1 package ExtUtils::Liblist;
3 # Broken out of MakeMaker from version 4.11
5 $VERSION = substr q$Revision: 1.25 $, 10;
12 if ($^O eq 'VMS') { return &_vms_ext; }
13 elsif($^O eq 'MSWin32') { return &_win32_ext; }
14 else { return &_unix_os2_ext; }
18 my($self,$potential_libs, $verbose) = @_;
19 if ($^O =~ 'os2' and $Config{libs}) {
20 # Dynamic libraries are not transitive, so we may need including
21 # the libraries linked against perl.dll again.
23 $potential_libs .= " " if $potential_libs;
24 $potential_libs .= $Config{libs};
26 return ("", "", "", "") unless $potential_libs;
27 warn "Potential libraries are '$potential_libs':\n" if $verbose;
29 my($so) = $Config{'so'};
30 my($libs) = $Config{'libs'};
31 my $Config_libext = $Config{lib_ext} || ".a";
34 # compute $extralibs, $bsloadlibs and $ldloadlibs from
36 # this is a rewrite of Andy Dougherty's extliblist in perl
38 my(@searchpath); # from "-L/path" entries in $potential_libs
39 my(@libpath) = split " ", $Config{'libpth'};
40 my(@ldloadlibs, @bsloadlibs, @extralibs, @ld_run_path, %ld_run_path_seen);
41 my($fullname, $thislib, $thispth, @fullname);
42 my($pwd) = cwd(); # from Cwd.pm
45 foreach $thislib (split ' ', $potential_libs){
47 # Handle possible linker path arguments.
48 if ($thislib =~ s/^(-[LR])//){ # save path flag type
51 warn "$ptype$thislib ignored, directory does not exist\n"
55 unless ($self->file_name_is_absolute($thislib)) {
56 warn "Warning: $ptype$thislib changed to $ptype$pwd/$thislib\n";
57 $thislib = $self->catdir($pwd,$thislib);
59 push(@searchpath, $thislib);
60 push(@extralibs, "$ptype$thislib");
61 push(@ldloadlibs, "$ptype$thislib");
65 # Handle possible library arguments.
66 unless ($thislib =~ s/^-l//){
67 warn "Unrecognized argument in LIBS ignored: '$thislib'\n";
72 foreach $thispth (@searchpath, @libpath){
74 # Try to find the full name of the library. We need this to
75 # determine whether it's a dynamically-loadable library or not.
76 # This tends to be subject to various os-specific quirks.
77 # For gcc-2.6.2 on linux (March 1995), DLD can not load
78 # .sa libraries, with the exception of libm.sa, so we
79 # deliberately skip them.
81 $self->lsdir($thispth,"^\Qlib$thislib.$so.\E[0-9]+")){
82 # Take care that libfoo.so.10 wins against libfoo.so.9.
83 # Compare two libraries to find the most recent version
84 # number. E.g. if you have libfoo.so.9.0.7 and
85 # libfoo.so.10.1, first convert all digits into two
86 # decimal places. Then we'll add ".00" to the shorter
87 # strings so that we're comparing strings of equal length
88 # Thus we'll compare libfoo.so.09.07.00 with
89 # libfoo.so.10.01.00. Some libraries might have letters
90 # in the version. We don't know what they mean, but will
91 # try to skip them gracefully -- we'll set any letter to
92 # '0'. Finally, sort in reverse so we can take the
95 #TODO: iterate through the directory instead of sorting
97 $fullname = "$thispth/" .
100 $ma =~ tr/A-Za-z/0/s;
101 $ma =~ s/\b(\d)\b/0$1/g;
102 $mb =~ tr/A-Za-z/0/s;
103 $mb =~ s/\b(\d)\b/0$1/g;
104 while (length($ma) < length($mb)) { $ma .= ".00"; }
105 while (length($mb) < length($ma)) { $mb .= ".00"; }
106 # Comparison deliberately backwards
107 $mb cmp $ma;} @fullname)[0];
108 } elsif (-f ($fullname="$thispth/lib$thislib.$so")
109 && (($Config{'dlsrc'} ne "dl_dld.xs") || ($thislib eq "m"))){
110 } elsif (-f ($fullname="$thispth/lib${thislib}_s$Config_libext")
111 && ($thislib .= "_s") ){ # we must explicitly use _s version
112 } elsif (-f ($fullname="$thispth/lib$thislib$Config_libext")){
113 } elsif (-f ($fullname="$thispth/$thislib$Config_libext")){
114 } elsif (-f ($fullname="$thispth/Slib$thislib$Config_libext")){
115 } elsif ($^O eq 'dgux'
116 && -l ($fullname="$thispth/lib$thislib$Config_libext")
117 && readlink($fullname) =~ /^elink:/) {
118 # Some of DG's libraries look like misconnected symbolic
119 # links, but development tools can follow them. (They
122 # libm.a -> elink:${SDE_PATH:-/usr}/sde/\
123 # ${TARGET_BINARY_INTERFACE:-m88kdgux}/usr/lib/libm.a
125 # , the compilation tools expand the environment variables.)
