{
    "mode": "man",
    "parameter": "gcov",
    "section": "1",
    "url": "https://www.chedong.com/phpMan.php/man/gcov/1/json",
    "generated": "2026-08-13T08:05:01Z",
    "synopsis": "gcov [-v|--version] [-h|--help]\n[-a|--all-blocks]\n[-b|--branch-probabilities]\n[-c|--branch-counts]\n[-d|--display-progress]\n[-f|--function-summaries]\n[-j|--json-format]\n[-H|--human-readable]\n[-k|--use-colors]\n[-l|--long-file-names]\n[-m|--demangled-names]\n[-n|--no-output]\n[-o|--object-directory directory|file]\n[-p|--preserve-paths]\n[-q|--use-hotness-colors]\n[-r|--relative-only]\n[-s|--source-prefix directory]\n[-t|--stdout]\n[-u|--unconditional-branches]\n[-x|--hash-filenames]\nfiles",
    "sections": {
        "NAME": {
            "content": "gcov - coverage testing tool\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "gcov [-v|--version] [-h|--help]\n[-a|--all-blocks]\n[-b|--branch-probabilities]\n[-c|--branch-counts]\n[-d|--display-progress]\n[-f|--function-summaries]\n[-j|--json-format]\n[-H|--human-readable]\n[-k|--use-colors]\n[-l|--long-file-names]\n[-m|--demangled-names]\n[-n|--no-output]\n[-o|--object-directory directory|file]\n[-p|--preserve-paths]\n[-q|--use-hotness-colors]\n[-r|--relative-only]\n[-s|--source-prefix directory]\n[-t|--stdout]\n[-u|--unconditional-branches]\n[-x|--hash-filenames]\nfiles\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "gcov is a test coverage program.  Use it in concert with GCC to analyze your programs to help\ncreate more efficient, faster running code and to discover untested parts of your program.\nYou can use gcov as a profiling tool to help discover where your optimization efforts will\nbest affect your code.  You can also use gcov along with the other profiling tool, gprof, to\nassess which parts of your code use the greatest amount of computing time.\n\nProfiling tools help you analyze your code's performance.  Using a profiler such as gcov or\ngprof, you can find out some basic performance statistics, such as:\n\n*   how often each line of code executes\n\n*   what lines of code are actually executed\n\n*   how much computing time each section of code uses\n\nOnce  you  know  these  things  about how your code works when compiled, you can look at each\nmodule to see which modules should be optimized.  gcov helps you determine where to  work  on\noptimization.\n\nSoftware  developers  also  use  coverage  testing  in  concert with testsuites, to make sure\nsoftware is actually good enough for a release.  Testsuites can verify that a  program  works\nas  expected;  a  coverage  program  tests to see how much of the program is exercised by the\ntestsuite.  Developers can then determine what kinds of test cases need to be  added  to  the\ntestsuites to create both better testing and a better final product.\n\nYou  should  compile  your  code  without  optimization  if  you plan to use gcov because the\noptimization, by combining some lines of code into one function, may not  give  you  as  much\ninformation  as  you  need  to  look  for `hot spots' where the code is using a great deal of\ncomputer time.  Likewise,  because  gcov  accumulates  statistics  by  line  (at  the  lowest\nresolution),  it  works  best with a programming style that places only one statement on each\nline.  If you use complicated macros that expand to loops or to other control structures, the\nstatistics are less helpful---they only report on the line where the macro call appears.   If\nyour  complex  macros  behave  like  functions, you can replace them with inline functions to\nsolve this problem.\n\ngcov creates a logfile called sourcefile.gcov which indicates how many times each line  of  a\nsource file sourcefile.c has executed.  You can use these logfiles along with gprof to aid in\nfine-tuning  the  performance  of  your programs.  gprof gives timing information you can use\nalong with the information you get from gcov.\n\ngcov works only on code compiled with GCC.  It is not compatible with any other profiling  or\ntest coverage mechanism.\n",
            "subsections": []
        },
        "OPTIONS": {
            "content": "",
            "subsections": [
                {
                    "name": "-a",
                    "content": "",
                    "flag": "-a"
                },
                {
                    "name": "--all-blocks",
                    "content": "Write individual execution counts for every basic block.  Normally gcov outputs execution\ncounts  only for the main blocks of a line.  With this option you can determine if blocks\nwithin a single line are not being executed.\n",
                    "long": "--all-blocks"
                },
                {
                    "name": "-b",
                    "content": "",
                    "flag": "-b"
                },
                {
                    "name": "--branch-probabilities",
                    "content": "Write branch frequencies to the output  file,  and  write  branch  summary  info  to  the\nstandard output.  This option allows you to see how often each branch in your program was\ntaken.  Unconditional branches will not be shown, unless the -u option is given.\n",
                    "long": "--branch-probabilities"
                },
                {
                    "name": "-c",
                    "content": "",
                    "flag": "-c"
                },
                {
                    "name": "--branch-counts",
                    "content": "Write  branch  frequencies as the number of branches taken, rather than the percentage of\nbranches taken.\n",
                    "long": "--branch-counts"
                },
                {
                    "name": "-d",
                    "content": "",
                    "flag": "-d"
                },
                {
                    "name": "--display-progress",
                    "content": "Display the progress on the standard output.\n",
                    "long": "--display-progress"
                },
                {
                    "name": "-f",
                    "content": "",
                    "flag": "-f"
                },
                {
                    "name": "--function-summaries",
                    "content": "Output summaries for each function in addition to the file level summary.\n",
                    "long": "--function-summaries"
                },
                {
                    "name": "-h",
                    "content": "",
                    "flag": "-h"
                },
                {
                    "name": "--help",
                    "content": "Display help about using gcov (on the  standard  output),  and  exit  without  doing  any\nfurther processing.\n",
                    "long": "--help"
                },
                {
                    "name": "-j",
                    "content": "",
                    "flag": "-j"
                },
                {
                    "name": "--json-format",
