moment.   This  makes  the use of the data speculation much more
           conservative.  The default setting is disabled.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
           If enabled, control-speculative instructions are chosen for schedule only if there are no
           other choices at the moment.  This makes the use of the  control  speculation  much  more
           conservative.  The default setting is disabled.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
           If   enabled,   speculative   dependencies  are  considered  during  computation  of  the
           instructions priorities.  This makes the use of the speculation a bit more  conservative.
           The default setting is disabled.

       -msched-spec-ldc
           Use a simple data speculation check.  This option is on by default.

       -msched-control-spec-ldc
           Use a simple check for control speculation.  This option is on by default.

       -msched-stop-bits-after-every-cycle
           Place a stop bit after every cycle when scheduling.  This option is on by default.

       -msched-fp-mem-deps-zero-cost
           Assume  that  floating-point  stores  and  loads  are not likely to cause a conflict when
           placed into the same instruction group.  This option is disabled by default.

       -msel-sched-dont-check-control-spec
           Generate checks for control speculation in selective scheduling.  This flag  is  disabled
           by default.

       -msched-max-memory-insns=max-insns
           Limit  on  the  number  of  memory  insns per instruction group, giving lower priority to
           subsequent memory insns attempting to schedule in the same instruction group.  Frequently
           useful to prevent cache bank conflicts.  The default value is 1.

       -msched-max-memory-insns-hard-limit
           Makes  the limit specified by msched-max-memory-insns a hard limit, disallowing more than
           that number in an instruction group.  Otherwise, the limit is "soft", meaning  that  non-
           memory  operations  are  preferred  when  the limit is reached, but memory operations may
           still be scheduled.

       LM32 Options

       These -m options are defined for the LatticeMico32 architecture:

       -mbarrel-shift-enabled
           Enable barrel-shift instructions.

       -mdivide-enabled
           Enable divide and modulus instructions.

       -mmultiply-enabled
           Enable multiply instructions.

       -msign-extend-enabled
           Enable sign extend instructions.

       -muser-enabled
           Enable user-defined instructions.

       M32C Options

       -mcpu=name
           Select the CPU for which code is generated.  name may be one  of  r8c  for  the  R8C/Tiny
           series,  m16c  for the M16C (up to /60) series, m32cm for the M16C/80 series, or m32c for
           the M32C/80 series.

       -msim
           Specifies that the program will be run  on  the  simulator.   This  causes  an  alternate
           runtime  library to be linked in which supports, for example, file I/O.  You must not use
           this option when generating programs that will run on real  hardware;  you  must  provide
           your own runtime library for whatever I/O functions are needed.

       -memregs=number
           Specifies  the  number  of memory-based pseudo-registers GCC uses during code generation.
           These pseudo-registers are used like real registers, so there is a tradeoff between GCC's
           ability to fit the code into available registers, and the performance  penalty  of  using
           memory  instead  of  registers.  Note that all modules in a program must be compiled with
           the same value for this option.  Because of that, you must not use this option with GCC's
           default runtime libraries.

       M32R/D Options

       These -m options are defined for Renesas M32R/D architectures:

       -m32r2
           Generate code for the M32R/2.

       -m32rx
           Generate code for the M32R/X.

       -m32r
           Generate code for the M32R.  This is the default.

       -mmodel=small
           Assume all objects live in the lower 16MB of memory  (so  that  their  addresses  can  be
           loaded  with  the  "ld24" instruction), and assume all subroutines are reachable with the
           "bl" instruction.  This is the default.

           The addressability of a particular object can be set with the "model" attribute.

       -mmodel=medium
           Assume objects may be anywhere in  the  32-bit  address  space  (the  compiler  generates
           "seth/add3"  instructions  to  load  their  addresses),  and  assume  all subroutines are
           reachable with the "bl" instruction.

       -mmodel=large
           Assume objects may be anywhere in  the  32-bit  address  space  (the  compiler  generates
           "seth/add3"  instructions  to  load  their  addresses), and assume subroutines may not be
           reachable  with  the  "bl"  instruction  (the  compiler   generates   the   much   slower
           "seth/add3/jl" instruction sequence).

       -msdata=none
           Disable  use  of  the small data area.  Variables are put into one of ".data", ".bss", or
           ".rodata" (unless the "section" attribute has been specified).  This is the default.

           The small data area consists of sections ".sdata" and ".sbss".  Objects may be explicitly
           put in the small data area with the "section" attribute using one of these sections.

       -msdata=sdata
           Put small global and static data in the small data area, but do not generate special code
           to reference them.

       -msdata=use
           Put small  global  and  static  data  in  the  small  data  area,  and  generate  special
           instructions to reference them.

       -G num
           Put  global and static objects less than or equal to num bytes into the small data or BSS
           sections instead of the normal data or BSS sections.  The default value of num is 8.  The
           -msdata option must be set to one of sdata or use for this option to have any effect.

           All modules should be compiled with the same -G  num  value.   Compiling  with  different
           values  of  num  may  or  may  not  work;  if  it  doesn't  the  linker  gives  an  error
           message---incorrect code is not generated.

       -mdebug
           Makes the M32R-specific code in the compiler display some statistics that might  help  in
           debugging programs.

       -malign-loops
           Align all loops to a 32-byte boundary.

       -mno-align-loops
           Do not enforce a 32-byte alignment for loops.  This is the default.

       -missue-rate=number
           Issue number instructions per cycle.  number can only be 1 or 2.

       -mbranch-cost=number
           number can only be 1 or 2.  If it is 1 then branches are preferred over conditional code,
           if it is 2, then the opposite applies.

       -mflush-trap=number
           Specifies  the  trap number to use to flush the cache.  The default is 12.  Valid numbers
           are between 0 and 15 inclusive.

       -mno-flush-trap
           Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
           Specifies the name of the operating system function to call  to  flush  the  cache.   The
           default is _flush_cache, but a function call is only used if a trap is not available.

       -mno-flush-func
           Indicates that there is no OS function for flushing the cache.

       M680x0 Options

       These  are  the  -m options defined for M680x0 and ColdFire processors.  The default settings
       depend on which architecture was selected when the compiler was configured; the defaults  for
       the most common choices are given below.

       -march=arch
           Generate   code   for  a  specific  M680x0  or  ColdFire  instruction  set  architecture.
           Permissible values of arch for M680x0 architectures  are:  68000,  68010,  68020,  68030,
           68040, 68060 and cpu32.  ColdFire architectures are selected according to Freescale's ISA
           classification and the permissible values are: isaa, isaaplus, isab and isac.

           GCC  defines  a macro "__mcfarch__" whenever it is generating code for a ColdFire target.
           The arch in this macro is one of the -march arguments given above.

           When used together, -march and -mtune select code  that  runs  on  a  family  of  similar
           processors but that is optimized for a particular microarchitecture.

       -mcpu=cpu
           Generate  code  for a specific M680x0 or ColdFire processor.  The M680x0 cpus are: 68000,
           68010, 68020, 68030, 68040, 68060, 68302, 68332 and cpu32.  The ColdFire cpus  are  given
           by the table below, which also classifies the CPUs into families:

           Family : -mcpu arguments
           51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm
           5206 : 5202 5204 5206
           5206e : 5206e
           5208 : 5207 5208
           5211a : 5210a 5211a
           5213 : 5211 5212 5213
           5216 : 5214 5216
           52235 : 52230 52231 52232 52233 52234 52235
           5225 : 5224 5225
           52259 : 52252 52254 52255 52256 52258 52259
           5235 : 5232 5233 5234 5235 523x
           5249 : 5249
           5250 : 5250
           5271 : 5270 5271
           5272 : 5272
           5275 : 5274 5275
           5282 : 5280 5281 5282 528x
           53017 : 53011 53012 53013 53014 53015 53016 53017
           5307 : 5307
           5329 : 5327 5328 5329 532x
           5373 : 5372 5373 537x
           5407 : 5407
           5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483 5484 5485

           -mcpu=cpu  overrides  -march=arch  if arch is compatible with cpu.  Other combinations of
           -mcpu and -march are rejected.

           GCC defines the macro "__mcf_cpu_cpu" when ColdFire target  cpu  is  selected.   It  also
           defines "__mcf_family_family", where the value of family is given by the table above.

       -mtune=tune
           Tune the code for a particular microarchitecture within the constraints set by -march and
           -mcpu.   The  M680x0 microarchitectures are: 68000, 68010, 68020, 68030, 68040, 68060 and
           cpu32.  The ColdFire microarchitectures are: cfv1, cfv2, cfv3, cfv4 and cfv4e.

           You can also use -mtune=68020-40 for code that needs to run  relatively  well  on  68020,
           68030  and 68040 targets.  -mtune=68020-60 is similar but includes 68060 targets as well.
           These two  options  select  the  same  tuning  decisions  as  -m68020-40  and  -m68020-60
           respectively.

           GCC  defines  the  macros  "__mcarch" and "__mcarch__" when tuning for 680x0 architecture
           arch.  It also defines "mcarch" unless either -ansi or a non-GNU -std option is used.  If
           GCC  is  tuning  for  a  range  of  architectures,  as  selected  by  -mtune=68020-40  or
           -mtune=68020-60, it defines the macros for every architecture in the range.

           GCC also defines the macro "__muarch__" when tuning for ColdFire microarchitecture uarch,
           where uarch is one of the arguments given above.

       -m68000
       -mc68000
           Generate  output  for  a  68000.  This is the default when the compiler is configured for
           68000-based systems.  It is equivalent to -march=68000.

           Use this option for microcontrollers with a 68000 or EC000  core,  including  the  68008,
           68302, 68306, 68307, 68322, 68328 and 68356.

       -m68010
           Generate  output  for  a  68010.  This is the default when the compiler is configured for
           68010-based systems.  It is equivalent to -march=68010.

       -m68020
       -mc68020
           Generate output for a 68020.  This is the default when the  compiler  is  configured  for
           68020-based systems.  It is equivalent to -march=68020.

       -m68030
           Generate  output  for  a  68030.  This is the default when the compiler is configured for
           68030-based systems.  It is equivalent to -march=68030.

       -m68040
           Generate output for a 68040.  This is the default when the  compiler  is  configured  for
           68040-based systems.  It is equivalent to -march=68040.

           This  option  inhibits  the  use  of 68881/68882 instructions that have to be emulated by
           software on the 68040.  Use this option if your 68040 does not have code to emulate those
           instructions.

       -m68060
           Generate output for a 68060.  This is the default when the  compiler  is  configured  for
           68060-based systems.  It is equivalent to -march=68060.

           This  option  inhibits  the  use  of  68020  and 68881/68882 instructions that have to be
           emulated by software on the 68060.  Use this option if your 68060 does not have  code  to
           emulate those instructions.

       -mcpu32
           Generate  output  for  a  CPU32.  This is the default when the compiler is configured for
           CPU32-based systems.  It is equivalent to -march=cpu32.

           Use this option for microcontrollers with a CPU32 or CPU32+ core,  including  the  68330,
           68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349 and 68360.

       -m5200
           Generate  output  for  a  520X  ColdFire  CPU.   This is the default when the compiler is
           configured for 520X-based systems.  It is equivalent to -mcpu=5206, and is now deprecated
           in favor of that option.

           Use this option for microcontroller with a 5200 core,  including  the  MCF5202,  MCF5203,
           MCF5204 and MCF5206.

       -m5206e
           Generate  output  for a 5206e ColdFire CPU.  The option is now deprecated in favor of the
           equivalent -mcpu=5206e.

       -m528x
           Generate output for a member of the ColdFire 528X family.  The option is  now  deprecated
           in favor of the equivalent -mcpu=528x.

       -m5307
           Generate  output  for  a ColdFire 5307 CPU.  The option is now deprecated in favor of the
           equivalent -mcpu=5307.

       -m5407
           Generate output for a ColdFire 5407 CPU.  The option is now deprecated in  favor  of  the
           equivalent -mcpu=5407.

       -mcfv4e
           Generate  output  for  a  ColdFire V4e family CPU (e.g. 547x/548x).  This includes use of
           hardware floating-point instructions.  The option is equivalent to -mcpu=547x, and is now
           deprecated in favor of that option.

       -m68020-40
           Generate output for a 68040, without using any of the new instructions.  This results  in
           code  that  can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040.
           The generated code does use the 68881 instructions that are emulated on the 68040.

           The option is equivalent to -march=68020 -mtune=68020-40.

       -m68020-60
           Generate output for a 68060, without using any of the new instructions.  This results  in
           code  that  can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040.
           The generated code does use the 68881 instructions that are emulated on the 68060.

           The option is equivalent to -march=68020 -mtune=68020-60.

       -mhard-float
       -m68881
           Generate floating-point instructions.  This is the default for 68020 and above,  and  for
           ColdFire  devices  that  have  an  FPU.   It defines the macro "__HAVE_68881__" on M680x0
           targets and "__mcffpu__" on ColdFire targets.

       -msoft-float
           Do not generate floating-point instructions; use library  calls  instead.   This  is  the
           default for 68000, 68010, and 68832 targets.  It is also the default for ColdFire devices
           that have no FPU.

       -mdiv
       -mno-div
           Generate  (do  not  generate)  ColdFire  hardware  divide and remainder instructions.  If
           -march is used without -mcpu, the default is "on" for ColdFire  architectures  and  "off"
           for  M680x0  architectures.   Otherwise, the default is taken from the target CPU (either
           the default CPU, or the one specified by -mcpu).  For example, the default is  "off"  for
           -mcpu=5206 and "on" for -mcpu=5206e.

           GCC defines the macro "__mcfhwdiv__" when this option is enabled.

       -mshort
           Consider  type  "int"  to  be  16  bits wide, like "short int".  Additionally, parameters
           passed on the stack are also aligned to a 16-bit  boundary  even  on  targets  whose  API
           mandates promotion to 32-bit.

       -mno-short
           Do not consider type "int" to be 16 bits wide.  This is the default.

       -mnobitfield
       -mno-bitfield
           Do  not  use  the  bit-field instructions.  The -m68000, -mcpu32 and -m5200 options imply
           -mnobitfield.

       -mbitfield
           Do use the bit-field instructions.  The -m68020 option implies -mbitfield.  This  is  the
           default if you use a configuration designed for a 68020.

       -mrtd
           Use  a different function-calling convention, in which functions that take a fixed number
           of arguments return  with  the  "rtd"  instruction,  which  pops  their  arguments  while
           returning.   This  saves  one instruction in the caller since there is no need to pop the
           arguments there.

           This calling convention is incompatible with the one normally used on Unix, so you cannot
           use it if you need to call libraries compiled with the Unix compiler.

           Also, you must provide function prototypes for all functions that take  variable  numbers
           of  arguments  (including  "printf");  otherwise incorrect code is generated for calls to
           those functions.

           In addition, seriously incorrect code results if  you  call  a  function  with  too  many
           arguments.  (Normally, extra arguments are harmlessly ignored.)

           The  "rtd"  instruction  is  supported by the 68010, 68020, 68030, 68040, 68060 and CPU32
           processors, but not by the 68000 or 5200.

           The default is -mno-rtd.

       -malign-int
       -mno-align-int
           Control whether GCC aligns "int", "long",  "long  long",  "float",  "double",  and  "long
           double"   variables   on   a   32-bit   boundary   (-malign-int)  or  a  16-bit  boundary
           (-mno-align-int).  Aligning variables  on  32-bit  boundaries  produces  code  that  runs
           somewhat faster on processors with 32-bit busses at the expense of more memory.

           Warning:  if  you  use the -malign-int switch, GCC aligns structures containing the above
           types differently than most published application binary interface specifications for the
           m68k.

           Use the pc-relative addressing mode of the 68000 directly,  instead  of  using  a  global
           offset  table.   At  present, this option implies -fpic, allowing at most a 16-bit offset
           for pc-relative addressing.  -fPIC is not presently supported with -mpcrel,  though  this
           could be supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
           Do not (do) assume that unaligned memory references are handled by the system.

       -msep-data
           Generate  code  that  allows the data segment to be located in a different area of memory
           from the text segment.  This  allows  for  execute-in-place  in  an  environment  without
           virtual memory management.  This option implies -fPIC.

       -mno-sep-data
           Generate  code  that assumes that the data segment follows the text segment.  This is the
           default.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID method.  This allows  for
           execute-in-place   and   shared  libraries  in  an  environment  without  virtual  memory
           management.  This option implies -fPIC.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are being used.  This is  the
           default.

       -mshared-library-id=n
           Specifies  the  identification  number  of  the  ID-based  shared library being compiled.
           Specifying a value of 0 generates more compact code; specifying other values  forces  the
           allocation of that number to the current library, but is no more space- or time-efficient
           than omitting this option.

       -mxgot
       -mno-xgot
           When  generating  position-independent code for ColdFire, generate code that works if the
           GOT has more than 8192 entries.  This code is  larger  and  slower  than  code  generated
           without this option.  On M680x0 processors, this option is not needed; -fPIC suffices.

           GCC  normally  uses  a  single  instruction  to  load values from the GOT.  While this is
           relatively efficient, it only works if the GOT  is  smaller  than  about  64k.   Anything
           larger causes the linker to report an error such as:

                   relocation truncated to fit: R_68K_GOT16O foobar

           If  this  happens,  you should recompile your code with -mxgot.  It should then work with
           very large GOTs.  However, code generated with -mxgot is less efficient, since it takes 4
           instructions to fetch the value of a global symbol.

           Note that some linkers, including newer versions of the GNU linker, can  create  multiple
           GOTs and sort GOT entries.  If you have such a linker, you should only need to use -mxgot
           when  compiling  a single object file that accesses more than 8192 GOT entries.  Very few
           do.

           These options have no effect unless GCC is generating position-independent code.

       -mlong-jump-table-offsets
           Use 32-bit offsets in "switch" tables.  The default is to use 16-bit offsets.

       MCore Options

       These are the -m options defined for the Motorola M*Core processors.

       -mhardlit
       -mno-hardlit
           Inline constants into the code stream if it can be done in two instructions or less.

       -mdiv
       -mno-div
           Use the divide instruction.  (Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
           Allow arbitrary-sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
           Always treat bit-fields as "int"-sized.

       -m4byte-functions
       -mno-4byte-functions
           Force all functions to be aligned to a 4-byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
           Emit callgraph information.

       -mslow-bytes
       -mno-slow-bytes
           Prefer word access when reading byte quantities.

       -mlittle-endian
       -mbig-endian
           Generate code for a little-endian target.

       -m210
       -m340
           Generate code for the 210 processor.

       -mno-lsim
           Assume that runtime  support  has  been  provided  and  so  omit  the  simulator  library
           (libsim.a) from the linker command line.

       -mstack-increment=size
           Set the maximum amount for a single stack increment operation.  Large values can increase
           the speed of programs that contain functions that need a large amount of stack space, but
           they  can  also  trigger  a  segmentation  fault  if the stack is extended too much.  The
           default value is 0x1000.

       MeP Options

       -mabsdiff
           Enables the "abs" instruction, which is the absolute difference between two registers.

       -mall-opts
           Enables all  the  optional  instructions---average,  multiply,  divide,  bit  operations,
           leading zero, absolute difference, min/max, clip, and saturation.

       -maverage
           Enables the "ave" instruction, which computes the average of two registers.

       -mbased=n
           Variables  of  size  n  bytes  or  smaller are placed in the ".based" section by default.
           Based variables use the $tp register as a base register, and there is a 128-byte limit to
           the ".based" section.

       -mbitops
           Enables the  bit  operation  instructions---bit  test  ("btstm"),  set  ("bsetm"),  clear
           ("bclrm"), invert ("bnotm"), and test-and-set ("tas").

       -mc=name
           Selects which section constant data is placed in.  name may be tiny, near, or far.

       -mclip
           Enables  the  "clip" instruction.  Note that -mclip is not useful unless you also provide
           -mminmax.

       -mconfig=name
           Selects one of the built-in core configurations.  Each MeP chip has one or  more  modules
           in  it;  each module has a core CPU and a variety of coprocessors, optional instructions,
           and  peripherals.   The  "MeP-Integrator"  tool,  not  part  of   GCC,   provides   these
           configurations  through  this  option;  using  this  option  is the same as using all the
           corresponding command-line options.  The default configuration is default.

       -mcop
           Enables the coprocessor instructions.  By default, this is a  32-bit  coprocessor.   Note
           that the coprocessor is normally enabled via the -mconfig= option.

       -mcop32
           Enables the 32-bit coprocessor's instructions.

       -mcop64
           Enables the 64-bit coprocessor's instructions.

       -mivc2
           Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW coprocessor.

       -mdc
           Causes constant variables to be placed in the ".near" section.

       -mdiv
           Enables the "div" and "divu" instructions.

       -meb
           Generate big-endian code.

       -mel
           Generate little-endian code.

       -mio-volatile
           Tells  the  compiler that any variable marked with the "io" attribute is to be considered
           volatile.

       -ml Causes variables to be assigned to the ".far" section by default.

       -mleadz
           Enables the "leadz" (leading zero) instruction.

       -mm Causes variables to be assigned to the ".near" section by default.

       -mminmax
           Enables the "min" and "max" instructions.

       -mmult
           Enables the multiplication and multiply-accumulate instructions.

       -mno-opts
           Disables all the optional instructions enabled by -mall-opts.

       -mrepeat
           Enables the "repeat" and "erepeat" instructions, used for low-overhead looping.

       -ms Causes all variables to default to the ".tiny" section.  Note that there is a  65536-byte
           limit to this section.  Accesses to these variables use the %gp base register.

       -msatur
           Enables  the saturation instructions.  Note that the compiler does not currently generate
           these itself, but this option is included for compatibility with other tools, like "as".

       -msdram
           Link the SDRAM-based runtime instead of the default ROM-based runtime.

       -msim
           Link the simulator run-time libraries.

       -msimnovec
           Link the simulator runtime libraries, excluding built-in support for reset and  exception
           vectors and tables.

       -mtf
           Causes  all  functions  to default to the ".far" section.  Without this option, functions
           default to the ".near" section.

       -mtiny=n
           Variables that are n bytes or smaller  are  allocated  to  the  ".tiny"  section.   These
           variables  use  the  $gp  base register.  The default for this option is 4, but note that
           there's a 65536-byte limit to the ".tiny" section.

       MicroBlaze Options

       -msoft-float
           Use software emulation for floating point (default).

       -mhard-float
           Use hardware floating-point instructions.

       -mmemcpy
           Do not optimize block moves, use "memcpy".

       -mno-clearbss
           This option is deprecated.  Use -fno-zero-initialized-in-bss instead.

       -mcpu=cpu-type
           Use features of, and schedule code for, the given  CPU.   Supported  values  are  in  the
           format  vX.YY.Z,  where  X  is  a  major  version,  YY  is  the  minor  version, and Z is
           compatibility code.  Example values are v3.00.a, v4.00.b, v5.00.a, v5.00.b, v6.00.a.

       -mxl-soft-mul
           Use software multiply emulation (default).

       -mxl-soft-div
           Use software emulation for divides (default).

       -mxl-barrel-shift
           Use the hardware barrel shifter.

       -mxl-pattern-compare
           Use pattern compare instructions.

       -msmall-divides
           Use table lookup optimization for small signed integer divisions.

       -mxl-stack-check
           This option is deprecated.  Use -fstack-check instead.

       -mxl-gp-opt
           Use GP-relative ".sdata"/".sbss" sections.

       -mxl-multiply-high
           Use multiply high instructions for high part of 32x32 multiply.

       -mxl-float-convert
           Use hardware floating-point conversion instructions.

       -mxl-float-sqrt
           Use hardware floating-point square root instruction.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.

       -mxl-reorder
           Use reorder instructions (swap and byte reversed load/store).

       -mxl-mode-app-model
           Select application model app-model.  Valid models are

           executable
               normal executable (default), uses startup code crt0.o.

           -mpic-data-is-text-relative
               Assume that the displacement between the text and data segments is  fixed  at  static
               link  time.   This  allows data to be referenced by offset from start of text address
               instead of GOT since PC-relative addressing is not supported.

           xmdstub
               for use with Xilinx Microprocessor Debugger  (XMD)  based  software  intrusive  debug
               agent called xmdstub. This uses startup file crt1.o and sets the start address of the
               program to 0x800.

           bootstrap
               for  applications  that  are loaded using a bootloader.  This model uses startup file
               crt2.o which does not contain a processor reset vector handler. This is suitable  for
               transferring  control  on  a  processor  reset  to  the  bootloader  rather  than the
               application.

           novectors
               for applications that do not require any of the MicroBlaze vectors. This  option  may
               be  useful  for applications running within a monitoring application. This model uses
               crt3.o as a startup file.

           Option -xl-mode-app-model is a deprecated alias for -mxl-mode-app-model.

       MIPS Options

       -EB Generate big-endian code.

       -EL Generate little-endian code.  This is the default for mips*el-*-* configurations.

       -march=arch
           Generate code that runs on arch, which can be the name of a generic MIPS ISA, or the name
           of a particular processor.  The ISA  names  are:  mips1,  mips2,  mips3,  mips4,  mips32,
           mips32r2,   mips32r3,  mips32r5,  mips32r6,  mips64,  mips64r2,  mips64r3,  mips64r5  and
           mips64r6.  The processor names are: 4kc, 4km, 4kp, 4ksc, 4kec,  4kem,  4kep,  4ksd,  5kc,
           5kf,  20kc,  24kc,  24kf2_1,  24kf1_1, 24kec, 24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1,
           34kn, 74kc, 74kf2_1,  74kf1_1,  74kf3_2,  1004kc,  1004kf2_1,  1004kf1_1,  i6400,  i6500,
           interaptiv,  loongson2e, loongson2f, loongson3a, gs464, gs464e, gs264e, m4k, m14k, m14kc,
           m14ke, m14kec, m5100, m5101, octeon, octeon+,  octeon2,  octeon3,  orion,  p5600,  p6600,
           r2000,  r3000,  r3900,  r4000,  r4400,  r4600, r4650, r4700, r5900, r6000, r8000, rm7000,
           rm9000, r10000, r12000, r14000, r16000, sb1, sr71000,  vr4100,  vr4111,  vr4120,  vr4130,
           vr4300, vr5000, vr5400, vr5500, xlr and xlp.  The special value from-abi selects the most
           compatible  architecture  for  the selected ABI (that is, mips1 for 32-bit ABIs and mips3
           for 64-bit ABIs).

           The native Linux/GNU toolchain also supports the value native,  which  selects  the  best
           architecture  option for the host processor.  -march=native has no effect if GCC does not
           recognize the processor.

           In processor names, a final 000 can  be  abbreviated  as  k  (for  example,  -march=r2k).
           Prefixes are optional, and vr may be written r.

           Names  of  the  form  nf2_1 refer to processors with FPUs clocked at half the rate of the
           core, names of the form nf1_1 refer to processors with FPUs clocked at the same  rate  as
           the  core,  and  names of the form nf3_2 refer to processors with FPUs clocked a ratio of
           3:2 with respect to the core.  For compatibility reasons, nf is accepted as a synonym for
           nf2_1 while nx and bfx are accepted as synonyms for nf1_1.

           GCC defines two macros based on the value of this option.   The  first  is  "_MIPS_ARCH",
           which  gives  the  name  of  target  architecture,  as a string.  The second has the form
           "_MIPS_ARCH_foo", where foo is the  capitalized  value  of  "_MIPS_ARCH".   For  example,
           -march=r2000 sets "_MIPS_ARCH" to "r2000" and defines the macro "_MIPS_ARCH_R2000".

           Note  that  the "_MIPS_ARCH" macro uses the processor names given above.  In other words,
           it has the full prefix and does not abbreviate 000 as k.  In the case  of  from-abi,  the
           macro  names the resolved architecture (either "mips1" or "mips3").  It names the default
           architecture when no -march option is given.

       -mtune=arch
           Optimize for arch.  Among other things, this option controls  the  way  instructions  are
           scheduled,  and  the perceived cost of arithmetic operations.  The list of arch values is
           the same as for -march.

           When this option is not used, GCC optimizes for the processor specified  by  -march.   By
           using  -march  and -mtune together, it is possible to generate code that runs on a family
           of processors, but optimize the code for one particular member of that family.

           -mtune defines the macros "_MIPS_TUNE" and "_MIPS_TUNE_foo", which work in the  same  way
           as the -march ones described above.

       -mips1
           Equivalent to -march=mips1.

       -mips2
           Equivalent to -march=mips2.

       -mips3
           Equivalent to -march=mips3.

       -mips4
           Equivalent to -march=mips4.

       -mips32
           Equivalent to -march=mips32.

       -mips32r3
           Equivalent to -march=mips32r3.

       -mips32r5
           Equivalent to -march=mips32r5.

       -mips32r6
           Equivalent to -march=mips32r6.

       -mips64
           Equivalent to -march=mips64.

       -mips64r2
           Equivalent to -march=mips64r2.

       -mips64r3
           Equivalent to -march=mips64r3.

       -mips64r5
           Equivalent to -march=mips64r5.

       -mips64r6
           Equivalent to -march=mips64r6.

       -mips16
       -mno-mips16
           Generate  (do  not  generate)  MIPS16  code.   If  GCC  is  targeting  a MIPS32 or MIPS64
           architecture, it makes use of the MIPS16e ASE.

           MIPS16 code generation can also be  controlled  on  a  per-function  basis  by  means  of
           "mips16" and "nomips16" attributes.

       -mflip-mips16
           Generate  MIPS16  code  on alternating functions.  This option is provided for regression
           testing of mixed MIPS16/non-MIPS16 code generation, and is not intended for ordinary  use
           in compiling user code.

       -minterlink-compressed
       -mno-interlink-compressed
           Require  (do  not  require) that code using the standard (uncompressed) MIPS ISA be link-
           compatible with MIPS16 and microMIPS code, and vice versa.

           For example, code using the standard ISA encoding  cannot  jump  directly  to  MIPS16  or
           microMIPS  code;  it  must either use a call or an indirect jump.  -minterlink-compressed
           therefore disables direct jumps unless GCC knows that the  target  of  the  jump  is  not
           compressed.

       -minterlink-mips16
       -mno-interlink-mips16
           Aliases  of  -minterlink-compressed and -mno-interlink-compressed.  These options predate
           the microMIPS ASE and are retained for backwards compatibility.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
           Generate code for the given ABI.

           Note that the EABI has a 32-bit and a 64-bit variant.  GCC normally generates 64-bit code
           when you select a 64-bit architecture, but you can use -mgp32 to get 32-bit code instead.

           For information about the O64 ABI, see <http://gcc.gnu.org/projects/mipso64-abi.html>.

           GCC supports a variant of the o32 ABI in which floating-point  registers  are  64  rather
           than  32  bits  wide.   You  can  select this combination with -mabi=32 -mfp64.  This ABI
           relies on the "mthc1" and "mfhc1"  instructions  and  is  therefore  only  supported  for
           MIPS32R2, MIPS32R3 and MIPS32R5 processors.

           The register assignments for arguments and return values remain the same, but each scalar
           value  is passed in a single 64-bit register rather than a pair of 32-bit registers.  For
           example, scalar floating-point values are returned in $f0 only, not a $f0/$f1 pair.   The
           set  of  call-saved  registers  also  remains  the same in that the even-numbered double-
           precision registers are saved.

           Two additional variants of the o32 ABI are supported to enable a transition  from  32-bit
           to  64-bit  registers.   These  are FPXX (-mfpxx) and FP64A (-mfp64 -mno-odd-spreg).  The
           FPXX extension mandates that all code must execute correctly when  run  using  32-bit  or
           64-bit  registers.   The  code can be interlinked with either FP32 or FP64, but not both.
           The FP64A extension is similar to the FP64 extension but forbids the use of  odd-numbered
           single-precision  registers.  This can be used in conjunction with the "FRE" mode of FPUs
           in MIPS32R5 processors and allows both FP32 and FP64A code to interlink and  run  in  the
           same process without changing FPU modes.

       -mabicalls
       -mno-abicalls
           Generate  (do  not  generate)  code  that  is  suitable  for  SVR4-style dynamic objects.
           -mabicalls is the default for SVR4-based systems.

       -mshared
       -mno-shared
           Generate (do not  generate)  code  that  is  fully  position-independent,  and  that  can
           therefore be linked into shared libraries.  This option only affects -mabicalls.

           All  -mabicalls  code  has traditionally been position-independent, regardless of options
           like -fPIC and -fpic.  However, as an extension, the GNU toolchain allows executables  to
           use  absolute  accesses  for  locally-binding  symbols.   It  can  also  use  shorter  GP
           initialization sequences and generate direct calls to  locally-defined  functions.   This
           mode is selected by -mno-shared.

           -mno-shared  depends  on  binutils  2.16 or higher and generates objects that can only be
           linked by the GNU linker.  However, the option does not  affect  the  ABI  of  the  final
           executable;  it only affects the ABI of relocatable objects.  Using -mno-shared generally
           makes executables both smaller and quicker.

           -mshared is the default.

