ExtUtils::Liblist - phpMan

NAME
    ExtUtils::Liblist - determine libraries to use and how to use them

SYNOPSIS
      require ExtUtils::Liblist;

      $MM->ext($potential_libs, $verbose, $need_names);

      # Usually you can get away with:
      ExtUtils::Liblist->ext($potential_libs, $verbose, $need_names)

DESCRIPTION
    This utility takes a list of libraries in the form "-llib1 -llib2
    -llib3" and returns lines suitable for inclusion in an extension
    Makefile. Extra library paths may be included with the form
    "-L/another/path" this will affect the searches for all subsequent
    libraries.

    It returns an array of four or five scalar values: EXTRALIBS,
    BSLOADLIBS, LDLOADLIBS, LD_RUN_PATH, and, optionally, a reference to the
    array of the filenames of actual libraries. Some of these don't mean
    anything unless on Unix. See the details about those platform specifics
    below. The list of the filenames is returned only if $need_names
    argument is true.

    Dependent libraries can be linked in one of three ways:

    * For static extensions

      by the ld command when the perl binary is linked with the extension
      library. See EXTRALIBS below.

    * For dynamic extensions at build/link time

      by the ld command when the shared object is built/linked. See
      LDLOADLIBS below.

    * For dynamic extensions at load time

      by the DynaLoader when the shared object is loaded. See BSLOADLIBS
      below.

  EXTRALIBS
    List of libraries that need to be linked with when linking a perl binary
    which includes this extension. Only those libraries that actually exist
    are included. These are written to a file and used when linking perl.

  LDLOADLIBS and LD_RUN_PATH
    List of those libraries which can or must be linked into the shared
    library when created using ld. These may be static or dynamic libraries.
    LD_RUN_PATH is a colon separated list of the directories in LDLOADLIBS.
    It is passed as an environment variable to the process that links the
    shared library.

  BSLOADLIBS
    List of those libraries that are needed but can be linked in dynamically
    at run time on this platform. SunOS/Solaris does not need this because
    ld records the information (from LDLOADLIBS) into the object file. This
    list is used to create a .bs (bootstrap) file.

PORTABILITY
    This module deals with a lot of system dependencies and has quite a few
    architecture specific "if"s in the code.

  VMS implementation
    The version of ext() which is executed under VMS differs from the
    Unix-OS/2 version in several respects:

    * Input library and path specifications are accepted with or without the
      "-l" and "-L" prefixes used by Unix linkers. If neither prefix is
      present, a token is considered a directory to search if it is in fact
      a directory, and a library to search for otherwise. Authors who wish
      their extensions to be portable to Unix or OS/2 should use the Unix
      prefixes, since the Unix-OS/2 version of ext() requires them.

    * Wherever possible, shareable images are preferred to object libraries,
      and object libraries to plain object files. In accordance with VMS
      naming conventions, ext() looks for files named *lib*shr and *lib*rtl;
      it also looks for *lib*lib and lib*lib* to accommodate Unix
      conventions used in some ported software.

    * For each library that is found, an appropriate directive for a linker
      options file is generated. The return values are space-separated
      strings of these directives, rather than elements used on the linker
      command line.

    * LDLOADLIBS contains both the libraries found based on $potential_libs
      and the CRTLs, if any, specified in Config.pm. EXTRALIBS contains just
      those libraries found based on $potential_libs. BSLOADLIBS and
      LD_RUN_PATH are always empty.

    In addition, an attempt is made to recognize several common Unix library
    names, and filter them out or convert them to their VMS equivalents, as
    appropriate.

    In general, the VMS version of ext() should properly handle input from
    extensions originally designed for a Unix or VMS environment. If you
    encounter problems, or discover cases where the search could be
    improved, please let us know.

  Win32 implementation
    The version of ext() which is executed under Win32 differs from the
    Unix-OS/2 version in several respects:

    * If $potential_libs is empty, the return value will be empty.
      Otherwise, the libraries specified by $Config{perllibs} (see
      Config.pm) will be appended to the list of $potential_libs. The
      libraries will be searched for in the directories specified in
      $potential_libs, $Config{libpth}, and in
      "$Config{installarchlib}/CORE". For each library that is found, a
      space-separated list of fully qualified library pathnames is
      generated.