                    "content": "Output  gcov  file  in  an  easy-to-parse JSON intermediate format which does not require\nsource code for generation.  The JSON file is compressed with gzip compression  algorithm\nand the files have .gcov.json.gz extension.\n\nStructure of the JSON is following:\n\n{\n\"currentworkingdirectory\": \"foo/bar\",\n\"datafile\": \"a.out\",\n\"formatversion\": \"1\",\n\"gccversion\": \"11.1.1 20210510\"\n\"files\": [\"$file\"]\n}\n\nFields of the root element have following semantics:\n\n*   currentworkingdirectory: working directory where a compilation unit was compiled\n\n*   datafile: name of the data file (GCDA)\n\n*   formatversion: semantic version of the format\n\n*   gccversion: version of the GCC compiler\n\nEach file has the following form:\n\n{\n\"file\": \"a.c\",\n\"functions\": [\"$function\"],\n\"lines\": [\"$line\"]\n}\n\nFields of the file element have following semantics:\n\n*   filename: name of the source file\n\nEach function has the following form:\n\n{\n\"blocks\": 2,\n\"blocksexecuted\": 2,\n\"demangledname\": \"foo\",\n\"endcolumn\": 1,\n\"endline\": 4,\n\"executioncount\": 1,\n\"name\": \"foo\",\n\"startcolumn\": 5,\n\"startline\": 1\n}\n\nFields of the function element have following semantics:\n\n*   blocks: number of blocks that are in the function\n\n*   blocksexecuted: number of executed blocks of the function\n\n*   demangledname: demangled name of the function\n\n*   endcolumn: column in the source file where the function ends\n\n*   endline: line in the source file where the function ends\n\n*   executioncount: number of executions of the function\n\n*   name: name of the function\n\n*   startcolumn: column in the source file where the function begins\n\n*   startline: line in the source file where the function begins\n\nNote  that line numbers and column numbers number from 1.  In the current implementation,\nstartline and startcolumn do not include any template parameters and the leading return\ntype but that this is likely to be fixed in the future.\n\nEach line has the following form:\n\n{\n\"branches\": [\"$branch\"],\n\"count\": 2,\n\"linenumber\": 15,\n\"unexecutedblock\": false,\n\"functionname\": \"foo\",\n}\n\nBranches are present only with -b option.  Fields of  the  line  element  have  following\nsemantics:\n\n*   count: number of executions of the line\n\n*   linenumber: line number\n\n*   unexecutedblock:  flag  whether  the  line  contains  an  unexecuted  block (not all\nstatements on the line are executed)\n\n*   functionname: a name of a function this line belongs to (for a line with an  inlined\nstatements can be not set)\n\nEach branch has the following form:\n\n{\n\"count\": 11,\n\"fallthrough\": true,\n\"throw\": false\n}\n\nFields of the branch element have following semantics:\n\n*   count: number of executions of the branch\n\n*   fallthrough: true when the branch is a fall through branch\n\n*   throw: true when the branch is an exceptional branch\n",
                    "long": "--json-format"
                },
                {
                    "name": "-H",
                    "content": "",
                    "flag": "-H"
                },
                {
                    "name": "--human-readable",
                    "content": "Write counts in human readable format (like 24.6k).\n",
                    "long": "--human-readable"
                },
                {
                    "name": "-k",
                    "content": "",
                    "flag": "-k"
                },
                {
                    "name": "--use-colors",
                    "content": "Use  colors  for  lines  of  code  that  have  zero  coverage.  We use red color for non-\nexceptional lines and cyan for exceptional.  Same colors are used for basic  blocks  with\n-a option.\n",
                    "long": "--use-colors"
                },
                {
                    "name": "-l",
                    "content": "",
                    "flag": "-l"
                },
                {
                    "name": "--long-file-names",
                    "content": "Create  long  file  names for included source files.  For example, if the header file x.h\ncontains code, and was included in the file a.c, then running gcov on the file  a.c  will\nproduce  an  output file called a.c##x.h.gcov instead of x.h.gcov.  This can be useful if\nx.h  is  included  in  multiple  source  files  and  you  want  to  see  the   individual\ncontributions.  If you use the -p option, both the including and included file names will\nbe complete path names.\n",
                    "long": "--long-file-names"
                },
                {
                    "name": "-m",
                    "content": "",
                    "flag": "-m"
                },
                {
                    "name": "--demangled-names",
                    "content": "Display  demangled  function  names  in  output.  The default is to show mangled function\nnames.\n",
                    "long": "--demangled-names"
                },
                {
                    "name": "-n",
                    "content": "",
                    "flag": "-n"
                },
                {
                    "name": "--no-output",
                    "content": "Do not create the gcov output file.\n",
                    "long": "--no-output"
                },
                {
                    "name": "-o _",
                    "content": "--object-directory directory\n--object-file file\nSpecify either the directory containing the gcov data files, or  the  object  path  name.\nThe  .gcno,  and  .gcda data files are searched for using this option.  If a directory is\nspecified, the data files are in that directory and named  after  the  input  file  name,\nwithout  its extension.  If a file is specified here, the data files are named after that\nfile, without its extension.\n",
                    "flag": "-o"
                },
                {
                    "name": "-p",
                    "content": "",
                    "flag": "-p"
                },
                {
                    "name": "--preserve-paths",
                    "content": "Preserve complete path information in the names of generated .gcov files.   Without  this\noption, just the filename component is used.  With this option, all directories are used,\nwith  /  characters  translated  to  #  characters,  .  directory  components removed and\nunremoveable ..  components renamed to ^.  This is useful if sourcefiles are  in  several\ndifferent directories.\n",
                    "long": "--preserve-paths"
                },
                {
                    "name": "-q",
                    "content": "",
                    "flag": "-q"
                },
                {
                    "name": "--use-hotness-colors",
                    "content": "Emit perf-like colored output for hot lines.  Legend of the color scale is printed at the\nvery beginning of the output file.\n",
                    "long": "--use-hotness-colors"
                },
                {
                    "name": "-r",
                    "content": "",
                    "flag": "-r"
                },
                {