       -mplt
       -mno-plt
           Assume (do not assume) that  the  static  and  dynamic  linkers  support  PLTs  and  copy
           relocations.   This  option  only  affects -mno-shared -mabicalls.  For the n64 ABI, this
           option has no effect without -msym32.

           You can make -mplt the default by configuring GCC with --with-mips-plt.  The  default  is
           -mno-plt otherwise.

       -mxgot
       -mno-xgot
           Lift (do not lift) the usual restrictions on the size of the global offset table.

           GCC  normally  uses  a  single  instruction  to  load values from the GOT.  While this is
           relatively efficient, it only works if the GOT  is  smaller  than  about  64k.   Anything
           larger causes the linker to report an error such as:

                   relocation truncated to fit: R_MIPS_GOT16 foobar

           If  this happens, you should recompile your code with -mxgot.  This works with very large
           GOTs, although the code is also less efficient, since  it  takes  three  instructions  to
           fetch the value of a global symbol.

           Note  that  some linkers can create multiple GOTs.  If you have such a linker, you should
           only need to use -mxgot when a single object file accesses more than 64k's worth  of  GOT
           entries.  Very few do.

           These options have no effect unless GCC is generating position independent code.

       -mgp32
           Assume that general-purpose registers are 32 bits wide.

       -mgp64
           Assume that general-purpose registers are 64 bits wide.

       -mfp32
           Assume that floating-point registers are 32 bits wide.

       -mfp64
           Assume that floating-point registers are 64 bits wide.

       -mfpxx
           Do not assume the width of floating-point registers.

       -mhard-float
           Use floating-point coprocessor instructions.

       -msoft-float
           Do   not   use   floating-point   coprocessor   instructions.   Implement  floating-point
           calculations using library calls instead.

       -mno-float
           Equivalent to -msoft-float, but additionally asserts that the program being compiled does
           not perform any floating-point operations.  This option is presently  supported  only  by
           some  bare-metal MIPS configurations, where it may select a special set of libraries that
           lack all floating-point support (including,  for  example,  the  floating-point  "printf"
           formats).    If  code  compiled  with  -mno-float  accidentally  contains  floating-point
           operations, it is likely to suffer a link-time or run-time failure.

       -msingle-float
           Assume that the floating-point coprocessor only supports single-precision operations.

       -mdouble-float
           Assume that the floating-point coprocessor supports double-precision operations.  This is
           the default.

       -modd-spreg
       -mno-odd-spreg
           Enable the use of odd-numbered single-precision floating-point registers for the o32 ABI.
           This is the default for processors that are known to support these registers.  When using
           the o32 FPXX ABI, -mno-odd-spreg is set by default.

       -mabs=2008
       -mabs=legacy
           These options control the treatment of the special not-a-number (NaN) IEEE 754  floating-
           point data with the "abs.fmt" and "neg.fmt" machine instructions.

           By  default  or when -mabs=legacy is used the legacy treatment is selected.  In this case
           these instructions are considered arithmetic  and  avoided  where  correct  operation  is
           required  and  the  input operand might be a NaN.  A longer sequence of instructions that
           manipulate the sign bit of floating-point datum  manually  is  used  instead  unless  the
           -ffinite-math-only option has also been specified.

           The  -mabs=2008  option  selects  the  IEEE  754-2008  treatment.   In  this  case  these
           instructions are considered non-arithmetic  and  therefore  operating  correctly  in  all
           cases,  including in particular where the input operand is a NaN.  These instructions are
           therefore always used for the respective operations.

       -mnan=2008
       -mnan=legacy
           These options control the encoding of the special not-a-number (NaN) IEEE  754  floating-
           point data.

           The -mnan=legacy option selects the legacy encoding.  In this case quiet NaNs (qNaNs) are
           denoted  by  the first bit of their trailing significand field being 0, whereas signaling
           NaNs (sNaNs) are denoted by the first bit of their trailing significand field being 1.

           The -mnan=2008 option selects the IEEE 754-2008 encoding.  In this case qNaNs are denoted
           by the first bit of their trailing significand field being 1, whereas sNaNs  are  denoted
           by the first bit of their trailing significand field being 0.

           The default is -mnan=legacy unless GCC has been configured with --with-nan=2008.

       -mllsc
       -mno-llsc
           Use  (do  not  use)  ll,  sc,  and  sync instructions to implement atomic memory built-in
           functions.  When neither option is specified, GCC uses the  instructions  if  the  target
           architecture supports them.

           -mllsc  is  useful  if the runtime environment can emulate the instructions and -mno-llsc
           can be useful when compiling for nonstandard  ISAs.   You  can  make  either  option  the
           default by configuring GCC with --with-llsc and --without-llsc respectively.  --with-llsc
           is the default for some configurations; see the installation documentation for details.

       -mdsp
       -mno-dsp
           Use (do not use) revision 1 of the MIPS DSP ASE.
             This   option   defines   the   preprocessor   macro  "__mips_dsp".   It  also  defines
           "__mips_dsp_rev" to 1.

       -mdspr2
       -mno-dspr2
           Use (do not use) revision 2 of the MIPS DSP ASE.
             This option defines the preprocessor macros "__mips_dsp" and "__mips_dspr2".   It  also
           defines "__mips_dsp_rev" to 2.

       -msmartmips
       -mno-smartmips
           Use (do not use) the MIPS SmartMIPS ASE.

       -mpaired-single
       -mno-paired-single
           Use (do not use) paired-single floating-point instructions.
             This option requires hardware floating-point support to be enabled.

       -mdmx
       -mno-mdmx
           Use (do not use) MIPS Digital Media Extension instructions.  This option can only be used
           when generating 64-bit code and requires hardware floating-point support to be enabled.

       -mips3d
       -mno-mips3d
           Use (do not use) the MIPS-3D ASE.  The option -mips3d implies -mpaired-single.

       -mmicromips
       -mno-micromips
           Generate (do not generate) microMIPS code.

           MicroMIPS  code  generation  can  also  be controlled on a per-function basis by means of
           "micromips" and "nomicromips" attributes.

       -mmt
       -mno-mt
           Use (do not use) MT Multithreading instructions.

       -mmcu
       -mno-mcu
           Use (do not use) the MIPS MCU ASE instructions.

       -meva
       -mno-eva
           Use (do not use) the MIPS Enhanced Virtual Addressing instructions.

       -mvirt
       -mno-virt
           Use (do not use) the MIPS Virtualization (VZ) instructions.

       -mxpa
       -mno-xpa
           Use (do not use) the MIPS eXtended Physical Address (XPA) instructions.

       -mcrc
       -mno-crc
           Use (do not use) the MIPS Cyclic Redundancy Check (CRC) instructions.

       -mginv
       -mno-ginv
           Use (do not use) the MIPS Global INValidate (GINV) instructions.

       -mloongson-mmi
       -mno-loongson-mmi
           Use (do not use) the MIPS Loongson MultiMedia extensions Instructions (MMI).

       -mloongson-ext
       -mno-loongson-ext
           Use (do not use) the MIPS Loongson EXTensions (EXT) instructions.

       -mloongson-ext2
       -mno-loongson-ext2
           Use (do not use) the MIPS Loongson EXTensions r2 (EXT2) instructions.

       -mlong64
           Force "long" types to be 64 bits wide.  See -mlong32 for an explanation  of  the  default
           and the way that the pointer size is determined.

       -mlong32
           Force "long", "int", and pointer types to be 32 bits wide.

           The  default  size of "int"s, "long"s and pointers depends on the ABI.  All the supported
           ABIs use 32-bit "int"s.  The n64 ABI uses 64-bit "long"s, as does the  64-bit  EABI;  the
           others  use  32-bit  "long"s.  Pointers are the same size as "long"s, or the same size as
           integer registers, whichever is smaller.

       -msym32
       -mno-sym32
           Assume (do not assume) that all symbols have 32-bit values, regardless  of  the  selected
           ABI.   This  option  is  useful in combination with -mabi=64 and -mno-abicalls because it
           allows GCC to generate shorter and faster references to symbolic addresses.

       -G num
           Put definitions of externally-visible data in a small data section if  that  data  is  no
           bigger  than  num  bytes.  GCC can then generate more efficient accesses to the data; see
           -mgpopt for details.

           The default -G option depends on the configuration.

       -mlocal-sdata
       -mno-local-sdata
           Extend (do not extend) the -G behavior to local data too, such as to static variables  in
           C.  -mlocal-sdata is the default for all configurations.

           If  the linker complains that an application is using too much small data, you might want
           to try rebuilding the less performance-critical parts with -mno-local-sdata.   You  might
           also  want  to  build  large libraries with -mno-local-sdata, so that the libraries leave
           more room for the main program.

       -mextern-sdata
       -mno-extern-sdata
           Assume (do not assume) that externally-defined data is in a small  data  section  if  the
           size  of  that  data  is  within  the  -G  limit.   -mextern-sdata is the default for all
           configurations.

           If you compile a module Mod with -mextern-sdata -G num  -mgpopt,  and  Mod  references  a
           variable Var that is no bigger than num bytes, you must make sure that Var is placed in a
           small  data  section.   If Var is defined by another module, you must either compile that
           module with a high-enough -G setting or attach a "section" attribute to Var's definition.
           If Var is common, you must link the application with a high-enough -G setting.

           The easiest way of satisfying these restrictions is to compile and link every module with
           the same -G option.  However, you may wish to  build  a  library  that  supports  several
           different  small  data limits.  You can do this by compiling the library with the highest
           supported -G setting and additionally using -mno-extern-sdata to stop  the  library  from
           making assumptions about externally-defined data.

       -mgpopt
       -mno-gpopt
           Use  (do  not  use) GP-relative accesses for symbols that are known to be in a small data
           section; see -G, -mlocal-sdata and  -mextern-sdata.   -mgpopt  is  the  default  for  all
           configurations.

           -mno-gpopt  is useful for cases where the $gp register might not hold the value of "_gp".
           For example, if the code is part of a library that might  be  used  in  a  boot  monitor,
           programs  that  call  boot  monitor  routines  pass  an  unknown  value in $gp.  (In such
           situations, the boot monitor itself is usually compiled with -G0.)

           -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

       -membedded-data
       -mno-embedded-data
           Allocate variables to the read-only data section first if  possible,  then  next  in  the
           small  data section if possible, otherwise in data.  This gives slightly slower code than
           the default, but reduces the amount of RAM required  when  executing,  and  thus  may  be
           preferred for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
           Put  uninitialized  "const" variables in the read-only data section.  This option is only
           meaningful in conjunction with -membedded-data.

       -mcode-readable=setting
           Specify whether GCC may generate code that reads from  executable  sections.   There  are
           three possible settings:

           -mcode-readable=yes
               Instructions may freely access executable sections.  This is the default setting.

           -mcode-readable=pcrel
               MIPS16  PC-relative  load  instructions  can  access  executable  sections, but other
               instructions must not do so.  This option is useful on 4KSc and 4KSd processors  when
               the  code  TLBs  have the Read Inhibit bit set.  It is also useful on processors that
               can be configured to have a dual instruction/data SRAM interface and that,  like  the
               M4K, automatically redirect PC-relative loads to the instruction RAM.

           -mcode-readable=no
               Instructions  must  not  access  executable  sections.   This option can be useful on
               targets that are configured to have a dual instruction/data SRAM interface  but  that
               (unlike  the  M4K) do not automatically redirect PC-relative loads to the instruction
               RAM.

       -msplit-addresses
       -mno-split-addresses
           Enable (disable) use of the %hi() and %lo() assembler relocation operators.  This  option
           has been superseded by -mexplicit-relocs but is retained for backwards compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
           Use  (do  not  use)  assembler relocation operators when dealing with symbolic addresses.
           The alternative, selected by -mno-explicit-relocs, is to use assembler macros instead.

           -mexplicit-relocs is the default if GCC was configured to use an assembler that  supports
           relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
           Trap (do not trap) on integer division by zero.

           The default is -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
           MIPS  systems  check  for  division  by zero by generating either a conditional trap or a
           break instruction.  Using traps results in smaller code, but is only supported on MIPS II
           and later.  Also, some versions of the Linux kernel have a bug that  prevents  trap  from
           generating  the  proper signal ("SIGFPE").  Use -mdivide-traps to allow conditional traps
           on architectures that support them and -mdivide-breaks to force the use of breaks.

           The default is usually -mdivide-traps, but this can be overridden at configure time using
           --with-divide=breaks.   Divide-by-zero  checks   can   be   completely   disabled   using
           -mno-check-zero-division.

       -mload-store-pairs
       -mno-load-store-pairs
           Enable  (disable)  an  optimization  that pairs consecutive load or store instructions to
           enable load/store bonding.  This option is enabled by default but only takes effect  when
           the selected architecture is known to support bonding.

       -mmemcpy
       -mno-memcpy
           Force  (do  not  force)  the use of "memcpy" for non-trivial block moves.  The default is
           -mno-memcpy, which allows GCC to inline most constant-sized copies.

       -mlong-calls
       -mno-long-calls
           Disable (do not disable) use of the "jal" instruction.  Calling functions using "jal"  is
           more efficient but requires the caller and callee to be in the same 256 megabyte segment.

           This option has no effect on abicalls code.  The default is -mno-long-calls.

       -mmad
       -mno-mad
           Enable  (disable)  use  of  the  "mad", "madu" and "mul" instructions, as provided by the
           R4650 ISA.

       -mimadd
       -mno-imadd
           Enable (disable) use of the "madd" and  "msub"  integer  instructions.   The  default  is
           -mimadd  on  architectures that support "madd" and "msub" except for the 74k architecture
           where it was found to generate slower code.

       -mfused-madd
       -mno-fused-madd
           Enable (disable) use of the floating-point multiply-accumulate  instructions,  when  they
           are available.  The default is -mfused-madd.

           On the R8000 CPU when multiply-accumulate instructions are used, the intermediate product
           is  calculated  to  infinite  precision and is not subject to the FCSR Flush to Zero bit.
           This may be undesirable in  some  circumstances.   On  other  processors  the  result  is
           numerically  identical  to  the  equivalent  computation  using  separate  multiply, add,
           subtract and negate instructions.

       -nocpp
           Tell the MIPS assembler to not run its preprocessor over user assembler files (with a  .s
           suffix) when assembling them.

       -mfix-24k
       -mno-fix-24k
           Work  around the 24K E48 (lost data on stores during refill) errata.  The workarounds are
           implemented by the assembler rather than by GCC.

       -mfix-r4000
       -mno-fix-r4000
           Work around certain R4000 CPU errata:

           -   A double-word  or  a  variable  shift  may  give  an  incorrect  result  if  executed
               immediately after starting an integer division.

           -   A  double-word  or a variable shift may give an incorrect result if executed while an
               integer multiplication is in progress.

           -   An integer division may give an incorrect result if started in  a  delay  slot  of  a
               taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
           Work around certain R4400 CPU errata:

           -   A  double-word  or  a  variable  shift  may  give  an  incorrect  result  if executed
               immediately after starting an integer division.

       -mfix-r10000
       -mno-fix-r10000
           Work around certain R10000 errata:

           -   "ll"/"sc" sequences may not behave atomically on revisions prior to  3.0.   They  may
               deadlock on revisions 2.6 and earlier.

           This  option  can  only  be  used  if  the  target  architecture  supports  branch-likely
           instructions.  -mfix-r10000 is the default when -march=r10000 is used; -mno-fix-r10000 is
           the default otherwise.

       -mfix-r5900
       -mno-fix-r5900
           Do not attempt to schedule the preceding instruction into the  delay  slot  of  a  branch
           instruction  placed  at  the  end of a short loop of six instructions or fewer and always
           schedule a "nop" instruction there instead.  The short loop bug under certain  conditions
           causes loops to execute only once or twice, due to a hardware bug in the R5900 chip.  The
           workaround is implemented by the assembler rather than by GCC.

       -mfix-rm7000
       -mno-fix-rm7000
           Work  around  the RM7000 "dmult"/"dmultu" errata.  The workarounds are implemented by the
           assembler rather than by GCC.

       -mfix-vr4120
       -mno-fix-vr4120
           Work around certain VR4120 errata:

           -   "dmultu" does not always produce the correct result.

           -   "div" and "ddiv" do not always produce the correct result if one of the  operands  is
               negative.

           The  workarounds  for  the  division  errata  rely  on special functions in libgcc.a.  At
           present, these functions are only provided by the "mips64vr*-elf" configurations.

           Other VR4120 errata require a NOP to be inserted between certain pairs  of  instructions.
           These errata are handled by the assembler, not by GCC itself.

       -mfix-vr4130
           Work  around  the  VR4130  "mflo"/"mfhi"  errata.  The workarounds are implemented by the
           assembler rather than by GCC, although GCC avoids using "mflo" and "mfhi" if  the  VR4130
           "macc", "macchi", "dmacc" and "dmacchi" instructions are available instead.

       -mfix-sb1
       -mno-fix-sb1
           Work  around  certain  SB-1  CPU core errata.  (This flag currently works around the SB-1
           revision 2 "F1" and "F2" floating-point errata.)

       -mr10k-cache-barrier=setting
           Specify whether GCC should insert cache barriers to avoid the side effects of speculation
           on R10K processors.

           In common with many processors, the R10K tries to predict the outcome  of  a  conditional
           branch  and speculatively executes instructions from the "taken" branch.  It later aborts
           these instructions if the predicted outcome is wrong.  However, on the R10K, even aborted
           instructions can have side effects.

           This problem only affects kernel stores and, depending on the system, kernel  loads.   As
           an example, a speculatively-executed store may load the target memory into cache and mark
           the  cache  line as dirty, even if the store itself is later aborted.  If a DMA operation
           writes to the same area of memory before the "dirty" line is  flushed,  the  cached  data
           overwrites  the  DMA-ed  data.   See  the  R10K  processor manual for a full description,
           including other potential problems.

           One workaround is to insert cache barrier instructions before every  memory  access  that
           might  be  speculatively  executed  and  that  might  have  side effects even if aborted.
           -mr10k-cache-barrier=setting  controls  GCC's  implementation  of  this  workaround.   It
           assumes  that  aborted  accesses  to any byte in the following regions does not have side
           effects:

           1.  the memory occupied by the current function's stack frame;

           2.  the memory occupied by an incoming stack argument;

           3.  the memory occupied by an object with a link-time-constant address.

           It is the kernel's responsibility to ensure that speculative accesses  to  these  regions
           are indeed safe.

           If the input program contains a function declaration such as:

                   void foo (void);

           then  the  implementation  of  "foo"  must  allow  "j  foo"  and "jal foo" to be executed
           speculatively.  GCC honors this restriction for functions it compiles itself.  It expects
           non-GCC functions (such as hand-written assembly code) to do the same.

           The option has three forms:

           -mr10k-cache-barrier=load-store
               Insert a cache barrier before a load or store that might  be  speculatively  executed
               and that might have side effects even if aborted.

           -mr10k-cache-barrier=store
               Insert  a  cache barrier before a store that might be speculatively executed and that
               might have side effects even if aborted.

           -mr10k-cache-barrier=none
               Disable the insertion of cache barriers.  This is the default setting.

       -mflush-func=func
       -mno-flush-func
           Specifies the function to call to flush the I and D caches,  or  to  not  call  any  such
           function.   If  called,  the  function  must  take  the  same  arguments  as  the  common
           "_flush_func", that is, the address of the memory range for  which  the  cache  is  being
           flushed,  the  size  of  the  memory range, and the number 3 (to flush both caches).  The
           default  depends  on  the  target  GCC  was  configured  for,  but  commonly  is   either
           "_flush_func" or "__cpu_flush".

       mbranch-cost=num
           Set  the  cost  of  branches  to  roughly num "simple" instructions.  This cost is only a
           heuristic and is not guaranteed to produce consistent results across  releases.   A  zero
           cost redundantly selects the default, which is based on the -mtune setting.

       -mbranch-likely
       -mno-branch-likely
           Enable  or  disable  use of Branch Likely instructions, regardless of the default for the
           selected architecture.  By default, Branch Likely instructions may be generated  if  they
           are  supported  by  the selected architecture.  An exception is for the MIPS32 and MIPS64
           architectures and processors that implement those architectures; for those, Branch Likely
           instructions are not be generated by default because the MIPS32 and MIPS64  architectures
           specifically deprecate their use.

       -mcompact-branches=never
       -mcompact-branches=optimal
       -mcompact-branches=always
           These  options  control  which  form  of  branches  will  be  generated.   The default is
           -mcompact-branches=optimal.

           The -mcompact-branches=never option ensures that compact branch instructions  will  never
           be generated.

           The  -mcompact-branches=always  option  ensures that a compact branch instruction will be
           generated if available.  If a compact branch instruction is not available, a  delay  slot
           form of the branch will be used instead.

           This option is supported from MIPS Release 6 onwards.

           The -mcompact-branches=optimal option will cause a delay slot branch to be used if one is
           available  in  the  current  ISA and the delay slot is successfully filled.  If the delay
           slot is not filled, a compact branch will be chosen if one is available.

       -mfp-exceptions
       -mno-fp-exceptions
           Specifies whether FP exceptions are  enabled.   This  affects  how  FP  instructions  are
           scheduled for some processors.  The default is that FP exceptions are enabled.

           For  instance,  on  the  SB-1,  if FP exceptions are disabled, and we are emitting 64-bit
           code, then we can use both FP pipes.  Otherwise, we can only use one FP pipe.

       -mvr4130-align
       -mno-vr4130-align
           The VR4130 pipeline is two-way superscalar, but can only issue two instructions  together
           if  the  first  one  is 8-byte aligned.  When this option is enabled, GCC aligns pairs of
           instructions that it thinks should execute in parallel.

           This option only has an effect when optimizing for the VR4130.  It  normally  makes  code
           faster, but at the expense of making it bigger.  It is enabled by default at optimization
           level -O3.

       -msynci
       -mno-synci
           Enable  (disable)  generation  of  "synci" instructions on architectures that support it.
           The "synci" instructions (if enabled) are  generated  when  "__builtin___clear_cache"  is
           compiled.

           This  option defaults to -mno-synci, but the default can be overridden by configuring GCC
           with --with-synci.

           When compiling code for single processor systems, it is generally safe  to  use  "synci".
           However,  on many multi-core (SMP) systems, it does not invalidate the instruction caches
           on all cores and may lead to undefined behavior.

       -mrelax-pic-calls
       -mno-relax-pic-calls
           Try to turn PIC calls that are normally dispatched via register $25  into  direct  calls.
           This  is  only possible if the linker can resolve the destination at link time and if the
           destination is within range for a direct call.

           -mrelax-pic-calls is the default if GCC was configured to use an assembler and  a  linker
           that  support  the  ".reloc" assembly directive and -mexplicit-relocs is in effect.  With
           -mno-explicit-relocs, this optimization can be performed by the assembler and the  linker
           alone without help from the compiler.

       -mmcount-ra-address
       -mno-mcount-ra-address
           Emit  (do  not  emit)  code that allows "_mcount" to modify the calling function's return
           address.  When enabled, this option extends the usual "_mcount" interface with a new  ra-
           address  parameter, which has type "intptr_t *" and is passed in register $12.  "_mcount"
           can then modify the return address by doing both of the following:

           *   Returning the new address in register $31.

           *   Storing the new address in "*ra-address", if ra-address is nonnull.

           The default is -mno-mcount-ra-address.

       -mframe-header-opt
       -mno-frame-header-opt
           Enable (disable) frame header optimization in the o32  ABI.   When  using  the  o32  ABI,
           calling  functions  will  allocate 16 bytes on the stack for the called function to write
           out register arguments.  When enabled, this optimization will suppress the allocation  of
           the frame header if it can be determined that it is unused.

           This optimization is off by default at all optimization levels.

       -mlxc1-sxc1
       -mno-lxc1-sxc1
           When  applicable,  enable  (disable) the generation of "lwxc1", "swxc1", "ldxc1", "sdxc1"
           instructions.  Enabled by default.

       -mmadd4
       -mno-madd4
           When applicable, enable (disable) the generation  of  4-operand  "madd.s",  "madd.d"  and
           related instructions.  Enabled by default.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
           Specify  that  intrinsic  library  functions  are  being  compiled, passing all values in
           registers, no matter the size.

       -mepsilon
       -mno-epsilon
           Generate floating-point comparison instructions that compare with  respect  to  the  "rE"
           epsilon register.

       -mabi=mmixware
       -mabi=gnu
           Generate  code  that  passes  function  parameters  and return values that (in the called
           function) are seen as registers $0 and up, as opposed to the GNU ABI  which  uses  global
           registers $231 and up.

       -mzero-extend
       -mno-zero-extend
           When  reading  data  from  memory  in  sizes shorter than 64 bits, use (do not use) zero-
           extending load instructions by default, rather than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
           Make the result of a division yielding a remainder have the same  sign  as  the  divisor.
           With  the  default,  -mno-knuthdiv,  the  sign  of  the remainder follows the sign of the
           dividend.  Both methods are arithmetically valid, the  latter  being  almost  exclusively
           used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
           Prepend (do not prepend) a : to all global symbols, so the assembly code can be used with
           the "PREFIX" assembly directive.

       -melf
           Generate  an executable in the ELF format, rather than the default mmo format used by the
           mmix simulator.

       -mbranch-predict
       -mno-branch-predict
           Use (do  not  use)  the  probable-branch  instructions,  when  static  branch  prediction
           indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
           Generate  (do  not  generate)  code  that  uses  base  addresses.   Using  a base address
           automatically generates a request (handled  by  the  assembler  and  the  linker)  for  a
           constant  to  be  set up in a global register.  The register is used for one or more base
           address requests within the range 0 to 255 from the value  held  in  the  register.   The
           generally  leads  to short and fast code, but the number of different data items that can
           be addressed is limited.  This means that a program that uses lots  of  static  data  may
           require -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
           Force (do not force) generated code to have a single exit point in each function.

       MN10300 Options

       These -m options are defined for Matsushita MN10300 architectures:

       -mmult-bug
           Generate  code  to  avoid  bugs  in the multiply instructions for the MN10300 processors.
           This is the default.

       -mno-mult-bug
           Do not generate code  to  avoid  bugs  in  the  multiply  instructions  for  the  MN10300
           processors.

       -mam33
           Generate code using features specific to the AM33 processor.

       -mno-am33
           Do not generate code using features specific to the AM33 processor.  This is the default.

       -mam33-2
           Generate code using features specific to the AM33/2.0 processor.

       -mam34
           Generate code using features specific to the AM34 processor.

       -mtune=cpu-type
           Use  the  timing  characteristics of the indicated CPU type when scheduling instructions.
           This does not change the targeted processor type.  The CPU type must be one  of  mn10300,
           am33, am33-2 or am34.

       -mreturn-pointer-on-d0
           When  generating  a  function that returns a pointer, return the pointer in both "a0" and
           "d0".  Otherwise, the pointer is returned  only  in  "a0",  and  attempts  to  call  such
           functions  without a prototype result in errors.  Note that this option is on by default;
           use -mno-return-pointer-on-d0 to disable it.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       -mrelax
           Indicate to the linker that it should perform a relaxation optimization pass  to  shorten
           branches,  calls and absolute memory addresses.  This option only has an effect when used
           on the command line for the final link step.

           This option makes symbolic debugging impossible.

       -mliw
           Allow the compiler to generate Long Instruction Word instructions if the  target  is  the
           AM33  or  later.   This  is  the  default.   This  option  defines the preprocessor macro
           "__LIW__".

       -mno-liw
           Do not allow the compiler to generate Long Instruction Word  instructions.   This  option
           defines the preprocessor macro "__NO_LIW__".

       -msetlb
           Allow  the  compiler to generate the SETLB and Lcc instructions if the target is the AM33
           or later.  This is the default.  This option defines the preprocessor macro "__SETLB__".

       -mno-setlb
           Do not allow the compiler to generate SETLB or Lcc instructions.  This option defines the
           preprocessor macro "__NO_SETLB__".

       Moxie Options

       -meb
           Generate big-endian code.  This is the default for moxie-*-* configurations.

       -mel
           Generate little-endian code.

       -mmul.x
           Generate  mul.x  and  umul.x  instructions.   This  is  the  default   for   moxiebox-*-*
           configurations.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       MSP430 Options

       These options are defined for the MSP430:

       -masm-hex
           Force  assembly  output  to always use hex constants.  Normally such constants are signed
           decimals, but this option is available for testsuite and/or aesthetic purposes.

       -mmcu=
           Select the MCU to target.  This is used to create a C preprocessor symbol based upon  the
           MCU  name, converted to upper case and pre- and post-fixed with __.  This in turn is used
           by the msp430.h header file to select an MCU-specific supplementary header file.

           The option also sets the ISA to use.  If the MCU name  is  one  that  is  known  to  only
           support the 430 ISA then that is selected, otherwise the 430X ISA is selected.  A generic
           MCU name of msp430 can also be used to select the 430 ISA.  Similarly the generic msp430x
           MCU name selects the 430X ISA.

           In  addition  an  MCU-specific  linker  script  is added to the linker command line.  The
           script's name is the name of the MCU with .ld appended.  Thus specifying -mmcu=xxx on the
           gcc command line defines the C preprocessor symbol "__XXX__"  and  cause  the  linker  to
           search for a script called xxx.ld.

           The  ISA  and  hardware multiply supported for the different MCUs is hard-coded into GCC.
           However, an external devices.csv file can be used to extend device support  beyond  those
           that have been hard-coded.

           GCC searches for the devices.csv file using the following methods in the given precedence
           order,  where  the  first method takes precendence over the second which takes precedence
           over the third.

           Include path specified with "-I" and "-L"
               devices.csv will be searched for in each of  the  directories  specified  by  include
               paths and linker library search paths.

           Path specified by the environment variable MSP430_GCC_INCLUDE_DIR
               Define  the  value  of  the global environment variable MSP430_GCC_INCLUDE_DIR to the
               full path to the directory containing devices.csv, and GCC will search this directory
               for devices.csv.  If devices.csv is found, this directory will also be registered  as
               an  include  path,  and linker library path.  Header files and linker scripts in this
               directory can therefore be used without manually specifying  "-I"  and  "-L"  on  the
               command line.

           The msp430-elf{,bare}/include/devices directory
               Finally,  GCC  will examine msp430-elf{,bare}/include/devices from the toolchain root
               directory.  This directory does not exist in a default installation, but if the  user
               has  created  it  and  copied  devices.csv there, then the MCU data will be read.  As
               above, this directory will also be registered as an include path, and linker  library
               path.

           If  none  of  the  above search methods find devices.csv, then the hard-coded MCU data is
           used.

       -mwarn-mcu
       -mno-warn-mcu
           This option enables or disables warnings about conflicts between the MCU  name  specified
           by  the  -mmcu  option  and  the ISA set by the -mcpu option and/or the hardware multiply
           support set by the -mhwmult option.  It also  toggles  warnings  about  unrecognized  MCU
           names.  This option is on by default.

       -mcpu=
           Specifies  the  ISA  to  use.   Accepted  values are msp430, msp430x and msp430xv2.  This
           option is deprecated.  The -mmcu= option should be used to select the ISA.

       -msim
           Link to the simulator runtime libraries and linker script.  Overrides  any  scripts  that
           would be selected by the -mmcu= option.

       -mlarge
           Use large-model addressing (20-bit pointers, 20-bit "size_t").

       -msmall
           Use small-model addressing (16-bit pointers, 16-bit "size_t").

       -mrelax
           This  option  is  passed  to  the  assembler and linker, and allows the linker to perform
           certain optimizations that cannot be done until the final link.

       mhwmult=
           Describes the type of hardware multiply supported by the  target.   Accepted  values  are
           none  for  no hardware multiply, 16bit for the original 16-bit-only multiply supported by
           early MCUs.  32bit for the 16/32-bit multiply supported by later MCUs  and  f5series  for
           the  16/32-bit  multiply supported by F5-series MCUs.  A value of auto can also be given.
           This tells GCC to deduce the hardware multiply support based upon the MCU  name  provided
           by  the  -mmcu  option.   If  no  -mmcu  option  is  specified  or if the MCU name is not
           recognized then no hardware multiply support is assumed.  "auto" is the default setting.

           Hardware multiplies are normally performed by calling  a  library  routine.   This  saves
           space  in  the  generated  code.   When  compiling  at -O3 or higher however the hardware
           multiplier is invoked inline.  This makes for bigger, but faster code.

           The hardware multiply routines disable interrupts whilst running and restore the previous
           interrupt state when they finish.  This makes them safe to use inside interrupt  handlers
           as well as in normal code.

       -minrt
           Enable the use of a minimum runtime environment - no static initializers or constructors.
           This  is  intended for memory-constrained devices.  The compiler includes special symbols
           in some objects that tell the linker and runtime which code fragments are required.

       -mtiny-printf
           Enable reduced code size "printf" and "puts" library functions.  The tiny implementations
           of these functions are not reentrant, so must be  used  with  caution  in  multi-threaded
           applications.

           Support  for streams has been removed and the string to be printed will always be sent to
           stdout via the "write" syscall.  The string is not buffered before it is sent to write.

