1 package ExtUtils::Liblist;
4 # Broken out of MakeMaker from version 4.11
6 our $VERSION = substr q$Revision: 1.25 $, 10;
13 if ($^O eq 'VMS') { return &_vms_ext; }
14 elsif($^O eq 'MSWin32') { return &_win32_ext; }
15 else { return &_unix_os2_ext; }
19 my($self,$potential_libs, $verbose) = @_;
20 if ($^O =~ 'os2' and $Config{perllibs}) {
21 # Dynamic libraries are not transitive, so we may need including
22 # the libraries linked against perl.dll again.
24 $potential_libs .= " " if $potential_libs;
25 $potential_libs .= $Config{perllibs};
27 return ("", "", "", "") unless $potential_libs;
28 warn "Potential libraries are '$potential_libs':\n" if $verbose;
30 my($so) = $Config{'so'};
31 my($libs) = $Config{'perllibs'};
32 my $Config_libext = $Config{lib_ext} || ".a";
35 # compute $extralibs, $bsloadlibs and $ldloadlibs from
37 # this is a rewrite of Andy Dougherty's extliblist in perl
39 my(@searchpath); # from "-L/path" entries in $potential_libs
40 my(@libpath) = split " ", $Config{'libpth'};
41 my(@ldloadlibs, @bsloadlibs, @extralibs, @ld_run_path, %ld_run_path_seen);
42 my($fullname, $thislib, $thispth, @fullname);
43 my($pwd) = cwd(); # from Cwd.pm
46 foreach $thislib (split ' ', $potential_libs){
48 # Handle possible linker path arguments.
49 if ($thislib =~ s/^(-[LR])//){ # save path flag type
52 warn "$ptype$thislib ignored, directory does not exist\n"
56 unless ($self->file_name_is_absolute($thislib)) {
57 warn "Warning: $ptype$thislib changed to $ptype$pwd/$thislib\n";
58 $thislib = $self->catdir($pwd,$thislib);
60 push(@searchpath, $thislib);
61 push(@extralibs, "$ptype$thislib");
62 push(@ldloadlibs, "$ptype$thislib");
66 # Handle possible library arguments.
67 unless ($thislib =~ s/^-l//){
68 warn "Unrecognized argument in LIBS ignored: '$thislib'\n";
73 foreach $thispth (@searchpath, @libpath){
75 # Try to find the full name of the library. We need this to
76 # determine whether it's a dynamically-loadable library or not.
77 # This tends to be subject to various os-specific quirks.
78 # For gcc-2.6.2 on linux (March 1995), DLD can not load
79 # .sa libraries, with the exception of libm.sa, so we
80 # deliberately skip them.
82 $self->lsdir($thispth,"^\Qlib$thislib.$so.\E[0-9]+")){
83 # Take care that libfoo.so.10 wins against libfoo.so.9.
84 # Compare two libraries to find the most recent version
85 # number. E.g. if you have libfoo.so.9.0.7 and
86 # libfoo.so.10.1, first convert all digits into two
87 # decimal places. Then we'll add ".00" to the shorter
88 # strings so that we're comparing strings of equal length
89 # Thus we'll compare libfoo.so.09.07.00 with
90 # libfoo.so.10.01.00. Some libraries might have letters
91 # in the version. We don't know what they mean, but will
92 # try to skip them gracefully -- we'll set any letter to
93 # '0'. Finally, sort in reverse so we can take the
96 #TODO: iterate through the directory instead of sorting
98 $fullname = "$thispth/" .
101 $ma =~ tr/A-Za-z/0/s;
102 $ma =~ s/\b(\d)\b/0$1/g;
103 $mb =~ tr/A-Za-z/0/s;
104 $mb =~ s/\b(\d)\b/0$1/g;
105 while (length($ma) < length($mb)) { $ma .= ".00"; }
106 while (length($mb) < length($ma)) { $mb .= ".00"; }
107 # Comparison deliberately backwards
108 $mb cmp $ma;} @fullname)[0];
109 } elsif (-f ($fullname="$thispth/lib$thislib.$so")
110 && (($Config{'dlsrc'} ne "dl_dld.xs") || ($thislib eq "m"))){
111 } elsif (-f ($fullname="$thispth/lib${thislib}_s$Config_libext")
112 && (! $Config{'archname'} =~ /RM\d\d\d-svr4/)
113 && ($thislib .= "_s") ){ # we must explicitly use _s version
114 } elsif (-f ($fullname="$thispth/lib$thislib$Config_libext")){
115 } elsif (-f ($fullname="$thispth/$thislib$Config_libext")){
116 } elsif (-f ($fullname="$thispth/Slib$thislib$Config_libext")){
117 } elsif ($^O eq 'dgux'
118 && -l ($fullname="$thispth/lib$thislib$Config_libext")
119 && readlink($fullname) =~ /^elink:/s) {
120 # Some of DG's libraries look like misconnected symbolic
121 # links, but development tools can follow them. (They
124 # libm.a -> elink:${SDE_PATH:-/usr}/sde/\
125 # ${TARGET_BINARY_INTERFACE:-m88kdgux}/usr/lib/libm.a
127 # , the compilation tools expand the environment variables.)