127 warn "$thislib not found in $thispth\n" if $verbose;
130 warn "'-l$thislib' found at $fullname\n" if $verbose;
131 my($fullnamedir) = dirname($fullname);
132 push @ld_run_path, $fullnamedir unless $ld_run_path_seen{$fullnamedir}++;
136 # Now update library lists
138 # what do we know about this library...
139 my $is_dyna = ($fullname !~ /\Q$Config_libext\E$/);
140 my $in_perl = ($libs =~ /\B-l\Q$ {thislib}\E\b/s);
142 # Do not add it into the list if it is already linked in
143 # with the main perl executable.
144 # We have to special-case the NeXT, because math and ndbm
145 # are both in libsys_s
147 ($Config{'osname'} eq 'next' &&
148 ($thislib eq 'm' || $thislib eq 'ndbm')) ){
149 push(@extralibs, "-l$thislib");
152 # We might be able to load this archive file dynamically
153 if ( ($Config{'dlsrc'} =~ /dl_next/ && $Config{'osvers'} lt '4_0')
154 || ($Config{'dlsrc'} =~ /dl_dld/) )
156 # We push -l$thislib instead of $fullname because
157 # it avoids hardwiring a fixed path into the .bs file.
158 # Mkbootstrap will automatically add dl_findfile() to
159 # the .bs file if it sees a name in the -l format.
160 # USE THIS, when dl_findfile() is fixed:
161 # push(@bsloadlibs, "-l$thislib");
162 # OLD USE WAS while checking results against old_extliblist
163 push(@bsloadlibs, "$fullname");
166 # For SunOS4, do not add in this shared library if
167 # it is already linked in the main perl executable
168 push(@ldloadlibs, "-l$thislib")
169 unless ($in_perl and $^O eq 'sunos');
171 push(@ldloadlibs, "-l$thislib");
174 last; # found one here so don't bother looking further
176 warn "Note (probably harmless): "
177 ."No library found for -l$thislib\n"
180 return ('','','','') unless $found;
181 ("@extralibs", "@bsloadlibs", "@ldloadlibs",join(":",@ld_run_path));
186 require Text::ParseWords;
188 my($self, $potential_libs, $verbose) = @_;
190 # If user did not supply a list, we punt.
191 # (caller should probably use the list in $Config{libs})
192 return ("", "", "", "") unless $potential_libs;
194 my $cc = $Config{cc};
195 my $VC = 1 if $cc =~ /^cl/i;
196 my $BC = 1 if $cc =~ /^bcc/i;
197 my $GC = 1 if $cc =~ /^gcc/i;
198 my $so = $Config{'so'};
199 my $libs = $Config{'libs'};
200 my $libpth = $Config{'libpth'};
201 my $libext = $Config{'lib_ext'} || ".lib";
203 if ($libs and $potential_libs !~ /:nodefault/i) {
204 # If Config.pm defines a set of default libs, we always
205 # tack them on to the user-supplied list, unless the user
206 # specified :nodefault
208 $potential_libs .= " " if $potential_libs;
209 $potential_libs .= $libs;
211 warn "Potential libraries are '$potential_libs':\n" if $verbose;
213 # normalize to forward slashes
215 $potential_libs =~ s,\\,/,g;
217 # compute $extralibs from $potential_libs
219 my @searchpath; # from "-L/path" in $potential_libs
220 my @libpath = Text::ParseWords::quotewords('\s+', 0, $libpth);
222 my $pwd = cwd(); # from Cwd.pm
226 my($fullname, $thislib, $thispth);
228 # add "$Config{installarchlib}/CORE" to default search path
229 push @libpath, "$Config{installarchlib}/CORE";
231 foreach (Text::ParseWords::quotewords('\s+', 0, $potential_libs)){
235 # see if entry is a flag
237 $search = 0 if lc eq ':nosearch';
238 $search = 1 if lc eq ':search';
239 warn "Ignoring unknown flag '$thislib'\n"
240 if $verbose and !/^:(no)?(search|default)$/i;
244 # if searching is disabled, do compiler-specific translations
246 s/^-l(.+)$/$1.lib/ unless $GC;
247 s/^-L/-libpath:/ if $VC;
248 push(@extralibs, $_);
253 # handle possible linker path arguments
254 if (s/^-L// and not -d) {
255 warn "$thislib ignored, directory does not exist\n"
260 unless ($self->file_name_is_absolute($_)) {
261 warn "Warning: '$thislib' changed to '-L$pwd/$_'\n";
262 $_ = $self->catdir($pwd,$_);
264 push(@searchpath, $_);