           This   option   requires   Newlib   Nano   IO,   so   GCC   must   be   configured   with
           --enable-newlib-nano-formatted-io.

       -mmax-inline-shift=
           This  option  takes an integer between 0 and 64 inclusive, and sets the maximum number of
           inline shift instructions which should be emitted to  perform  a  shift  operation  by  a
           constant amount.  When this value needs to be exceeded, an mspabi helper function is used
           instead.  The default value is 4.

           This  only  affects  cases where a shift by multiple positions cannot be completed with a
           single instruction (e.g. all shifts >1 on the 430 ISA).

           Shifts of a 32-bit value are at least twice as costly,  so  the  value  passed  for  this
           option is divided by 2 and the resulting value used instead.

       -mcode-region=
       -mdata-region=
           These options tell the compiler where to place functions and data that do not have one of
           the  "lower",  "upper",  "either"  or "section" attributes.  Possible values are "lower",
           "upper", "either" or "any".  The first three behave  like  the  corresponding  attribute.
           The  fourth  possible value - "any" - is the default.  It leaves placement entirely up to
           the linker script and how it assigns the standard sections (".text", ".data", etc) to the
           memory regions.

       -msilicon-errata=
           This option passes on a request to assembler to enable the fixes for  the  named  silicon
           errata.

       -msilicon-errata-warn=
           This  option  passes  on  a  request  to  the assembler to enable warning messages when a
           silicon errata might need to be applied.

       -mwarn-devices-csv
       -mno-warn-devices-csv
           Warn if devices.csv is not found or there are problem parsing it (default: on).

       NDS32 Options

       These options are defined for NDS32 implementations:

       -mbig-endian
           Generate code in big-endian mode.

       -mlittle-endian
           Generate code in little-endian mode.

       -mreduced-regs
           Use reduced-set registers for register allocation.

       -mfull-regs
           Use full-set registers for register allocation.

       -mcmov
           Generate conditional move instructions.

       -mno-cmov
           Do not generate conditional move instructions.

       -mext-perf
           Generate performance extension instructions.

       -mno-ext-perf
           Do not generate performance extension instructions.

       -mext-perf2
           Generate performance extension 2 instructions.

       -mno-ext-perf2
           Do not generate performance extension 2 instructions.

       -mext-string
           Generate string extension instructions.

       -mno-ext-string
           Do not generate string extension instructions.

       -mv3push
           Generate v3 push25/pop25 instructions.

       -mno-v3push
           Do not generate v3 push25/pop25 instructions.

       -m16-bit
           Generate 16-bit instructions.

       -mno-16-bit
           Do not generate 16-bit instructions.

       -misr-vector-size=num
           Specify the size of each interrupt vector, which must be 4 or 16.

       -mcache-block-size=num
           Specify the size of each cache block, which must be a power of 2 between 4 and 512.

       -march=arch
           Specify the name of the target architecture.

       -mcmodel=code-model
           Set the code model to one of

           small
               All the data and read-only data segments must be within 512KB addressing space.   The
               text segment must be within 16MB addressing space.

           medium
               The  data segment must be within 512KB while the read-only data segment can be within
               4GB addressing space.  The text segment should be still within 16MB addressing space.

           large
               All the text and data segments can be within 4GB addressing space.

       -mctor-dtor
           Enable constructor/destructor feature.

       -mrelax
           Guide linker to relax instructions.

       Nios II Options

       These are the options defined for the Altera Nios II processor.

       -G num
           Put global and static objects less than or equal to num bytes into the small data or  BSS
           sections instead of the normal data or BSS sections.  The default value of num is 8.

       -mgpopt=option
       -mgpopt
       -mno-gpopt
           Generate  (do  not  generate)  GP-relative  accesses.   The  following  option  names are
           recognized:

           none
               Do not generate GP-relative accesses.

           local
               Generate GP-relative accesses for small data objects that are not external, weak,  or
               uninitialized  common symbols.  Also use GP-relative addressing for objects that have
               been explicitly placed in a small data section via a "section" attribute.

           global
               As for local, but also generate GP-relative accesses for small data objects that  are
               external, weak, or common.  If you use this option, you must ensure that all parts of
               your program (including libraries) are compiled with the same -G setting.

           data
               Generate  GP-relative  accesses for all data objects in the program.  If you use this
               option, the entire data and BSS segments of your program must fit in  64K  of  memory
               and you must use an appropriate linker script to allocate them within the addressable
               range of the global pointer.

           all Generate  GP-relative  addresses  for function pointers as well as data pointers.  If
               you use this option, the entire text, data, and BSS segments of your program must fit
               in 64K of memory and you must use an  appropriate  linker  script  to  allocate  them
               within the addressable range of the global pointer.

           -mgpopt is equivalent to -mgpopt=local, and -mno-gpopt is equivalent to -mgpopt=none.

           The  default  is  -mgpopt  except  when -fpic or -fPIC is specified to generate position-
           independent code.  Note that the Nios II ABI does not permit  GP-relative  accesses  from
           shared libraries.

           You  may  need to specify -mno-gpopt explicitly when building programs that include large
           amounts of small data, including large GOT data  sections.   In  this  case,  the  16-bit
           offset  for  GP-relative addressing may not be large enough to allow access to the entire
           small data section.

       -mgprel-sec=regexp
           This option specifies additional section names  that  can  be  accessed  via  GP-relative
           addressing.   It  is  most  useful  in  conjunction with "section" attributes on variable
           declarations and a custom  linker  script.   The  regexp  is  a  POSIX  Extended  Regular
           Expression.

           This option does not affect the behavior of the -G option, and the specified sections are
           in  addition to the standard ".sdata" and ".sbss" small-data sections that are recognized
           by -mgpopt.

       -mr0rel-sec=regexp
           This option specifies names of sections that can be accessed via  a  16-bit  offset  from
           "r0"; that is, in the low 32K or high 32K of the 32-bit address space.  It is most useful
           in  conjunction  with  "section"  attributes on variable declarations and a custom linker
           script.  The regexp is a POSIX Extended Regular Expression.

           In contrast to the use of GP-relative addressing for small data, zero-based addressing is
           never generated by default and there are no conventional section names used  in  standard
           linker scripts for sections in the low or high areas of memory.

       -mel
       -meb
           Generate little-endian (default) or big-endian (experimental) code, respectively.

       -march=arch
           This  specifies  the  name  of  the  target  Nios II architecture.  GCC uses this name to
           determine  what  kind  of  instructions  it  can  emit  when  generating  assembly  code.
           Permissible names are: r1, r2.

           The  preprocessor  macro  "__nios2_arch__"  is  available to programs, with value 1 or 2,
           indicating the targeted ISA level.

       -mbypass-cache
       -mno-bypass-cache
           Force all load and store instructions to always bypass cache by using I/O variants of the
           instructions. The default is not to bypass the cache.

       -mno-cache-volatile
       -mcache-volatile
           Volatile memory access bypass the cache using the I/O variants  of  the  load  and  store
           instructions. The default is not to bypass the cache.

       -mno-fast-sw-div
       -mfast-sw-div
           Do  not  use  table-based  fast  divide for small numbers. The default is to use the fast
           divide at -O3 and above.

       -mno-hw-mul
       -mhw-mul
       -mno-hw-mulx
       -mhw-mulx
       -mno-hw-div
       -mhw-div
           Enable or disable emitting  "mul",  "mulx"  and  "div"  family  of  instructions  by  the
           compiler. The default is to emit "mul" and not emit "div" and "mulx".

       -mbmx
       -mno-bmx
       -mcdx
       -mno-cdx
           Enable  or disable generation of Nios II R2 BMX (bit manipulation) and CDX (code density)
           instructions.   Enabling  these  instructions  also  requires  -march=r2.   Since   these
           instructions  are  optional extensions to the R2 architecture, the default is not to emit
           them.

       -mcustom-insn=N
       -mno-custom-insn
           Each -mcustom-insn=N option enables use of a custom  instruction  with  encoding  N  when
           generating  code  that  uses  insn.   For  example,  -mcustom-fadds=253  generates custom
           instruction 253 for single-precision floating-point add operations instead of the default
           behavior of using a library call.

           The following values of insn are supported.  Except as  otherwise  noted,  floating-point
           operations  are  expected to be implemented with normal IEEE 754 semantics and correspond
           directly to the C operators or the equivalent GCC built-in functions.

           Single-precision floating point:

           fadds, fsubs, fdivs, fmuls
               Binary arithmetic operations.

           fnegs
               Unary negation.

           fabss
               Unary absolute value.

           fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts, fcmpnes
               Comparison operations.

           fmins, fmaxs
               Floating-point minimum  and  maximum.   These  instructions  are  only  generated  if
               -ffinite-math-only is specified.

           fsqrts
               Unary square root operation.

           fcoss, fsins, ftans, fatans, fexps, flogs
               Floating-point  trigonometric and exponential functions.  These instructions are only
               generated if -funsafe-math-optimizations is also specified.

           Double-precision floating point:

           faddd, fsubd, fdivd, fmuld
               Binary arithmetic operations.

           fnegd
               Unary negation.

           fabsd
               Unary absolute value.

           fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd, fcmpned
               Comparison operations.

           fmind, fmaxd
               Double-precision minimum and maximum.   These  instructions  are  only  generated  if
               -ffinite-math-only is specified.

           fsqrtd
               Unary square root operation.

           fcosd, fsind, ftand, fatand, fexpd, flogd
               Double-precision  trigonometric  and  exponential  functions.  These instructions are
               only generated if -funsafe-math-optimizations is also specified.

           Conversions:

           fextsd
               Conversion from single precision to double precision.

           ftruncds
               Conversion from double precision to single precision.

           fixsi, fixsu, fixdi, fixdu
               Conversion from floating point to signed or unsigned integer types,  with  truncation
               towards zero.

           round
               Conversion  from  single-precision  floating point to signed integer, rounding to the
               nearest integer and ties away from zero.  This corresponds to the "__builtin_lroundf"
               function when -fno-math-errno is used.

           floatis, floatus, floatid, floatud
               Conversion from signed or unsigned integer types to floating-point types.

           In addition, all of the following transfer instructions for internal registers  X  and  Y
           must  be provided to use any of the double-precision floating-point instructions.  Custom
           instructions taking two double-precision source operands expect the first operand in  the
           64-bit  register X.  The other operand (or only operand of a unary operation) is given to
           the custom arithmetic instruction with the least significant half in source register src1
           and the most significant half in src2.  A  custom  instruction  that  returns  a  double-
           precision result returns the most significant 32 bits in the destination register and the
           other  half  in  32-bit  register  Y.   GCC  automatically  generates  the necessary code
           sequences to write register X and/or read register Y when double-precision floating-point
           instructions are used.

           fwrx
               Write src1 into the least significant half of X and src2 into  the  most  significant
               half of X.

           fwry
               Write src1 into Y.

           frdxhi, frdxlo
               Read the most or least (respectively) significant half of X and store it in dest.

           frdy
               Read the value of Y and store it into dest.

           Note  that you can gain more local control over generation of Nios II custom instructions
           by using the target("custom-insn=N") and target("no-custom-insn") function attributes  or
           pragmas.

       -mcustom-fpu-cfg=name
           This  option  enables  a  predefined,  named  set  of  custom  instruction encodings (see
           -mcustom-insn above).  Currently, the following sets are defined:

           -mcustom-fpu-cfg=60-1   is   equivalent   to:    -mcustom-fmuls=252    -mcustom-fadds=253
           -mcustom-fsubs=254 -fsingle-precision-constant

           -mcustom-fpu-cfg=60-2    is    equivalent   to:   -mcustom-fmuls=252   -mcustom-fadds=253
           -mcustom-fsubs=254 -mcustom-fdivs=255 -fsingle-precision-constant

           -mcustom-fpu-cfg=72-3   is   equivalent   to:   -mcustom-floatus=243   -mcustom-fixsi=244
           -mcustom-floatis=245   -mcustom-fcmpgts=246   -mcustom-fcmples=249   -mcustom-fcmpeqs=250
           -mcustom-fcmpnes=251     -mcustom-fmuls=252     -mcustom-fadds=253     -mcustom-fsubs=254
           -mcustom-fdivs=255 -fsingle-precision-constant

           -mcustom-fpu-cfg=fph2    is    equivalent   to:   -mcustom-fabss=224   -mcustom-fnegs=225
           -mcustom-fcmpnes=226   -mcustom-fcmpeqs=227   -mcustom-fcmpges=228   -mcustom-fcmpgts=229
           -mcustom-fcmples=230     -mcustom-fcmplts=231    -mcustom-fmaxs=232    -mcustom-fmins=233
           -mcustom-round=248    -mcustom-fixsi=249     -mcustom-floatis=250     -mcustom-fsqrts=251
           -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255

           Custom  instruction assignments given by individual -mcustom-insn= options override those
           given by -mcustom-fpu-cfg=, regardless of the order of the options on the command line.

           Note that you can gain more local control over selection of a FPU configuration by  using
           the target("custom-fpu-cfg=name") function attribute or pragma.

           The name fph2 is an abbreviation for Nios II Floating Point Hardware 2 Component.  Please
           note  that  the  custom instructions enabled by -mcustom-fmins=233 and -mcustom-fmaxs=234
           are only generated if -ffinite-math-only is specified.  The custom instruction enabled by
           -mcustom-round=248 is only generated if -fno-math-errno is specified.  In contrast to the
           other configurations, -fsingle-precision-constant is not set.

       These additional -m options are available for the Altera Nios II ELF (bare-metal) target:

       -mhal
           Link with HAL BSP.  This suppresses linking with the GCC-provided C runtime  startup  and
           termination  code,  and  is typically used in conjunction with -msys-crt0= to specify the
           location of the alternate startup code provided by the HAL BSP.

       -msmallc
           Link with a limited version of the C library, -lsmallc, rather than Newlib.

       -msys-crt0=startfile
           startfile is the file name of the startfile (crt0) to use when linking.  This  option  is
           only useful in conjunction with -mhal.

       -msys-lib=systemlib
           systemlib  is  the  library  name  of  the  library  that provides low-level system calls
           required by the C library, e.g. "read" and "write".  This option  is  typically  used  to
           link with a library provided by a HAL BSP.

       Nvidia PTX Options

       These options are defined for Nvidia PTX:

       -m64
           Ignored, but preserved for backward compatibility.  Only 64-bit ABI is supported.

       -misa=ISA-string
           Generate  code  for given the specified PTX ISA (e.g. sm_35).  ISA strings must be lower-
           case.  Valid ISA strings include sm_30 and sm_35.  The default ISA is sm_35.

       -mmainkernel
           Link in code for a  __main  kernel.   This  is  for  stand-alone  instead  of  offloading
           execution.

       -moptimize
           Apply  partitioned  execution  optimizations.   This  is  the  default  when any level of
           optimization is selected.

       -msoft-stack
           Generate code that does not use ".local" memory directly for stack  storage.  Instead,  a
           per-warp  stack  pointer  is  maintained  explicitly.  This enables variable-length stack
           allocation (with variable-length arrays or "alloca"), and when global memory is used  for
           underlying  storage,  makes it possible to access automatic variables from other threads,
           or with atomic instructions. This code generation variant is used for OpenMP  offloading,
           but the option is exposed on its own for the purpose of testing the compiler; to generate
           code suitable for linking into programs using OpenMP offloading, use option -mgomp.

       -muniform-simt
           Switch  to code generation variant that allows to execute all threads in each warp, while
           maintaining memory state and side effects as if only one thread in each warp  was  active
           outside  of  OpenMP  SIMD  regions.   All atomic operations and calls to runtime (malloc,
           free, vprintf) are conditionally executed (iff current lane index equals the master  lane
           index),  and  the  register  being  assigned is copied via a shuffle instruction from the
           master lane.  Outside of SIMD regions lane 0 is the  master;  inside,  each  thread  sees
           itself  as  the master.  Shared memory array "int __nvptx_uni[]" stores all-zeros or all-
           ones bitmasks for each warp, indicating current mode (0 outside of SIMD  regions).   Each
           thread can bitwise-and the bitmask at position "tid.y" with current lane index to compute
           the master lane index.

       -mgomp
           Generate  code  for  use  in  OpenMP  offloading: enables -msoft-stack and -muniform-simt
           options, and selects corresponding multilib variant.

       OpenRISC Options

       These options are defined for OpenRISC:

       -mboard=name
           Configure a board specific runtime.  This will be passed to the linker for  newlib  board
           library linking.  The default is "or1ksim".

       -mnewlib
           This  option  is  ignored;  it  is  for compatibility purposes only.  This used to select
           linker and preprocessor options for use with newlib.

       -msoft-div
       -mhard-div
           Select software or hardware divide ("l.div", "l.divu")  instructions.   This  default  is
           hardware divide.

       -msoft-mul
       -mhard-mul
           Select  software  or hardware multiply ("l.mul", "l.muli") instructions.  This default is
           hardware multiply.

       -msoft-float
       -mhard-float
           Select software or hardware for floating point operations.  The default is software.

       -mdouble-float
           When -mhard-float is selected, enables  generation  of  double-precision  floating  point
           instructions.   By  default  functions  from  libgcc are used to perform double-precision
           floating point operations.

       -munordered-float
           When -mhard-float is selected, enables generation of unordered floating point compare and
           set flag ("lf.sfun*") instructions.  By default functions from libgcc are used to perform
           unordered floating point compare and set flag operations.

       -mcmov
           Enable generation of conditional move ("l.cmov") instructions.  By default the equivalent
           will be generated using set and branch.

       -mror
           Enable generation of rotate right ("l.ror")  instructions.   By  default  functions  from
           libgcc are used to perform rotate right operations.

       -mrori
           Enable  generation  of  rotate  right with immediate ("l.rori") instructions.  By default
           functions from libgcc are used to perform rotate right with immediate operations.

       -msext
           Enable generation of sign extension ("l.ext*") instructions.  By default memory loads are
           used to perform sign extension.

       -msfimm
           Enable generation of compare and set flag with  immediate  ("l.sf*i")  instructions.   By
           default extra instructions will be generated to store the immediate to a register first.

       -mshftimm
           Enable  generation  of  shift with immediate ("l.srai", "l.srli", "l.slli") instructions.
           By default extra instructions will be generated to store  the  immediate  to  a  register
           first.

       PDP-11 Options

       These options are defined for the PDP-11:

       -mfpu
           Use  hardware  FPP  floating  point.   This  is  the default.  (FIS floating point on the
           PDP-11/40 is not supported.)  Implies -m45.

       -msoft-float
           Do not use hardware floating point.

       -mac0
           Return floating-point results in ac0 (fr0 in Unix assembler syntax).

       -mno-ac0
           Return floating-point results in memory.  This is the default.

       -m40
           Generate code for a PDP-11/40.  Implies -msoft-float -mno-split.

       -m45
           Generate code for a PDP-11/45.  This is the default.

       -m10
           Generate code for a PDP-11/10.  Implies -msoft-float -mno-split.

       -mint16
       -mno-int32
           Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
           Use 32-bit "int".

       -msplit
           Target has split instruction and data space.  Implies -m45.

       -munix-asm
           Use Unix assembler syntax.

       -mdec-asm
           Use DEC assembler syntax.

       -mgnu-asm
           Use GNU assembler syntax.  This is the default.

       -mlra
           Use the new LRA register allocator.  By default, the old "reload" allocator is used.

       picoChip Options

       These -m options are defined for picoChip implementations:

       -mae=ae_type
           Set the instruction set, register set, and instruction scheduling  parameters  for  array
           element type ae_type.  Supported values for ae_type are ANY, MUL, and MAC.

           -mae=ANY  selects  a completely generic AE type.  Code generated with this option runs on
           any of the other AE types.  The code is not as efficient as it would be if compiled for a
           specific AE type, and some types of operation (e.g., multiplication) do not work properly
           on all types of AE.

           -mae=MUL selects a MUL AE type.  This is the most useful AE type for compiled  code,  and
           is the default.

           -mae=MAC selects a DSP-style MAC AE.  Code compiled with this option may suffer from poor
           performance  of  byte  (char)  manipulation,  since  the DSP AE does not provide hardware
           support for byte load/stores.

       -msymbol-as-address
           Enable the compiler to directly  use  a  symbol  name  as  an  address  in  a  load/store
           instruction, without first loading it into a register.  Typically, the use of this option
           generates  larger  programs,  which run faster than when the option isn't used.  However,
           the results vary from program to program, so it is left as a  user  option,  rather  than
           being permanently enabled.

       -mno-inefficient-warnings
           Disables  warnings  about  the  generation  of  inefficient  code.  These warnings can be
           generated, for example, when compiling code that performs byte-level memory operations on
           the MAC AE type.  The MAC AE has no hardware support for byte-level memory operations, so
           all byte load/stores must be  synthesized  from  word  load/store  operations.   This  is
           inefficient  and  a  warning is generated to indicate that you should rewrite the code to
           avoid byte operations, or to target an AE type that has the necessary  hardware  support.
           This option disables these warnings.

       PowerPC Options

       These are listed under

       PRU Options

       These command-line options are defined for PRU target:

       -minrt
           Link  with  a  minimum  runtime  environment, with no support for static initializers and
           constructors.  Using this option can significantly reduce  the  size  of  the  final  ELF
           binary.   Beware that the compiler could still generate code with static initializers and
           constructors.  It is up to the programmer to ensure that the source program will not  use
           those features.

       -mmcu=mcu
           Specify the PRU MCU variant to use.  Check Newlib for the exact list of supported MCUs.

       -mno-relax
           Make  GCC  pass  the  --no-relax command-line option to the linker instead of the --relax
           option.

       -mloop
           Allow (or do not allow) GCC to use the LOOP instruction.

       -mabi=variant
           Specify the ABI variant to output code for.  -mabi=ti selects the unmodified TI ABI while
           -mabi=gnu selects a GNU variant that copes more naturally with certain  GCC  assumptions.
           These are the differences:

           Function Pointer Size
               TI  ABI specifies that function (code) pointers are 16-bit, whereas GNU supports only
               32-bit data and code pointers.

           Optional Return Value Pointer
               Function return values larger than 64 bits are passed by using a  hidden  pointer  as
               the first argument of the function.  TI ABI, though, mandates that the pointer can be
               NULL  in  case  the  caller  is  not using the returned value.  GNU always passes and
               expects a valid return value pointer.

           The current -mabi=ti implementation simply raises a compile error when any of  the  above
           code constructs is detected.  As a consequence the standard C library cannot be built and
           it is omitted when linking with -mabi=ti.

           Relaxation  is a GNU feature and for safety reasons is disabled when using -mabi=ti.  The
           TI toolchain does not emit relocations for QBBx instructions, so the  GNU  linker  cannot
           adjust them when shortening adjacent LDI32 pseudo instructions.

       RISC-V Options

       These command-line options are defined for RISC-V targets:

       -mbranch-cost=n
           Set the cost of branches to roughly n instructions.

       -mplt
       -mno-plt
           When  generating  PIC  code, do or don't allow the use of PLTs. Ignored for non-PIC.  The
           default is -mplt.

       -mabi=ABI-string
           Specify integer and floating-point calling convention.  ABI-string  contains  two  parts:
           the  size  of integer types and the registers used for floating-point types.  For example
           -march=rv64ifd -mabi=lp64d means that long and pointers are 64-bit  (implicitly  defining
           int  to  be  32-bit),  and  that floating-point values up to 64 bits wide are passed in F
           registers.  Contrast  this  with  -march=rv64ifd  -mabi=lp64f,  which  still  allows  the
           compiler to generate code that uses the F and D extensions but only allows floating-point
           values  up  to  32  bits long to be passed in registers; or -march=rv64ifd -mabi=lp64, in
           which no floating-point arguments will be passed in registers.

           The default for this argument is system dependent, users  who  want  a  specific  calling
           convention  should  specify  one  explicitly.   The valid calling conventions are: ilp32,
           ilp32f, ilp32d, lp64, lp64f, and lp64d.   Some  calling  conventions  are  impossible  to
           implement  on  some  ISAs: for example, -march=rv32if -mabi=ilp32d is invalid because the
           ABI requires 64-bit values be passed in F registers, but F registers  are  only  32  bits
           wide.   There  is  also the ilp32e ABI that can only be used with the rv32e architecture.
           This ABI is not well specified at present, and is subject to change.

       -mfdiv
       -mno-fdiv
           Do or don't use hardware  floating-point  divide  and  square  root  instructions.   This
           requires  the F or D extensions for floating-point registers.  The default is to use them
           if the specified architecture has these instructions.

       -mdiv
       -mno-div
           Do or don't use  hardware  instructions  for  integer  division.   This  requires  the  M
           extension.   The  default  is  to  use  them  if  the  specified  architecture  has these
           instructions.

       -march=ISA-string
           Generate code for given RISC-V ISA  (e.g.  rv64im).   ISA  strings  must  be  lower-case.
           Examples include rv64i, rv32g, rv32e, and rv32imaf.

           When -march= is not specified, use the setting from -mcpu.

           If  both  -march  and  -mcpu=  are not specified, the default for this argument is system
           dependent,  users  who  want  a  specific  architecture  extensions  should  specify  one
           explicitly.

       -mcpu=processor-string
           Use  architecture  of  and  optimize  the  output  for  the given processor, specified by
           particular CPU name.  Permissible values for this  option  are:  sifive-e20,  sifive-e21,
           sifive-e24,  sifive-e31,  sifive-e34,  sifive-e76,  sifive-s21,  sifive-s51,  sifive-s54,
           sifive-s76, sifive-u54, and sifive-u74.

       -mtune=processor-string
           Optimize the output for the given processor, specified by microarchitecture or particular
           CPU  name.   Permissible  values  for   this   option   are:   rocket,   sifive-3-series,
           sifive-5-series, sifive-7-series, size, and all valid options for -mcpu=.

           When  -mtune= is not specified, use the setting from -mcpu, the default is rocket if both
           are not specified.

           The size choice is not intended  for  use  by  end-users.   This  is  used  when  -Os  is
           specified.   It  overrides  the  instruction  cost info provided by -mtune=, but does not
           override the pipeline info.   This  helps  reduce  code  size  while  still  giving  good
           performance.

       -mpreferred-stack-boundary=num
           Attempt  to  keep  the  stack  boundary  aligned  to a 2 raised to num byte boundary.  If
           -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128-bits).

           Warning: If you use this switch, then you must build all modules  with  the  same  value,
           including any libraries.  This includes the system libraries and startup modules.

       -msmall-data-limit=n
           Put global and static data smaller than n bytes into a special section (on some targets).

       -msave-restore
       -mno-save-restore
           Do  or don't use smaller but slower prologue and epilogue code that uses library function
           calls.  The default is to use fast inline prologues and epilogues.

       -mshorten-memrefs
       -mno-shorten-memrefs
           Do or do not attempt to make more use of compressed load/store instructions by  replacing
           a load/store of 'base register + large offset' with a new load/store of 'new base + small
           offset'.   If  the new base gets stored in a compressed register, then the new load/store
           can be compressed.  Currently targets 32-bit integer load/stores only.

       -mstrict-align
       -mno-strict-align
           Do not or do generate unaligned memory accesses.  The default is set depending on whether
           the processor we are optimizing for supports fast unaligned access or not.

       -mcmodel=medlow
           Generate code for the medium-low code model.  The  program  and  its  statically  defined
           symbols  must  lie  within  a  single  2  GiB address range and must lie between absolute
           addresses -2 GiB and +2 GiB. Programs can be statically or dynamically  linked.  This  is
           the default code model.

       -mcmodel=medany
           Generate  code  for  the  medium-any  code  model. The program and its statically defined
           symbols must be within any single 2 GiB address range.  Programs  can  be  statically  or
           dynamically linked.

       -mexplicit-relocs
       -mno-exlicit-relocs
           Use  or  do  not use assembler relocation operators when dealing with symbolic addresses.
           The alternative is to use assembler macros instead, which may limit optimization.

       -mrelax
       -mno-relax
           Take advantage of linker relaxations to reduce the number  of  instructions  required  to
           materialize symbol addresses. The default is to take advantage of linker relaxations.

       -memit-attribute
       -mno-emit-attribute
           Emit  (do  not emit) RISC-V attribute to record extra information into ELF objects.  This
           feature requires at least binutils 2.32.

       -malign-data=type
           Control how GCC aligns variables and constants  of  array,  structure,  or  union  types.
           Supported  values  for  type are xlen which uses x register width as the alignment value,
           and natural which uses natural alignment.  xlen is the default.

       -mbig-endian
           Generate big-endian code.  This is the default when GCC is configured for a riscv64be-*-*
           or riscv32be-*-* target.

       -mlittle-endian
           Generate little-endian  code.   This  is  the  default  when  GCC  is  configured  for  a
           riscv64-*-* or riscv32-*-* but not a riscv64be-*-* or riscv32be-*-* target.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
           Generate stack protection code using canary at guard.  Supported locations are global for
           a global canary or tls for per-thread canary in the TLS block.

           With    the    latter    choice    the    options   -mstack-protector-guard-reg=reg   and
           -mstack-protector-guard-offset=offset furthermore specify which register to use  as  base
           register  for  reading the canary, and from what offset from that base register. There is
           no default register or offset as this is entirely for use within the Linux kernel.

       RL78 Options

       -msim
           Links in additional target libraries to support operation within a simulator.

       -mmul=none
       -mmul=g10
       -mmul=g13
       -mmul=g14
       -mmul=rl78
           Specifies the type of hardware multiplication and  division  support  to  be  used.   The
           simplest  is  "none",  which uses software for both multiplication and division.  This is
           the default.  The "g13" value is for the hardware multiply/divide peripheral found on the
           RL78/G13 (S2 core) targets.  The "g14" value selects the use of  the  multiplication  and
           division  instructions supported by the RL78/G14 (S3 core) parts.  The value "rl78" is an
           alias for "g14" and the value "mg10" is an alias for "none".

           In addition a C preprocessor macro is defined, based upon the  setting  of  this  option.
           Possible values are: "__RL78_MUL_NONE__", "__RL78_MUL_G13__" or "__RL78_MUL_G14__".

       -mcpu=g10
       -mcpu=g13
       -mcpu=g14
       -mcpu=rl78
           Specifies the RL78 core to target.  The default is the G14 core, also known as an S3 core
           or  just RL78.  The G13 or S2 core does not have multiply or divide instructions, instead
           it uses a hardware peripheral for these operations.  The G10 or S1  core  does  not  have
           register banks, so it uses a different calling convention.

           If  this  option  is  set  it  also selects the type of hardware multiply support to use,
           unless this is overridden by an explicit -mmul=none option on  the  command  line.   Thus
           specifying  -mcpu=g13  enables  the  use  of  the  G13  hardware  multiply peripheral and
           specifying -mcpu=g10 disables the use of hardware multiplications altogether.

           Note, although  the  RL78/G14  core  is  the  default  target,  specifying  -mcpu=g14  or
           -mcpu=rl78  on  the  command line does change the behavior of the toolchain since it also
           enables G14 hardware multiply support.  If these options are not specified on the command
           line then software multiplication routines will be used even though the code targets  the
           RL78  core.  This is for backwards compatibility with older toolchains which did not have
           hardware multiply and divide support.

           In addition a C preprocessor macro is defined, based upon the  setting  of  this  option.
           Possible values are: "__RL78_G10__", "__RL78_G13__" or "__RL78_G14__".

       -mg10
       -mg13
       -mg14
       -mrl78
           These  are  aliases for the corresponding -mcpu= option.  They are provided for backwards
           compatibility.

       -mallregs
           Allow the compiler  to  use  all  of  the  available  registers.   By  default  registers
           "r24..r31"  are  reserved  for use in interrupt handlers.  With this option enabled these
           registers can be used in ordinary functions as well.

       -m64bit-doubles
       -m32bit-doubles
           Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles)  in
           size.  The default is -m32bit-doubles.

       -msave-mduc-in-interrupts
       -mno-save-mduc-in-interrupts
           Specifies  that  interrupt handler functions should preserve the MDUC registers.  This is
           only necessary if normal code might use  the  MDUC  registers,  for  example  because  it
           performs  multiplication  and  division  operations.   The  default is to ignore the MDUC
           registers as this makes the interrupt handlers faster.  The target option -mg13 needs  to
           be passed for this to work as this feature is only available on the G13 target (S2 core).
           The  MDUC registers will only be saved if the interrupt handler performs a multiplication
           or division operation or it calls another function.

       IBM RS/6000 and PowerPC Options

       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mpopcntd
       -mno-popcntd
       -mfprnd
       -mno-fprnd
       -mcmpb
       -mno-cmpb
       -mhard-dfp
       -mno-hard-dfp
           You use these options to specify which instructions are available on  the  processor  you
           are  using.   The  default  value  of  these  options is determined when configuring GCC.
           Specifying the -mcpu=cpu_type overrides the specification of these options.  We recommend
           you use the -mcpu=cpu_type option rather than the options listed above.