129 warn "$thislib not found in $thispth\n" if $verbose;
132 warn "'-l$thislib' found at $fullname\n" if $verbose;
133 my($fullnamedir) = dirname($fullname);
134 push @ld_run_path, $fullnamedir unless $ld_run_path_seen{$fullnamedir}++;
138 # Now update library lists
140 # what do we know about this library...
141 my $is_dyna = ($fullname !~ /\Q$Config_libext\E\z/);
142 my $in_perl = ($libs =~ /\B-l\Q$ {thislib}\E\b/s);
144 # Do not add it into the list if it is already linked in
145 # with the main perl executable.
146 # We have to special-case the NeXT, because math and ndbm
147 # are both in libsys_s
149 ($Config{'osname'} eq 'next' &&
150 ($thislib eq 'm' || $thislib eq 'ndbm')) ){
151 push(@extralibs, "-l$thislib");
154 # We might be able to load this archive file dynamically
155 if ( ($Config{'dlsrc'} =~ /dl_next/ && $Config{'osvers'} lt '4_0')
156 || ($Config{'dlsrc'} =~ /dl_dld/) )
158 # We push -l$thislib instead of $fullname because
159 # it avoids hardwiring a fixed path into the .bs file.
160 # Mkbootstrap will automatically add dl_findfile() to
161 # the .bs file if it sees a name in the -l format.
162 # USE THIS, when dl_findfile() is fixed:
163 # push(@bsloadlibs, "-l$thislib");
164 # OLD USE WAS while checking results against old_extliblist
165 push(@bsloadlibs, "$fullname");
168 # For SunOS4, do not add in this shared library if
169 # it is already linked in the main perl executable
170 push(@ldloadlibs, "-l$thislib")
171 unless ($in_perl and $^O eq 'sunos');
173 push(@ldloadlibs, "-l$thislib");
176 last; # found one here so don't bother looking further
178 warn "Note (probably harmless): "
179 ."No library found for -l$thislib\n"
182 return ('','','','') unless $found;
183 ("@extralibs", "@bsloadlibs", "@ldloadlibs",join(":",@ld_run_path));
188 require Text::ParseWords;
190 my($self, $potential_libs, $verbose) = @_;
192 # If user did not supply a list, we punt.
193 # (caller should probably use the list in $Config{libs})
194 return ("", "", "", "") unless $potential_libs;
196 my $cc = $Config{cc};
197 my $VC = 1 if $cc =~ /^cl/i;
198 my $BC = 1 if $cc =~ /^bcc/i;
199 my $GC = 1 if $cc =~ /^gcc/i;
200 my $so = $Config{'so'};
201 my $libs = $Config{'perllibs'};
202 my $libpth = $Config{'libpth'};
203 my $libext = $Config{'lib_ext'} || ".lib";
205 if ($libs and $potential_libs !~ /:nodefault/i) {
206 # If Config.pm defines a set of default libs, we always
207 # tack them on to the user-supplied list, unless the user
208 # specified :nodefault
210 $potential_libs .= " " if $potential_libs;
211 $potential_libs .= $libs;
213 warn "Potential libraries are '$potential_libs':\n" if $verbose;
215 # normalize to forward slashes
217 $potential_libs =~ s,\\,/,g;
219 # compute $extralibs from $potential_libs
221 my @searchpath; # from "-L/path" in $potential_libs
222 my @libpath = Text::ParseWords::quotewords('\s+', 0, $libpth);
224 my $pwd = cwd(); # from Cwd.pm
228 my($fullname, $thislib, $thispth);
230 # add "$Config{installarchlib}/CORE" to default search path
231 push @libpath, "$Config{installarchlib}/CORE";
233 if ($VC and exists $ENV{LIB} and $ENV{LIB}) {
234 push @libpath, split /;/, $ENV{LIB};
237 foreach (Text::ParseWords::quotewords('\s+', 0, $potential_libs)){
241 # see if entry is a flag
243 $search = 0 if lc eq ':nosearch';
244 $search = 1 if lc eq ':search';
245 warn "Ignoring unknown flag '$thislib'\n"