    * Input library and path specifications are accepted with or without the
      "-l" and "-L" prefixes used by Unix linkers.

      An entry of the form "-La:\foo" specifies the "a:\foo" directory to
      look for the libraries that follow.

      An entry of the form "-lfoo" specifies the library "foo", which may be
      spelled differently depending on what kind of compiler you are using.
      If you are using GCC, it gets translated to "libfoo.a", but for other
      win32 compilers, it becomes "foo.lib". If no files are found by those
      translated names, one more attempt is made to find them using either
      "foo.a" or "libfoo.lib", depending on whether GCC or some other win32
      compiler is being used, respectively.

      If neither the "-L" or "-l" prefix is present in an entry, the entry
      is considered a directory to search if it is in fact a directory, and
      a library to search for otherwise. The $Config{lib_ext} suffix will be
      appended to any entries that are not directories and don't already
      have the suffix.

      Note that the "-L" and "-l" prefixes are not required, but authors who
      wish their extensions to be portable to Unix or OS/2 should use the
      prefixes, since the Unix-OS/2 version of ext() requires them.

    * Entries cannot be plain object files, as many Win32 compilers will not
      handle object files in the place of libraries.

    * Entries in $potential_libs beginning with a colon and followed by
      alphanumeric characters are treated as flags. Unknown flags will be
      ignored.

      An entry that matches "/:nodefault/i" disables the appending of
      default libraries found in $Config{perllibs} (this should be only
      needed very rarely).

      An entry that matches "/:nosearch/i" disables all searching for the
      libraries specified after it. Translation of "-Lfoo" and "-lfoo" still
      happens as appropriate (depending on compiler being used, as reflected
      by $Config{cc}), but the entries are not verified to be valid files or
      directories.

      An entry that matches "/:search/i" reenables searching for the
      libraries specified after it. You can put it at the end to enable
      searching for default libraries specified by $Config{perllibs}.

    * The libraries specified may be a mixture of static libraries and
      import libraries (to link with DLLs). Since both kinds are used pretty
      transparently on the Win32 platform, we do not attempt to distinguish
      between them.

    * LDLOADLIBS and EXTRALIBS are always identical under Win32, and
      BSLOADLIBS and LD_RUN_PATH are always empty (this may change in
      future).

    * You must make sure that any paths and path components are properly
      surrounded with double-quotes if they contain spaces. For example,
      $potential_libs could be (literally):

              "-Lc:\Program Files\vc\lib" msvcrt.lib "la test\foo bar.lib"

      Note how the first and last entries are protected by quotes in order
      to protect the spaces.

    * Since this module is most often used only indirectly from extension
      "Makefile.PL" files, here is an example "Makefile.PL" entry to add a
      library to the build process for an extension:

              LIBS => ['-lgl']

      When using GCC, that entry specifies that MakeMaker should first look
      for "libgl.a" (followed by "gl.a") in all the locations specified by
      $Config{libpth}.

      When using a compiler other than GCC, the above entry will search for
      "gl.lib" (followed by "libgl.lib").

      If the library happens to be in a location not in $Config{libpth}, you
      need:

              LIBS => ['-Lc:\gllibs -lgl']

      Here is a less often used example:

              LIBS => ['-lgl', ':nosearch -Ld:\mesalibs -lmesa -luser32']

      This specifies a search for library "gl" as before. If that search
      fails to find the library, it looks at the next item in the list. The
      ":nosearch" flag will prevent searching for the libraries that follow,
      so it simply returns the value as "-Ld:\mesalibs -lmesa -luser32",
      since GCC can use that value as is with its linker.

      When using the Visual C compiler, the second item is returned as
      "-libpath:d:\mesalibs mesa.lib user32.lib".

      When using the Borland compiler, the second item is returned as
      "-Ld:\mesalibs mesa.lib user32.lib", and MakeMaker takes care of
      moving the "-Ld:\mesalibs" to the correct place in the linker command
      line.

SEE ALSO
    ExtUtils::MakeMaker