           Specifying  -mpowerpc-gpopt  allows  GCC  to  use  the  optional   PowerPC   architecture
           instructions  in  the  General  Purpose  group,  including  floating-point  square  root.
           Specifying  -mpowerpc-gfxopt  allows  GCC  to  use  the  optional  PowerPC   architecture
           instructions in the Graphics group, including floating-point select.

           The  -mmfcrf  option  allows  GCC  to  generate  the  move  from condition register field
           instruction implemented on the POWER4 processor and other  processors  that  support  the
           PowerPC V2.01 architecture.  The -mpopcntb option allows GCC to generate the popcount and
           double-precision  FP  reciprocal estimate instruction implemented on the POWER5 processor
           and other processors that support the PowerPC V2.02 architecture.  The  -mpopcntd  option
           allows  GCC  to generate the popcount instruction implemented on the POWER7 processor and
           other processors that support the PowerPC V2.06 architecture.  The -mfprnd option  allows
           GCC to generate the FP round to integer instructions implemented on the POWER5+ processor
           and  other  processors  that  support  the PowerPC V2.03 architecture.  The -mcmpb option
           allows GCC to generate the compare bytes instruction implemented on the POWER6  processor
           and  other processors that support the PowerPC V2.05 architecture.  The -mhard-dfp option
           allows GCC to generate the decimal floating-point instructions implemented on some  POWER
           processors.

           The -mpowerpc64 option allows GCC to generate the additional 64-bit instructions that are
           found  in  the  full  PowerPC64  architecture  and  to  treat  GPRs as 64-bit, doubleword
           quantities.  GCC defaults to -mno-powerpc64.

       -mcpu=cpu_type
           Set architecture type, register usage, and instruction scheduling parameters for  machine
           type  cpu_type.  Supported values for cpu_type are 401, 403, 405, 405fp, 440, 440fp, 464,
           464fp, 476, 476fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400,  7450,  750,
           801,  821,  823,  860,  970,  8540,  a2,  e300c2, e300c3, e500mc, e500mc64, e5500, e6500,
           ec603e, G3, G4, G5, titan, power3, power4,  power5,  power5+,  power6,  power6x,  power7,
           power8, power9, power10, powerpc, powerpc64, powerpc64le, rs64, and native.

           -mcpu=powerpc, -mcpu=powerpc64, and -mcpu=powerpc64le specify pure 32-bit PowerPC (either
           endian),  64-bit big endian PowerPC and 64-bit little endian PowerPC architecture machine
           types, with an appropriate, generic processor model assumed for scheduling purposes.

           Specifying  native  as  cpu  type  detects  and  selects  the  architecture  option  that
           corresponds to the host processor of the system performing the compilation.  -mcpu=native
           has no effect if GCC does not recognize the processor.

           The  other options specify a specific processor.  Code generated under those options runs
           best on that processor, and may not run at all on others.

           The -mcpu options automatically enable or disable the following options:

           -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple -mpopcntb   -mpopcntd   -mpowerpc64
           -mpowerpc-gpopt   -mpowerpc-gfxopt  -mmulhw   -mdlmzb   -mmfpgpr   -mvsx  -mcrypto  -mhtm
           -mpower8-fusion    -mpower8-vector   -mquad-memory    -mquad-memory-atomic     -mfloat128
           -mfloat128-hardware -mprefixed -mpcrel -mmma -mrop-protect

           The  particular  options  set  for  any  particular CPU varies between compiler versions,
           depending on what setting seems  to  produce  optimal  code  for  that  CPU;  it  doesn't
           necessarily reflect the actual hardware's capabilities.  If you wish to set an individual
           option  to  a particular value, you may specify it after the -mcpu option, like -mcpu=970
           -mno-altivec.

           On AIX, the -maltivec and -mpowerpc64 options are not enabled or disabled  by  the  -mcpu
           option  at  present  because  AIX  does not have full support for these options.  You may
           still enable or disable them individually if you're sure it'll work in your environment.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not  set  the
           architecture  type  or  register  usage,  as  -mcpu=cpu_type  does.   The same values for
           cpu_type are used for -mtune as for -mcpu.  If both are  specified,  the  code  generated
           uses  the  architecture  and registers set by -mcpu, but the scheduling parameters set by
           -mtune.

       -mcmodel=small
           Generate PowerPC64 code for the small model: The TOC is limited to 64k.

       -mcmodel=medium
           Generate PowerPC64 code for the medium model: The TOC and other static data may be up  to
           a total of 4G in size.  This is the default for 64-bit Linux.

       -mcmodel=large
           Generate PowerPC64 code for the large model: The TOC may be up to 4G in size.  Other data
           and code is only limited by the 64-bit address space.

       -maltivec
       -mno-altivec
           Generate  code  that uses (does not use) AltiVec instructions, and also enable the use of
           built-in functions that allow more direct access to the AltiVec instruction set.  You may
           also need to set -mabi=altivec to adjust the current ABI with AltiVec ABI enhancements.

           When -maltivec is used, the element order for AltiVec  intrinsics  such  as  "vec_splat",
           "vec_extract", and "vec_insert" match array element order corresponding to the endianness
           of  the  target.   That  is,  element  zero  identifies  the leftmost element in a vector
           register when targeting a big-endian platform, and identifies the rightmost element in  a
           vector register when targeting a little-endian platform.

       -mvrsave
       -mno-vrsave
           Generate VRSAVE instructions when generating AltiVec code.

       -msecure-plt
           Generate  code  that  allows  ld and ld.so to build executables and shared libraries with
           non-executable ".plt" and ".got" sections.  This is a PowerPC 32-bit SYSV ABI option.

       -mbss-plt
           Generate code that uses a BSS ".plt" section that ld.so fills in, and requires ".plt" and
           ".got" sections that are both writable and executable.  This is a PowerPC 32-bit SYSV ABI
           option.

       -misel
       -mno-isel
           This switch enables or disables the generation of ISEL instructions.

       -mvsx
       -mno-vsx
           Generate code that uses (does not use) vector/scalar (VSX) instructions, and also  enable
           the use of built-in functions that allow more direct access to the VSX instruction set.

       -mcrypto
       -mno-crypto
           Enable  the  use  (disable)  of  the  built-in  functions that allow direct access to the
           cryptographic instructions that were added in version 2.07 of the PowerPC ISA.

       -mhtm
       -mno-htm
           Enable (disable) the use of the built-in  functions  that  allow  direct  access  to  the
           Hardware  Transactional  Memory (HTM) instructions that were added in version 2.07 of the
           PowerPC ISA.

       -mpower8-fusion
       -mno-power8-fusion
           Generate code that keeps (does not keeps) some integer operations adjacent  so  that  the
           instructions can be fused together on power8 and later processors.

       -mpower8-vector
       -mno-power8-vector
           Generate code that uses (does not use) the vector and scalar instructions that were added
           in version 2.07 of the PowerPC ISA.  Also enable the use of built-in functions that allow
           more direct access to the vector instructions.

       -mquad-memory
       -mno-quad-memory
           Generate code that uses (does not use) the non-atomic quad word memory instructions.  The
           -mquad-memory option requires use of 64-bit mode.

       -mquad-memory-atomic
       -mno-quad-memory-atomic
           Generate  code  that  uses  (does not use) the atomic quad word memory instructions.  The
           -mquad-memory-atomic option requires use of 64-bit mode.

       -mfloat128
       -mno-float128
           Enable/disable the __float128 keyword for IEEE 128-bit  floating  point  and  use  either
           software emulation for IEEE 128-bit floating point or hardware instructions.

           The  VSX  instruction  set (-mvsx) must be enabled to use the IEEE 128-bit floating point
           support.  The IEEE 128-bit floating point is only supported on Linux.

           The default for -mfloat128 is enabled on PowerPC Linux systems using the VSX  instruction
           set, and disabled on other systems.

           If  you  use  the  ISA  3.0 instruction set (-mpower9-vector or -mcpu=power9) on a 64-bit
           system, the IEEE 128-bit floating point support will also enable the  generation  of  ISA
           3.0  IEEE  128-bit  floating  point  instructions.   Otherwise,  if you do not specify to
           generate ISA 3.0 instructions or you are targeting  a  32-bit  big  endian  system,  IEEE
           128-bit floating point will be done with software emulation.

       -mfloat128-hardware
       -mno-float128-hardware
           Enable/disable using ISA 3.0 hardware instructions to support the __float128 data type.

           The default for -mfloat128-hardware is enabled on PowerPC Linux systems using the ISA 3.0
           instruction set, and disabled on other systems.

       -m32
       -m64
           Generate  code  for  32-bit  or 64-bit environments of Darwin and SVR4 targets (including
           GNU/Linux).  The 32-bit environment sets int, long and pointer to 32 bits  and  generates
           code  that  runs  on any PowerPC variant.  The 64-bit environment sets int to 32 bits and
           long and pointer to 64 bits, and generates code for PowerPC64, as for -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
           Modify generation of the TOC (Table Of Contents), which is created for  every  executable
           file.   The  -mfull-toc  option  is  selected by default.  In that case, GCC allocates at
           least one TOC entry for each unique non-automatic variable  reference  in  your  program.
           GCC  also  places  floating-point constants in the TOC.  However, only 16,384 entries are
           available in the TOC.

           If you receive a linker error message that saying you have overflowed the  available  TOC
           space,  you  can  reduce  the  amount  of  TOC  space  used  with  the -mno-fp-in-toc and
           -mno-sum-in-toc  options.   -mno-fp-in-toc  prevents  GCC  from  putting   floating-point
           constants in the TOC and -mno-sum-in-toc forces GCC to generate code to calculate the sum
           of  an  address and a constant at run time instead of putting that sum into the TOC.  You
           may specify one or both of these options.  Each  causes  GCC  to  produce  very  slightly
           slower and larger code at the expense of conserving TOC space.

           If  you  still  run  out of space in the TOC even when you specify both of these options,
           specify -mminimal-toc instead.  This option causes GCC to make only  one  TOC  entry  for
           every  file.   When  you specify this option, GCC produces code that is slower and larger
           but which uses extremely little TOC space.  You may wish to use this option only on files
           that contain less frequently-executed code.

       -maix64
       -maix32
           Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit  "long"  type,  and
           the infrastructure needed to support them.  Specifying -maix64 implies -mpowerpc64, while
           -maix32 disables the 64-bit ABI and implies -mno-powerpc64.  GCC defaults to -maix32.

       -mxl-compat
       -mno-xl-compat
           Produce  code  that  conforms  more  closely to IBM XL compiler semantics when using AIX-
           compatible ABI.   Pass  floating-point  arguments  to  prototyped  functions  beyond  the
           register  save  area (RSA) on the stack in addition to argument FPRs.  Do not assume that
           most significant double in 128-bit long double value is properly rounded  when  comparing
           values and converting to double.  Use XL symbol names for long double support routines.

           The AIX calling convention was extended but not initially documented to handle an obscure
           K&R  C  case  of  calling  a  function that takes the address of its arguments with fewer
           arguments than declared.  IBM XL compilers access floating-point arguments  that  do  not
           fit  in  the  RSA  from  the  stack  when  a subroutine is compiled without optimization.
           Because always storing floating-point arguments on the stack is  inefficient  and  rarely
           needed,  this  option  is  not  enabled  by  default  and  only is necessary when calling
           subroutines compiled by IBM XL compilers without optimization.

       -mpe
           Support IBM RS/6000 SP Parallel Environment (PE).  Link an  application  written  to  use
           message  passing  with special startup code to enable the application to run.  The system
           must have PE installed in the standard location (/usr/lpp/ppe.poe/), or  the  specs  file
           must be overridden with the -specs= option to specify the appropriate directory location.
           The  Parallel  Environment  does not support threads, so the -mpe option and the -pthread
           option are incompatible.

       -malign-natural
       -malign-power
           On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option -malign-natural overrides
           the ABI-defined alignment of larger types,  such  as  floating-point  doubles,  on  their
           natural  size-based  boundary.  The option -malign-power instructs GCC to follow the ABI-
           specified alignment rules.  GCC defaults to the standard alignment defined in the ABI.

           On 64-bit Darwin, natural alignment is the default, and -malign-power is not supported.

       -msoft-float
       -mhard-float
           Generate code that does  not  use  (uses)  the  floating-point  register  set.   Software
           floating-point  emulation  is  provided  if you use the -msoft-float option, and pass the
           option to GCC when linking.

       -mmultiple
       -mno-multiple
           Generate code that uses (does not use) the load multiple word instructions and the  store
           multiple  word  instructions.   These  instructions  are  generated  by  default on POWER
           systems, and not generated on PowerPC systems.  Do not use  -mmultiple  on  little-endian
           PowerPC  systems,  since  those instructions do not work when the processor is in little-
           endian mode.  The exceptions are PPC740 and PPC750 which  permit  these  instructions  in
           little-endian mode.

       -mupdate
       -mno-update
           Generate  code  that  uses  (does not use) the load or store instructions that update the
           base register to the address of the calculated memory location.  These  instructions  are
           generated  by  default.  If you use -mno-update, there is a small window between the time
           that the stack pointer is updated and the address of the previous frame is stored,  which
           means  code  that  walks  the  stack frame across interrupts or signals may get corrupted
           data.

       -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses
           Generate code that tries  to  avoid  (not  avoid)  the  use  of  indexed  load  or  store
           instructions.  These instructions can incur a performance penalty on Power6 processors in
           certain situations, such as when stepping through large arrays that cross a 16M boundary.
           This option is enabled by default when targeting Power6 and disabled otherwise.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses  (does  not  use)  the  floating-point  multiply  and  accumulate
           instructions.   These instructions are generated by default if hardware floating point is
           used.  The machine-dependent -mfused-madd option is now mapped to the machine-independent
           -ffp-contract=fast option, and -mno-fused-madd is mapped to -ffp-contract=off.

       -mmulhw
       -mno-mulhw
           Generate code that uses (does not use) the  half-word  multiply  and  multiply-accumulate
           instructions  on  the  IBM  405,  440,  464  and  476 processors.  These instructions are
           generated by default when targeting those processors.

       -mdlmzb
       -mno-dlmzb
           Generate code that uses (does not use) the string-search dlmzb  instruction  on  the  IBM
           405,  440,  464  and  476  processors.   This  instruction  is  generated by default when
           targeting those processors.

       -mno-bit-align
       -mbit-align
           On System V.4 and embedded PowerPC systems do not (do) force structures and  unions  that
           contain bit-fields to be aligned to the base type of the bit-field.

           For  example,  by  default  a structure containing nothing but 8 "unsigned" bit-fields of
           length 1 is aligned to  a  4-byte  boundary  and  has  a  size  of  4  bytes.   By  using
           -mno-bit-align, the structure is aligned to a 1-byte boundary and is 1 byte in size.

       -mno-strict-align
       -mstrict-align
           On  System  V.4  and  embedded  PowerPC  systems do not (do) assume that unaligned memory
           references are handled by the system.

       -mrelocatable
       -mno-relocatable
           Generate code that allows (does not allow) a static  executable  to  be  relocated  to  a
           different  address  at run time.  A simple embedded PowerPC system loader should relocate
           the entire contents of ".got2" and 4-byte locations listed in  the  ".fixup"  section,  a
           table of 32-bit addresses generated by this option.  For this to work, all objects linked
           together  must  be  compiled with -mrelocatable or -mrelocatable-lib.  -mrelocatable code
           aligns the stack to an 8-byte boundary.

       -mrelocatable-lib
       -mno-relocatable-lib
           Like -mrelocatable, -mrelocatable-lib  generates  a  ".fixup"  section  to  allow  static
           executables  to  be relocated at run time, but -mrelocatable-lib does not use the smaller
           stack alignment of -mrelocatable.  Objects compiled with -mrelocatable-lib may be  linked
           with objects compiled with any combination of the -mrelocatable options.

       -mno-toc
       -mtoc
           On  System V.4 and embedded PowerPC systems do not (do) assume that register 2 contains a
           pointer to a global area pointing to the addresses used in the program.

       -mlittle
       -mlittle-endian
           On System V.4 and embedded PowerPC systems compile code  for  the  processor  in  little-
           endian mode.  The -mlittle-endian option is the same as -mlittle.

       -mbig
       -mbig-endian
           On  System  V.4 and embedded PowerPC systems compile code for the processor in big-endian
           mode.  The -mbig-endian option is the same as -mbig.

       -mdynamic-no-pic
           On Darwin and Mac OS X systems, compile code so that it is not relocatable, but that  its
           external  references  are  relocatable.  The resulting code is suitable for applications,
           but not shared libraries.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than loading  it  in  the
           prologue  for  each  function.   The  runtime system is responsible for initializing this
           register with an appropriate value before execution begins.

       -mprioritize-restricted-insns=priority
           This  option  controls  the  priority  that  is  assigned  to  dispatch-slot   restricted
           instructions during the second scheduling pass.  The argument priority takes the value 0,
           1, or 2 to assign no, highest, or second-highest (respectively) priority to dispatch-slot
           restricted instructions.

       -msched-costly-dep=dependence_type
           This  option  controls  which  dependences  are  considered  costly  by the target during
           instruction scheduling.  The argument dependence_type takes one of the following values:

           no  No dependence is costly.

           all All dependences are costly.

           true_store_to_load
               A true dependence from store to load is costly.

           store_to_load
               Any dependence from store to load is costly.

           number
               Any dependence for which the latency is greater than or equal to number is costly.

       -minsert-sched-nops=scheme
           This option controls which NOP insertion scheme is  used  during  the  second  scheduling
           pass.  The argument scheme takes one of the following values:

           no  Don't insert NOPs.

           pad Pad  with  NOPs  any  dispatch  group  that  has vacant issue slots, according to the
               scheduler's grouping.

           regroup_exact
               Insert NOPs to force costly dependent insns into separate groups.  Insert exactly  as
               many  NOPs  as  needed  to  force  an insn to a new group, according to the estimated
               processor grouping.

           number
               Insert NOPs to force costly dependent insns into separate groups.  Insert number NOPs
               to force an insn to a new group.

       -mcall-sysv
           On System V.4 and embedded PowerPC systems compile code using  calling  conventions  that
           adhere  to  the  March  1995  draft of the System V Application Binary Interface, PowerPC
           processor  supplement.   This  is  the  default   unless   you   configured   GCC   using
           powerpc-*-eabiaix.

       -mcall-sysv-eabi
       -mcall-eabi
           Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
           Specify both -mcall-sysv and -mno-eabi options.

       -mcall-aixdesc
           On System V.4 and embedded PowerPC systems compile code for the AIX operating system.

       -mcall-linux
           On System V.4 and embedded PowerPC systems compile code for the Linux-based GNU system.

       -mcall-freebsd
           On System V.4 and embedded PowerPC systems compile code for the FreeBSD operating system.

       -mcall-netbsd
           On System V.4 and embedded PowerPC systems compile code for the NetBSD operating system.

       -mcall-openbsd
           On System V.4 and embedded PowerPC systems compile code for the OpenBSD operating system.

       -mtraceback=traceback_type
           Select  the  type of traceback table. Valid values for traceback_type are full, part, and
           no.

       -maix-struct-return
           Return all structures in memory (as specified by the AIX ABI).

       -msvr4-struct-return
           Return structures smaller than 8 bytes in registers (as specified by the SVR4 ABI).

       -mabi=abi-type
           Extend the current ABI with a particular extension,  or  remove  such  extension.   Valid
           values  are:  altivec,  no-altivec,  ibmlongdouble, ieeelongdouble, elfv1, elfv2, and for
           AIX: vec-extabi, vec-default.

       -mabi=ibmlongdouble
           Change the current ABI to use IBM extended-precision long double.  This is not likely  to
           work if your system defaults to using IEEE extended-precision long double.  If you change
           the  long  double  type  from  IEEE extended-precision, the compiler will issue a warning
           unless you use the -Wno-psabi option.  Requires -mlong-double-128 to be enabled.

       -mabi=ieeelongdouble
           Change the current ABI to use IEEE extended-precision long double.  This is not likely to
           work if your system defaults to using IBM extended-precision long double.  If you  change
           the  long  double  type  from  IBM  extended-precision, the compiler will issue a warning
           unless you use the -Wno-psabi option.  Requires -mlong-double-128 to be enabled.

       -mabi=elfv1
           Change the current ABI to use the ELFv1 ABI.  This is  the  default  ABI  for  big-endian
           PowerPC  64-bit Linux.  Overriding the default ABI requires special system support and is
           likely to fail in spectacular ways.

       -mabi=elfv2
           Change the current ABI to use the ELFv2 ABI.  This is the default ABI  for  little-endian
           PowerPC  64-bit Linux.  Overriding the default ABI requires special system support and is
           likely to fail in spectacular ways.

       -mgnu-attribute
       -mno-gnu-attribute
           Emit .gnu_attribute assembly directives to  set  tag/value  pairs  in  a  .gnu.attributes
           section that specify ABI variations in function parameters or return values.

       -mprototype
       -mno-prototype
           On  System  V.4  and  embedded PowerPC systems assume that all calls to variable argument
           functions are properly prototyped.  Otherwise, the compiler must  insert  an  instruction
           before  every  non-prototyped  call  to set or clear bit 6 of the condition code register
           ("CR") to indicate  whether  floating-point  values  are  passed  in  the  floating-point
           registers in case the function takes variable arguments.  With -mprototype, only calls to
           prototyped variable argument functions set or clear the bit.

       -msim
           On embedded PowerPC systems, assume that the startup module is called sim-crt0.o and that
           the   standard   C   libraries  are  libsim.a  and  libc.a.   This  is  the  default  for
           powerpc-*-eabisim configurations.

       -mmvme
           On embedded PowerPC systems, assume that the startup module  is  called  crt0.o  and  the
           standard C libraries are libmvme.a and libc.a.

       -mads
           On  embedded  PowerPC  systems,  assume  that the startup module is called crt0.o and the
           standard C libraries are libads.a and libc.a.

       -myellowknife
           On embedded PowerPC systems, assume that the startup module  is  called  crt0.o  and  the
           standard C libraries are libyk.a and libc.a.

       -mvxworks
           On  System V.4 and embedded PowerPC systems, specify that you are compiling for a VxWorks
           system.

       -memb
           On embedded PowerPC systems, set the "PPC_EMB" bit in the ELF flags  header  to  indicate
           that eabi extended relocations are used.

       -meabi
       -mno-eabi
           On  System  V.4  and  embedded  PowerPC  systems  do  (do  not)  adhere  to  the Embedded
           Applications Binary Interface (EABI), which is a set of modifications to the  System  V.4
           specifications.   Selecting -meabi means that the stack is aligned to an 8-byte boundary,
           a function "__eabi" is called from "main" to set up the EABI environment, and the -msdata
           option can use both "r2" and "r13" to point to two separate small data areas.   Selecting
           -mno-eabi  means  that the stack is aligned to a 16-byte boundary, no EABI initialization
           function is called from "main", and the -msdata option only uses  "r13"  to  point  to  a
           single  small  data area.  The -meabi option is on by default if you configured GCC using
           one of the powerpc*-*-eabi* options.

       -msdata=eabi
           On System V.4 and embedded PowerPC systems, put  small  initialized  "const"  global  and
           static  data  in  the ".sdata2" section, which is pointed to by register "r2".  Put small
           initialized non-"const" global and static data in the ".sdata" section, which is  pointed
           to  by  register  "r13".   Put  small uninitialized global and static data in the ".sbss"
           section, which  is  adjacent  to  the  ".sdata"  section.   The  -msdata=eabi  option  is
           incompatible  with the -mrelocatable option.  The -msdata=eabi option also sets the -memb
           option.

       -msdata=sysv
           On System V.4 and embedded PowerPC systems, put small  global  and  static  data  in  the
           ".sdata"  section, which is pointed to by register "r13".  Put small uninitialized global
           and static data in the ".sbss" section, which is adjacent to the ".sdata"  section.   The
           -msdata=sysv option is incompatible with the -mrelocatable option.

       -msdata=default
       -msdata
           On  System  V.4 and embedded PowerPC systems, if -meabi is used, compile code the same as
           -msdata=eabi, otherwise compile code the same as -msdata=sysv.

       -msdata=data
           On System V.4 and embedded PowerPC  systems,  put  small  global  data  in  the  ".sdata"
           section.   Put  small  uninitialized  global  data  in  the  ".sbss" section.  Do not use
           register "r13" to address small data however.  This is the default behavior unless  other
           -msdata options are used.

       -msdata=none
       -mno-sdata
           On  embedded  PowerPC  systems, put all initialized global and static data in the ".data"
           section, and all uninitialized data in the ".bss" section.

       -mreadonly-in-sdata
           Put read-only objects in the ".sdata" section as well.  This is the default.

       -mblock-move-inline-limit=num
           Inline all block moves (such as calls to "memcpy" or structure copies) less than or equal
           to num bytes.  The minimum value for num is 32 bytes on 32-bit targets and  64  bytes  on
           64-bit targets.  The default value is target-specific.

       -mblock-compare-inline-limit=num
           Generate  non-looping  inline  code  for all block compares (such as calls to "memcmp" or
           structure compares) less than or equal to num bytes. If num is 0,  all  inline  expansion
           (non-loop and loop) of block compare is disabled. The default value is target-specific.

       -mblock-compare-inline-loop-limit=num
           Generate an inline expansion using loop code for all block compares that are less than or
           equal  to  num  bytes,  but  greater  than  the  limit  for non-loop inline block compare
           expansion. If the block length is not constant, at most num bytes will be compared before
           "memcmp" is called to compare the remainder of the block. The default  value  is  target-
           specific.

       -mstring-compare-inline-limit=num
           Compare at most num string bytes with inline code.  If the difference or end of string is
           not found at the end of the inline compare a call to "strcmp" or "strncmp" will take care
           of the rest of the comparison. The default is 64 bytes.

       -G num
           On  embedded PowerPC systems, put global and static items less than or equal to num bytes
           into the small data or BSS sections instead of  the  normal  data  or  BSS  section.   By
           default,  num  is 8.  The -G num switch is also passed to the linker.  All modules should
           be compiled with the same -G num value.

       -mregnames
       -mno-regnames
           On System V.4 and embedded PowerPC systems  do  (do  not)  emit  register  names  in  the
           assembly language output using symbolic forms.

       -mlongcall
       -mno-longcall
           By default assume that all calls are far away so that a longer and more expensive calling
           sequence  is  required.  This is required for calls farther than 32 megabytes (33,554,432
           bytes) from the current location.  A short call is generated if the  compiler  knows  the
           call cannot be that far away.  This setting can be overridden by the "shortcall" function
           attribute, or by #pragma longcall(0).

           Some  linkers are capable of detecting out-of-range calls and generating glue code on the
           fly.  On these systems, long calls are unnecessary and generate slower code.  As of  this
           writing, the AIX linker can do this, as can the GNU linker for PowerPC/64.  It is planned
           to add this feature to the GNU linker for 32-bit PowerPC systems as well.

           On  PowerPC64  ELFv2  and 32-bit PowerPC systems with newer GNU linkers, GCC can generate
           long calls using an inline PLT call sequence (see -mpltseq).  PowerPC with -mbss-plt  and
           PowerPC64 ELFv1 (big-endian) do not support inline PLT calls.

           On  Darwin/PPC  systems,  "#pragma  longcall" generates "jbsr callee, L42", plus a branch
           island (glue code).  The two target addresses represent the callee and the branch island.
           The Darwin/PPC linker prefers the first address and generates a "bl callee"  if  the  PPC
           "bl" instruction reaches the callee directly; otherwise, the linker generates "bl L42" to
           call  the  branch  island.   The  branch  island  is  appended to the body of the calling
           function; it computes the full 32-bit address of the callee and jumps to it.

           On Mach-O (Darwin) systems, this option directs the compiler emit to the glue  for  every
           direct call, and the Darwin linker decides whether to use or discard it.

           In  the  future,  GCC  may ignore all longcall specifications when the linker is known to
           generate glue.

       -mpltseq
       -mno-pltseq
           Implement (do not implement) -fno-plt and long calls using an inline  PLT  call  sequence
           that  supports  lazy  linking  and  long calls to functions in dlopen'd shared libraries.
           Inline PLT calls are only supported on PowerPC64 ELFv2 and 32-bit  PowerPC  systems  with
           newer GNU linkers, and are enabled by default if the support is detected when configuring
           GCC,  and,  in  the case of 32-bit PowerPC, if GCC is configured with --enable-secureplt.
           -mpltseq code and  -mbss-plt  32-bit  PowerPC  relocatable  objects  may  not  be  linked
           together.

       -mtls-markers
       -mno-tls-markers
           Mark  (do  not  mark) calls to "__tls_get_addr" with a relocation specifying the function
           argument.  The relocation allows the linker to  reliably  associate  function  call  with
           argument  setup  instructions  for  TLS  optimization, which in turn allows GCC to better
           schedule the sequence.

       -mrecip
       -mno-recip
           This option enables use of the reciprocal estimate and reciprocal  square  root  estimate
           instructions  with additional Newton-Raphson steps to increase precision instead of doing
           a divide or square root and divide for floating-point  arguments.   You  should  use  the
           -ffast-math   option   when  using  -mrecip  (or  at  least  -funsafe-math-optimizations,
           -ffinite-math-only, -freciprocal-math  and  -fno-trapping-math).   Note  that  while  the
           throughput  of the sequence is generally higher than the throughput of the non-reciprocal
           instruction, the precision of the sequence can be decreased by up  to  2  ulp  (i.e.  the
           inverse of 1.0 equals 0.99999994) for reciprocal square roots.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may be used.  opt is a comma-
           separated list of options, which may be preceded by a "!" to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable   the  reciprocal  approximation  instructions  for  both  single  and  double
               precision.

           divf
               Enable the single-precision reciprocal approximation instructions.

           divd
               Enable the double-precision reciprocal approximation instructions.

           rsqrt
               Enable the reciprocal square root approximation  instructions  for  both  single  and
               double precision.

           rsqrtf
               Enable the single-precision reciprocal square root approximation instructions.

           rsqrtd
               Enable the double-precision reciprocal square root approximation instructions.

           So, for example, -mrecip=all,!rsqrtd enables all of the reciprocal estimate instructions,
           except  for  the  "FRSQRTE", "XSRSQRTEDP", and "XVRSQRTEDP" instructions which handle the
           double-precision reciprocal square root calculations.

       -mrecip-precision
       -mno-recip-precision
           Assume (do not assume) that the reciprocal estimate instructions provide higher-precision
           estimates than is mandated by the PowerPC ABI.  Selecting -mcpu=power6,  -mcpu=power7  or
           -mcpu=power8  automatically  selects -mrecip-precision.  The double-precision square root
           estimate instructions are not generated by default on low-precision machines, since  they
           do not provide an estimate that converges after three steps.

       -mveclibabi=type
           Specifies  the ABI type to use for vectorizing intrinsics using an external library.  The
           only type supported at present  is  mass,  which  specifies  to  use  IBM's  Mathematical
           Acceleration  Subsystem  (MASS)  libraries  for  vectorizing  intrinsics  using  external
           libraries.  GCC currently  emits  calls  to  "acosd2",  "acosf4",  "acoshd2",  "acoshf4",
           "asind2",  "asinf4",  "asinhd2",  "asinhf4",  "atan2d2",  "atan2f4",  "atand2", "atanf4",
           "atanhd2", "atanhf4", "cbrtd2", "cbrtf4", "cosd2", "cosf4", "coshd2", "coshf4", "erfcd2",
           "erfcf4", "erfd2", "erff4", "exp2d2", "exp2f4", "expd2", "expf4",  "expm1d2",  "expm1f4",
           "hypotd2", "hypotf4", "lgammad2", "lgammaf4", "log10d2", "log10f4", "log1pd2", "log1pf4",
           "log2d2",  "log2f4",  "logd2",  "logf4",  "powd2",  "powf4",  "sind2", "sinf4", "sinhd2",
           "sinhf4", "sqrtd2", "sqrtf4", "tand2", "tanf4", "tanhd2", and  "tanhf4"  when  generating
           code  for  power7.   Both  -ftree-vectorize  and -funsafe-math-optimizations must also be
           enabled.  The MASS libraries must be specified at link time.

       -mfriz
       -mno-friz
           Generate (do not generate) the "friz" instruction  when  the  -funsafe-math-optimizations
           option  is  used to optimize rounding of floating-point values to 64-bit integer and back
           to floating point.  The "friz"  instruction  does  not  return  the  same  value  if  the
           floating-point number is too large to fit in an integer.

       -mpointers-to-nested-functions
       -mno-pointers-to-nested-functions
           Generate (do not generate) code to load up the static chain register ("r11") when calling
           through  a  pointer  on AIX and 64-bit Linux systems where a function pointer points to a
           3-word descriptor giving the function address, TOC value to be loaded in  register  "r2",
           and    static    chain    value    to    be    loaded    in    register    "r11".     The
           -mpointers-to-nested-functions is on by default.  You cannot  call  through  pointers  to
           nested functions or pointers to functions compiled in other languages that use the static
           chain if you use -mno-pointers-to-nested-functions.