246 if $verbose and !/^:(no)?(search|default)$/i;
250 # if searching is disabled, do compiler-specific translations
252 s/^-l(.+)$/$1.lib/ unless $GC;
253 s/^-L/-libpath:/ if $VC;
254 push(@extralibs, $_);
259 # handle possible linker path arguments
260 if (s/^-L// and not -d) {
261 warn "$thislib ignored, directory does not exist\n"
266 unless ($self->file_name_is_absolute($_)) {
267 warn "Warning: '$thislib' changed to '-L$pwd/$_'\n";
268 $_ = $self->catdir($pwd,$_);
270 push(@searchpath, $_);
274 # handle possible library arguments
275 if (s/^-l// and $GC and !/^lib/i) {
278 $_ .= $libext if !/\Q$libext\E$/i;
283 # look for the file itself
285 warn "'$thislib' found as '$_'\n" if $verbose;
287 push(@extralibs, $_);
292 foreach $thispth (@searchpath, @libpath){
293 unless (-f ($fullname="$thispth\\$_")) {
294 warn "'$thislib' not found as '$fullname'\n" if $verbose;
297 warn "'$thislib' found as '$fullname'\n" if $verbose;
300 push(@extralibs, $fullname);
304 # do another pass with (or without) leading 'lib' if they used -l
305 if (!$found_lib and $thislib =~ /^-l/ and !$secondpass++) {
307 goto LOOKAGAIN if s/^lib//i;
316 warn "Note (probably harmless): "
317 ."No library found for '$thislib'\n"
322 return ('','','','') unless $found;
324 # make sure paths with spaces are properly quoted
325 @extralibs = map { (/\s/ && !/^".*"$/) ? qq["$_"] : $_ } @extralibs;
326 $lib = join(' ',@extralibs);
328 # normalize back to backward slashes (to help braindead tools)
329 # XXX this may break equally braindead GNU tools that don't understand
330 # backslashes, either. Seems like one can't win here. Cursed be CP/M.
333 warn "Result: $lib\n" if $verbose;
334 wantarray ? ($lib, '', $lib, '') : $lib;
339 my($self, $potential_libs,$verbose) = @_;
341 my($dbgqual) = $self->{OPTIMIZE} || $Config{'optimize'} ||
342 $self->{CCFLAS} || $Config{'ccflags'};
343 @crtls = ( ($dbgqual =~ m-/Debug-i ? $Config{'dbgprefix'} : '')
345 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'perllibs'});
346 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'libc'});
347 # In general, we pass through the basic libraries from %Config unchanged.
348 # The one exception is that if we're building in the Perl source tree, and
349 # a library spec could be resolved via a logical name, we go to some trouble
350 # to insure that the copy in the local tree is used, rather than one to
351 # which a system-wide logical may point.
352 if ($self->{PERL_SRC}) {
353 my($lib,$locspec,$type);
354 foreach $lib (@crtls) {
355 if (($locspec,$type) = $lib =~ m-^([\w$\-]+)(/\w+)?- and $locspec =~ /perl/i) {
356 if (lc $type eq '/share') { $locspec .= $Config{'exe_ext'}; }
357 elsif (lc $type eq '/library') { $locspec .= $Config{'lib_ext'}; }
358 else { $locspec .= $Config{'obj_ext'}; }
359 $locspec = $self->catfile($self->{PERL_SRC},$locspec);
360 $lib = "$locspec$type" if -e $locspec;
364 $crtlstr = @crtls ? join(' ',@crtls) : '';
366 unless ($potential_libs) {
367 warn "Result:\n\tEXTRALIBS: \n\tLDLOADLIBS: $crtlstr\n" if $verbose;
368 return ('', '', $crtlstr, '');
371 my(@dirs,@libs,$dir,$lib,%found,@fndlibs,$ldlib);
373 my($so,$lib_ext,$obj_ext) = @Config{'so','lib_ext','obj_ext'};
374 # List of common Unix library names and there VMS equivalents
375 # (VMS equivalent of '' indicates that the library is automatially
376 # searched by the linker, and should be skipped here.)