268 # handle possible library arguments
269 if (s/^-l// and $GC and !/^lib/i) {
272 $_ .= $libext if !/\Q$libext\E$/i;
277 # look for the file itself
279 warn "'$thislib' found as '$_'\n" if $verbose;
281 push(@extralibs, $_);
286 foreach $thispth (@searchpath, @libpath){
287 unless (-f ($fullname="$thispth\\$_")) {
288 warn "'$thislib' not found as '$fullname'\n" if $verbose;
291 warn "'$thislib' found as '$fullname'\n" if $verbose;
294 push(@extralibs, $fullname);
298 # do another pass with (or without) leading 'lib' if they used -l
299 if (!$found_lib and $thislib =~ /^-l/ and !$secondpass++) {
301 goto LOOKAGAIN if s/^lib//i;
310 warn "Note (probably harmless): "
311 ."No library found for '$thislib'\n"
316 return ('','','','') unless $found;
318 # make sure paths with spaces are properly quoted
319 @extralibs = map { (/\s/ && !/^".*"$/) ? qq["$_"] : $_ } @extralibs;
320 $lib = join(' ',@extralibs);
322 # normalize back to backward slashes (to help braindead tools)
323 # XXX this may break equally braindead GNU tools that don't understand
324 # backslashes, either. Seems like one can't win here. Cursed be CP/M.
327 warn "Result: $lib\n" if $verbose;
328 wantarray ? ($lib, '', $lib, '') : $lib;
333 my($self, $potential_libs,$verbose) = @_;
335 my($dbgqual) = $self->{OPTIMIZE} || $Config{'optimize'} ||
336 $self->{CCFLAS} || $Config{'ccflags'};
337 @crtls = ( ($dbgqual =~ m-/Debug-i ? $Config{'dbgprefix'} : '')
339 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'libs'});
340 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'libc'});
341 # In general, we pass through the basic libraries from %Config unchanged.
342 # The one exception is that if we're building in the Perl source tree, and
343 # a library spec could be resolved via a logical name, we go to some trouble
344 # to insure that the copy in the local tree is used, rather than one to
345 # which a system-wide logical may point.
346 if ($self->{PERL_SRC}) {
347 my($lib,$locspec,$type);
348 foreach $lib (@crtls) {
349 if (($locspec,$type) = $lib =~ m-^([\w$\-]+)(/\w+)?- and $locspec =~ /perl/i) {
350 if (lc $type eq '/share') { $locspec .= $Config{'exe_ext'}; }
351 elsif (lc $type eq '/library') { $locspec .= $Config{'lib_ext'}; }
352 else { $locspec .= $Config{'obj_ext'}; }
353 $locspec = $self->catfile($self->{PERL_SRC},$locspec);
354 $lib = "$locspec$type" if -e $locspec;
358 $crtlstr = @crtls ? join(' ',@crtls) : '';
360 unless ($potential_libs) {
361 warn "Result:\n\tEXTRALIBS: \n\tLDLOADLIBS: $crtlstr\n" if $verbose;
362 return ('', '', $crtlstr, '');
365 my(@dirs,@libs,$dir,$lib,%sh,%olb,%obj,$ldlib);
367 my($so,$lib_ext,$obj_ext) = @Config{'so','lib_ext','obj_ext'};
368 # List of common Unix library names and there VMS equivalents
369 # (VMS equivalent of '' indicates that the library is automatially
370 # searched by the linker, and should be skipped here.)
371 my %libmap = ( 'm' => '', 'f77' => '', 'F77' => '', 'V77' => '', 'c' => '',
372 'malloc' => '', 'crypt' => '', 'resolv' => '', 'c_s' => '',
373 'socket' => '', 'X11' => 'DECW$XLIBSHR',
374 'Xt' => 'DECW$XTSHR', 'Xm' => 'DECW$XMLIBSHR',
375 'Xmu' => 'DECW$XMULIBSHR');
376 if ($Config{'vms_cc_type'} ne 'decc') { $libmap{'curses'} = 'VAXCCURSE'; }
378 warn "Potential libraries are '$potential_libs'\n" if $verbose;
380 # First, sort out directories and library names in the input
381 foreach $lib (split ' ',$potential_libs) {
382 push(@dirs,$1), next if $lib =~ /^-L(.*)/;
383 push(@dirs,$lib), next if $lib =~ /[:>\]]$/;
384 push(@dirs,$lib), next if -d $lib;
385 push(@libs,$1), next if $lib =~ /^-l(.*)/;
388 push(@dirs,split(' ',$Config{'libpth'}));
390 # Now make sure we've got VMS-syntax absolute directory specs
391 # (We don't, however, check whether someone's hidden a relative
392 # path in a logical name.)