                    "name": "--relative-only",
                    "content": "Only  output information about source files with a relative pathname (after source prefix\nelision).  Absolute paths are usually system header files  and  coverage  of  any  inline\nfunctions therein is normally uninteresting.\n",
                    "long": "--relative-only"
                },
                {
                    "name": "-s _",
                    "content": "--source-prefix directory\nA prefix for source file names to remove when generating the output coverage files.  This\noption  is  useful  when building in a separate directory, and the pathname to the source\ndirectory is not wanted when determining the output file names.  Note  that  this  prefix\ndetection is applied before determining whether the source file is absolute.\n",
                    "flag": "-s"
                },
                {
                    "name": "-t",
                    "content": "",
                    "flag": "-t"
                },
                {
                    "name": "--stdout",
                    "content": "Output to standard output instead of output files.\n",
                    "long": "--stdout"
                },
                {
                    "name": "-u",
                    "content": "",
                    "flag": "-u"
                },
                {
                    "name": "--unconditional-branches",
                    "content": "When   branch   probabilities   are  given,  include  those  of  unconditional  branches.\nUnconditional branches are normally not interesting.\n",
                    "long": "--unconditional-branches"
                },
                {
                    "name": "-v",
                    "content": "",
                    "flag": "-v"
                },
                {
                    "name": "--version",
                    "content": "Display the gcov version number (on the standard output),  and  exit  without  doing  any\nfurther processing.\n",
                    "long": "--version"
                },
                {
                    "name": "-w",
                    "content": "",
                    "flag": "-w"
                },
                {
                    "name": "--verbose",
                    "content": "Print verbose informations related to basic blocks and arcs.\n",
                    "long": "--verbose"
                },
                {
                    "name": "-x",
                    "content": "",
                    "flag": "-x"
                },
                {
                    "name": "--hash-filenames",
                    "content": "When using --preserve-paths, gcov uses the full pathname of the source files to create an\noutput  filename.   This  can lead to long filenames that can overflow filesystem limits.\nThis option creates names  of  the  form  source-file##md5.gcov,  where  the  source-file\ncomponent  is  the  final filename part and the md5 component is calculated from the full\nmangled name that would have been used otherwise.  The option is an  alternative  to  the\n--preserve-paths on systems which have a filesystem limit.\n\ngcov should be run with the current directory the same as that when you invoked the compiler.\nOtherwise  it  will  not  be  able  to  locate  the source files.  gcov produces files called\nmangledname.gcov in the current directory.  These contain the  coverage  information  of  the\nsource  file they correspond to.  One .gcov file is produced for each source (or header) file\ncontaining code, which was compiled to produce the data files.  The mangledname part  of  the\noutput  file  name  is  usually  simply  the  source  file  name,  but  can be something more\ncomplicated if the -l or -p options are given.  Refer to those options for details.\n\nIf you invoke gcov with multiple input files, the contributions  from  each  input  file  are\nsummed.   Typically you would invoke it with the same list of files as the final link of your\nexecutable.\n\nThe .gcov files contain the : separated fields along with program source code.  The format is\n\n<executioncount>:<linenumber>:<source line text>\n\nAdditional block information may succeed each line, when requested by  command  line  option.\nThe  executioncount is - for lines containing no code.  Unexecuted lines are marked ##### or\n=====, depending on whether they are reachable by non-exceptional paths or  only  exceptional\npaths  such  as  C++ exception handlers, respectively. Given the -a option, unexecuted blocks\nare marked $$$$$ or %%%%%,  depending  on  whether  a  basic  block  is  reachable  via  non-\nexceptional  or  exceptional  paths.   Executed  basic  blocks  having  a statement with zero\nexecutioncount end with * character and are colored with magenta color with the  -k  option.\nThis functionality is not supported in Ada.\n\nNote  that  GCC  can  completely  remove  the  bodies of functions that are not needed -- for\ninstance if they are inlined everywhere.  Such functions are marked  with  -,  which  can  be\nconfusing.   Use  the  -fkeep-inline-functions  and -fkeep-static-functions options to retain\nthese functions and allow gcov to properly show their executioncount.\n\nSome lines of information at the start have linenumber of zero.  These preamble lines are of\nthe form\n\n-:0:<tag>:<value>\n\nThe ordering and number of these  preamble  lines  will  be  augmented  as  gcov  development\nprogresses  ---  do  not  rely  on  them remaining unchanged.  Use tag to locate a particular\npreamble line.\n\nThe additional block information is of the form\n\n<tag> <information>\n\nThe information is human readable, but designed to be simple enough for machine parsing too.\n\nWhen printing percentages, 0% and 100% are only printed when the values are  exactly  0%  and\n100%  respectively.   Other  values  which  would conventionally be rounded to 0% or 100% are\ninstead printed as the nearest non-boundary value.\n\nWhen using gcov, you must first compile your program with a special  GCC  option  --coverage.\nThis  tells  the compiler to generate additional information needed by gcov (basically a flow\ngraph of the program) and also includes additional code in the object  files  for  generating\nthe  extra  profiling  information  needed by gcov.  These additional files are placed in the\ndirectory where the object file is located.\n\nRunning the program will cause profile output to be generated.  For each source file compiled\nwith -fprofile-arcs, an accompanying .gcda file will be placed in the object file directory.\n\nRunning gcov with your program's source file names as arguments will now produce a listing of\nthe code along with frequency of execution for each line.  For example, if  your  program  is\ncalled tmp.cpp, this is what you see when you use the basic gcov facility:\n\n$ g++ --coverage tmp.cpp -c\n$ g++ --coverage tmp.o\n$ a.out\n$ gcov tmp.cpp -m\nFile 'tmp.cpp'\nLines executed:92.86% of 14\nCreating 'tmp.cpp.gcov'\n\nThe file tmp.cpp.gcov contains output from gcov.  