377 my %libmap = ( 'm' => '', 'f77' => '', 'F77' => '', 'V77' => '', 'c' => '',
378 'malloc' => '', 'crypt' => '', 'resolv' => '', 'c_s' => '',
379 'socket' => '', 'X11' => 'DECW$XLIBSHR',
380 'Xt' => 'DECW$XTSHR', 'Xm' => 'DECW$XMLIBSHR',
381 'Xmu' => 'DECW$XMULIBSHR');
382 if ($Config{'vms_cc_type'} ne 'decc') { $libmap{'curses'} = 'VAXCCURSE'; }
384 warn "Potential libraries are '$potential_libs'\n" if $verbose;
386 # First, sort out directories and library names in the input
387 foreach $lib (split ' ',$potential_libs) {
388 push(@dirs,$1), next if $lib =~ /^-L(.*)/;
389 push(@dirs,$lib), next if $lib =~ /[:>\]]$/;
390 push(@dirs,$lib), next if -d $lib;
391 push(@libs,$1), next if $lib =~ /^-l(.*)/;
394 push(@dirs,split(' ',$Config{'libpth'}));
396 # Now make sure we've got VMS-syntax absolute directory specs
397 # (We don't, however, check whether someone's hidden a relative
398 # path in a logical name.)
399 foreach $dir (@dirs) {
401 warn "Skipping nonexistent Directory $dir\n" if $verbose > 1;
405 warn "Resolving directory $dir\n" if $verbose;
406 if ($self->file_name_is_absolute($dir)) { $dir = $self->fixpath($dir,1); }
407 else { $dir = $self->catdir($cwd,$dir); }
409 @dirs = grep { length($_) } @dirs;
410 unshift(@dirs,''); # Check each $lib without additions first
412 LIB: foreach $lib (@libs) {
413 if (exists $libmap{$lib}) {
414 next unless length $libmap{$lib};
415 $lib = $libmap{$lib};
418 my(@variants,$variant,$name,$test,$cand);
421 # If we don't have a file type, consider it a possibly abbreviated name and
422 # check for common variants. We try these first to grab libraries before
423 # a like-named executable image (e.g. -lperl resolves to perlshr.exe
425 if ($lib !~ /\.[^:>\]]*$/) {
426 push(@variants,"${lib}shr","${lib}rtl","${lib}lib");
427 push(@variants,"lib$lib") if $lib !~ /[:>\]]/;
429 push(@variants,$lib);
430 warn "Looking for $lib\n" if $verbose;
431 foreach $variant (@variants) {
432 foreach $dir (@dirs) {
435 $name = "$dir$variant";
436 warn "\tChecking $name\n" if $verbose > 2;
437 if (-f ($test = VMS::Filespec::rmsexpand($name))) {
438 # It's got its own suffix, so we'll have to figure out the type
439 if ($test =~ /(?:$so|exe)$/i) { $type = 'SHR'; }
440 elsif ($test =~ /(?:$lib_ext|olb)$/i) { $type = 'OLB'; }
441 elsif ($test =~ /(?:$obj_ext|obj)$/i) {
442 warn "Note (probably harmless): "
443 ."Plain object file $test found in library list\n";
447 warn "Note (probably harmless): "
448 ."Unknown library type for $test; assuming shared\n";
452 elsif (-f ($test = VMS::Filespec::rmsexpand($name,$so)) or
453 -f ($test = VMS::Filespec::rmsexpand($name,'.exe'))) {
455 $name = $test unless $test =~ /exe;?\d*$/i;
457 elsif (not length($ctype) and # If we've got a lib already, don't bother
458 ( -f ($test = VMS::Filespec::rmsexpand($name,$lib_ext)) or
459 -f ($test = VMS::Filespec::rmsexpand($name,'.olb')))) {
461 $name = $test unless $test =~ /olb;?\d*$/i;
463 elsif (not length($ctype) and # If we've got a lib already, don't bother
464 ( -f ($test = VMS::Filespec::rmsexpand($name,$obj_ext)) or
465 -f ($test = VMS::Filespec::rmsexpand($name,'.obj')))) {
466 warn "Note (probably harmless): "
467 ."Plain object file $test found in library list\n";
469 $name = $test unless $test =~ /obj;?\d*$/i;
472 $ctype = $type; $cand = $name;
473 last if $ctype eq 'SHR';
477 # This has to precede any other CRTLs, so just make it first
478 if ($cand eq 'VAXCCURSE') { unshift @{$found{$ctype}}, $cand; }
479 else { push @{$found{$ctype}}, $cand; }
480 warn "\tFound as $cand (really $test), type $ctype\n" if $verbose > 1;
484 warn "Note (probably harmless): "
485 ."No library found for $lib\n";
488 push @fndlibs, @{$found{OBJ}} if exists $found{OBJ};
489 push @fndlibs, map { "$_/Library" } @{$found{OLB}} if exists $found{OLB};
490 push @fndlibs, map { "$_/Share" } @{$found{SHR}} if exists $found{SHR};
491 $lib = join(' ',@fndlibs);
493 $ldlib = $crtlstr ? "$lib $crtlstr" : $lib;
494 warn "Result:\n\tEXTRALIBS: $lib\n\tLDLOADLIBS: $ldlib\n" if $verbose;
495 wantarray ? ($lib, '', $ldlib, '') : $lib;
504 ExtUtils::Liblist - determine libraries to use and how to use them
508 C<require ExtUtils::Liblist;>
510 C<ExtUtils::Liblist::ext($self, $potential_libs, $verbose);>
