require ExtUtils::Liblist; $MM->ext($potential_libs, $verbose, $need_names); # Usually you can get away with: ExtUtils::Liblist->ext($potential_libs, $verbose, $need_names)
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:
by the ld command when the perl binary is linked with the extension library. See EXTRALIBS below.
by the ld command when the shared object is built/linked. See LDLOADLIBS below.
by the DynaLoader when the shared object is loaded. See BSLOADLIBS below.
Fedora extension: This generation of LD_RUN_PATH is disabled by default. To use the generated LD_RUN_PATH for all links, set the USE_MM_LD_RUN_PATH MakeMaker object attribute / argument, (or set the $USE_MM_LD_RUN_PATH environment variable).
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.
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.
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}.
"-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.
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.