Here is a sample:\n\n-:    0:Source:tmp.cpp\n-:    0:Working directory:/home/gcc/testcase\n-:    0:Graph:tmp.gcno\n-:    0:Data:tmp.gcda\n-:    0:Runs:1\n-:    0:Programs:1\n-:    1:#include <stdio.h>\n-:    2:\n-:    3:template<class T>\n-:    4:class Foo\n-:    5:{\n-:    6:  public:\n1*:    7:  Foo(): b (1000) {}\n------------------\nFoo<char>::Foo():\n#####:    7:  Foo(): b (1000) {}\n------------------\nFoo<int>::Foo():\n1:    7:  Foo(): b (1000) {}\n------------------\n2*:    8:  void inc () { b++; }\n------------------\nFoo<char>::inc():\n#####:    8:  void inc () { b++; }\n------------------\nFoo<int>::inc():\n2:    8:  void inc () { b++; }\n------------------\n-:    9:\n-:   10:  private:\n-:   11:  int b;\n-:   12:};\n-:   13:\n-:   14:template class Foo<int>;\n-:   15:template class Foo<char>;\n-:   16:\n-:   17:int\n1:   18:main (void)\n-:   19:{\n-:   20:  int i, total;\n1:   21:  Foo<int> counter;\n-:   22:\n1:   23:  counter.inc();\n1:   24:  counter.inc();\n1:   25:  total = 0;\n-:   26:\n11:   27:  for (i = 0; i < 10; i++)\n10:   28:    total += i;\n-:   29:\n1*:   30:  int v = total > 100 ? 1 : 2;\n-:   31:\n1:   32:  if (total != 45)\n#####:   33:    printf (\"Failure\\n\");\n-:   34:  else\n1:   35:    printf (\"Success\\n\");\n1:   36:  return 0;\n-:   37:}\n\nNote  that  line  7  is  shown in the report multiple times.  First occurrence presents total\nnumber of execution of  the  line  and  the  next  two  belong  to  instances  of  class  Foo\nconstructors.   As  you  can also see, line 30 contains some unexecuted basic blocks and thus\nexecution count has asterisk symbol.\n\nWhen you use the -a option, you will get individual block counts, and the output  looks  like\nthis:\n\n-:    0:Source:tmp.cpp\n-:    0:Working directory:/home/gcc/testcase\n-:    0:Graph:tmp.gcno\n-:    0:Data:tmp.gcda\n-:    0:Runs:1\n-:    0:Programs:1\n-:    1:#include <stdio.h>\n-:    2:\n-:    3:template<class T>\n-:    4:class Foo\n-:    5:{\n-:    6:  public:\n1*:    7:  Foo(): b (1000) {}\n------------------\nFoo<char>::Foo():\n#####:    7:  Foo(): b (1000) {}\n------------------\nFoo<int>::Foo():\n1:    7:  Foo(): b (1000) {}\n------------------\n2*:    8:  void inc () { b++; }\n------------------\nFoo<char>::inc():\n#####:    8:  void inc () { b++; }\n------------------\nFoo<int>::inc():\n2:    8:  void inc () { b++; }\n------------------\n-:    9:\n-:   10:  private:\n-:   11:  int b;\n-:   12:};\n-:   13:\n-:   14:template class Foo<int>;\n-:   15:template class Foo<char>;\n-:   16:\n-:   17:int\n1:   18:main (void)\n-:   19:{\n-:   20:  int i, total;\n1:   21:  Foo<int> counter;\n1:   21-block  0\n-:   22:\n1:   23:  counter.inc();\n1:   23-block  0\n1:   24:  counter.inc();\n1:   24-block  0\n1:   25:  total = 0;\n-:   26:\n11:   27:  for (i = 0; i < 10; i++)\n1:   27-block  0\n11:   27-block  1\n10:   28:    total += i;\n10:   28-block  0\n-:   29:\n1*:   30:  int v = total > 100 ? 1 : 2;\n1:   30-block  0\n%%%%%:   30-block  1\n1:   30-block  2\n-:   31:\n1:   32:  if (total != 45)\n1:   32-block  0\n#####:   33:    printf (\"Failure\\n\");\n%%%%%:   33-block  0\n-:   34:  else\n1:   35:    printf (\"Success\\n\");\n1:   35-block  0\n1:   36:  return 0;\n1:   36-block  0\n-:   37:}\n\nIn  this  mode,  each basic block is only shown on one line -- the last line of the block.  A\nmulti-line block will only contribute to the execution count of that  last  line,  and  other\nlines  will  not  be  shown  to contain code, unless previous blocks end on those lines.  The\ntotal execution count of a line is shown and subsequent lines show the execution  counts  for\nindividual blocks that end on that line.  After each block, the branch and call counts of the\nblock will be shown, if the -b option is given.\n\nBecause  of  the  way  GCC  instruments calls, a call count can be shown after a line with no\nindividual blocks.  As you can see, line 33 contains a basic block that was not executed.\n\nWhen you use the -b option, your output looks like this:\n\n-:    0:Source:tmp.cpp\n-:    0:Working directory:/home/gcc/testcase\n-:    0:Graph:tmp.gcno\n-:    0:Data:tmp.gcda\n-:    0:Runs:1\n-:    0:Programs:1\n-:    1:#include <stdio.h>\n-:    2:\n-:    3:template<class T>\n-:    4:class Foo\n-:    5:{\n-:    6:  public:\n1*:    7:  Foo(): b (1000) {}\n------------------\nFoo<char>::Foo():\nfunction Foo<char>::Foo() called 0 returned 0% blocks executed 0%\n#####:    7:  Foo(): b (1000) {}\n------------------\nFoo<int>::Foo():\nfunction Foo<int>::Foo() called 1 returned 100% blocks executed 100%\n1:    7:  Foo(): b (1000) {}\n------------------\n2*:    8:  void inc () { b++; }\n------------------\nFoo<char>::inc():\nfunction Foo<char>::inc() called 0 returned 0% blocks executed 0%\n#####:    8:  void inc () { b++; }\n------------------\nFoo<int>::inc():\nfunction Foo<int>::inc() called 2 returned 100% blocks executed 100%\n2:    8:  void inc () { b++; }\n------------------\n-:    9:\n-:   10:  private:\n-:   11:  int b;\n-:   12:};\n-:   13:\n-:   14:template class Foo<int>;\n-:   15:template class Foo<char>;\n-:   16:\n-:   17:int\nfunction main called 1 returned 100% blocks executed 81%\n1:   18:main (void)\n-:   19:{\n-:   20:  int i, total;\n1:   21:  Foo<int> counter;\ncall    0 returned 100%\nbranch  1 taken 100% (fallthrough)\nbranch  2 taken 0% (throw)\n-:   22:\n1:   23:  counter.inc();\ncall    0 returned 100%\nbranch  1 taken 100% (fallthrough)\nbranch  2 taken 0% (throw)\n1:   24:  counter.inc();\ncall    0 returned 100%\nbranch  1 taken 100% (fallthrough)\nbranch  2 taken 0% (throw)\n1:   25:  total = 0;\n-:   26:\n11:   27:  for (i = 0; i < 10; i++)\nbranch  0 taken 91% (fallthrough)\nbranch  1 taken 9%\n10:   28:    total += i;\n-:   29:\n1*:   30:  int v = total > 100 ? 1 : 2;\nbranch  0 taken 0% (fallthrough)\nbranch  1 taken 100%\n-:   31:\n1:   32:  if (total != 45)\nbranch  0 taken 0% (fallthrough)\nbranch  1 taken 100%\n#####:   33:    printf (\"Failure\\n\");\ncall    0 never executed\nbranch  1 never executed\nbranch  2 never executed\n-:   34:  else\n1:   35:    printf (\"Success\\n\");\ncall    0 returned 100%\nbranch  1 taken 100% (fallthrough)\nbranch  2 taken 0% (throw)\n1:   36:  return 0;\n-:   37:}\n\nFor each function, a line is printed showing how many times the function is called, how  many\ntimes it returns and what percentage of the function's blocks were executed.\n\nFor each basic block, a line is printed after the last line of the basic block describing the\nbranch  or  call  that ends the basic block.  There can be multiple branches and calls listed\nfor a single source line if there are multiple basic blocks that end on that line.   In  this\ncase,  the  branches  and calls are each given a number.  There is no simple way to map these\nbranches and calls back to source constructs.  In general, though, the lowest numbered branch\nor call will correspond to the leftmost construct on the source line.\n\nFor a branch, if it was executed at least once, then a percentage indicating  the  number  of\ntimes  the  branch  was  taken divided by the number of times the branch was executed will be\nprinted.  Otherwise, the message \"never executed\" is printed.