       -msave-toc-indirect
       -mno-save-toc-indirect
           Generate  (do  not generate) code to save the TOC value in the reserved stack location in
           the function prologue if the function calls through a pointer on  AIX  and  64-bit  Linux
           systems.  If the TOC value is not saved in the prologue, it is saved just before the call
           through the pointer.  The -mno-save-toc-indirect option is the default.

       -mcompat-align-parm
       -mno-compat-align-parm
           Generate  (do not generate) code to pass structure parameters with a maximum alignment of
           64 bits, for compatibility with older versions of GCC.

           Older versions of GCC (prior to 4.9.0) incorrectly did not align a structure parameter on
           a 128-bit boundary when that structure contained a member  requiring  128-bit  alignment.
           This  is  corrected  in more recent versions of GCC.  This option may be used to generate
           code that is compatible with functions compiled with older versions of GCC.

           The -mno-compat-align-parm option is the default.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
       -mstack-protector-guard-symbol=symbol
           Generate stack protection code using canary at guard.  Supported locations are global for
           global canary or tls for per-thread canary in the TLS block (the default  with  GNU  libc
           version 2.4 or later).

           With    the    latter    choice    the    options   -mstack-protector-guard-reg=reg   and
           -mstack-protector-guard-offset=offset furthermore specify which register to use  as  base
           register  for  reading  the  canary,  and  from  what offset from that base register. The
           default    for     those     is     as     specified     in     the     relevant     ABI.
           -mstack-protector-guard-symbol=symbol  overrides  the offset with a symbol reference to a
           canary in the TLS block.

       -mpcrel
       -mno-pcrel
           Generate (do not generate) pc-relative addressing.  The -mpcrel option requires that  the
           medium  code  model  (-mcmodel=medium)  and  prefixed addressing (-mprefixed) options are
           enabled.

       -mprefixed
       -mno-prefixed
           Generate (do not generate) addressing modes using prefixed load and  store  instructions.
           The -mprefixed option requires that the option -mcpu=power10 (or later) is enabled.

       -mmma
       -mno-mma
           Generate  (do  not  generate)  the  MMA  instructions.  The -mma option requires that the
           option -mcpu=power10 (or later) is enabled.

       -mrop-protect
       -mno-rop-protect
           Generate (do not generate) ROP protection instructions when the target processor supports
           them.  Currently this option disables the shrink-wrap optimization (-fshrink-wrap).

       -mprivileged
       -mno-privileged
           Generate (do not generate) code that will run in privileged state.

       -mblock-ops-unaligned-vsx
       -mno-block-ops-unaligned-vsx
           Generate (do not generate) unaligned  vsx  loads  and  stores  for  inline  expansion  of
           "memcpy" and "memmove".

       RX Options

       These command-line options are defined for RX targets:

       -m64bit-doubles
       -m32bit-doubles
           Make  the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles) in
           size.  The default is -m32bit-doubles.  Note RX floating-point  hardware  only  works  on
           32-bit values, which is why the default is -m32bit-doubles.

       -fpu
       -nofpu
           Enables  (-fpu)  or disables (-nofpu) the use of RX floating-point hardware.  The default
           is enabled for the RX600 series and disabled for the RX200 series.

           Floating-point instructions are only generated for 32-bit floating-point values, however,
           so the FPU hardware is not used for doubles if the -m64bit-doubles option is used.

           Note If the -fpu option is  enabled  then  -funsafe-math-optimizations  is  also  enabled
           automatically.  This is because the RX FPU instructions are themselves unsafe.

       -mcpu=name
           Selects  the  type  of  RX  CPU to be targeted.  Currently three types are supported, the
           generic RX600 and RX200 series hardware and the  specific  RX610  CPU.   The  default  is
           RX600.

           The  only  difference  between  RX600  and  RX610  is that the RX610 does not support the
           "MVTIPL" instruction.

           The RX200 series does not have a hardware floating-point unit and so -nofpu is enabled by
           default when this type is selected.

       -mbig-endian-data
       -mlittle-endian-data
           Store data (but not code) in the big-endian format.  The default is -mlittle-endian-data,
           i.e. to store data in the little-endian format.

       -msmall-data-limit=N
           Specifies the maximum size in bytes of global and static variables which  can  be  placed
           into the small data area.  Using the small data area can lead to smaller and faster code,
           but  the  size  of area is limited and it is up to the programmer to ensure that the area
           does not overflow.  Also when the small data area is  used  one  of  the  RX's  registers
           (usually  "r13")  is reserved for use pointing to this area, so it is no longer available
           for use by the compiler.  This could result in slower and/or larger code if variables are
           pushed onto the stack instead of being held in this register.

           Note, common variables (variables that have not been initialized) and constants  are  not
           placed  into  the  small  data  area as they are assigned to other sections in the output
           executable.

           The default value is zero, which disables  this  feature.   Note,  this  feature  is  not
           enabled  by  default with higher optimization levels (-O2 etc) because of the potentially
           detrimental effects of reserving a register.  It is up to the  programmer  to  experiment
           and discover whether this feature is of benefit to their program.  See the description of
           the -mpid option for a description of how the actual register to hold the small data area
           pointer is chosen.

       -msim
       -mno-sim
           Use the simulator runtime.  The default is to use the libgloss board-specific runtime.

       -mas100-syntax
       -mno-as100-syntax
           When  generating  assembler  output  use a syntax that is compatible with Renesas's AS100
           assembler.  This syntax can also be handled  by  the  GAS  assembler,  but  it  has  some
           restrictions so it is not generated by default.

       -mmax-constant-size=N
           Specifies  the  maximum size, in bytes, of a constant that can be used as an operand in a
           RX instruction.  Although the RX instruction set does allow constants of up to 4 bytes in
           length to be used in instructions, a longer value equates to a longer instruction.   Thus
           in  some  circumstances  it  can be beneficial to restrict the size of constants that are
           used in instructions.  Constants that are too big are instead placed into a constant pool
           and referenced via register indirection.

           The value N can be between 0 and 4.  A value of 0 (the default) or 4 means that constants
           of any size are allowed.

       -mrelax
           Enable linker relaxation.  Linker relaxation is a process whereby the linker attempts  to
           reduce  the  size  of  a  program  by  finding  shorter versions of various instructions.
           Disabled by default.

       -mint-register=N
           Specify the number of registers to reserve for fast  interrupt  handler  functions.   The
           value  N  can be between 0 and 4.  A value of 1 means that register "r13" is reserved for
           the exclusive use of fast interrupt handlers.  A value of 2 reserves "r13" and "r12".   A
           value  of  3  reserves  "r13",  "r12"  and "r11", and a value of 4 reserves "r13" through
           "r10".  A value of 0, the default, does not reserve any registers.

       -msave-acc-in-interrupts
           Specifies that interrupt handler functions  should  preserve  the  accumulator  register.
           This  is  only  necessary  if normal code might use the accumulator register, for example
           because it performs 64-bit multiplications.  The default is to ignore the accumulator  as
           this makes the interrupt handlers faster.

       -mpid
       -mno-pid
           Enables the generation of position independent data.  When enabled any access to constant
           data  is  done  via  an  offset  from a base address held in a register.  This allows the
           location of constant data to be determined at run time without requiring  the  executable
           to  be  relocated,  which  is  a  benefit  to  embedded  applications  with  tight memory
           constraints.  Data that can be modified is not affected by this option.

           Note, using this feature reserves a register, usually "r13", for the constant  data  base
           address.   This  can  result  in  slower  and/or  larger  code, especially in complicated
           functions.

           The actual register chosen to hold the constant data base address  depends  upon  whether
           the  -msmall-data-limit  and/or  the  -mint-register  command-line  options  are enabled.
           Starting with register "r13" and proceeding downwards, registers are allocated  first  to
           satisfy  the  requirements  of -mint-register, then -mpid and finally -msmall-data-limit.
           Thus it is possible for the small data area register to be "r8" if both  -mint-register=4
           and -mpid are specified on the command line.

           By  default  this  feature  is not enabled.  The default can be restored via the -mno-pid
           command-line option.

       -mno-warn-multiple-fast-interrupts
       -mwarn-multiple-fast-interrupts
           Prevents GCC from issuing a warning message if it finds  more  than  one  fast  interrupt
           handler  when  it  is compiling a file.  The default is to issue a warning for each extra
           fast interrupt handler found, as the RX only supports one such interrupt.

       -mallow-string-insns
       -mno-allow-string-insns
           Enables or disables the use of the string  manipulation  instructions  "SMOVF",  "SCMPU",
           "SMOVB",  "SMOVU", "SUNTIL" "SWHILE" and also the "RMPA" instruction.  These instructions
           may prefetch data, which is not safe to do if accessing an I/O  register.   (See  section
           12.2.7 of the RX62N Group User's Manual for more information).

           The  default  is  to allow these instructions, but it is not possible for GCC to reliably
           detect all circumstances where a string instruction  might  be  used  to  access  an  I/O
           register,  so their use cannot be disabled automatically.  Instead it is reliant upon the
           programmer to use the -mno-allow-string-insns option if their program accesses I/O space.

           When  the  instructions   are   enabled   GCC   defines   the   C   preprocessor   symbol
           "__RX_ALLOW_STRING_INSNS__",       otherwise       it       defines       the      symbol
           "__RX_DISALLOW_STRING_INSNS__".

       -mjsr
       -mno-jsr
           Use only (or not only) "JSR" instructions to access functions.  This option can  be  used
           when code size exceeds the range of "BSR" instructions.  Note that -mno-jsr does not mean
           to not use "JSR" but instead means that any type of branch may be used.

       Note: The generic GCC command-line option -ffixed-reg has special significance to the RX port
       when  used  with  the  "interrupt"  function  attribute.  This attribute indicates a function
       intended to process fast interrupts.  GCC ensures that it  only  uses  the  registers  "r10",
       "r11",  "r12"  and/or  "r13"  and  only  provided  that  the  normal use of the corresponding
       registers have been restricted via the -ffixed-reg or -mint-register command-line options.

       S/390 and zSeries Options

       These are the -m options defined for the S/390 and zSeries architecture.

       -mhard-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions  and  registers  for  floating-
           point  operations.   When  -msoft-float  is  specified, functions in libgcc.a are used to
           perform  floating-point  operations.   When  -mhard-float  is  specified,  the   compiler
           generates IEEE floating-point instructions.  This is the default.

       -mhard-dfp
       -mno-hard-dfp
           Use  (do  not use) the hardware decimal-floating-point instructions for decimal-floating-
           point operations.  When -mno-hard-dfp is specified, functions in  libgcc.a  are  used  to
           perform  decimal-floating-point  operations.   When -mhard-dfp is specified, the compiler
           generates  decimal-floating-point  hardware  instructions.   This  is  the  default   for
           -march=z9-ec or higher.

       -mlong-double-64
       -mlong-double-128
           These  switches control the size of "long double" type. A size of 64 bits makes the "long
           double" type equivalent to the "double" type. This is the default.

       -mbackchain
       -mno-backchain
           Store (do not store) the address of the caller's frame  as  backchain  pointer  into  the
           callee's  stack  frame.  A backchain may be needed to allow debugging using tools that do
           not understand DWARF call frame information.  When -mno-packed-stack is  in  effect,  the
           backchain  pointer  is stored at the bottom of the stack frame; when -mpacked-stack is in
           effect, the backchain is placed into the topmost word of the 96/160  byte  register  save
           area.

           In  general,  code  compiled  with -mbackchain is call-compatible with code compiled with
           -mno-backchain; however, use of the backchain for  debugging  purposes  usually  requires
           that  the  whole  binary  is  built  with  -mbackchain.   Note  that  the  combination of
           -mbackchain, -mpacked-stack and -mhard-float is not supported.  In order to build a linux
           kernel use -msoft-float.

           The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
           Use (do not use) the packed stack  layout.   When  -mno-packed-stack  is  specified,  the
           compiler uses the all fields of the 96/160 byte register save area only for their default
           purpose;  unused  fields  still  take  up stack space.  When -mpacked-stack is specified,
           register save slots are densely packed at the top of the register save area; unused space
           is reused for other purposes, allowing for more efficient  use  of  the  available  stack
           space.  However, when -mbackchain is also in effect, the topmost word of the save area is
           always  used  to store the backchain, and the return address register is always saved two
           words below the backchain.

           As long as the stack frame backchain is not used, code generated with  -mpacked-stack  is
           call-compatible  with  code  generated  with  -mno-packed-stack.   Note that some non-FSF
           releases of GCC 2.95 for S/390 or zSeries  generated  code  that  uses  the  stack  frame
           backchain at run time, not just for debugging purposes.  Such code is not call-compatible
           with  code compiled with -mpacked-stack.  Also, note that the combination of -mbackchain,
           -mpacked-stack and -mhard-float is not supported.  In order to build a linux  kernel  use
           -msoft-float.

           The default is to not use the packed stack layout.

       -msmall-exec
       -mno-small-exec
           Generate  (or  do not generate) code using the "bras" instruction to do subroutine calls.
           This only works reliably if the total executable size does not exceed 64k.   The  default
           is to use the "basr" instruction instead, which does not have this limitation.

       -m64
       -m31
           When  -m31  is  specified,  generate code compliant to the GNU/Linux for S/390 ABI.  When
           -m64 is specified, generate code compliant to the GNU/Linux for zSeries ABI.  This allows
           GCC in particular to generate 64-bit instructions.  For the s390 targets, the default  is
           -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
           When   -mzarch   is   specified,  generate  code  using  the  instructions  available  on
           z/Architecture.  When -mesa is specified, generate code using the instructions  available
           on  ESA/390.   Note that -mesa is not possible with -m64.  When generating code compliant
           to the GNU/Linux for S/390 ABI, the default is -mesa.  When generating code compliant  to
           the GNU/Linux for zSeries ABI, the default is -mzarch.

       -mhtm
       -mno-htm
           The  -mhtm option enables a set of builtins making use of instructions available with the
           transactional execution  facility  introduced  with  the  IBM  zEnterprise  EC12  machine
           generation  S/390  System  z  Built-in Functions.  -mhtm is enabled by default when using
           -march=zEC12.

       -mvx
       -mno-vx
           When -mvx is specified, generate code using the instructions available  with  the  vector
           extension  facility  introduced with the IBM z13 machine generation.  This option changes
           the ABI for some vector type values with regard to alignment and calling conventions.  In
           case vector type values are being used in an ABI-relevant context  a  GAS  .gnu_attribute
           command will be added to mark the resulting binary with the ABI used.  -mvx is enabled by
           default when using -march=z13.

       -mzvector
       -mno-zvector
           The  -mzvector  option enables vector language extensions and builtins using instructions
           available with the  vector  extension  facility  introduced  with  the  IBM  z13  machine
           generation.  This option adds support for vector to be used as a keyword to define vector
           type  variables and arguments.  vector is only available when GNU extensions are enabled.
           It will not be expanded when requesting strict standard compliance  e.g.  with  -std=c99.
           In  addition  to the GCC low-level builtins -mzvector enables a set of builtins added for
           compatibility with AltiVec-style implementations like Power and Cell.  In order  to  make
           use  of  these  builtins  the header file vecintrin.h needs to be included.  -mzvector is
           disabled by default.

       -mmvcle
       -mno-mvcle
           Generate (or do not generate) code using the "mvcle" instruction to perform block  moves.
           When  -mno-mvcle  is  specified,  use  a  "mvc" loop instead.  This is the default unless
           optimizing for size.

       -mdebug
       -mno-debug
           Print (or do not print) additional debug information when compiling.  The default  is  to
           not print debug information.

       -march=cpu-type
           Generate code that runs on cpu-type, which is the name of a system representing a certain
           processor  type.   Possible  values  for  cpu-type  are  z900/arch5,  z990/arch6, z9-109,
           z9-ec/arch7,  z10/arch8,   z196/arch9,   zEC12,   z13/arch11,   z14/arch12,   z15/arch13,
           z16/arch14, and native.

           The default is -march=z900.

           Specifying  native as cpu type can be used to select the best architecture option for the
           host processor.  -march=native has no effect if GCC does not recognize the processor.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the  ABI  and
           the  set  of  available  instructions.   The  list  of cpu-type values is the same as for
           -march.  The default is the value used for -march.

       -mtpf-trace
       -mno-tpf-trace
           Generate code that adds (does not add) in TPF OS specific branches to trace  routines  in
           the operating system.  This option is off by default, even when compiling for the TPF OS.

       -mtpf-trace-skip
       -mno-tpf-trace-skip
           Generate  code  that  changes  (does  not  change)  the default branch targets enabled by
           -mtpf-trace to point to specialized trace routines providing the ability  of  selectively
           skipping function trace entries for the TPF OS.  This option is off by default, even when
           compiling for the TPF OS and specifying -mtpf-trace.

       -mfused-madd
       -mno-fused-madd
           Generate  code  that  uses  (does  not  use)  the  floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point  is
           used.

       -mwarn-framesize=framesize
           Emit  a  warning if the current function exceeds the given frame size.  Because this is a
           compile-time check it doesn't need to be a real problem when the  program  runs.   It  is
           intended  to  identify functions that most probably cause a stack overflow.  It is useful
           to be used in an environment with limited stack size e.g. the linux kernel.

       -mwarn-dynamicstack
           Emit a warning if the function calls "alloca" or uses dynamically-sized arrays.  This  is
           generally a bad idea with a limited stack size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
           If  these  options  are  provided the S/390 back end emits additional instructions in the
           function prologue that trigger a trap if the stack size is stack-guard  bytes  above  the
           stack-size  (remember that the stack on S/390 grows downward).  If the stack-guard option
           is omitted the smallest power of 2 larger than the frame size of the compiled function is
           chosen.  These options are intended to be used to help debugging stack overflow problems.
           The additionally emitted code causes only little overhead and hence can also be  used  in
           production-like  systems  without greater performance degradation.  The given values have
           to be exact powers of 2 and  stack-size  has  to  be  greater  than  stack-guard  without
           exceeding  64k.   In  order  to be efficient the extra code makes the assumption that the
           stack starts at an address aligned to the value given  by  stack-size.   The  stack-guard
           option can only be used in conjunction with stack-size.

       -mhotpatch=pre-halfwords,post-halfwords
           If  the  hotpatch  option is enabled, a "hot-patching" function prologue is generated for
           all functions in the compilation unit.  The funtion label is  prepended  with  the  given
           number of two-byte NOP instructions (pre-halfwords, maximum 1000000).  After the label, 2
           *  post-halfwords  bytes  are  appended,  using  the  largest  NOP  like instructions the
           architecture allows (maximum 1000000).

           If both arguments are zero, hotpatching is disabled.

           This option can be overridden for individual functions with the "hotpatch" attribute.

       Score Options

       These options are defined for Score implementations:

       -meb
           Compile code for big-endian mode.  This is the default.

       -mel
           Compile code for little-endian mode.

       -mnhwloop
           Disable generation of "bcnz" instructions.

       -muls
           Enable generation of unaligned load and store instructions.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mscore5
           Specify the SCORE5 as the target architecture.

       -mscore5u
           Specify the SCORE5U of the target architecture.

       -mscore7
           Specify the SCORE7 as the target architecture. This is the default.

       -mscore7d
           Specify the SCORE7D as the target architecture.

       SH Options

       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
           Generate code for the SH2e.

       -m2a-nofpu
           Generate code for the SH2a without FPU, or  for  a  SH2a-FPU  in  such  a  way  that  the
           floating-point unit is not used.

       -m2a-single-only
           Generate  code  for  the  SH2a-FPU, in such a way that no double-precision floating-point
           operations are used.

       -m2a-single
           Generate code for the SH2a-FPU assuming the floating-point unit  is  in  single-precision
           mode by default.

       -m2a
           Generate  code  for  the SH2a-FPU assuming the floating-point unit is in double-precision
           mode by default.

       -m3 Generate code for the SH3.

       -m3e
           Generate code for the SH3e.

       -m4-nofpu
           Generate code for the SH4 without a floating-point unit.

       -m4-single-only
           Generate code for the SH4 with a floating-point unit that only supports  single-precision
           arithmetic.

       -m4-single
           Generate code for the SH4 assuming the floating-point unit is in single-precision mode by
           default.

       -m4 Generate code for the SH4.

       -m4-100
           Generate code for SH4-100.

       -m4-100-nofpu
           Generate code for SH4-100 in such a way that the floating-point unit is not used.

       -m4-100-single
           Generate code for SH4-100 assuming the floating-point unit is in single-precision mode by
           default.

       -m4-100-single-only
           Generate  code  for  SH4-100  in  such  a  way  that  no  double-precision floating-point
           operations are used.

       -m4-200
           Generate code for SH4-200.

       -m4-200-nofpu
           Generate code for SH4-200 without in such a way that the floating-point unit is not used.

       -m4-200-single
           Generate code for SH4-200 assuming the floating-point unit is in single-precision mode by
           default.

       -m4-200-single-only
           Generate code  for  SH4-200  in  such  a  way  that  no  double-precision  floating-point
           operations are used.

       -m4-300
           Generate code for SH4-300.

       -m4-300-nofpu
           Generate code for SH4-300 without in such a way that the floating-point unit is not used.

       -m4-300-single
           Generate  code  for  SH4-300  in  such  a  way  that  no  double-precision floating-point
           operations are used.

       -m4-300-single-only
           Generate code  for  SH4-300  in  such  a  way  that  no  double-precision  floating-point
           operations are used.

       -m4-340
           Generate code for SH4-340 (no MMU, no FPU).

       -m4-500
           Generate code for SH4-500 (no FPU).  Passes -isa=sh4-nofpu to the assembler.

       -m4a-nofpu
           Generate code for the SH4al-dsp, or for a SH4a in such a way that the floating-point unit
           is not used.

       -m4a-single-only
           Generate  code  for  the  SH4a,  in  such  a  way that no double-precision floating-point
           operations are used.

       -m4a-single
           Generate code for the SH4a assuming the floating-point unit is in  single-precision  mode
           by default.

       -m4a
           Generate code for the SH4a.

       -m4al
           Same  as -m4a-nofpu, except that it implicitly passes -dsp to the assembler.  GCC doesn't
           generate any DSP instructions at the moment.

       -mb Compile code for the processor in big-endian mode.

       -ml Compile code for the processor in little-endian mode.

       -mdalign
           Align doubles at 64-bit boundaries.  Note that this changes the calling conventions,  and
           thus some functions from the standard C library do not work unless you recompile it first
           with -mdalign.

       -mrelax
           Shorten  some  address  references  at  link  time, when possible; uses the linker option
           -relax.

       -mbigtable
           Use 32-bit offsets in "switch" tables.  The default is to use 16-bit offsets.

       -mbitops
           Enable the use of bit manipulation instructions on SH2A.

       -mfmovd
           Enable the use of the instruction "fmovd".  Check -mdalign for alignment constraints.

       -mrenesas
           Comply with the calling conventions defined by Renesas.

       -mno-renesas
           Comply with the calling conventions defined for GCC before the Renesas  conventions  were
           available.  This option is the default for all targets of the SH toolchain.

       -mnomacsave
           Mark the "MAC" register as call-clobbered, even if -mrenesas is given.

       -mieee
       -mno-ieee
           Control  the IEEE compliance of floating-point comparisons, which affects the handling of
           cases where the result of a comparison is unordered.  By  default  -mieee  is  implicitly
           enabled.   If -ffinite-math-only is enabled -mno-ieee is implicitly set, which results in
           faster floating-point greater-equal and less-equal comparisons.   The  implicit  settings
           can be overridden by specifying either -mieee or -mno-ieee.

       -minline-ic_invalidate
           Inline  code  to  invalidate  instruction  cache entries after setting up nested function
           trampolines.  This option has no effect if -musermode is in effect and the selected  code
           generation  option  (e.g.  -m4) does not allow the use of the "icbi" instruction.  If the
           selected code generation option does not allow the use of  the  "icbi"  instruction,  and
           -musermode  is  not in effect, the inlined code manipulates the instruction cache address
           array directly with an associative write.  This not only requires privileged mode at  run
           time,  but  it  also  fails  if the cache line had been mapped via the TLB and has become
           unmapped.

       -misize
           Dump instruction size and location in the assembly code.

       -mpadstruct
           This option is deprecated.   It  pads  structures  to  multiple  of  4  bytes,  which  is
           incompatible with the SH ABI.

       -matomic-model=model
           Sets  the model of atomic operations and additional parameters as a comma separated list.
           For details on the atomic built-in functions see __atomic Builtins.  The following models
           and parameters are supported:

           none
               Disable compiler generated  atomic  sequences  and  emit  library  calls  for  atomic
               operations.  This is the default if the target is not "sh*-*-linux*".

           soft-gusa
               Generate  GNU/Linux compatible gUSA software atomic sequences for the atomic built-in
               functions.  The generated  atomic  sequences  require  additional  support  from  the
               interrupt/exception  handling  code  of the system and are only suitable for SH3* and
               SH4* single-core systems.  This option is enabled  by  default  when  the  target  is
               "sh*-*-linux*" and SH3* or SH4*.  When the target is SH4A, this option also partially
               utilizes  the  hardware  atomic  instructions  "movli.l" and "movco.l" to create more
               efficient code, unless strict is specified.

           soft-tcb
               Generate software atomic sequences that use a variable in the thread  control  block.
               This  is  a  variation  of the gUSA sequences which can also be used on SH1* and SH2*
               targets.   The  generated  atomic  sequences  require  additional  support  from  the
               interrupt/exception handling code of the system and are only suitable for single-core
               systems.   When  using  this  model, the gbr-offset= parameter has to be specified as
               well.

           soft-imask
               Generate software atomic sequences that temporarily  disable  interrupts  by  setting
               "SR.IMASK  =  1111".   This model works only when the program runs in privileged mode
               and  is  only  suitable  for  single-core  systems.   Additional  support  from   the
               interrupt/exception  handling  code  of  the  system  is not required.  This model is
               enabled by default when the target is "sh*-*-linux*" and SH1* or SH2*.

           hard-llcs
               Generate hardware atomic sequences using the  "movli.l"  and  "movco.l"  instructions
               only.   This is only available on SH4A and is suitable for multi-core systems.  Since
               the hardware instructions support only 32 bit atomic variables access to 8 or 16  bit
               variables  is  emulated with 32 bit accesses.  Code compiled with this option is also
               compatible with other software atomic model interrupt/exception handling  systems  if
               executed on an SH4A system.  Additional support from the interrupt/exception handling
               code of the system is not required for this model.

           gbr-offset=
               This  parameter  specifies  the offset in bytes of the variable in the thread control
               block structure that should be used by the generated atomic sequences when the  soft-
               tcb  model  has  been  selected.   For  other  models this parameter is ignored.  The
               specified value must be an integer multiple of four and in the range 0-1020.

           strict
               This parameter prevents mixed usage of multiple  atomic  models,  even  if  they  are
               compatible,  and  makes the compiler generate atomic sequences of the specified model
               only.

       -mtas
           Generate the "tas.b" opcode for "__atomic_test_and_set".  Notice that  depending  on  the
           particular  hardware  and software configuration this can degrade overall performance due
           to the operand cache line flushes that are implied by the "tas.b" instruction.  On multi-
           core SH4A processors the "tas.b" instruction must be  used  with  caution  since  it  can
           result in data corruption for certain cache configurations.

       -mprefergot
           When  generating  position-independent  code, emit function calls using the Global Offset
           Table instead of the Procedure Linkage Table.

       -musermode
       -mno-usermode
           Don't allow (allow) the compiler generating privileged mode code.  Specifying  -musermode
           also  implies  -mno-inline-ic_invalidate if the inlined code would not work in user mode.
           -musermode is the default when the target is "sh*-*-linux*".  If the target  is  SH1*  or
           SH2* -musermode has no effect, since there is no user mode.

       -multcost=number
           Set the cost to assume for a multiply insn.

       -mdiv=strategy
           Set  the  division  strategy to be used for integer division operations.  strategy can be
           one of:

           call-div1
               Calls a library function that uses the single-step  division  instruction  "div1"  to
               perform  the  operation.   Division by zero calculates an unspecified result and does
               not trap.  This is the default except for SH4, SH2A and SHcompact.

           call-fp
               Calls a library function that performs the operation  in  double  precision  floating
               point.   Division by zero causes a floating-point exception.  This is the default for
               SHcompact with FPU.  Specifying this for targets that do not have a double  precision
               FPU defaults to "call-div1".

           call-table
               Calls  a  library function that uses a lookup table for small divisors and the "div1"
               instruction with case distinction for larger divisors.  Division by  zero  calculates
               an  unspecified  result  and does not trap.  This is the default for SH4.  Specifying
               this for targets that do not have dynamic shift instructions defaults to "call-div1".

           When a division strategy has not been specified the default strategy is selected based on
           the current target.  For SH2A the default strategy  is  to  use  the  "divs"  and  "divu"
           instructions instead of library function calls.

       -maccumulate-outgoing-args
           Reserve  space  once  for  outgoing arguments in the function prologue rather than around
           each call.  Generally beneficial for performance and size.  Also needed for unwinding  to
           avoid changing the stack frame around conditional code.

       -mdivsi3_libfunc=name
           Set  the name of the library function used for 32-bit signed division to name.  This only
           affects the name used in the call division strategies, and the compiler still expects the
           same sets of input/output/clobbered registers as if this option were not present.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register  is
           one  that  the register allocator cannot use.  This is useful when compiling kernel code.
           A register range is specified as two registers separated by a  dash.   Multiple  register
           ranges can be specified separated by a comma.

       -mbranch-cost=num
           Assume num to be the cost for a branch instruction.  Higher numbers make the compiler try
           to  generate  more  branch-free code if possible.  If not specified the value is selected
           depending on the processor type that is being compiled for.

       -mzdcbranch
       -mno-zdcbranch
           Assume (do not assume) that zero displacement conditional branch  instructions  "bt"  and
           "bf"  are  fast.   If  -mzdcbranch  is  specified, the compiler prefers zero displacement
           branch code sequences.  This is enabled by default when generating code for SH4 and SH4A.
           It can be explicitly disabled by specifying -mno-zdcbranch.

       -mcbranch-force-delay-slot
           Force the usage of delay slots for conditional branches, which stuffs the delay slot with
           a "nop" if a suitable instruction cannot be found.  By default this option  is  disabled.
           It can be enabled to work around hardware bugs as found in the original SH7055.

       -mfused-madd
       -mno-fused-madd
           Generate  code  that  uses  (does  not  use)  the  floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point  is
           used.  The machine-dependent -mfused-madd option is now mapped to the machine-independent
           -ffp-contract=fast option, and -mno-fused-madd is mapped to -ffp-contract=off.

       -mfsca
       -mno-fsca
           Allow  or  disallow  the  compiler  to  emit  the  "fsca" instruction for sine and cosine
           approximations.    The   option   -mfsca   must   be    used    in    combination    with
           -funsafe-math-optimizations.   It  is  enabled  by default when generating code for SH4A.
           Using    -mno-fsca    disables    sine    and    cosine    approximations     even     if
           -funsafe-math-optimizations is in effect.

       -mfsrra
       -mno-fsrra
           Allow or disallow the compiler to emit the "fsrra" instruction for reciprocal square root
           approximations.     The    option    -mfsrra   must   be   used   in   combination   with
           -funsafe-math-optimizations and  -ffinite-math-only.   It  is  enabled  by  default  when
           generating   code   for   SH4A.    Using   -mno-fsrra  disables  reciprocal  square  root
           approximations even if -funsafe-math-optimizations and -ffinite-math-only are in effect.

       -mpretend-cmove
           Prefer zero-displacement conditional branches for conditional move instruction  patterns.
           This can result in faster code on the SH4 processor.

       -mfdpic
           Generate code using the FDPIC ABI.

       Solaris 2 Options

       These -m options are supported on Solaris 2:

       -mclear-hwcap
           -mclear-hwcap  tells  the  compiler  to remove the hardware capabilities generated by the
           Solaris assembler.  This is only necessary when  object  files  use  ISA  extensions  not
           supported by the current machine, but check at runtime whether or not to use them.

       -mimpure-text
           -mimpure-text, used in addition to -shared, tells the compiler to not pass -z text to the
           linker  when linking a shared object.  Using this option, you can link position-dependent
           code into a shared object.

           -mimpure-text suppresses the "relocations remain  against  allocatable  but  non-writable
           sections"  linker  error  message.   However,  the necessary relocations trigger copy-on-
           write, and the shared object is not actually shared across processes.  Instead  of  using
           -mimpure-text, you should compile all source code with -fpic or -fPIC.

       These switches are supported in addition to the above on Solaris 2:

       -pthreads
           This is a synonym for -pthread.

       SPARC Options

       These -m options are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
           Specify  -mapp-regs  to generate output using the global registers 2 through 4, which the
           SPARC SVR4 ABI reserves for applications.   Like  the  global  register  1,  each  global
           register  2  through  4  is  then  treated  as an allocable register that is clobbered by
           function calls.  This is the default.