514 This utility takes a list of libraries in the form C<-llib1 -llib2
515 -llib3> and prints out lines suitable for inclusion in an extension
516 Makefile. Extra library paths may be included with the form
517 C<-L/another/path> this will affect the searches for all subsequent
520 It returns an array of four scalar values: EXTRALIBS, BSLOADLIBS,
521 LDLOADLIBS, and LD_RUN_PATH. Some of these don't mean anything
522 on VMS and Win32. See the details about those platform specifics
525 Dependent libraries can be linked in one of three ways:
529 =item * For static extensions
531 by the ld command when the perl binary is linked with the extension
532 library. See EXTRALIBS below.
534 =item * For dynamic extensions
536 by the ld command when the shared object is built/linked. See
539 =item * For dynamic extensions
541 by the DynaLoader when the shared object is loaded. See BSLOADLIBS
548 List of libraries that need to be linked with when linking a perl
549 binary which includes this extension. Only those libraries that
550 actually exist are included. These are written to a file and used
553 =head2 LDLOADLIBS and LD_RUN_PATH
555 List of those libraries which can or must be linked into the shared
556 library when created using ld. These may be static or dynamic
557 libraries. LD_RUN_PATH is a colon separated list of the directories
558 in LDLOADLIBS. It is passed as an environment variable to the process
559 that links the shared library.
563 List of those libraries that are needed but can be linked in
564 dynamically at run time on this platform. SunOS/Solaris does not need
565 this because ld records the information (from LDLOADLIBS) into the
566 object file. This list is used to create a .bs (bootstrap) file.
570 This module deals with a lot of system dependencies and has quite a
571 few architecture specific C<if>s in the code.
573 =head2 VMS implementation
575 The version of ext() which is executed under VMS differs from the
576 Unix-OS/2 version in several respects:
582 Input library and path specifications are accepted with or without the
583 C<-l> and C<-L> prefixes used by Unix linkers. If neither prefix is
584 present, a token is considered a directory to search if it is in fact
585 a directory, and a library to search for otherwise. Authors who wish
586 their extensions to be portable to Unix or OS/2 should use the Unix
587 prefixes, since the Unix-OS/2 version of ext() requires them.
591 Wherever possible, shareable images are preferred to object libraries,
592 and object libraries to plain object files. In accordance with VMS
593 naming conventions, ext() looks for files named I<lib>shr and I<lib>rtl;
594 it also looks for I<lib>lib and libI<lib> to accommodate Unix conventions
595 used in some ported software.
599 For each library that is found, an appropriate directive for a linker options
600 file is generated. The return values are space-separated strings of
601 these directives, rather than elements used on the linker command line.
605 LDLOADLIBS contains both the libraries found based on C<$potential_libs> and
606 the CRTLs, if any, specified in Config.pm. EXTRALIBS contains just those
607 libraries found based on C<$potential_libs>. BSLOADLIBS and LD_RUN_PATH
612 In addition, an attempt is made to recognize several common Unix library
613 names, and filter them out or convert them to their VMS equivalents, as
616 In general, the VMS version of ext() should properly handle input from
617 extensions originally designed for a Unix or VMS environment. If you
618 encounter problems, or discover cases where the search could be improved,
621 =head2 Win32 implementation
623 The version of ext() which is executed under Win32 differs from the
624 Unix-OS/2 version in several respects:
630 If C<$potential_libs> is empty, the return value will be empty.
631 Otherwise, the libraries specified by C<$Config{perllibs}> (see Config.pm)
632 will be appended to the list of C<$potential_libs>. The libraries
633 will be searched for in the directories specified in C<$potential_libs>,
634 C<$Config{libpth}>, and in C<$Config{installarchlib}/CORE>.
635 For each library that is found, a space-separated list of fully qualified
636 library pathnames is generated.