\n\nFor a call, if it was executed at least once, then a  percentage  indicating  the  number  of\ntimes the call returned divided by the number of times the call was executed will be printed.\nThis  will  usually be 100%, but may be less for functions that call \"exit\" or \"longjmp\", and\nthus may not return every time they are called.\n\nThe execution counts are cumulative.  If the example  program  were  executed  again  without\nremoving  the  .gcda  file,  the  count  for  the number of times each line in the source was\nexecuted would be added to the results of the previous run(s).  This is potentially useful in\nseveral ways.  For example, it could be used to accumulate data over a number of program runs\nas part of a test verification suite, or to provide more accurate long-term information  over\na large number of program runs.\n\nThe  data  in the .gcda files is saved immediately before the program exits.  For each source\nfile compiled with -fprofile-arcs, the profiling code first attempts to read in  an  existing\n.gcda file; if the file doesn't match the executable (differing number of basic block counts)\nit  will  ignore  the  contents  of  the  file.  It then adds in the new execution counts and\nfinally writes the data to the file.\n",
                    "long": "--hash-filenames"
                },
                {
                    "name": "Using gcov with GCC Optimization",
                    "content": "If you plan to use gcov to help optimize your code, you must first compile your program  with\na  special GCC option --coverage.  Aside from that, you can use any other GCC options; but if\nyou want to prove that every single line in your program was executed, you should not compile\nwith optimization at the same time.  On some machines the optimizer can eliminate some simple\ncode lines by combining them with other lines.  For example, code like this:\n\nif (a != b)\nc = 1;\nelse\nc = 0;\n\ncan be compiled into one instruction on some machines.  In this case, there  is  no  way  for\ngcov  to  calculate separate execution counts for each line because there isn't separate code\nfor each line.  Hence the gcov output looks like  this  if  you  compiled  the  program  with\noptimization:\n\n100:   12:if (a != b)\n100:   13:  c = 1;\n100:   14:else\n100:   15:  c = 0;\n\nThe  output  shows that this block of code, combined by optimization, executed 100 times.  In\none sense this result is correct, because there was only  one  instruction  representing  all\nfour  of  these lines.  However, the output does not indicate how many times the result was 0\nand how many times the result was 1.\n\nInlineable functions can create unexpected line counts.  Line counts are shown for the source\ncode of the inlineable function, but what is shown depends on where the function is  inlined,\nor if it is not inlined at all.\n\nIf  the  function is not inlined, the compiler must emit an out of line copy of the function,\nin any object file that needs it.  If fileA.o and fileB.o both contain out of line bodies  of\na  particular  inlineable  function,  they  will  also  both contain coverage counts for that\nfunction.  When fileA.o and fileB.o are linked together, the linker will,  on  many  systems,\nselect  one  of those out of line bodies for all calls to that function, and remove or ignore\nthe other.  Unfortunately, it will not remove the coverage counters for the  unused  function\nbody.  Hence when instrumented, all but one use of that function will show zero counts.\n\nIf  the function is inlined in several places, the block structure in each location might not\nbe the same.  For instance, a condition might now be  calculable  at  compile  time  in  some\ninstances.  Because the coverage of all the uses of the inline function will be shown for the\nsame source lines, the line counts themselves might seem inconsistent.\n\nLong-running applications can use the \"gcovreset\" and \"gcovdump\" facilities to restrict\nprofile collection to the program region of interest. Calling \"gcovreset(void)\" will clear\nall run-time profile counters to zero, and calling \"gcovdump(void)\" will cause the profile\ninformation  collected  at  that  point  to  be  dumped  to .gcda output files.  Instrumented\napplications use a static destructor with priority 99 to invoke the  \"gcovdump\"  function.\nThus \"gcovdump\" is executed after all user defined static destructors, as well as handlers\nregistered with \"atexit\".\n\nIf    an   executable   loads   a   dynamic   shared   object   via   dlopen   functionality,"
                },
                {
                    "name": "-Wl,--dynamic-list-data",
                    "content": "Profiling run-time library reports various errors related to profile manipulation and profile\nsaving.   Errors  are  printed  into  standard  error  output  or  GCOVERRORFILE  file,  if\nenvironment  variable  is used.  In order to terminate immediately after an errors occurs set\nGCOVEXITATERROR environment variable.  That can help users to find profile clashing  which\nleads to a misleading profile.\n"
                }
            ]
        },
        "SEE ALSO": {
            "content": "gpl(7), gfdl(7), fsf-funding(7), gcc(1) and the Info entry for gcc.\n",
            "subsections": []
        },
        "COPYRIGHT": {
            "content": "Copyright (c) 1996-2023 Free Software Foundation, Inc.\n\nPermission  is granted to copy, distribute and/or modify this document under the terms of the\nGNU Free Documentation License, Version 1.3 or  any  later  version  published  by  the  Free\nSoftware  Foundation;  with  the  Invariant  Sections  being \"GNU General Public License\" and\n\"Funding Free Software\", the Front-Cover texts being (a) (see below), and with the Back-Cover\nTexts being (b) (see below).  A copy of the license is included in the gfdl(7) man page.\n\n(a) The FSF's Front-Cover Text is:\n\nA GNU Manual\n\n(b) The FSF's Back-Cover Text is:\n\nYou have freedom to copy and modify this GNU Manual, like GNU\nsoftware.  Copies published by the Free Software Foundation raise\nfunds for GNU development.\n\ngcc-13.3.0                                   2024-05-21                                      GCOV(1)",
            "subsections": []
        }
    },
    "summary": "gcov - coverage testing tool",
    "flags": [
        {
            "flag": "-a",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--all-blocks",
            "arg": null,
            "description": "Write individual execution counts for every basic block. Normally gcov outputs execution counts only for the main blocks of a line. With this option you can determine if blocks within a single line are not being executed."
        },
        {
            "flag": "-b",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--branch-probabilities",
            "arg": null,
            "description": "Write branch frequencies to the output file, and write branch summary info to the standard output. This option allows you to see how often each branch in your program was taken. Unconditional branches will not be shown, unless the -u option is given."