           To  be  fully  SVR4  ABI-compliant  at  the  cost  of  some  performance  loss,   specify
           -mno-app-regs.  You should compile libraries and system software with this option.

       -mflat
       -mno-flat
           With  -mflat,  the compiler does not generate save/restore instructions and uses a "flat"
           or single register window model.  This model is  compatible  with  the  regular  register
           window  model.   The  local registers and the input registers (0--5) are still treated as
           "call-saved" registers and are saved on the stack as needed.

           With -mno-flat (the default), the compiler generates  save/restore  instructions  (except
           for leaf functions).  This is the normal operating mode.

       -mfpu
       -mhard-float
           Generate output containing floating-point instructions.  This is the default.

       -mno-fpu
       -msoft-float
           Generate  output  containing  library  calls  for floating point.  Warning: the requisite
           libraries are not available for all  SPARC  targets.   Normally  the  facilities  of  the
           machine's  usual  C  compiler  are  used,  but  this  cannot  be  done directly in cross-
           compilation.  You must make your own arrangements to provide suitable  library  functions
           for  cross-compilation.   The  embedded targets sparc-*-aout and sparclite-*-* do provide
           software floating-point support.

           -msoft-float changes the calling convention in the output file;  therefore,  it  is  only
           useful  if  you  compile  all  of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to
           work.

       -mhard-quad-float
           Generate output containing quad-word (long double) floating-point instructions.

       -msoft-quad-float
           Generate output containing library  calls  for  quad-word  (long  double)  floating-point
           instructions.   The  functions  called are those specified in the SPARC ABI.  This is the
           default.

           As of this writing, there are no SPARC implementations that have hardware support for the
           quad-word floating-point instructions.  They all invoke a trap handler for one  of  these
           instructions,  and then the trap handler emulates the effect of the instruction.  Because
           of the trap handler overhead, this is much slower than calling the ABI library  routines.
           Thus the -msoft-quad-float option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
           Assume that doubles have 8-byte alignment.  This is the default.

           With -munaligned-doubles, GCC assumes that doubles have 8-byte alignment only if they are
           contained  in  another  type, or if they have an absolute address.  Otherwise, it assumes
           they have 4-byte alignment.   Specifying  this  option  avoids  some  rare  compatibility
           problems  with  code  generated  by  other  compilers.   It is not the default because it
           results in a performance loss, especially for floating-point code.

       -muser-mode
       -mno-user-mode
           Do not generate code that can only run in supervisor mode.  This is relevant only for the
           "casa" instruction emitted for the LEON3 processor.  This is the default.

       -mfaster-structs
       -mno-faster-structs
           With -mfaster-structs, the compiler assumes that structures should have 8-byte alignment.
           This enables the use of pairs of "ldd" and "std" instructions  for  copies  in  structure
           assignment,  in  place  of  twice  as many "ld" and "st" pairs.  However, the use of this
           changed alignment directly violates the SPARC ABI.  Thus, it's intended only for  use  on
           targets  where  the  developer  acknowledges that their resulting code is not directly in
           line with the rules of the ABI.

       -mstd-struct-return
       -mno-std-struct-return
           With -mstd-struct-return, the compiler generates checking  code  in  functions  returning
           structures  or  unions to detect size mismatches between the two sides of function calls,
           as per the 32-bit ABI.

           The default is -mno-std-struct-return.  This option has no effect in 64-bit mode.

       -mlra
       -mno-lra
           Enable Local Register Allocation.  This is the default for SPARC since GCC 7 so  -mno-lra
           needs to be passed to get old Reload.

       -mcpu=cpu_type
           Set  the instruction set, register set, and instruction scheduling parameters for machine
           type  cpu_type.   Supported  values  for  cpu_type  are  v7,  cypress,  v8,   supersparc,
           hypersparc,  leon,  leon3, leon3v7, leon5, sparclite, f930, f934, sparclite86x, sparclet,
           tsc701, v9, ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7  and
           m8.

           Native  Solaris and GNU/Linux toolchains also support the value native, which selects the
           best architecture option for the host processor.  -mcpu=native has no effect if GCC  does
           not recognize the processor.

           Default instruction scheduling parameters are used for values that select an architecture
           and not an implementation.  These are v7, v8, sparclite, sparclet, v9.

           Here is a list of each supported architecture and their supported implementations.

           v7  cypress, leon3v7

           v8  supersparc, hypersparc, leon, leon3, leon5

           sparclite
               f930, f934, sparclite86x

           sparclet
               tsc701

           v9  ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7, m8

           By  default  (unless  configured otherwise), GCC generates code for the V7 variant of the
           SPARC architecture.  With -mcpu=cypress, the compiler additionally optimizes it  for  the
           Cypress  CY7C602  chip, as used in the SPARCStation/SPARCServer 3xx series.  This is also
           appropriate for the older SPARCStation 1, 2, IPX etc.

           With -mcpu=v8, GCC generates code for the V8 variant of the SPARC architecture.  The only
           difference from V7 code is that the compiler  emits  the  integer  multiply  and  integer
           divide  instructions which exist in SPARC-V8 but not in SPARC-V7.  With -mcpu=supersparc,
           the compiler  additionally  optimizes  it  for  the  SuperSPARC  chip,  as  used  in  the
           SPARCStation 10, 1000 and 2000 series.

           With  -mcpu=sparclite,  GCC  generates  code  for  the  SPARClite  variant  of  the SPARC
           architecture.  This adds the integer multiply,  integer  divide  step  and  scan  ("ffs")
           instructions which exist in SPARClite but not in SPARC-V7.  With -mcpu=f930, the compiler
           additionally  optimizes it for the Fujitsu MB86930 chip, which is the original SPARClite,
           with no FPU.  With -mcpu=f934, the compiler additionally optimizes  it  for  the  Fujitsu
           MB86934 chip, which is the more recent SPARClite with FPU.

           With   -mcpu=sparclet,  GCC  generates  code  for  the  SPARClet  variant  of  the  SPARC
           architecture.  This adds the integer multiply, multiply/accumulate, integer  divide  step
           and  scan  ("ffs")  instructions  which  exist  in  SPARClet  but  not in SPARC-V7.  With
           -mcpu=tsc701, the compiler additionally optimizes it for the TEMIC SPARClet chip.

           With -mcpu=v9, GCC generates code for the V9 variant of  the  SPARC  architecture.   This
           adds  64-bit  integer  and  floating-point move instructions, 3 additional floating-point
           condition code registers and conditional move instructions.  With  -mcpu=ultrasparc,  the
           compiler  additionally  optimizes  it  for  the  Sun  UltraSPARC  I/II/IIi  chips.   With
           -mcpu=ultrasparc3,  the  compiler  additionally  optimizes  it  for  the  Sun  UltraSPARC
           III/III+/IIIi/IIIi+/IV/IV+   chips.    With   -mcpu=niagara,  the  compiler  additionally
           optimizes it for Sun UltraSPARC T1 chips.  With -mcpu=niagara2, the compiler additionally
           optimizes it for Sun UltraSPARC T2 chips. With -mcpu=niagara3, the compiler  additionally
           optimizes it for Sun UltraSPARC T3 chips.  With -mcpu=niagara4, the compiler additionally
           optimizes it for Sun UltraSPARC T4 chips.  With -mcpu=niagara7, the compiler additionally
           optimizes  it  for  Oracle  SPARC  M7  chips.   With  -mcpu=m8, the compiler additionally
           optimizes it for Oracle M8 chips.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not  set  the
           instruction set or register set that the option -mcpu=cpu_type does.

           The  same  values for -mcpu=cpu_type can be used for -mtune=cpu_type, but the only useful
           values are those that  select  a  particular  CPU  implementation.   Those  are  cypress,
           supersparc,  hypersparc,  leon,  leon3, leon3v7, leon5, f930, f934, sparclite86x, tsc701,
           ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7  and  m8.   With
           native Solaris and GNU/Linux toolchains, native can also be used.

       -mv8plus
       -mno-v8plus
           With  -mv8plus, GCC generates code for the SPARC-V8+ ABI.  The difference from the V8 ABI
           is that the global and out registers are considered 64 bits wide.   This  is  enabled  by
           default on Solaris in 32-bit mode for all SPARC-V9 processors.

       -mvis
       -mno-vis
           With  -mvis, GCC generates code that takes advantage of the UltraSPARC Visual Instruction
           Set extensions.  The default is -mno-vis.

       -mvis2
       -mno-vis2
           With -mvis2, GCC generates code that takes advantage of version  2.0  of  the  UltraSPARC
           Visual  Instruction  Set  extensions.   The  default  is -mvis2 when targeting a cpu that
           supports such instructions, such as UltraSPARC-III and later.  Setting -mvis2  also  sets
           -mvis.

       -mvis3
       -mno-vis3
           With  -mvis3,  GCC  generates  code that takes advantage of version 3.0 of the UltraSPARC
           Visual Instruction Set extensions.  The default is  -mvis3  when  targeting  a  cpu  that
           supports such instructions, such as niagara-3 and later.  Setting -mvis3 also sets -mvis2
           and -mvis.

       -mvis4
       -mno-vis4
           With  -mvis4,  GCC  generates  code that takes advantage of version 4.0 of the UltraSPARC
           Visual Instruction Set extensions.  The default is  -mvis4  when  targeting  a  cpu  that
           supports  such  instructions,  such  as  niagara-7  and  later.  Setting -mvis4 also sets
           -mvis3, -mvis2 and -mvis.

       -mvis4b
       -mno-vis4b
           With -mvis4b, GCC generates code that takes advantage of version 4.0  of  the  UltraSPARC
           Visual Instruction Set extensions, plus the additional VIS instructions introduced in the
           Oracle  SPARC  Architecture  2017.   The  default  is  -mvis4b  when targeting a cpu that
           supports such instructions, such as m8 and later.   Setting  -mvis4b  also  sets  -mvis4,
           -mvis3, -mvis2 and -mvis.

       -mcbcond
       -mno-cbcond
           With  -mcbcond,  GCC  generates  code that takes advantage of the UltraSPARC Compare-and-
           Branch-on-Condition instructions.  The default is -mcbcond  when  targeting  a  CPU  that
           supports such instructions, such as Niagara-4 and later.

       -mfmaf
       -mno-fmaf
           With -mfmaf, GCC generates code that takes advantage of the UltraSPARC Fused Multiply-Add
           Floating-point  instructions.   The  default is -mfmaf when targeting a CPU that supports
           such instructions, such as Niagara-3 and later.

       -mfsmuld
       -mno-fsmuld
           With -mfsmuld, GCC generates code that takes advantage  of  the  Floating-point  Multiply
           Single  to  Double  (FsMULd)  instruction.   The default is -mfsmuld when targeting a CPU
           supporting the architecture versions V8 or V9 with FPU except -mcpu=leon.

       -mpopc
       -mno-popc
           With -mpopc, GCC generates code that takes advantage of the UltraSPARC  Population  Count
           instruction.   The  default  is  -mpopc  when  targeting  a  CPU  that  supports  such an
           instruction, such as Niagara-2 and later.

       -msubxc
       -mno-subxc
           With -msubxc, GCC generates  code  that  takes  advantage  of  the  UltraSPARC  Subtract-
           Extended-with-Carry  instruction.   The  default  is  -msubxc  when  targeting a CPU that
           supports such an instruction, such as Niagara-7 and later.

       -mfix-at697f
           Enable the documented workaround for the single erratum of  the  Atmel  AT697F  processor
           (which corresponds to erratum #13 of the AT697E processor).

       -mfix-ut699
           Enable  the  documented  workarounds  for  the  floating-point  errata and the data cache
           nullify errata of the UT699 processor.

       -mfix-ut700
           Enable the documented workaround for the back-to-back store errata  of  the  UT699E/UT700
           processor.

       -mfix-gr712rc
           Enable  the  documented  workaround  for  the  back-to-back  store  errata of the GR712RC
           processor.

       These -m options are supported in addition to the above  on  SPARC-V9  processors  in  64-bit
       environments:

       -m32
       -m64
           Generate  code for a 32-bit or 64-bit environment.  The 32-bit environment sets int, long
           and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and  pointer
           to 64 bits.

       -mcmodel=which
           Set the code model to one of

           medlow
               The  Medium/Low  code  model: 64-bit addresses, programs must be linked in the low 32
               bits of memory.  Programs can be statically or dynamically linked.

           medmid
               The Medium/Middle code model: 64-bit addresses, programs must be linked in the low 44
               bits of memory, the text and data segments must be less than 2GB in size and the data
               segment must be located within 2GB of the text segment.

           medany
               The Medium/Anywhere code model: 64-bit addresses, programs may be linked anywhere  in
               memory, the text and data segments must be less than 2GB in size and the data segment
               must be located within 2GB of the text segment.

           embmedany
               The  Medium/Anywhere  code model for embedded systems: 64-bit addresses, the text and
               data segments must be less than  2GB  in  size,  both  starting  anywhere  in  memory
               (determined  at  link  time).  The global register %g4 points to the base of the data
               segment.  Programs are statically linked and PIC is not supported.

       -mmemory-model=mem-model
           Set the memory model in force on the processor to one of

           default
               The default memory model for the processor and operating system.

           rmo Relaxed Memory Order

           pso Partial Store Order

           tso Total Store Order

           sc  Sequential Consistency

           These memory models are formally defined in  Appendix  D  of  the  SPARC-V9  architecture
           manual, as set in the processor's "PSTATE.MM" field.

       -mstack-bias
       -mno-stack-bias
           With  -mstack-bias, GCC assumes that the stack pointer, and frame pointer if present, are
           offset by -2047 which must be added back when making stack frame references.  This is the
           default in 64-bit mode.  Otherwise, assume no such offset is present.

       Options for System V

       These additional options are available on System V Release 4  for  compatibility  with  other
       compilers on those systems:

       -G  Create a shared object.  It is recommended that -symbolic or -shared be used instead.

       -Qy Identify  the  versions  of  each  tool  used  by  the  compiler, in a ".ident" assembler
           directive in the output.

       -Qn Refrain from adding ".ident" directives to the output file (this is the default).

       -YP,dirs
           Search the directories dirs, and no others, for libraries specified with -l.

       -Ym,dir
           Look in the directory dir to find the M4 preprocessor.  The assembler uses this option.

       TILE-Gx Options

       These -m options are supported on the TILE-Gx:

       -mcmodel=small
           Generate code for the small model.  The distance for direct calls is limited to  500M  in
           either  direction.   PC-relative  addresses  are 32 bits.  Absolute addresses support the
           full address range.

       -mcmodel=large
           Generate code for the large model.  There is no limitation on call distance,  pc-relative
           addresses, or absolute addresses.

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only supported type is tilegx.

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int, long,
           and  pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and pointer
           to 64 bits.

       -mbig-endian
       -mlittle-endian
           Generate code in big/little endian mode, respectively.

       TILEPro Options

       These -m options are supported on the TILEPro:

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only supported type is tilepro.

       -m32
           Generate code for a 32-bit environment, which sets int, long, and  pointer  to  32  bits.
           This is the only supported behavior so the flag is essentially ignored.

       V850 Options

       These -m options are defined for V850 implementations:

       -mlong-calls
       -mno-long-calls
           Treat  all  calls  as  being  far  away (near).  If calls are assumed to be far away, the
           compiler always loads the function's address into a register, and calls indirect  through
           the pointer.

       -mno-ep
       -mep
           Do  not  optimize  (do  optimize)  basic blocks that use the same index pointer 4 or more
           times to copy pointer into the "ep"  register,  and  use  the  shorter  "sld"  and  "sst"
           instructions.  The -mep option is on by default if you optimize.

       -mno-prolog-function
       -mprolog-function
           Do  not use (do use) external functions to save and restore registers at the prologue and
           epilogue of a function.  The external functions are slower, but use less  code  space  if
           more  than one function saves the same number of registers.  The -mprolog-function option
           is on by default if you optimize.

       -mspace
           Try to make the code as small as possible.  At present, this just turns on the  -mep  and
           -mprolog-function options.

       -mtda=n
           Put static or global variables whose size is n bytes or less into the tiny data area that
           register "ep" points to.  The tiny data area can hold up to 256 bytes in total (128 bytes
           for byte references).

       -msda=n
           Put  static  or  global  variables whose size is n bytes or less into the small data area
           that register "gp" points to.  The small data area can hold up to 64 kilobytes.

       -mzda=n
           Put static or global variables whose size is n bytes or less into the first 32  kilobytes
           of memory.

       -mv850
           Specify that the target processor is the V850.

       -mv850e3v5
           Specify   that   the  target  processor  is  the  V850E3V5.   The  preprocessor  constant
           "__v850e3v5__" is defined if this option is used.

       -mv850e2v4
           Specify that the target processor is the V850E3V5.  This is an alias for  the  -mv850e3v5
           option.

       -mv850e2v3
           Specify   that   the  target  processor  is  the  V850E2V3.   The  preprocessor  constant
           "__v850e2v3__" is defined if this option is used.

       -mv850e2
           Specify that the target processor is the V850E2.  The preprocessor constant  "__v850e2__"
           is defined if this option is used.

       -mv850e1
           Specify that the target processor is the V850E1.  The preprocessor constants "__v850e1__"
           and "__v850e__" are defined if this option is used.

       -mv850es
           Specify  that  the  target  processor  is  the V850ES.  This is an alias for the -mv850e1
           option.

       -mv850e
           Specify that the target processor is the V850E.  The preprocessor constant "__v850e__" is
           defined if this option is used.

           If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor -mv850e2v3 nor -mv850e3v5 are
           defined then a default target processor is chosen and the relevant __v850*__ preprocessor
           constant is defined.

           The preprocessor constants "__v850" and "__v851__"  are  always  defined,  regardless  of
           which processor variant is the target.

       -mdisable-callt
       -mno-disable-callt
           This  option  suppresses  generation  of  the  "CALLT" instruction for the v850e, v850e1,
           v850e2, v850e2v3 and v850e3v5 flavors of the v850 architecture.

           This option is enabled by default when the RH850 ABI is in  use  (see  -mrh850-abi),  and
           disabled  by  default  when  the  GCC  ABI  is in use.  If "CALLT" instructions are being
           generated then the C preprocessor symbol "__V850_CALLT__" is defined.

       -mrelax
       -mno-relax
           Pass on (or do not pass on) the -mrelax command-line option to the assembler.

       -mlong-jumps
       -mno-long-jumps
           Disable (or re-enable) the generation of PC-relative jump instructions.

       -msoft-float
       -mhard-float
           Disable (or re-enable) the generation of  hardware  floating  point  instructions.   This
           option  is  only  significant  when  the  target  architecture is V850E2V3 or higher.  If
           hardware floating point instructions are being generated then the C  preprocessor  symbol
           "__FPU_OK__" is defined, otherwise the symbol "__NO_FPU__" is defined.

       -mloop
           Enables the use of the e3v5 LOOP instruction.  The use of this instruction is not enabled
           by default when the e3v5 architecture is selected because its use is still experimental.

       -mrh850-abi
       -mghs
           Enables  support  for the RH850 version of the V850 ABI.  This is the default.  With this
           version of the ABI the following rules apply:

           *   Integer sized structures and unions are returned via a memory pointer rather  than  a
               register.

           *   Large structures and unions (more than 8 bytes in size) are passed by value.

           *   Functions are aligned to 16-bit boundaries.

           *   The -m8byte-align command-line option is supported.

           *   The    -mdisable-callt    command-line   option   is   enabled   by   default.    The
               -mno-disable-callt command-line option is not supported.

           When this version of the ABI is enabled the C preprocessor symbol "__V850_RH850_ABI__" is
           defined.

       -mgcc-abi
           Enables support for the old GCC version of the V850 ABI.  With this version  of  the  ABI
           the following rules apply:

           *   Integer sized structures and unions are returned in register "r10".

           *   Large structures and unions (more than 8 bytes in size) are passed by reference.

           *   Functions are aligned to 32-bit boundaries, unless optimizing for size.

           *   The -m8byte-align command-line option is not supported.

           *   The -mdisable-callt command-line option is supported but not enabled by default.

           When  this  version of the ABI is enabled the C preprocessor symbol "__V850_GCC_ABI__" is
           defined.

       -m8byte-align
       -mno-8byte-align
           Enables support for "double" and "long long" types to be aligned  on  8-byte  boundaries.
           The  default  is  to  restrict  the  alignment  of  all objects to at most 4-bytes.  When
           -m8byte-align is in effect the C preprocessor symbol "__V850_8BYTE_ALIGN__" is defined.

       -mbig-switch
           Generate  code  suitable  for  big  switch  tables.   Use  this  option   only   if   the
           assembler/linker complain about out of range branches within a switch table.

       -mapp-regs
           This  option  causes  r2  and  r5 to be used in the code generated by the compiler.  This
           setting is the default.

       -mno-app-regs
           This option causes r2 and r5 to be treated as fixed registers.

       VAX Options

       These -m options are defined for the VAX:

       -munix
           Do not output certain jump instructions ("aobleq" and so on) that the Unix assembler  for
           the VAX cannot handle across long ranges.

       -mgnu
           Do  output  those  jump  instructions,  on the assumption that the GNU assembler is being
           used.

       -mg Output code for G-format floating-point numbers instead of D-format.

       Visium Options

       -mdebug
           A program which performs file I/O and is destined to run  on  an  MCM  target  should  be
           linked  with  this  option.   It causes the libraries libc.a and libdebug.a to be linked.
           The program should be run on the target under the control of  the  GDB  remote  debugging
           stub.

       -msim
           A  program  which  performs  file  I/O  and is destined to run on the simulator should be
           linked with option.  This causes libraries libc.a and libsim.a to be linked.

       -mfpu
       -mhard-float
           Generate code containing floating-point instructions.  This is the default.

       -mno-fpu
       -msoft-float
           Generate code containing library calls for floating-point.

           -msoft-float changes the calling convention in the output file;  therefore,  it  is  only
           useful  if  you  compile  all  of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to
           work.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling parameters for  machine
           type cpu_type.  Supported values for cpu_type are mcm, gr5 and gr6.

           mcm is a synonym of gr5 present for backward compatibility.

           By  default  (unless configured otherwise), GCC generates code for the GR5 variant of the
           Visium architecture.

           With -mcpu=gr6, GCC generates code for the GR6 variant of the Visium  architecture.   The
           only difference from GR5 code is that the compiler will generate block move instructions.

       -mtune=cpu_type
           Set  the  instruction scheduling parameters for machine type cpu_type, but do not set the
           instruction set or register set that the option -mcpu=cpu_type would.

       -msv-mode
           Generate code for the supervisor mode, where there are no restrictions on the  access  to
           general registers.  This is the default.

       -muser-mode
           Generate code for the user mode, where the access to some general registers is forbidden:
           on  the  GR5,  registers  r24  to  r31  cannot be accessed in this mode; on the GR6, only
           registers r29 to r31 are affected.

       VMS Options

       These -m options are defined for the VMS implementations:

       -mvms-return-codes
           Return VMS condition codes from "main". The default is to  return  POSIX-style  condition
           (e.g. error) codes.

       -mdebug-main=prefix
           Flag  the  first  routine  whose  name  starts  with  prefix  as the main routine for the
           debugger.

       -mmalloc64
           Default to 64-bit memory allocation routines.

       -mpointer-size=size
           Set the default size of pointers. Possible options for size are 32 or short  for  32  bit
           pointers,  64  or  long  for 64 bit pointers, and no for supporting only 32 bit pointers.
           The later option disables "pragma pointer_size".

       VxWorks Options

       The options in this section are defined for all VxWorks targets.   Options  specific  to  the
       target hardware are listed with the other options for that target.

       -mrtp
           GCC  can  generate  code  for  both VxWorks kernels and real time processes (RTPs).  This
           option switches from the former to the latter.  It also defines  the  preprocessor  macro
           "__RTP__".

       -non-static
           Link  an  RTP  executable  against  shared  libraries  rather than static libraries.  The
           options -static and -shared can also be used for RTPs; -static is the default.

       -Bstatic
       -Bdynamic
           These options are passed down to the linker.  They are  defined  for  compatibility  with
           Diab.

       -Xbind-lazy
           Enable  lazy  binding  of function calls.  This option is equivalent to -Wl,-z,now and is
           defined for compatibility with Diab.

       -Xbind-now
           Disable lazy binding of function calls.  This option is the default and  is  defined  for
           compatibility with Diab.

       x86 Options

       These -m options are defined for the x86 family of computers.

       -march=cpu-type
           Generate  instructions  for  the  machine type cpu-type.  In contrast to -mtune=cpu-type,
           which merely tunes the generated code for the specified cpu-type, -march=cpu-type  allows
           GCC  to generate code that may not run at all on processors other than the one indicated.
           Specifying -march=cpu-type implies -mtune=cpu-type, except where noted otherwise.

           The choices for cpu-type are:

           native
               This selects the CPU to generate code for at  compilation  time  by  determining  the
               processor type of the compiling machine.  Using -march=native enables all instruction
               subsets  supported  by the local machine (hence the result might not run on different
               machines).  Using -mtune=native produces code optimized for the local  machine  under
               the constraints of the selected instruction set.

           x86-64
               A generic CPU with 64-bit extensions.

           x86-64-v2
           x86-64-v3
           x86-64-v4
               These choices for cpu-type select the corresponding micro-architecture level from the
               x86-64  psABI.  On ABIs other than the x86-64 psABI they select the same CPU features
               as the x86-64 psABI documents for the particular micro-architecture level.

               Since these cpu-type values do not have a corresponding -mtune setting, using  -march
               with  these  values enables generic tuning.  Specific tuning can be enabled using the
               -mtune=other-cpu-type option with an appropriate other-cpu-type value.

           i386
               Original Intel i386 CPU.

           i486
               Intel i486 CPU.  (No scheduling is implemented for this chip.)

           i586
           pentium
               Intel Pentium CPU with no MMX support.

           lakemont
               Intel Lakemont MCU, based on Intel Pentium CPU.

           pentium-mmx
               Intel Pentium MMX CPU, based on Pentium core with MMX instruction set support.

           pentiumpro
               Intel Pentium Pro CPU.

           i686
               When used with -march, the Pentium Pro instruction set is used, so the code  runs  on
               all i686 family chips.  When used with -mtune, it has the same meaning as generic.

           pentium2
               Intel Pentium II CPU, based on Pentium Pro core with MMX instruction set support.

           pentium3
           pentium3m
               Intel  Pentium  III  CPU,  based on Pentium Pro core with MMX and SSE instruction set
               support.

           pentium-m
               Intel Pentium M; low-power version of Intel Pentium III CPU with MMX,  SSE  and  SSE2
               instruction set support.  Used by Centrino notebooks.

           pentium4
           pentium4m
               Intel Pentium 4 CPU with MMX, SSE and SSE2 instruction set support.

           prescott
               Improved  version of Intel Pentium 4 CPU with MMX, SSE, SSE2 and SSE3 instruction set
               support.

           nocona
               Improved version of Intel Pentium 4 CPU with 64-bit extensions, MMX,  SSE,  SSE2  and
               SSE3 instruction set support.

           core2
               Intel  Core  2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 instruction
               set support.

           nehalem
               Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2
               and POPCNT instruction set support.

           westmere
               Intel Westmere CPU with 64-bit extensions,  MMX,  SSE,  SSE2,  SSE3,  SSSE3,  SSE4.1,
               SSE4.2, POPCNT, AES and PCLMUL instruction set support.

           sandybridge
               Intel  Sandy  Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AVX, AES and PCLMUL instruction set support.

           ivybridge
               Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE,  SSE2,  SSE3,  SSSE3,  SSE4.1,
               SSE4.2, POPCNT, AVX, AES, PCLMUL, FSGSBASE, RDRND and F16C instruction set support.

           haswell
               Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2,  POPCNT,  AVX,  AVX2,  AES,  PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2 and F16C
               instruction set support.

           broadwell
               Intel Broadwell CPU with 64-bit extensions,  MOVBE,  MMX,  SSE,  SSE2,  SSE3,  SSSE3,
               SSE4.1,  SSE4.2,  POPCNT,  AVX,  AVX2,  AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED ADCX and PREFETCHW instruction set support.

           skylake
               Intel Skylake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AVX, AVX2, AES,  PCLMUL,  FSGSBASE,  RDRND,  FMA,  BMI,  BMI2,  F16C,
               RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC and XSAVES instruction set support.

           bonnell
               Intel  Bonnell  CPU  with  64-bit  extensions,  MOVBE, MMX, SSE, SSE2, SSE3 and SSSE3
               instruction set support.

           silvermont
               Intel Silvermont CPU with 64-bit extensions, MOVBE,  MMX,  SSE,  SSE2,  SSE3,  SSSE3,
               SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL and RDRND instruction set support.

           goldmont
               Intel  Goldmont  CPU  with  64-bit  extensions,  MOVBE,  MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2,  POPCNT,  AES,  PREFETCHW,  PCLMUL,  RDRND,  XSAVE,  XSAVEC,  XSAVES,
               XSAVEOPT and FSGSBASE instruction set support.

           goldmont-plus
               Intel  Goldmont  Plus CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2,  POPCNT,  AES,  PREFETCHW,  PCLMUL,  RDRND,  XSAVE,  XSAVEC,  XSAVES,
               XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX and UMIP instruction set support.

           tremont
               Intel Tremont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2,  POPCNT,  AES,  PREFETCHW,  PCLMUL,  RDRND,  XSAVE, XSAVEC, XSAVES, XSAVEOPT,
               FSGSBASE, PTWRITE, RDPID, SGX, UMIP, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B, CLDEMOTE and
               WAITPKG instruction set support.

           knl Intel Knight's Landing CPU with 64-bit  extensions,  MOVBE,  MMX,  SSE,  SSE2,  SSE3,
               SSSE3,  SSE4.1,  SSE4.2,  POPCNT,  AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI,
               BMI2, F16C, RDSEED, ADCX, PREFETCHW, PREFETCHWT1,  AVX512F,  AVX512PF,  AVX512ER  and
               AVX512CD instruction set support.

           knm Intel  Knights  Mill  CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL,  FSGSBASE,  RDRND,  FMA,  BMI,  BMI2,
               F16C,  RDSEED,  ADCX,  PREFETCHW, PREFETCHWT1, AVX512F, AVX512PF, AVX512ER, AVX512CD,
               AVX5124VNNIW, AVX5124FMAPS and AVX512VPOPCNTDQ instruction set support.

           skylake-avx512
               Intel Skylake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,  SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C,  RDSEED,  ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, CLWB, AVX512VL,
               AVX512BW, AVX512DQ and AVX512CD instruction set support.

           cannonlake
               Intel Cannonlake Server CPU with 64-bit extensions,  MOVBE,  MMX,  SSE,  SSE2,  SSE3,
               SSSE3,  SSE4.1,  SSE4.2,  POPCNT,  PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA,
               BMI, BMI2, F16C,  RDSEED,  ADCX,  PREFETCHW,  CLFLUSHOPT,  XSAVEC,  XSAVES,  AVX512F,
               AVX512VL,   AVX512BW,  AVX512DQ,  AVX512CD,  AVX512VBMI,  AVX512IFMA,  SHA  and  UMIP
               instruction set support.

           icelake-client
               Intel Icelake Client CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,  SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C,  RDSEED,  ADCX,  PREFETCHW,  CLFLUSHOPT,  XSAVEC,  XSAVES,  AVX512F,  AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP,  RDPID,  GFNI,
               AVX512VBMI2,  AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES instruction
               set support.

           icelake-server
               Intel Icelake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,  SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C,  RDSEED,  ADCX,  PREFETCHW,  CLFLUSHOPT,  XSAVEC,  XSAVES,  AVX512F,  AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP,  RDPID,  GFNI,
               AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES, PCONFIG and
               WBNOINVD instruction set support.

           cascadelake
               Intel  Cascadelake  CPU  with  64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F,  CLWB,  AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD and AVX512VNNI instruction set support.

           cooperlake
               Intel  cooperlake  CPU  with  64-bit  extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F,  CLWB,  AVX512VL,
               AVX512BW, AVX512DQ, AVX512CD, AVX512VNNI and AVX512BF16 instruction set support.

           tigerlake
               Intel  Tigerlake  CPU  with  64-bit  extensions,  MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C,  RDSEED,  ADCX,  PREFETCHW,  CLFLUSHOPT,  XSAVEC,  XSAVES,  AVX512F,  AVX512VL,
               AVX512BW,  AVX512DQ,  AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
               AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI,  VPCLMULQDQ,  VAES,  PCONFIG,
               WBNOINVD,  MOVDIRI,  MOVDIR64B,  AVX512VP2INTERSECT  and  KEYLOCKER  instruction  set
               support.