640 Input library and path specifications are accepted with or without the
641 C<-l> and C<-L> prefixes used by Unix linkers.
643 An entry of the form C<-La:\foo> specifies the C<a:\foo> directory to look
644 for the libraries that follow.
646 An entry of the form C<-lfoo> specifies the library C<foo>, which may be
647 spelled differently depending on what kind of compiler you are using. If
648 you are using GCC, it gets translated to C<libfoo.a>, but for other win32
649 compilers, it becomes C<foo.lib>. If no files are found by those translated
650 names, one more attempt is made to find them using either C<foo.a> or
651 C<libfoo.lib>, depending on whether GCC or some other win32 compiler is
652 being used, respectively.
654 If neither the C<-L> or C<-l> prefix is present in an entry, the entry is
655 considered a directory to search if it is in fact a directory, and a
656 library to search for otherwise. The C<$Config{lib_ext}> suffix will
657 be appended to any entries that are not directories and don't already have
660 Note that the C<-L> and C<-l> prefixes are B<not required>, but authors
661 who wish their extensions to be portable to Unix or OS/2 should use the
662 prefixes, since the Unix-OS/2 version of ext() requires them.
666 Entries cannot be plain object files, as many Win32 compilers will
667 not handle object files in the place of libraries.
671 Entries in C<$potential_libs> beginning with a colon and followed by
672 alphanumeric characters are treated as flags. Unknown flags will be ignored.
674 An entry that matches C</:nodefault/i> disables the appending of default
675 libraries found in C<$Config{perllibs}> (this should be only needed very rarely).
677 An entry that matches C</:nosearch/i> disables all searching for
678 the libraries specified after it. Translation of C<-Lfoo> and
679 C<-lfoo> still happens as appropriate (depending on compiler being used,
680 as reflected by C<$Config{cc}>), but the entries are not verified to be
681 valid files or directories.
683 An entry that matches C</:search/i> reenables searching for
684 the libraries specified after it. You can put it at the end to
685 enable searching for default libraries specified by C<$Config{perllibs}>.
689 The libraries specified may be a mixture of static libraries and
690 import libraries (to link with DLLs). Since both kinds are used
691 pretty transparently on the Win32 platform, we do not attempt to
692 distinguish between them.
696 LDLOADLIBS and EXTRALIBS are always identical under Win32, and BSLOADLIBS
697 and LD_RUN_PATH are always empty (this may change in future).
701 You must make sure that any paths and path components are properly
702 surrounded with double-quotes if they contain spaces. For example,
703 C<$potential_libs> could be (literally):
705 "-Lc:\Program Files\vc\lib" msvcrt.lib "la test\foo bar.lib"
707 Note how the first and last entries are protected by quotes in order
708 to protect the spaces.
712 Since this module is most often used only indirectly from extension
713 C<Makefile.PL> files, here is an example C<Makefile.PL> entry to add
714 a library to the build process for an extension:
718 When using GCC, that entry specifies that MakeMaker should first look
719 for C<libgl.a> (followed by C<gl.a>) in all the locations specified by
722 When using a compiler other than GCC, the above entry will search for
723 C<gl.lib> (followed by C<libgl.lib>).
725 If the library happens to be in a location not in C<$Config{libpth}>,
728 LIBS => ['-Lc:\gllibs -lgl']
730 Here is a less often used example:
732 LIBS => ['-lgl', ':nosearch -Ld:\mesalibs -lmesa -luser32']
734 This specifies a search for library C<gl> as before. If that search
735 fails to find the library, it looks at the next item in the list. The
736 C<:nosearch> flag will prevent searching for the libraries that follow,
737 so it simply returns the value as C<-Ld:\mesalibs -lmesa -luser32>,
738 since GCC can use that value as is with its linker.
740 When using the Visual C compiler, the second item is returned as
741 C<-libpath:d:\mesalibs mesa.lib user32.lib>.
743 When using the Borland compiler, the second item is returned as
744 C<-Ld:\mesalibs mesa.lib user32.lib>, and MakeMaker takes care of
745 moving the C<-Ld:\mesalibs> to the correct place in the linker
753 L<ExtUtils::MakeMaker>