        },
        {
            "flag": "-c",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--branch-counts",
            "arg": null,
            "description": "Write branch frequencies as the number of branches taken, rather than the percentage of branches taken."
        },
        {
            "flag": "-d",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--display-progress",
            "arg": null,
            "description": "Display the progress on the standard output."
        },
        {
            "flag": "-f",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--function-summaries",
            "arg": null,
            "description": "Output summaries for each function in addition to the file level summary."
        },
        {
            "flag": "-h",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--help",
            "arg": null,
            "description": "Display help about using gcov (on the standard output), and exit without doing any further processing."
        },
        {
            "flag": "-j",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--json-format",
            "arg": null,
            "description": "Output gcov file in an easy-to-parse JSON intermediate format which does not require source code for generation. The JSON file is compressed with gzip compression algorithm and the files have .gcov.json.gz extension. Structure of the JSON is following: { \"currentworkingdirectory\": \"foo/bar\", \"datafile\": \"a.out\", \"formatversion\": \"1\", \"gccversion\": \"11.1.1 20210510\" \"files\": [\"$file\"] } Fields of the root element have following semantics: * currentworkingdirectory: working directory where a compilation unit was compiled * datafile: name of the data file (GCDA) * formatversion: semantic version of the format * gccversion: version of the GCC compiler Each file has the following form: { \"file\": \"a.c\", \"functions\": [\"$function\"], \"lines\": [\"$line\"] } Fields of the file element have following semantics: * filename: name of the source file Each function has the following form: { \"blocks\": 2, \"blocksexecuted\": 2, \"demangledname\": \"foo\", \"endcolumn\": 1, \"endline\": 4, \"executioncount\": 1, \"name\": \"foo\", \"startcolumn\": 5, \"startline\": 1 } Fields of the function element have following semantics: * blocks: number of blocks that are in the function * blocksexecuted: number of executed blocks of the function * demangledname: demangled name of the function * endcolumn: column in the source file where the function ends * endline: line in the source file where the function ends * executioncount: number of executions of the function * name: name of the function * startcolumn: column in the source file where the function begins * startline: line in the source file where the function begins Note that line numbers and column numbers number from 1. In the current implementation, startline and startcolumn do not include any template parameters and the leading return type but that this is likely to be fixed in the future. Each line has the following form: { \"branches\": [\"$branch\"], \"count\": 2, \"linenumber\": 15, \"unexecutedblock\": false, \"functionname\": \"foo\", } Branches are present only with -b option. Fields of the line element have following semantics: * count: number of executions of the line * linenumber: line number * unexecutedblock: flag whether the line contains an unexecuted block (not all statements on the line are executed) * functionname: a name of a function this line belongs to (for a line with an inlined statements can be not set) Each branch has the following form: { \"count\": 11, \"fallthrough\": true, \"throw\": false } Fields of the branch element have following semantics: * count: number of executions of the branch * fallthrough: true when the branch is a fall through branch * throw: true when the branch is an exceptional branch"
        },
        {
            "flag": "-H",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--human-readable",
            "arg": null,
            "description": "Write counts in human readable format (like 24.6k)."
        },
        {
            "flag": "-k",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--use-colors",
            "arg": null,
            "description": "Use colors for lines of code that have zero coverage. We use red color for non- exceptional lines and cyan for exceptional. Same colors are used for basic blocks with -a option."
        },
        {
            "flag": "-l",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--long-file-names",
            "arg": null,
            "description": "Create long file names for included source files. For example, if the header file x.h contains code, and was included in the file a.c, then running gcov on the file a.c will produce an output file called a.c##x.h.gcov instead of x.h.gcov. This can be useful if x.h is included in multiple source files and you want to see the individual contributions. If you use the -p option, both the including and included file names will be complete path names."
        },
        {
            "flag": "-m",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--demangled-names",
            "arg": null,
            "description": "Display demangled function names in output. The default is to show mangled function names."
        },
        {
            "flag": "-n",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--no-output",
            "arg": null,
            "description": "Do not create the gcov output file."
        },
        {
            "flag": "-o",
            "long": null,
            "arg": null,
            "description": "--object-directory directory --object-file file Specify either the directory containing the gcov data files, or the object path name. The .gcno, and .gcda data files are searched for using this option. If a directory is specified, the data files are in that directory and named after the input file name, without its extension. If a file is specified here, the data files are named after that file, without its extension."
        },
        {
            "flag": "-p",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--preserve-paths",
            "arg": null,
            "description": "Preserve complete path information in the names of generated .gcov files. Without this option, just the filename component is used. With this option, all directories are used, with / characters translated to # characters, . directory components removed and unremoveable .. components renamed to ^. This is useful if sourcefiles are in several different directories."
        },
        {
            "flag": "-q",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--use-hotness-colors",
            "arg": null,
            "description": "Emit perf-like colored output for hot lines. Legend of the color scale is printed at the very beginning of the output file."
        },
        {
            "flag": "-r",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--relative-only",
            "arg": null,
            "description": "Only output information about source files with a relative pathname (after source prefix elision). Absolute paths are usually system header files and coverage of any inline functions therein is normally uninteresting."
        },
        {
            "flag": "-s",
            "long": null,
            "arg": null,
            "description": "--source-prefix directory A prefix for source file names to remove when generating the output coverage files. This option is useful when building in a separate directory, and the pathname to the source directory is not wanted when determining the output file names. Note that this prefix detection is applied before determining whether the source file is absolute."
        },
        {
            "flag": "-t",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--stdout",
            "arg": null,
            "description": "Output to standard output instead of output files."
        },
        {
            "flag": "-u",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--unconditional-branches",
            "arg": null,
            "description": "When branch probabilities are given, include those of unconditional branches. Unconditional branches are normally not interesting."
        },
        {
            "flag": "-v",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--version",
            "arg": null,
            "description": "Display the gcov version number (on the standard output), and exit without doing any further processing."
        },
        {
            "flag": "-w",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--verbose",
            "arg": null,
            "description": "Print verbose informations related to basic blocks and arcs."