           sapphirerapids
               Intel sapphirerapids CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,  SSSE3,
               SSE4.1,  SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C,
               AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX,  PREFETCHW,  AES,  CLFLUSHOPT,
               XSAVEC,   XSAVES,   SGX,   AVX512F,  AVX512VL,  AVX512BW,  AVX512DQ,  AVX512CD,  PKU,
               AVX512VBMI,  AVX512IFMA,  SHA,  AVX512VNNI,  GFNI,  VAES,   AVX512VBMI2   VPCLMULQDQ,
               AVX512BITALG,  RDPID,  AVX512VPOPCNTDQ,  PCONFIG, WBNOINVD, CLWB, MOVDIRI, MOVDIR64B,
               AVX512VP2INTERSECT, ENQCMD, CLDEMOTE, PTWRITE, WAITPKG, SERIALIZE,  TSXLDTRK,  UINTR,
               AMX-BF16, AMX-TILE, AMX-INT8, AVX-VNNI and AVX512BF16 instruction set support.

           alderlake
               Intel  Alderlake  CPU  with  64-bit  extensions,  MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2,  POPCNT,  AES,  PREFETCHW,  PCLMUL,  RDRND,  XSAVE,  XSAVEC,  XSAVES,
               XSAVEOPT,  FSGSBASE,  PTWRITE,  RDPID, SGX, UMIP, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B,
               CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT, PCONFIG, PKU,  VAES,
               VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL and AVX-VNNI instruction set support.

           rocketlake
               Intel  Rocketlake  CPU  with  64-bit  extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C,  RDSEED,  ADCX,  PREFETCHW,  CLFLUSHOPT,  XSAVEC,  XSAVES,  AVX512F,  AVX512VL,
               AVX512BW,  AVX512DQ,  AVX512CD, AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
               AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES  instruction
               set support.

           k6  AMD K6 CPU with MMX instruction set support.

           k6-2
           k6-3
               Improved versions of AMD K6 CPU with MMX and 3DNow! instruction set support.

           athlon
           athlon-tbird
               AMD  Athlon  CPU  with  MMX,  3dNOW!,  enhanced  3DNow! and SSE prefetch instructions
               support.

           athlon-4
           athlon-xp
           athlon-mp
               Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and  full  SSE  instruction
               set support.

           k8
           opteron
           athlon64
           athlon-fx
               Processors  based  on  the AMD K8 core with x86-64 instruction set support, including
               the AMD Opteron, Athlon 64, and Athlon 64 FX processors.  (This supersets  MMX,  SSE,
               SSE2, 3DNow!, enhanced 3DNow! and 64-bit instruction set extensions.)

           k8-sse3
           opteron-sse3
           athlon64-sse3
               Improved versions of AMD K8 cores with SSE3 instruction set support.

           amdfam10
           barcelona
               CPUs  based  on  AMD  Family  10h  cores  with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, SSE3,  SSE4A,  3DNow!,  enhanced  3DNow!,  ABM  and  64-bit
               instruction set extensions.)

           bdver1
               CPUs  based  on  AMD  Family  15h  cores  with x86-64 instruction set support.  (This
               supersets FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,
               SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver2
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This  supersets
               BMI,  TBM,  F16C,  FMA, FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3,
               SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver3
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This  supersets
               BMI,  TBM,  F16C,  FMA,  FMA4,  FSGSBASE, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE,
               SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver4
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This  supersets
               BMI,  BMI2,  TBM,  F16C, FMA, FMA4, FSGSBASE, AVX, AVX2, XOP, LWP, AES, PCLMUL, CX16,
               MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction
               set extensions.)

           znver1
               AMD Family 17h core based CPUs with x86-64 instruction set support.  (This  supersets
               BMI,  BMI2,  F16C,  FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES,
               PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC,
               XSAVES, CLFLUSHOPT, POPCNT, and 64-bit instruction set extensions.)

           znver2
               AMD Family 17h core based CPUs with x86-64 instruction set support.  (This  supersets
               BMI,  BMI2,  CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO,
               AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,  SSE4.1,  SSE4.2,  ABM,
               XSAVEC,  XSAVES,  CLFLUSHOPT,  POPCNT,  RDPID,  WBNOINVD,  and 64-bit instruction set
               extensions.)

           znver3
               AMD Family 19h core based CPUs with x86-64 instruction set support.  (This  supersets
               BMI,  BMI2,  CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO,
               AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,  SSE4.1,  SSE4.2,  ABM,
               XSAVEC,  XSAVES,  CLFLUSHOPT,  POPCNT,  RDPID,  WBNOINVD,  PKU, VPCLMULQDQ, VAES, and
               64-bit instruction set extensions.)

           znver4
               AMD Family 19h core based CPUs with x86-64 instruction set support.  (This  supersets
               BMI,  BMI2,  CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO,
               AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,  SSE4.1,  SSE4.2,  ABM,
               XSAVEC,  XSAVES, CLFLUSHOPT, POPCNT, RDPID, WBNOINVD, PKU, VPCLMULQDQ, VAES, AVX512F,
               AVX512DQ,  AVX512IFMA,  AVX512CD,   AVX512BW,   AVX512VL,   AVX512BF16,   AVX512VBMI,
               AVX512VBMI2,  AVX512VNNI,  AVX512BITALG, AVX512VPOPCNTDQ, GFNI and 64-bit instruction
               set extensions.)

           btver1
               CPUs based on AMD Family 14h  cores  with  x86-64  instruction  set  support.   (This
               supersets  MMX,  SSE,  SSE2, SSE3, SSSE3, SSE4A, CX16, ABM and 64-bit instruction set
               extensions.)

           btver2
               CPUs based on AMD Family 16h cores with x86-64 instruction set support. This includes
               MOVBE, F16C, BMI, AVX, PCLMUL, AES, SSE4.2, SSE4.1, CX16, ABM,  SSE4A,  SSSE3,  SSE3,
               SSE2, SSE, MMX and 64-bit instruction set extensions.

           winchip-c6
               IDT  WinChip  C6  CPU,  dealt in same way as i486 with additional MMX instruction set
               support.

           winchip2
               IDT WinChip 2 CPU, dealt  in  same  way  as  i486  with  additional  MMX  and  3DNow!
               instruction set support.

           c3  VIA  C3  CPU  with  MMX  and  3DNow!  instruction  set  support.   (No  scheduling is
               implemented for this chip.)

           c3-2
               VIA C3-2  (Nehemiah/C5XL)  CPU  with  MMX  and  SSE  instruction  set  support.   (No
               scheduling is implemented for this chip.)

           c7  VIA  C7  (Esther)  CPU  with  MMX,  SSE,  SSE2 and SSE3 instruction set support.  (No
               scheduling is implemented for this chip.)

           samuel-2
               VIA Eden Samuel 2 CPU with MMX and 3DNow! instruction set support.  (No scheduling is
               implemented for this chip.)

           nehemiah
               VIA Eden Nehemiah CPU with MMX and SSE instruction set support.   (No  scheduling  is
               implemented for this chip.)

           esther
               VIA  Eden  Esther  CPU  with  MMX,  SSE,  SSE2 and SSE3 instruction set support.  (No
               scheduling is implemented for this chip.)

           eden-x2
               VIA Eden X2 CPU with x86-64, MMX, SSE, SSE2 and SSE3 instruction  set  support.   (No
               scheduling is implemented for this chip.)

           eden-x4
               VIA  Eden  X4  CPU  with x86-64, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX and
               AVX2 instruction set support.  (No scheduling is implemented for this chip.)

           nano
               Generic VIA Nano CPU with x86-64, MMX, SSE, SSE2,  SSE3  and  SSSE3  instruction  set
               support.  (No scheduling is implemented for this chip.)

           nano-1000
               VIA  Nano  1xxx  CPU  with  x86-64,  MMX,  SSE,  SSE2, SSE3 and SSSE3 instruction set
               support.  (No scheduling is implemented for this chip.)

           nano-2000
               VIA Nano 2xxx CPU with x86-64,  MMX,  SSE,  SSE2,  SSE3  and  SSSE3  instruction  set
               support.  (No scheduling is implemented for this chip.)

           nano-3000
               VIA Nano 3xxx CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1 instruction set
               support.  (No scheduling is implemented for this chip.)

           nano-x2
               VIA  Nano  Dual  Core  CPU  with  x86-64,  MMX,  SSE,  SSE2,  SSE3,  SSSE3 and SSE4.1
               instruction set support.  (No scheduling is implemented for this chip.)

           nano-x4
               VIA Nano Quad  Core  CPU  with  x86-64,  MMX,  SSE,  SSE2,  SSE3,  SSSE3  and  SSE4.1
               instruction set support.  (No scheduling is implemented for this chip.)

           geode
               AMD Geode embedded processor with MMX and 3DNow! instruction set support.

       -mtune=cpu-type
           Tune  to  cpu-type everything applicable about the generated code, except for the ABI and
           the set of available instructions.  While picking a specific  cpu-type  schedules  things
           appropriately  for  that  particular  chip,  the compiler does not generate any code that
           cannot run on the default machine type unless you  use  a  -march=cpu-type  option.   For
           example,  if  GCC is configured for i686-pc-linux-gnu then -mtune=pentium4 generates code
           that is tuned for Pentium 4 but still runs on i686 machines.

           The choices for cpu-type are the same as for -march.   In  addition,  -mtune  supports  2
           extra choices for cpu-type:

           generic
               Produce  code optimized for the most common IA32/AMD64/EM64T processors.  If you know
               the CPU on which your code will run, then you should use the corresponding -mtune  or
               -march  option  instead  of -mtune=generic.  But, if you do not know exactly what CPU
               users of your application will have, then you should use this option.

               As new processors are deployed in the marketplace, the behavior of this  option  will
               change.   Therefore,  if  you  upgrade  to  a  newer  version of GCC, code generation
               controlled by this option will change to reflect the processors that are most  common
               at the time that version of GCC is released.

               There  is  no  -march=generic option because -march indicates the instruction set the
               compiler can use,  and  there  is  no  generic  instruction  set  applicable  to  all
               processors.   In  contrast,  -mtune  indicates  the  processor  (or,  in  this  case,
               collection of processors) for which the code is optimized.

           intel
               Produce code optimized for the most current Intel processors, which are  Haswell  and
               Silvermont for this version of GCC.  If you know the CPU on which your code will run,
               then   you   should  use  the  corresponding  -mtune  or  -march  option  instead  of
               -mtune=intel.  But, if you want your application performs better on both Haswell  and
               Silvermont, then you should use this option.

               As  new Intel processors are deployed in the marketplace, the behavior of this option
               will change.  Therefore, if you upgrade to a newer version of  GCC,  code  generation
               controlled by this option will change to reflect the most current Intel processors at
               the time that version of GCC is released.

               There  is  no  -march=intel  option  because -march indicates the instruction set the
               compiler can  use,  and  there  is  no  common  instruction  set  applicable  to  all
               processors.   In  contrast,  -mtune  indicates  the  processor  (or,  in  this  case,
               collection of processors) for which the code is optimized.

       -mcpu=cpu-type
           A deprecated synonym for -mtune.

       -mfpmath=unit
           Generate floating-point arithmetic for selected unit unit.  The choices for unit are:

           387 Use the standard 387 floating-point coprocessor present on the majority of chips  and
               emulated  otherwise.   Code  compiled  with  this option runs almost everywhere.  The
               temporary results are computed in 80-bit precision instead of the precision specified
               by the type, resulting in slightly different results compared to most of other chips.
               See -ffloat-store for more detailed description.

               This is the default choice for non-Darwin x86-32 targets.

           sse Use scalar floating-point instructions present in  the  SSE  instruction  set.   This
               instruction  set  is supported by Pentium III and newer chips, and in the AMD line by
               Athlon-4, Athlon XP and Athlon MP chips.  The earlier version of the SSE  instruction
               set supports only single-precision arithmetic, thus the double and extended-precision
               arithmetic  are still done using 387.  A later version, present only in Pentium 4 and
               AMD x86-64 chips, supports double-precision arithmetic too.

               For the x86-32 compiler, you must use -march=cpu-type, -msse or  -msse2  switches  to
               enable SSE extensions and make this option effective.  For the x86-64 compiler, these
               extensions are enabled by default.

               The  resulting  code should be considerably faster in the majority of cases and avoid
               the numerical instability problems of 387 code, but may break some existing code that
               expects temporaries to be 80 bits.

               This is the default choice for the x86-64 compiler, Darwin x86-32  targets,  and  the
               default  choice  for x86-32 targets with the SSE2 instruction set when -ffast-math is
               enabled.

           sse,387
           sse+387
           both
               Attempt to utilize both instruction sets  at  once.   This  effectively  doubles  the
               amount of available registers, and on chips with separate execution units for 387 and
               SSE  the  execution  resources  too.   Use  this  option  with  care,  as it is still
               experimental, because the GCC register allocator does not model  separate  functional
               units well, resulting in unstable performance.

       -masm=dialect
           Output  assembly instructions using selected dialect.  Also affects which dialect is used
           for basic "asm" and extended "asm". Supported choices  (in  dialect  order)  are  att  or
           intel. The default is att. Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
           Control  whether  or  not  the  compiler  uses  IEEE  floating-point  comparisons.  These
           correctly handle the case where the result of a comparison is unordered.

       -m80387
       -mhard-float
           Generate output containing 80387 instructions for floating point.

       -mno-80387
       -msoft-float
           Generate output containing library calls for floating point.

           Warning: the requisite libraries are not part of GCC.  Normally  the  facilities  of  the
           machine's  usual  C  compiler  are  used,  but  this  cannot  be  done directly in cross-
           compilation.  You must make your own arrangements to provide suitable  library  functions
           for cross-compilation.

           On  machines where a function returns floating-point results in the 80387 register stack,
           some floating-point opcodes may be emitted even if -msoft-float is used.

       -mno-fp-ret-in-387
           Do not use the FPU registers for return values of functions.

           The usual calling convention has functions return values of types "float" and "double" in
           an FPU register, even if there is no FPU.  The idea is that the operating  system  should
           emulate an FPU.

           The option -mno-fp-ret-in-387 causes such values to be returned in ordinary CPU registers
           instead.

       -mno-fancy-math-387
           Some  387  emulators do not support the "sin", "cos" and "sqrt" instructions for the 387.
           Specify this option to avoid generating those instructions.  This  option  is  overridden
           when  -march  indicates that the target CPU always has an FPU and so the instruction does
           not need emulation.  These instructions  are  not  generated  unless  you  also  use  the
           -funsafe-math-optimizations switch.

       -malign-double
       -mno-align-double
           Control  whether  GCC aligns "double", "long double", and "long long" variables on a two-
           word boundary or a one-word boundary.  Aligning "double" variables on a two-word boundary
           produces code that runs somewhat faster on a Pentium at the expense of more memory.

           On x86-64, -malign-double is enabled by default.

           Warning: if you use the -malign-double switch, structures containing the above types  are
           aligned  differently  than  the published application binary interface specifications for
           the x86-32 and are not binary compatible with structures in code  compiled  without  that
           switch.

       -m96bit-long-double
       -m128bit-long-double
           These  switches  control  the  size of "long double" type.  The x86-32 application binary
           interface specifies the size to be 96 bits, so  -m96bit-long-double  is  the  default  in
           32-bit mode.

           Modern  architectures  (Pentium and newer) prefer "long double" to be aligned to an 8- or
           16-byte boundary.  In arrays or structures conforming to the ABI, this is  not  possible.
           So  specifying -m128bit-long-double aligns "long double" to a 16-byte boundary by padding
           the "long double" with an additional 32-bit zero.

           In the x86-64 compiler, -m128bit-long-double is the default choice as its  ABI  specifies
           that "long double" is aligned on 16-byte boundary.

           Notice  that neither of these options enable any extra precision over the x87 standard of
           80 bits for a "long double".

           Warning: if you override the default value for your target ABI, this changes the size  of
           structures  and  arrays  containing  "long  double"  variables,  as well as modifying the
           function calling convention for functions taking  "long  double".   Hence  they  are  not
           binary-compatible with code compiled without that switch.

       -mlong-double-64
       -mlong-double-80
       -mlong-double-128
           These  switches control the size of "long double" type. A size of 64 bits makes the "long
           double" type equivalent to the "double" type. This is the default  for  32-bit  Bionic  C
           library.   A size of 128 bits makes the "long double" type equivalent to the "__float128"
           type. This is the default for 64-bit Bionic C library.

           Warning: if you override the default value for your target ABI, this changes the size  of
           structures  and  arrays  containing  "long  double"  variables,  as well as modifying the
           function calling convention for functions taking  "long  double".   Hence  they  are  not
           binary-compatible with code compiled without that switch.

       -malign-data=type
           Control  how  GCC  aligns variables.  Supported values for type are compat uses increased
           alignment value compatible uses  GCC  4.8  and  earlier,  abi  uses  alignment  value  as
           specified  by  the psABI, and cacheline uses increased alignment value to match the cache
           line size.  compat is the default.

       -mlarge-data-threshold=threshold
           When -mcmodel=medium is specified, data objects larger than threshold are placed  in  the
           large  data  section.   This  value  must  be the same across all objects linked into the
           binary, and defaults to 65535.

       -mrtd
           Use a different function-calling convention, in which functions that take a fixed  number
           of  arguments  return  with  the  "ret num" instruction, which pops their arguments while
           returning.  This saves one instruction in the caller since there is no need  to  pop  the
           arguments there.

           You can specify that an individual function is called with this calling sequence with the
           function  attribute  "stdcall".   You  can  also  override  the -mrtd option by using the
           function attribute "cdecl".

           Warning: this calling convention is incompatible with the one normally used on  Unix,  so
           you cannot use it if you need to call libraries compiled with the Unix compiler.

           Also,  you  must provide function prototypes for all functions that take variable numbers
           of arguments (including "printf"); otherwise incorrect code is  generated  for  calls  to
           those functions.

           In  addition,  seriously  incorrect  code  results  if  you call a function with too many
           arguments.  (Normally, extra arguments are harmlessly ignored.)

       -mregparm=num
           Control how many registers are used to pass integer arguments.  By default, no  registers
           are  used  to  pass arguments, and at most 3 registers can be used.  You can control this
           behavior for a specific function by using the function attribute "regparm".

           Warning: if you use this switch, and num is nonzero, then you must build all modules with
           the same value, including any libraries.  This includes the system libraries and  startup
           modules.

       -msseregparm
           Use  SSE  register  passing conventions for float and double arguments and return values.
           You can control this behavior for a specific function by  using  the  function  attribute
           "sseregparm".

           Warning:  if  you  use  this  switch then you must build all modules with the same value,
           including any libraries.  This includes the system libraries and startup modules.

       -mvect8-ret-in-mem
           Return 8-byte vectors in memory instead of MMX registers.  This is the default on VxWorks
           to match the ABI of the Sun Studio compilers until version 12.  Only use this  option  if
           you  need  to  remain  compatible  with existing code produced by those previous compiler
           versions or older versions of GCC.

       -mpc32
       -mpc64
       -mpc80
           Set 80387 floating-point precision to 32, 64 or 80 bits.  When -mpc32 is  specified,  the
           significands  of  results  of  floating-point  operations  are rounded to 24 bits (single
           precision); -mpc64 rounds the significands of results of floating-point operations to  53
           bits  (double  precision) and -mpc80 rounds the significands of results of floating-point
           operations to 64 bits (extended double precision),  which  is  the  default.   When  this
           option  is  used, floating-point operations in higher precisions are not available to the
           programmer without setting the FPU control word explicitly.

           Setting the rounding of floating-point operations to less than the default  80  bits  can
           speed  some  programs  by  2% or more.  Note that some mathematical libraries assume that
           extended-precision (80-bit) floating-point operations are enabled by default; routines in
           such libraries could suffer significant loss of  accuracy,  typically  through  so-called
           "catastrophic  cancellation",  when this option is used to set the precision to less than
           extended precision.

       -mdaz-ftz
           The flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the MXCSR register are used
           to control floating-point calculations.SSE and  AVX  instructions  including  scalar  and
           vector  instructions  could benefit from enabling the FTZ and DAZ flags when -mdaz-ftz is
           specified. Don't set FTZ/DAZ flags when -mno-daz-ftz is specified.

       -mstackrealign
           Realign the stack at entry.  On the x86, the -mstackrealign option generates an alternate
           prologue and epilogue that realigns the  run-time  stack  if  necessary.   This  supports
           mixing  legacy codes that keep 4-byte stack alignment with modern codes that keep 16-byte
           stack alignment for SSE compatibility.  See also the attribute "force_align_arg_pointer",
           applicable to individual functions.

       -mpreferred-stack-boundary=num
           Attempt to keep the stack boundary aligned to a  2  raised  to  num  byte  boundary.   If
           -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128 bits).

           Warning:  When  generating code for the x86-64 architecture with SSE extensions disabled,
           -mpreferred-stack-boundary=3 can be used to keep the stack boundary  aligned  to  8  byte
           boundary.  Since x86-64 ABI require 16 byte stack alignment, this is ABI incompatible and
           intended  to be used in controlled environment where stack space is important limitation.
           This option leads to wrong code when functions compiled  with  16  byte  stack  alignment
           (such  as  functions  from a standard library) are called with misaligned stack.  In this
           case, SSE instructions may lead to misaligned memory access traps.  In addition, variable
           arguments are handled incorrectly for 16 byte aligned objects (including x87 long  double
           and   __int128),   leading   to   wrong   results.   You  must  build  all  modules  with
           -mpreferred-stack-boundary=3,  including  any  libraries.   This  includes   the   system
           libraries and startup modules.

       -mincoming-stack-boundary=num
           Assume  the  incoming  stack  is  aligned  to  a  2  raised  to  num  byte  boundary.  If
           -mincoming-stack-boundary    is    not    specified,     the     one     specified     by
           -mpreferred-stack-boundary is used.

           On  Pentium  and  Pentium  Pro, "double" and "long double" values should be aligned to an
           8-byte  boundary  (see  -malign-double)  or  suffer  significant  run  time   performance
           penalties.  On Pentium III, the Streaming SIMD Extension (SSE) data type "__m128" may not
           work properly if it is not 16-byte aligned.

           To  ensure  proper  alignment  of this values on the stack, the stack boundary must be as
           aligned as that required by any value stored on the stack.  Further, every function  must
           be generated such that it keeps the stack aligned.  Thus calling a function compiled with
           a  higher  preferred stack boundary from a function compiled with a lower preferred stack
           boundary most likely misaligns the stack.  It is  recommended  that  libraries  that  use
           callbacks always use the default setting.

           This  extra  alignment does consume extra stack space, and generally increases code size.
           Code that is sensitive to stack space usage,  such  as  embedded  systems  and  operating
           system     kernels,    may    want    to    reduce    the    preferred    alignment    to
           -mpreferred-stack-boundary=2.

       -mmmx
       -msse
       -msse2
       -msse3
       -mssse3
       -msse4
       -msse4a
       -msse4.1
       -msse4.2
       -mavx
       -mavx2
       -mavx512f
       -mavx512pf
       -mavx512er
       -mavx512cd
       -mavx512vl
       -mavx512bw
       -mavx512dq
       -mavx512ifma
       -mavx512vbmi
       -msha
       -maes
       -mpclmul
       -mclflushopt
       -mclwb
       -mfsgsbase
       -mptwrite
       -mrdrnd
       -mf16c
       -mfma
       -mpconfig
       -mwbnoinvd
       -mfma4
       -mprfchw
       -mrdpid
       -mprefetchwt1
       -mrdseed
       -msgx
       -mxop
       -mlwp
       -m3dnow
       -m3dnowa
       -mpopcnt
       -mabm
       -madx
       -mbmi
       -mbmi2
       -mlzcnt
       -mfxsr
       -mxsave
       -mxsaveopt
       -mxsavec
       -mxsaves
       -mrtm
       -mhle
       -mtbm
       -mmwaitx
       -mclzero
       -mpku
       -mavx512vbmi2
       -mavx512bf16
       -mgfni
       -mvaes
       -mwaitpkg
       -mvpclmulqdq
       -mavx512bitalg
       -mmovdiri
       -mmovdir64b
       -menqcmd
       -muintr
       -mtsxldtrk
       -mavx512vpopcntdq
       -mavx512vp2intersect
       -mavx5124fmaps
       -mavx512vnni
       -mavxvnni
       -mavx5124vnniw
       -mcldemote
       -mserialize
       -mamx-tile
       -mamx-int8
       -mamx-bf16
       -mhreset
       -mkl
       -mwidekl
           These switches enable the use of instructions in the MMX, SSE, SSE2, SSE3,  SSSE3,  SSE4,
           SSE4A,  SSE4.1,  SSE4.2,  AVX,  AVX2,  AVX512F,  AVX512PF,  AVX512ER, AVX512CD, AVX512VL,
           AVX512BW, AVX512DQ, AVX512IFMA, AVX512VBMI, SHA, AES, PCLMUL, CLFLUSHOPT, CLWB, FSGSBASE,
           PTWRITE, RDRND, F16C,  FMA,  PCONFIG,  WBNOINVD,  FMA4,  PREFETCHW,  RDPID,  PREFETCHWT1,
           RDSEED, SGX, XOP, LWP, 3DNow!, enhanced 3DNow!, POPCNT, ABM, ADX, BMI, BMI2, LZCNT, FXSR,
           XSAVE,  XSAVEOPT,  XSAVEC, XSAVES, RTM, HLE, TBM, MWAITX, CLZERO, PKU, AVX512VBMI2, GFNI,
           VAES,  WAITPKG,  VPCLMULQDQ,  AVX512BITALG,  MOVDIRI,  MOVDIR64B,   AVX512BF16,   ENQCMD,
           AVX512VPOPCNTDQ,   AVX5124FMAPS,  AVX512VNNI,  AVX5124VNNIW,  SERIALIZE,  UINTR,  HRESET,
           AMXTILE, AMXINT8, AMXBF16, KL, WIDEKL, AVXVNNI or  CLDEMOTE  extended  instruction  sets.
           Each has a corresponding -mno- option to disable use of these instructions.

           These  extensions  are  also available as built-in functions: see x86 Built-in Functions,
           for details of the functions enabled and disabled by these switches.

           To generate SSE/SSE2 instructions automatically from floating-point code (as  opposed  to
           387 instructions), see -mfpmath=sse.

           GCC  depresses  SSEx  instructions  when  -mavx  is  used.  Instead, it generates new AVX
           instructions or AVX equivalence for all SSEx instructions when needed.

           These options enable GCC to use these  extended  instructions  in  generated  code,  even
           without  -mfpmath=sse.   Applications  that  perform  run-time CPU detection must compile
           separate files  for  each  supported  architecture,  using  the  appropriate  flags.   In
           particular,  the  file containing the CPU detection code should be compiled without these
           options.

       -mdump-tune-features
           This option instructs GCC to dump the names of the x86 performance  tuning  features  and
           default settings. The names can be used in -mtune-ctrl=feature-list.

       -mtune-ctrl=feature-list
           This  option  is used to do fine grain control of x86 code generation features.  feature-
           list is a comma separated list of feature  names.  See  also  -mdump-tune-features.  When
           specified, the feature is turned on if it is not preceded with ^, otherwise, it is turned
           off.   -mtune-ctrl=feature-list  is  intended  to be used by GCC developers. Using it may
           lead to code paths not covered by testing and can potentially result in compiler ICEs  or
           runtime errors.

       -mno-default
           This option instructs GCC to turn off all tunable features. See also -mtune-ctrl=feature-
           list and -mdump-tune-features.

       -mcld
           This  option  instructs GCC to emit a "cld" instruction in the prologue of functions that
           use string instructions.  String instructions depend on the DF  flag  to  select  between
           autoincrement  or  autodecrement mode.  While the ABI specifies the DF flag to be cleared
           on function entry, some operating systems violate this specification by not clearing  the
           DF flag in their exception dispatchers.  The exception handler can be invoked with the DF
           flag  set,  which  leads to wrong direction mode when string instructions are used.  This
           option can be enabled by default on 32-bit  x86  targets  by  configuring  GCC  with  the
           --enable-cld  configure  option.  Generation of "cld" instructions can be suppressed with
           the -mno-cld compiler option in this case.

       -mvzeroupper
           This option instructs GCC to emit a "vzeroupper" instruction before a transfer of control
           flow out of the function to minimize the AVX to SSE transition penalty as well as  remove
           unnecessary "zeroupper" intrinsics.

       -mprefer-avx128
           This  option  instructs  GCC  to  use  128-bit  AVX  instructions  instead of 256-bit AVX
           instructions in the auto-vectorizer.

       -mprefer-vector-width=opt
           This option instructs GCC to use opt-bit vector width in instructions instead of  default
           on the selected platform.

           none
               No extra limitations applied to GCC other than defined by the selected platform.

           128 Prefer 128-bit vector width for instructions.

           256 Prefer 256-bit vector width for instructions.

           512 Prefer 512-bit vector width for instructions.

       -mcx16
           This option enables GCC to generate "CMPXCHG16B" instructions in 64-bit code to implement
           compare-and-exchange  operations  on 16-byte aligned 128-bit objects.  This is useful for
           atomic updates of data structures exceeding one machine word in size.  The compiler  uses
           this  instruction to implement __sync Builtins.  However, for __atomic Builtins operating
           on 128-bit integers, a library call is always used.

       -msahf
           This option enables generation of  "SAHF"  instructions  in  64-bit  code.   Early  Intel
           Pentium  4  CPUs with Intel 64 support, prior to the introduction of Pentium 4 G1 step in
           December 2005, lacked the "LAHF" and "SAHF" instructions which are  supported  by  AMD64.
           These are load and store instructions, respectively, for certain status flags.  In 64-bit
           mode, the "SAHF" instruction is used to optimize "fmod", "drem", and "remainder" built-in
           functions; see Other Builtins for details.

       -mmovbe
           This  option  enables use of the "movbe" instruction to implement "__builtin_bswap32" and
           "__builtin_bswap64".

       -mshstk
           The -mshstk  option  enables  shadow  stack  built-in  functions  from  x86  Control-flow
           Enforcement Technology (CET).

       -mcrc32
           This      option      enables      built-in      functions      "__builtin_ia32_crc32qi",
           "__builtin_ia32_crc32hi",  "__builtin_ia32_crc32si"   and   "__builtin_ia32_crc32di"   to
           generate the "crc32" machine instruction.

       -mmwait
           This     option     enables     built-in    functions    "__builtin_ia32_monitor",    and
           "__builtin_ia32_mwait" to generate the "monitor" and "mwait" machine instructions.

       -mrecip
           This option enables use of "RCPSS"  and  "RSQRTSS"  instructions  (and  their  vectorized
           variants  "RCPPS"  and  "RSQRTPS")  with  an  additional  Newton-Raphson step to increase
           precision instead of "DIVSS" and "SQRTSS" (and their  vectorized  variants)  for  single-
           precision   floating-point   arguments.   These  instructions  are  generated  only  when
           -funsafe-math-optimizations   is   enabled   together   with    -ffinite-math-only    and
           -fno-trapping-math.   Note  that  while the throughput of the sequence is higher than the
           throughput of the non-reciprocal instruction,  the  precision  of  the  sequence  can  be
           decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994).

           Note  that  GCC  implements  "1.0f/sqrtf(x)" in terms of "RSQRTSS" (or "RSQRTPS") already
           with -ffast-math (or the above option combination), and doesn't need -mrecip.

           Also note that GCC emits the above  sequence  with  additional  Newton-Raphson  step  for
           vectorized single-float division and vectorized sqrtf(x) already with -ffast-math (or the
           above option combination), and doesn't need -mrecip.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may be used.  opt is a comma-
           separated list of options, which may be preceded by a ! to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable the approximation for scalar division.

           vec-div
               Enable the approximation for vectorized division.

           sqrt
               Enable the approximation for scalar square root.

           vec-sqrt
               Enable the approximation for vectorized square root.

           So,  for  example, -mrecip=all,!sqrt enables all of the reciprocal approximations, except
           for square root.

       -mveclibabi=type
           Specifies the ABI type to use for  vectorizing  intrinsics  using  an  external  library.
           Supported  values  for type are svml for the Intel short vector math library and acml for
           the  AMD  math  core  library.   To  use   this   option,   both   -ftree-vectorize   and
           -funsafe-math-optimizations  have  to  be  enabled,  and  an  SVML or ACML ABI-compatible
           library must be specified at link time.

           GCC  currently  emits  calls  to   "vmldExp2",   "vmldLn2",   "vmldLog102",   "vmldPow2",
           "vmldTanh2", "vmldTan2", "vmldAtan2", "vmldAtanh2", "vmldCbrt2", "vmldSinh2", "vmldSin2",
           "vmldAsinh2",    "vmldAsin2",   "vmldCosh2",   "vmldCos2",   "vmldAcosh2",   "vmldAcos2",
           "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsPow4",  "vmlsTanh4",  "vmlsTan4",  "vmlsAtan4",
           "vmlsAtanh4",    "vmlsCbrt4",   "vmlsSinh4",   "vmlsSin4",   "vmlsAsinh4",   "vmlsAsin4",
           "vmlsCosh4", "vmlsCos4", "vmlsAcosh4" and "vmlsAcos4"  for  corresponding  function  type
           when   -mveclibabi=svml   is   used,   and   "__vrd2_sin",   "__vrd2_cos",  "__vrd2_exp",
           "__vrd2_log", "__vrd2_log2", "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf",
           "__vrs4_logf", "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf"  for  the  corresponding
           function type when -mveclibabi=acml is used.