        },
        {
            "flag": "-x",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--hash-filenames",
            "arg": null,
            "description": "When using --preserve-paths, gcov uses the full pathname of the source files to create an output filename. This can lead to long filenames that can overflow filesystem limits. This option creates names of the form source-file##md5.gcov, where the source-file component is the final filename part and the md5 component is calculated from the full mangled name that would have been used otherwise. The option is an alternative to the --preserve-paths on systems which have a filesystem limit. gcov should be run with the current directory the same as that when you invoked the compiler. Otherwise it will not be able to locate the source files. gcov produces files called mangledname.gcov in the current directory. These contain the coverage information of the source file they correspond to. One .gcov file is produced for each source (or header) file containing code, which was compiled to produce the data files. The mangledname part of the output file name is usually simply the source file name, but can be something more complicated if the -l or -p options are given. Refer to those options for details. If you invoke gcov with multiple input files, the contributions from each input file are summed. Typically you would invoke it with the same list of files as the final link of your executable. The .gcov files contain the : separated fields along with program source code. The format is <executioncount>:<linenumber>:<source line text> Additional block information may succeed each line, when requested by command line option. The executioncount is - for lines containing no code. Unexecuted lines are marked ##### or =====, depending on whether they are reachable by non-exceptional paths or only exceptional paths such as C++ exception handlers, respectively. Given the -a option, unexecuted blocks are marked $$$$$ or %%%%%, depending on whether a basic block is reachable via non- exceptional or exceptional paths. Executed basic blocks having a statement with zero executioncount end with * character and are colored with magenta color with the -k option. This functionality is not supported in Ada. Note that GCC can completely remove the bodies of functions that are not needed -- for instance if they are inlined everywhere. Such functions are marked with -, which can be confusing. Use the -fkeep-inline-functions and -fkeep-static-functions options to retain these functions and allow gcov to properly show their executioncount. Some lines of information at the start have linenumber of zero. These preamble lines are of the form -:0:<tag>:<value> The ordering and number of these preamble lines will be augmented as gcov development progresses --- do not rely on them remaining unchanged. Use tag to locate a particular preamble line. The additional block information is of the form <tag> <information> The information is human readable, but designed to be simple enough for machine parsing too. When printing percentages, 0% and 100% are only printed when the values are exactly 0% and 100% respectively. Other values which would conventionally be rounded to 0% or 100% are instead printed as the nearest non-boundary value. When using gcov, you must first compile your program with a special GCC option --coverage. This tells the compiler to generate additional information needed by gcov (basically a flow graph of the program) and also includes additional code in the object files for generating the extra profiling information needed by gcov. These additional files are placed in the directory where the object file is located. Running the program will cause profile output to be generated. For each source file compiled with -fprofile-arcs, an accompanying .gcda file will be placed in the object file directory. Running gcov with your program's source file names as arguments will now produce a listing of the code along with frequency of execution for each line. For example, if your program is called tmp.cpp, this is what you see when you use the basic gcov facility: $ g++ --coverage tmp.cpp -c $ g++ --coverage tmp.o $ a.out $ gcov tmp.cpp -m File 'tmp.cpp' Lines executed:92.86% of 14 Creating 'tmp.cpp.gcov' The file tmp.cpp.gcov contains output from gcov. Here is a sample: -: 0:Source:tmp.cpp -: 0:Working directory:/home/gcc/testcase -: 0:Graph:tmp.gcno -: 0:Data:tmp.gcda -: 0:Runs:1 -: 0:Programs:1 -: 1:#include <stdio.h> -: 2: -: 3:template<class T> -: 4:class Foo -: 5:{ -: 6: public: 1*: 7: Foo(): b (1000) {} ------------------ Foo<char>::Foo(): #####: 7: Foo(): b (1000) {} ------------------ Foo<int>::Foo(): 1: 7: Foo(): b (1000) {} ------------------ 2*: 8: void inc () { b++; } ------------------ Foo<char>::inc(): #####: 8: void inc () { b++; } ------------------ Foo<int>::inc(): 2: 8: void inc () { b++; } ------------------ -: 9: -: 10: private: -: 11: int b; -: 12:}; -: 13: -: 14:template class Foo<int>; -: 15:template class Foo<char>; -: 16: -: 17:int 1: 18:main (void) -: 19:{ -: 20: int i, total; 1: 21: Foo<int> counter; -: 22: 1: 23: counter.inc(); 1: 24: counter.inc(); 1: 25: total = 0; -: 26: 11: 27: for (i = 0; i < 10; i++) 10: 28: total += i; -: 29: 1*: 30: int v = total > 100 ? 1 : 2; -: 31: 1: 32: if (total != 45) #####: 33: printf (\"Failure\\n\"); -: 34: else 1: 35: printf (\"Success\\n\"); 1: 36: return 0; -: 37:} Note that line 7 is shown in the report multiple times. First occurrence presents total number of execution of the line and the next two belong to instances of class Foo constructors. As you can also see, line 30 contains some unexecuted basic blocks and thus execution count has asterisk symbol. When you use the -a option, you will get individual block counts, and the output looks like this: -: 0:Source:tmp.cpp -: 0:Working directory:/home/gcc/testcase -: 0:Graph:tmp.gcno -: 0:Data:tmp.gcda -: 0:Runs:1 -: 0:Programs:1 -: 1:#include <stdio.h> -: 2: -: 3:template<class T> -: 4:class Foo -: 5:{ -: 6: public: 1*: 7: Foo(): b (1000) {} ------------------ Foo<char>::Foo(): #####: 7: Foo(): b (1000) {} ------------------ Foo<int>::Foo(): 1: 7: Foo(): b (1000) {} ------------------ 2*: 8: void inc () { b++; } ------------------ Foo<char>::inc(): #####: 8: void inc () { b++; } ------------------ Foo<int>::inc(): 2: 8: void inc () { b++; } ------------------ -: 9: -: 10: private: -: 11: int b; -: 12:}; -: 13: -: 14:template class Foo<int>; -: 15:template class Foo<char>; -: 16: -: 17:int 1: 18:main (void) -: 19:{ -: 20: int i, total; 1: 21: Foo<int> counter; 1: 21-block 0 -: 22: 1: 23: counter.inc(); 1: 23-block 0 1: 24: counter.inc(); 1: 24-block 0 1: 25: total = 0; -: 26: 11: 27: for (i = 0; i < 10; i++) 1: 27-block 0 11: 27-block 1 10: 28: total += i; 10: 28-block 0 -: 29: 1*: 30: int v = total > 100 ? 