       -mabi=name
           Generate  code for the specified calling convention.  Permissible values are sysv for the
           ABI used on GNU/Linux and other systems, and ms for the Microsoft ABI.  The default is to
           use the Microsoft ABI when targeting Microsoft Windows and the  SysV  ABI  on  all  other
           systems.   You  can  control  this  behavior for specific functions by using the function
           attributes "ms_abi" and "sysv_abi".

       -mforce-indirect-call
           Force all calls to functions to be indirect. This is useful when  using  Intel  Processor
           Trace where it generates more precise timing information for function calls.

       -mmanual-endbr
           Insert  ENDBR  instruction  at function entry only via the "cf_check" function attribute.
           This is useful  when  used  with  the  option  -fcf-protection=branch  to  control  ENDBR
           insertion at the function entry.

       -mcall-ms2sysv-xlogues
           Due  to  differences in 64-bit ABIs, any Microsoft ABI function that calls a System V ABI
           function must consider RSI, RDI and XMM6-15 as  clobbered.   By  default,  the  code  for
           saving  and  restoring  these  registers  is  emitted inline, resulting in fairly lengthy
           prologues and epilogues.  Using -mcall-ms2sysv-xlogues emits prologues and epilogues that
           use stubs in the static portion of libgcc to  perform  these  saves  and  restores,  thus
           reducing function size at the cost of a few extra instructions.

       -mtls-dialect=type
           Generate  code  to access thread-local storage using the gnu or gnu2 conventions.  gnu is
           the conservative default; gnu2 is more efficient, but it may add  compile-  and  run-time
           requirements that cannot be satisfied on all systems.

       -mpush-args
       -mno-push-args
           Use  PUSH  operations  to  store outgoing parameters.  This method is shorter and usually
           equally fast as method using SUB/MOV operations and is enabled by default.  In some cases
           disabling  it  may  improve  performance  because  of  improved  scheduling  and  reduced
           dependencies.

       -maccumulate-outgoing-args
           If  enabled,  the  maximum amount of space required for outgoing arguments is computed in
           the  function  prologue.   This  is  faster  on  most  modern  CPUs  because  of  reduced
           dependencies,  improved  scheduling  and  reduced  stack  usage  when the preferred stack
           boundary is not equal to 2.  The drawback is a  notable  increase  in  code  size.   This
           switch implies -mno-push-args.

       -mthreads
           Support  thread-safe  exception  handling  on  MinGW.   Programs that rely on thread-safe
           exception handling must compile and link  all  code  with  the  -mthreads  option.   When
           compiling,  -mthreads  defines  -D_MT;  when linking, it links in a special thread helper
           library -lmingwthrd which cleans up per-thread exception-handling data.

       -mms-bitfields
       -mno-ms-bitfields
           Enable/disable bit-field layout compatible with the native Microsoft Windows compiler.

           If "packed" is used on a structure, or if  bit-fields  are  used,  it  may  be  that  the
           Microsoft  ABI  lays  out  the  structure  differently  than  the  way GCC normally does.
           Particularly when moving packed data between functions compiled with GCC and  the  native
           Microsoft  compiler  (either via function call or as data in a file), it may be necessary
           to access either format.

           This option is enabled by default for Microsoft Windows targets.  This behavior can  also
           be  controlled  locally by use of variable or type attributes.  For more information, see
           x86 Variable Attributes and x86 Type Attributes.

           The Microsoft structure layout algorithm is fairly simple with the exception of the  bit-
           field  packing.   The  padding  and alignment of members of structures and whether a bit-
           field can straddle a storage-unit boundary are determine by these rules:

           1. Structure members are stored sequentially in the order in which they are
               declared: the first member has the lowest memory address  and  the  last  member  the
               highest.

           2. Every data object has an alignment requirement.  The alignment requirement
               for  all  data except structures, unions, and arrays is either the size of the object
               or the current packing size (specified with either the  "aligned"  attribute  or  the
               "pack" pragma), whichever is less.  For structures, unions, and arrays, the alignment
               requirement  is  the  largest  alignment requirement of its members.  Every object is
               allocated an offset so that:

                       offset % alignment_requirement == 0

           3. Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte allocation
               unit if the integral types are the same size and if the next bit-field fits into  the
               current allocation unit without crossing the boundary imposed by the common alignment
               requirements of the bit-fields.

           MSVC interprets zero-length bit-fields in the following ways:

           1. If a zero-length bit-field is inserted between two bit-fields that
               are normally coalesced, the bit-fields are not coalesced.

               For example:

                       struct
                        {
                          unsigned long bf_1 : 12;
                          unsigned long : 0;
                          unsigned long bf_2 : 12;
                        } t1;

               The  size of "t1" is 8 bytes with the zero-length bit-field.  If the zero-length bit-
               field were removed, "t1"'s size would be 4 bytes.

           2. If a zero-length bit-field is inserted after a bit-field, "foo", and the
               alignment of the zero-length bit-field is greater than the member  that  follows  it,
               "bar", "bar" is aligned as the type of the zero-length bit-field.

               For example:

                       struct
                        {
                          char foo : 4;
                          short : 0;
                          char bar;
                        } t2;

                       struct
                        {
                          char foo : 4;
                          short : 0;
                          double bar;
                        } t3;

               For  "t2",  "bar" is placed at offset 2, rather than offset 1.  Accordingly, the size
               of "t2" is 4.  For "t3", the zero-length bit-field does not affect the  alignment  of
               "bar" or, as a result, the size of the structure.

               Taking this into account, it is important to note the following:

               1. If a zero-length bit-field follows a normal bit-field, the type of the
                   zero-length  bit-field  may  affect  the alignment of the structure as whole. For
                   example, "t2" has a size of 4 bytes, since the zero-length  bit-field  follows  a
                   normal bit-field, and is of type short.

               2. Even if a zero-length bit-field is not followed by a normal bit-field, it may
                   still affect the alignment of the structure:

                           struct
                            {
                              char foo : 6;
                              long : 0;
                            } t4;

                   Here, "t4" takes up 4 bytes.

           3. Zero-length bit-fields following non-bit-field members are ignored:
                       struct
                        {
                          char foo;
                          long : 0;
                          char bar;
                        } t5;

               Here, "t5" takes up 2 bytes.

       -mno-align-stringops
           Do not align the destination of inlined string operations.  This switch reduces code size
           and improves performance in case the destination is already aligned, but GCC doesn't know
           about it.

       -minline-all-stringops
           By default GCC inlines string operations only when the destination is known to be aligned
           to  least a 4-byte boundary.  This enables more inlining and increases code size, but may
           improve performance of code that depends on fast "memcpy" and "memset" for short lengths.
           The option enables inline expansion of "strlen" for all pointer alignments.

       -minline-stringops-dynamically
           For string operations of unknown size, use run-time checks with  inline  code  for  small
           blocks and a library call for large blocks.

       -mstringop-strategy=alg
           Override the internal decision heuristic for the particular algorithm to use for inlining
           string operations.  The allowed values for alg are:

           rep_byte
           rep_4byte
           rep_8byte
               Expand using i386 "rep" prefix of the specified size.

           byte_loop
           loop
           unrolled_loop
               Expand into an inline loop.

           libcall
               Always use a library call.

       -mmemcpy-strategy=strategy
           Override  the  internal  decision  heuristic  to  decide  if "__builtin_memcpy" should be
           inlined and what inline algorithm to use when the expected size of the copy operation  is
           known.  strategy  is  a comma-separated list of alg:max_size:dest_align triplets.  alg is
           specified in -mstringop-strategy, max_size specifies the max byte size with which  inline
           algorithm alg is allowed.  For the last triplet, the max_size must be -1. The max_size of
           the  triplets  in  the list must be specified in increasing order.  The minimal byte size
           for alg is 0 for the first triplet and "max_size + 1" of the preceding range.

       -mmemset-strategy=strategy
           The  option  is  similar  to  -mmemcpy-strategy=   except   that   it   is   to   control
           "__builtin_memset" expansion.

       -momit-leaf-frame-pointer
           Don't  keep  the  frame  pointer  in  a  register  for  leaf  functions.  This avoids the
           instructions to save, set up, and restore frame pointers  and  makes  an  extra  register
           available  in  leaf  functions.   The  option -fomit-leaf-frame-pointer removes the frame
           pointer for leaf functions, which might make debugging harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
           Controls whether TLS variables may be accessed with offsets from the TLS segment register
           (%gs for 32-bit, %fs for 64-bit), or whether the  thread  base  pointer  must  be  added.
           Whether  or  not  this  is valid depends on the operating system, and whether it maps the
           segment to cover the entire TLS area.

           For systems that use the GNU C Library, the default is on.

       -msse2avx
       -mno-sse2avx
           Specify that the assembler should encode SSE instructions with VEX  prefix.   The  option
           -mavx turns this on by default.

       -mfentry
       -mno-fentry
           If  profiling is active (-pg), put the profiling counter call before the prologue.  Note:
           On x86 architectures the attribute "ms_hook_prologue" isn't possible at  the  moment  for
           -mfentry and -pg.

       -mrecord-mcount
       -mno-record-mcount
           If  profiling  is active (-pg), generate a __mcount_loc section that contains pointers to
           each profiling call. This is useful for automatically patching and out calls.

       -mnop-mcount
       -mno-nop-mcount
           If profiling is active (-pg), generate the calls to the profiling functions as NOPs. This
           is useful when they should be patched in later dynamically. This is  likely  only  useful
           together with -mrecord-mcount.

       -minstrument-return=type
           Instrument  function  exit  in -pg -mfentry instrumented functions with call to specified
           function. This only instruments true returns ending  with  ret,  but  not  sibling  calls
           ending  with  jump.  Valid  types  are none to not instrument, call to generate a call to
           __return__, or nop5 to generate a 5 byte nop.

       -mrecord-return
       -mno-record-return
           Generate a __return_loc section pointing to all return instrumentation code.

       -mfentry-name=name
           Set name of __fentry__ symbol called at function entry for -pg -mfentry functions.

       -mfentry-section=name
           Set name of section to record -mrecord-mcount calls (default __mcount_loc).

       -mskip-rax-setup
       -mno-skip-rax-setup
           When  generating  code  for  the  x86-64  architecture  with  SSE  extensions   disabled,
           -mskip-rax-setup  can  be used to skip setting up RAX register when there are no variable
           arguments passed in vector registers.

           Warning: Since RAX register is used to avoid unnecessarily  saving  vector  registers  on
           stack  when  passing variable arguments, the impacts of this option are callees may waste
           some stack space, misbehave or jump to a random location.  GCC 4.4 or  newer  don't  have
           those issues, regardless the RAX register value.

       -m8bit-idiv
       -mno-8bit-idiv
           On  some  processors,  like Intel Atom, 8-bit unsigned integer divide is much faster than
           32-bit/64-bit integer divide.  This option generates a run-time check.  If both  dividend
           and  divisor  are within range of 0 to 255, 8-bit unsigned integer divide is used instead
           of 32-bit/64-bit integer divide.

       -mavx256-split-unaligned-load
       -mavx256-split-unaligned-store
           Split 32-byte AVX unaligned load and store.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
           Generate stack protection code using canary at guard.  Supported locations are global for
           global canary or tls for per-thread canary in the TLS block (the default).   This  option
           has effect only when -fstack-protector or -fstack-protector-all is specified.

           With    the    latter    choice    the    options   -mstack-protector-guard-reg=reg   and
           -mstack-protector-guard-offset=offset furthermore specify which segment register (%fs  or
           %gs)  to use as base register for reading the canary, and from what offset from that base
           register.  The default for those is as specified in the relevant ABI.

       -mgeneral-regs-only
           Generate code that uses only the general-purpose registers.  This prevents  the  compiler
           from using floating-point, vector, mask and bound registers.

       -mindirect-branch=choice
           Convert  indirect  call  and jump with choice.  The default is keep, which keeps indirect
           call and jump unmodified.  thunk converts indirect call  and  jump  to  call  and  return
           thunk.   thunk-inline  converts  indirect call and jump to inlined call and return thunk.
           thunk-extern converts indirect call and jump to external call and return  thunk  provided
           in  a  separate  object  file.   You can control this behavior for a specific function by
           using the function attribute "indirect_branch".

           Note   that   -mcmodel=large   is   incompatible   with    -mindirect-branch=thunk    and
           -mindirect-branch=thunk-extern since the thunk function may not be reachable in the large
           code model.

           Note  that -mindirect-branch=thunk-extern is compatible with -fcf-protection=branch since
           the external thunk can be made to enable control-flow check.

       -mfunction-return=choice
           Convert function return with choice.  The default is keep, which  keeps  function  return
           unmodified.   thunk  converts  function  return  to  call and return thunk.  thunk-inline
           converts function return  to  inlined  call  and  return  thunk.   thunk-extern  converts
           function  return  to  external  call and return thunk provided in a separate object file.
           You can control this behavior for a specific function by  using  the  function  attribute
           "function_return".

           Note  that -mindirect-return=thunk-extern is compatible with -fcf-protection=branch since
           the external thunk can be made to enable control-flow check.

           Note   that   -mcmodel=large   is   incompatible   with    -mfunction-return=thunk    and
           -mfunction-return=thunk-extern since the thunk function may not be reachable in the large
           code model.

       -mindirect-branch-register
           Force indirect call and jump via register.

       -mharden-sls=choice
           Generate  code  to  mitigate  against  straight  line speculation (SLS) with choice.  The
           default is none which disables all SLS  hardening.   return  enables  SLS  hardening  for
           function  returns.   indirect-jmp  enables SLS hardening for indirect jumps.  all enables
           all SLS hardening.

       -mindirect-branch-cs-prefix
           Add CS prefix to call and jmp to indirect thunk with branch target in r8-r15 registers so
           that the call and jmp instruction length is 6 bytes to allow them  to  be  replaced  with
           lfence; call *%r8-r15 or lfence; jmp *%r8-r15 at run-time.

       These  -m  switches  are  supported  in  addition to the above on x86-64 processors in 64-bit
       environments.

       -m32
       -m64
       -mx32
       -m16
       -miamcu
           Generate code for a 16-bit, 32-bit or 64-bit environment.  The -m32  option  sets  "int",
           "long", and pointer types to 32 bits, and generates code that runs in 32-bit mode.

           The  -m64  option  sets  "int"  to  32  bits and "long" and pointer types to 64 bits, and
           generates code for the x86-64 architecture.  For Darwin only the -m64 option  also  turns
           off the -fno-pic and -mdynamic-no-pic options.

           The -mx32 option sets "int", "long", and pointer types to 32 bits, and generates code for
           the x86-64 architecture.

           The -m16 option is the same as -m32, except for that it outputs the ".code16gcc" assembly
           directive  at  the  beginning of the assembly output so that the binary can run in 16-bit
           mode.

           The -miamcu option generates code which conforms to Intel MCU  psABI.   It  requires  the
           -m32 option to be turned on.

       -mno-red-zone
           Do  not  use  a  so-called  "red  zone" for x86-64 code.  The red zone is mandated by the
           x86-64 ABI; it is a 128-byte area beyond the location of the stack pointer  that  is  not
           modified  by  signal  or  interrupt handlers and therefore can be used for temporary data
           without adjusting the stack pointer.  The flag -mno-red-zone disables this red zone.

       -mcmodel=small
           Generate code for the small code model: the program and its symbols must be linked in the
           lower 2 GB of the address space.  Pointers are 64 bits.  Programs can  be  statically  or
           dynamically linked.  This is the default code model.

       -mcmodel=kernel
           Generate  code  for  the  kernel code model.  The kernel runs in the negative 2 GB of the
           address space.  This model has to be used for Linux kernel code.

       -mcmodel=medium
           Generate code for the medium model: the program is linked  in  the  lower  2  GB  of  the
           address  space.   Small  symbols  are  also placed there.  Symbols with sizes larger than
           -mlarge-data-threshold are put into large data or BSS sections and can be  located  above
           2GB.  Programs can be statically or dynamically linked.

       -mcmodel=large
           Generate  code  for the large model.  This model makes no assumptions about addresses and
           sizes of sections.

       -maddress-mode=long
           Generate code for long  address  mode.   This  is  only  supported  for  64-bit  and  x32
           environments.  It is the default address mode for 64-bit environments.

       -maddress-mode=short
           Generate  code  for  short  address  mode.   This  is  only  supported for 32-bit and x32
           environments.  It is the default address mode for 32-bit and x32 environments.

       -mneeded
       -mno-needed
           Emit GNU_PROPERTY_X86_ISA_1_NEEDED GNU property for Linux target to indicate  the  micro-
           architecture ISA level required to execute the binary.

       x86 Windows Options

       These additional options are available for Microsoft Windows targets:

       -mconsole
           This  option  specifies that a console application is to be generated, by instructing the
           linker to set the PE header subsystem  type  required  for  console  applications.   This
           option  is  available  for  Cygwin  and  MinGW targets and is enabled by default on those
           targets.

       -mdll
           This option is available for Cygwin and MinGW  targets.   It  specifies  that  a  DLL---a
           dynamic link library---is to be generated, enabling the selection of the required runtime
           startup object and entry point.

       -mnop-fun-dllimport
           This option is available for Cygwin and MinGW targets.  It specifies that the "dllimport"
           attribute should be ignored.

       -mthread
           This  option  is  available  for  MinGW  targets. It specifies that MinGW-specific thread
           support is to be used.

       -municode
           This option is available for MinGW-w64 targets.  It  causes  the  "UNICODE"  preprocessor
           macro to be predefined, and chooses Unicode-capable runtime startup code.

       -mwin32
           This  option  is  available  for Cygwin and MinGW targets.  It specifies that the typical
           Microsoft Windows predefined macros are to be set in  the  pre-processor,  but  does  not
           influence the choice of runtime library/startup code.

       -mwindows
           This  option  is  available  for  Cygwin  and  MinGW  targets.   It  specifies that a GUI
           application is to be generated by instructing the linker to set the PE  header  subsystem
           type appropriately.

       -fno-set-stack-executable
           This option is available for MinGW targets. It specifies that the executable flag for the
           stack  used  by  nested  functions  isn't  set. This is necessary for binaries running in
           kernel mode of Microsoft Windows,  as  there  the  User32  API,  which  is  used  to  set
           executable privileges, isn't available.

       -fwritable-relocated-rdata
           This  option is available for MinGW and Cygwin targets.  It specifies that relocated-data
           in read-only section is put into the ".data" section.  This  is  a  necessary  for  older
           runtimes not supporting modification of ".rdata" sections for pseudo-relocation.

       -mpe-aligned-commons
           This  option  is  available  for  Cygwin  and  MinGW  targets.  It specifies that the GNU
           extension to the PE file format that permits the correct alignment  of  COMMON  variables
           should  be  used  when generating code.  It is enabled by default if GCC detects that the
           target assembler found during configuration supports the feature.

       See also under x86 Options for standard options.

       Xstormy16 Options

       These options are defined for Xstormy16:

       -msim
           Choose startup files and linker script suitable for the simulator.

       Xtensa Options

       These options are supported for Xtensa targets:

       -mconst16
       -mno-const16
           Enable or disable use  of  "CONST16"  instructions  for  loading  constant  values.   The
           "CONST16"  instruction  is currently not a standard option from Tensilica.  When enabled,
           "CONST16" instructions are always used in place of the standard "L32R" instructions.  The
           use of "CONST16" is enabled by default only if the "L32R" instruction is not available.

       -mfused-madd
       -mno-fused-madd
           Enable or disable use of fused multiply/add and  multiply/subtract  instructions  in  the
           floating-point  option.   This  has  no  effect  if the floating-point option is not also
           enabled.  Disabling fused multiply/add  and  multiply/subtract  instructions  forces  the
           compiler to use separate instructions for the multiply and add/subtract operations.  This
           may  be desirable in some cases where strict IEEE 754-compliant results are required: the
           fused multiply add/subtract instructions do not round the  intermediate  result,  thereby
           producing  results  with  more  bits  of  precision  than specified by the IEEE standard.
           Disabling fused multiply add/subtract instructions also ensures that the  program  output
           is  not  sensitive  to  the  compiler's  ability  to  combine  multiply  and add/subtract
           operations.

       -mserialize-volatile
       -mno-serialize-volatile
           When this option is enabled, GCC inserts "MEMW"  instructions  before  "volatile"  memory
           references  to  guarantee  sequential  consistency.  The default is -mserialize-volatile.
           Use -mno-serialize-volatile to omit the "MEMW" instructions.

       -mforce-no-pic
           For targets, like GNU/Linux, where all user-mode Xtensa code must be position-independent
           code (PIC), this option disables PIC for compiling kernel code.

       -mtext-section-literals
       -mno-text-section-literals
           These   options   control   the   treatment   of   literal   pools.    The   default   is
           -mno-text-section-literals,  which  places  literals  in a separate section in the output
           file.  This allows the literal pool to be placed in a data RAM/ROM, and  it  also  allows
           the  linker  to  combine  literal  pools  from  separate object files to remove redundant
           literals  and  improve  code  size.   With  -mtext-section-literals,  the  literals   are
           interspersed  in  the  text  section  in order to keep them as close as possible to their
           references.  This may be necessary for large assembly files.  Literals for each  function
           are placed right before that function.

       -mauto-litpools
       -mno-auto-litpools
           These options control the treatment of literal pools.  The default is -mno-auto-litpools,
           which   places   literals   in   a   separate   section   in   the   output  file  unless
           -mtext-section-literals is used.  With -mauto-litpools the literals are  interspersed  in
           the  text  section  by  the  assembler.   Compiler  does  not produce explicit ".literal"
           directives and loads literals into registers with "MOVI" instructions instead  of  "L32R"
           to  let  the assembler do relaxation and place literals as necessary.  This option allows
           assembler to create several literal pools per function and assemble very  big  functions,
           which may not be possible with -mtext-section-literals.

       -mtarget-align
       -mno-target-align
           When  this  option  is  enabled,  GCC  instructs  the  assembler  to  automatically align
           instructions to reduce branch penalties  at  the  expense  of  some  code  density.   The
           assembler  attempts  to  widen  density  instructions  to  align  branch  targets and the
           instructions following call instructions.  If there are not enough preceding safe density
           instructions to align a target, no widening is performed.  The default is -mtarget-align.
           These options do not affect the treatment of auto-aligned instructions like "LOOP", which
           the assembler always aligns, either by widening density instructions or by inserting  NOP
           instructions.

       -mlongcalls
       -mno-longcalls
           When  this  option  is  enabled, GCC instructs the assembler to translate direct calls to
           indirect calls unless it can determine that the target of a direct call is in  the  range
           allowed  by  the  call  instruction.   This  translation  typically  occurs  for calls to
           functions in other source files.  Specifically, the assembler translates a direct  "CALL"
           instruction   into  an  "L32R"  followed  by  a  "CALLX"  instruction.   The  default  is
           -mno-longcalls.  This option should be  used  in  programs  where  the  call  target  can
           potentially  be  out  of  range.   This  option  is implemented in the assembler, not the
           compiler,  so  the  assembly  code   generated   by   GCC   still   shows   direct   call
           instructions---look at the disassembled object code to see the actual instructions.  Note
           that  the  assembler uses an indirect call for every cross-file call, not just those that
           really are out of range.

       -mabi=name
           Generate code for the specified ABI.  Permissible values are: call0,  windowed.   Default
           ABI is chosen by the Xtensa core configuration.

       -mabi=call0
           When  this  option  is  enabled  function parameters are passed in registers "a2" through
           "a7", registers "a12" through "a15" are caller-saved, and register "a15" may be used as a
           frame pointer.  When this version of  the  ABI  is  enabled  the  C  preprocessor  symbol
           "__XTENSA_CALL0_ABI__" is defined.

       -mabi=windowed
           When  this  option  is  enabled function parameters are passed in registers "a10" through
           "a15", and called function rotates register window by 8 registers on entry  so  that  its
           arguments are found in registers "a2" through "a7".  Register "a7" may be used as a frame
           pointer.   Register window is rotated 8 registers back upon return.  When this version of
           the ABI is enabled the C preprocessor symbol "__XTENSA_WINDOWED_ABI__" is defined.

       zSeries Options

       These are listed under

ENVIRONMENT
       This section describes several environment variables that affect how GCC operates.   Some  of
       them  work  by  specifying directories or prefixes to use when searching for various kinds of
       files.  Some are used to specify other aspects of the compilation environment.

       Note that you can also specify places to search using options such as -B, -I and  -L.   These
       take  precedence  over  places  specified  using  environment  variables,  which in turn take
       precedence over those specified by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
           These environment variables control the way that GCC uses localization information  which
           allows  GCC  to  work  with  different  national  conventions.   GCC  inspects the locale
           categories LC_CTYPE and LC_MESSAGES if it has been configured to  do  so.   These  locale
           categories  can  be  set to any value supported by your installation.  A typical value is
           en_GB.UTF-8 for English in the United Kingdom encoded in UTF-8.

           The LC_CTYPE environment variable specifies character classification.   GCC  uses  it  to
           determine  the  character  boundaries  in  a  string;  this  is needed for some multibyte
           encodings that contain quote and escape characters that are otherwise  interpreted  as  a
           string end or escape.

           The  LC_MESSAGES  environment  variable  specifies  the  language  to  use  in diagnostic
           messages.

           If the LC_ALL environment variable is  set,  it  overrides  the  value  of  LC_CTYPE  and
           LC_MESSAGES;  otherwise,  LC_CTYPE  and  LC_MESSAGES  default  to  the  value of the LANG
           environment variable.  If none of these variables are set, GCC defaults to traditional  C
           English behavior.

       TMPDIR
           If  TMPDIR  is  set,  it  specifies  the  directory to use for temporary files.  GCC uses
           temporary files to hold the output of one stage of compilation which is  to  be  used  as
           input  to the next stage: for example, the output of the preprocessor, which is the input
           to the compiler proper.

       GCC_COMPARE_DEBUG
           Setting GCC_COMPARE_DEBUG is nearly equivalent to passing -fcompare-debug to the compiler
           driver.  See the documentation of this option for more details.

       GCC_EXEC_PREFIX
           If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the names of  the  subprograms
           executed  by  the compiler.  No slash is added when this prefix is combined with the name
           of a subprogram, but you can specify a prefix that ends with a slash if you wish.

           If GCC_EXEC_PREFIX is not set, GCC attempts to figure out an appropriate  prefix  to  use
           based on the pathname it is invoked with.

           If  GCC  cannot  find  the subprogram using the specified prefix, it tries looking in the
           usual places for the subprogram.

           The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where prefix is the prefix to the
           installed compiler. In many cases prefix is the  value  of  "prefix"  when  you  ran  the
           configure script.

           Other prefixes specified with -B take precedence over this prefix.

           This prefix is also used for finding files such as crt0.o that are used for linking.

           In  addition,  the  prefix is used in an unusual way in finding the directories to search
           for header files.  For each of the standard directories whose name normally  begins  with
           /usr/local/lib/gcc  (more  precisely,  with  the  value  of  GCC_INCLUDE_DIR),  GCC tries
           replacing that beginning with the specified prefix  to  produce  an  alternate  directory
           name.   Thus,  with  -Bfoo/,  GCC  searches  foo/bar just before it searches the standard
           directory /usr/local/lib/bar.  If a standard directory begins with the configured  prefix
           then the value of prefix is replaced by GCC_EXEC_PREFIX when looking for header files.

       COMPILER_PATH
           The value of COMPILER_PATH is a colon-separated list of directories, much like PATH.  GCC
           tries  the  directories  thus specified when searching for subprograms, if it cannot find
           the subprograms using GCC_EXEC_PREFIX.

       LIBRARY_PATH
           The value of LIBRARY_PATH is a colon-separated list of directories, much like PATH.  When
           configured as a native compiler, GCC tries the directories thus specified when  searching
           for  special  linker  files, if it cannot find them using GCC_EXEC_PREFIX.  Linking using
           GCC also uses these directories when searching for ordinary libraries for the  -l  option
           (but directories specified with -L come first).

       LANG
           This  variable is used to pass locale information to the compiler.  One way in which this
           information is used is to determine the character set to be used when character literals,
           string literals and comments are parsed in C and C++.  When the compiler is configured to
           allow multibyte characters, the following values for LANG are recognized:

           C-JIS
               Recognize JIS characters.

           C-SJIS
               Recognize SJIS characters.

           C-EUCJP
               Recognize EUCJP characters.

           If LANG is not defined, or if it has some other value, then the compiler uses "mblen" and
           "mbtowc"  as  defined  by  the  default  locale  to  recognize  and  translate  multibyte
           characters.

       GCC_EXTRA_DIAGNOSTIC_OUTPUT
           If  GCC_EXTRA_DIAGNOSTIC_OUTPUT  is  set  to one of the following values, then additional
           text   will   be    emitted    to    stderr    when    fix-it    hints    are    emitted.
           -fdiagnostics-parseable-fixits and -fno-diagnostics-parseable-fixits take precedence over
           this environment variable.

           fixits-v1
               Emit  parseable  fix-it  hints,  equivalent  to  -fdiagnostics-parseable-fixits.   In
               particular, columns are expressed as a count of bytes, starting at  byte  1  for  the
               initial column.

           fixits-v2
               As   "fixits-v1",   but   columns   are   expressed   as   display  columns,  as  per
               -fdiagnostics-column-unit=display.

       Some additional environment variables affect the behavior of the preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
           Each variable's value is a list of directories separated by  a  special  character,  much
           like  PATH,  in which to look for header files.  The special character, "PATH_SEPARATOR",
           is target-dependent and determined  at  GCC  build  time.   For  Microsoft  Windows-based
           targets it is a semicolon, and for almost all other targets it is a colon.

           CPATH  specifies  a list of directories to be searched as if specified with -I, but after
           any paths given with -I options on the command line.  This environment variable  is  used
           regardless of which language is being preprocessed.

           The remaining environment variables apply only when preprocessing the particular language
           indicated.   Each  specifies  a  list  of directories to be searched as if specified with
           -isystem, but after any paths given with -isystem options on the command line.

           In all these variables, an empty element instructs the compiler  to  search  its  current
           working  directory.   Empty  elements  can appear at the beginning or end of a path.  For
           instance, if the value of CPATH is ":/special/include",  that  has  the  same  effect  as
           -I. -I/special/include.

       DEPENDENCIES_OUTPUT
           If this variable is set, its value specifies how to output dependencies for Make based on
           the  non-system  header files processed by the compiler.  System header files are ignored
           in the dependency output.

           The value of DEPENDENCIES_OUTPUT can be just a file name, in which case  the  Make  rules
           are  written  to  that  file, guessing the target name from the source file name.  Or the
           value can have the form file target, in which case the rules are  written  to  file  file
           using target as the target name.

           In  other words, this environment variable is equivalent to combining the options -MM and
           -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
           This variable is the same as DEPENDENCIES_OUTPUT (see above), except that  system  header
           files  are not ignored, so it implies -M rather than -MM.  However, the dependence on the
           main input file is omitted.

       SOURCE_DATE_EPOCH
           If this variable is set, its value specifies a UNIX timestamp to be used  in  replacement
           of  the  current  date  and  time  in  the  "__DATE__" and "__TIME__" macros, so that the
           embedded timestamps become reproducible.

           The value of SOURCE_DATE_EPOCH must be a UNIX timestamp, defined as the number of seconds
           (excluding leap seconds) since 01 Jan 1970 00:00:00 represented in  ASCII;  identical  to
           the  output of "date +%s" on GNU/Linux and other systems that support the %s extension in
           the "date" command.

           The value should be a known timestamp such as the last modification time of the source or
           package and it should be set by the build process.

BUGS
       For instructions on reporting bugs, see <file:///usr/share/doc/gcc-11/README.Bugs>.

FOOTNOTES
       1.  On some systems, gcc -shared needs to build supplementary stub code for  constructors  to
           work.   On multi-libbed systems, gcc -shared must select the correct support libraries to
           link against.  Failing to supply the correct flags may lead to subtle defects.  Supplying
           them in cases where they are not necessary is innocuous.

SEE ALSO
       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1), dbx(1) and  the  Info
       entries for gcc, cpp, as, ld, binutils and gdb.

AUTHOR
       See  the  Info  entry  for gcc, or <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
       contributors to GCC.

COPYRIGHT
       Copyright (c) 1988-2021 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the terms of  the
       GNU  Free  Documentation  License,  Version  1.3  or  any later version published by the Free
       Software Foundation; with the Invariant Sections  being  "GNU  General  Public  License"  and
       "Funding Free Software", the Front-Cover texts being (a) (see below), and with the Back-Cover
       Texts being (b) (see below).  A copy of the license is included in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

            A GNU Manual

       (b) The FSF's Back-Cover Text is:

            You have freedom to copy and modify this GNU Manual, like GNU
            software.  Copies published by the Free Software Foundation raise
            funds for GNU development.

gcc-11                                       2024-07-19                                       GCC(1)