1 : 2; 1: 30-block 0 %%%%%: 30-block 1 1: 30-block 2 -: 31: 1: 32: if (total != 45) 1: 32-block 0 #####: 33: printf (\"Failure\\n\"); %%%%%: 33-block 0 -: 34: else 1: 35: printf (\"Success\\n\"); 1: 35-block 0 1: 36: return 0; 1: 36-block 0 -: 37:} In this mode, each basic block is only shown on one line -- the last line of the block. A multi-line block will only contribute to the execution count of that last line, and other lines will not be shown to contain code, unless previous blocks end on those lines. The total execution count of a line is shown and subsequent lines show the execution counts for individual blocks that end on that line. After each block, the branch and call counts of the block will be shown, if the -b option is given. Because of the way GCC instruments calls, a call count can be shown after a line with no individual blocks. As you can see, line 33 contains a basic block that was not executed. When you use the -b option, your output looks like this: -: 0:Source:tmp.cpp -: 0:Working directory:/home/gcc/testcase -: 0:Graph:tmp.gcno -: 0:Data:tmp.gcda -: 0:Runs:1 -: 0:Programs:1 -: 1:#include <stdio.h> -: 2: -: 3:template<class T> -: 4:class Foo -: 5:{ -: 6: public: 1*: 7: Foo(): b (1000) {} ------------------ Foo<char>::Foo(): function Foo<char>::Foo() called 0 returned 0% blocks executed 0% #####: 7: Foo(): b (1000) {} ------------------ Foo<int>::Foo(): function Foo<int>::Foo() called 1 returned 100% blocks executed 100% 1: 7: Foo(): b (1000) {} ------------------ 2*: 8: void inc () { b++; } ------------------ Foo<char>::inc(): function Foo<char>::inc() called 0 returned 0% blocks executed 0% #####: 8: void inc () { b++; } ------------------ Foo<int>::inc(): function Foo<int>::inc() called 2 returned 100% blocks executed 100% 2: 8: void inc () { b++; } ------------------ -: 9: -: 10: private: -: 11: int b; -: 12:}; -: 13: -: 14:template class Foo<int>; -: 15:template class Foo<char>; -: 16: -: 17:int function main called 1 returned 100% blocks executed 81% 1: 18:main (void) -: 19:{ -: 20: int i, total; 1: 21: Foo<int> counter; call 0 returned 100% branch 1 taken 100% (fallthrough) branch 2 taken 0% (throw) -: 22: 1: 23: counter.inc(); call 0 returned 100% branch 1 taken 100% (fallthrough) branch 2 taken 0% (throw) 1: 24: counter.inc(); call 0 returned 100% branch 1 taken 100% (fallthrough) branch 2 taken 0% (throw) 1: 25: total = 0; -: 26: 11: 27: for (i = 0; i < 10; i++) branch 0 taken 91% (fallthrough) branch 1 taken 9% 10: 28: total += i; -: 29: 1*: 30: int v = total > 100 ? 1 : 2; branch 0 taken 0% (fallthrough) branch 1 taken 100% -: 31: 1: 32: if (total != 45) branch 0 taken 0% (fallthrough) branch 1 taken 100% #####: 33: printf (\"Failure\\n\"); call 0 never executed branch 1 never executed branch 2 never executed -: 34: else 1: 35: printf (\"Success\\n\"); call 0 returned 100% branch 1 taken 100% (fallthrough) branch 2 taken 0% (throw) 1: 36: return 0; -: 37:} For each function, a line is printed showing how many times the function is called, how many times it returns and what percentage of the function's blocks were executed. For each basic block, a line is printed after the last line of the basic block describing the branch or call that ends the basic block. There can be multiple branches and calls listed for a single source line if there are multiple basic blocks that end on that line. In this case, the branches and calls are each given a number. There is no simple way to map these branches and calls back to source constructs. In general, though, the lowest numbered branch or call will correspond to the leftmost construct on the source line. For a branch, if it was executed at least once, then a percentage indicating the number of times the branch was taken divided by the number of times the branch was executed will be printed. Otherwise, the message \"never executed\" is printed. For a call, if it was executed at least once, then a percentage indicating the number of times the call returned divided by the number of times the call was executed will be printed. This will usually be 100%, but may be less for functions that call \"exit\" or \"longjmp\", and thus may not return every time they are called. The execution counts are cumulative. If the example program were executed again without removing the .gcda file, the count for the number of times each line in the source was executed would be added to the results of the previous run(s). This is potentially useful in several ways. For example, it could be used to accumulate data over a number of program runs as part of a test verification suite, or to provide more accurate long-term information over a large number of program runs. The data in the .gcda files is saved immediately before the program exits. For each source file compiled with -fprofile-arcs, the profiling code first attempts to read in an existing .gcda file; if the file doesn't match the executable (differing number of basic block counts) it will ignore the contents of the file. It then adds in the new execution counts and finally writes the data to the file."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Profiling run-time library reports various errors related to profile manipulation and profile saving. Errors are printed into standard error output or GCOVERRORFILE file, if environment variable is used. In order to terminate immediately after an errors occurs set GCOVEXITATERROR environment variable. That can help users to find profile clashing which leads to a misleading profile."
        }
    ],
    "examples": [],
    "see_also": [
        {
            "name": "gpl",
            "section": "7",
            "url": "https://www.chedong.com/phpMan.php/man/gpl/7/json"
        },
        {
            "name": "gfdl",
            "section": "7",
            "url": "https://www.chedong.com/phpMan.php/man/gfdl/7/json"
        },
        {
            "name": "fsf-funding",
            "section": "7",
            "url": "https://www.chedong.com/phpMan.php/man/fsf-funding/7/json"
        },
        {
            "name": "gcc",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/gcc/1/json"
        }
    ],
    "tldr": {
        "source": "official",
        "description": "Code coverage analysis and profiling tool that discovers untested parts of a program.",
        "examples": [
            {
                "description": "Generate a coverage report named `file.cpp.gcov`",
                "command": "gcov {{path/to/file.cpp}}"
            },
            {
                "description": "Write individual execution counts for every basic block",
                "command": "gcov {{-a|--all-blocks}} {{path/to/file.cpp}}"
            },
            {
                "description": "Write branch frequencies to the output file and print summary information to `stdout` as a percentage",
                "command": "gcov {{-b|--branch-probabilities}} {{path/to/file.cpp}}"
            },
            {
                "description": "Write branch frequencies as the number of branches taken, rather than the percentage",
                "command": "gcov {{-c|--branch-counts}} {{path/to/file.cpp}}"
            },
            {
                "description": "Do not create a `gcov` output file",
                "command": "gcov {{-n|--no-output}} {{path/to/file.cpp}}"
            },
            {
                "description": "Write file level as well as function level summaries",
                "command": "gcov {{-f|--function-summaries}} {{path/to/file.cpp}}"
            }
        ]
    }
}