393 foreach $dir (@dirs) {
395 warn "Skipping nonexistent Directory $dir\n" if $verbose > 1;
399 warn "Resolving directory $dir\n" if $verbose;
400 if ($self->file_name_is_absolute($dir)) { $dir = $self->fixpath($dir,1); }
401 else { $dir = $self->catdir($cwd,$dir); }
403 @dirs = grep { length($_) } @dirs;
404 unshift(@dirs,''); # Check each $lib without additions first
406 LIB: foreach $lib (@libs) {
407 if (exists $libmap{$lib}) {
408 next unless length $libmap{$lib};
409 $lib = $libmap{$lib};
412 my(@variants,$variant,$name,$test,$cand);
415 # If we don't have a file type, consider it a possibly abbreviated name and
416 # check for common variants. We try these first to grab libraries before
417 # a like-named executable image (e.g. -lperl resolves to perlshr.exe
419 if ($lib !~ /\.[^:>\]]*$/) {
420 push(@variants,"${lib}shr","${lib}rtl","${lib}lib");
421 push(@variants,"lib$lib") if $lib !~ /[:>\]]/;
423 push(@variants,$lib);
424 warn "Looking for $lib\n" if $verbose;
425 foreach $variant (@variants) {
426 foreach $dir (@dirs) {
429 $name = "$dir$variant";
430 warn "\tChecking $name\n" if $verbose > 2;
431 if (-f ($test = VMS::Filespec::rmsexpand($name))) {
432 # It's got its own suffix, so we'll have to figure out the type
433 if ($test =~ /(?:$so|exe)$/i) { $type = 'sh'; }
434 elsif ($test =~ /(?:$lib_ext|olb)$/i) { $type = 'olb'; }
435 elsif ($test =~ /(?:$obj_ext|obj)$/i) {
436 warn "Note (probably harmless): "
437 ."Plain object file $test found in library list\n";
441 warn "Note (probably harmless): "
442 ."Unknown library type for $test; assuming shared\n";
446 elsif (-f ($test = VMS::Filespec::rmsexpand($name,$so)) or
447 -f ($test = VMS::Filespec::rmsexpand($name,'.exe'))) {
449 $name = $test unless $test =~ /exe;?\d*$/i;
451 elsif (not length($ctype) and # If we've got a lib already, don't bother
452 ( -f ($test = VMS::Filespec::rmsexpand($name,$lib_ext)) or
453 -f ($test = VMS::Filespec::rmsexpand($name,'.olb')))) {
455 $name = $test unless $test =~ /olb;?\d*$/i;
457 elsif (not length($ctype) and # If we've got a lib already, don't bother
458 ( -f ($test = VMS::Filespec::rmsexpand($name,$obj_ext)) or
459 -f ($test = VMS::Filespec::rmsexpand($name,'.obj')))) {
460 warn "Note (probably harmless): "
461 ."Plain object file $test found in library list\n";
463 $name = $test unless $test =~ /obj;?\d*$/i;
466 $ctype = $type; $cand = $name;
467 last if $ctype eq 'sh';
471 eval '$' . $ctype . "{'$cand'}++";
472 die "Error recording library: $@" if $@;
473 warn "\tFound as $cand (really $test), type $ctype\n" if $verbose > 1;
477 warn "Note (probably harmless): "
478 ."No library found for $lib\n";
481 @libs = sort keys %obj;
482 # This has to precede any other CRTLs, so just make it first
483 if ($olb{VAXCCURSE}) {
484 push(@libs,"$olb{VAXCCURSE}/Library");
485 delete $olb{VAXCCURSE};
487 push(@libs, map { "$_/Library" } sort keys %olb);
488 push(@libs, map { "$_/Share" } sort keys %sh);
489 $lib = join(' ',@libs);
491 $ldlib = $crtlstr ? "$lib $crtlstr" : $lib;
492 warn "Result:\n\tEXTRALIBS: $lib\n\tLDLOADLIBS: $ldlib\n" if $verbose;
493 wantarray ? ($lib, '', $ldlib, '') : $lib;
502 ExtUtils::Liblist - determine libraries to use and how to use them
506 C<require ExtUtils::Liblist;>
508 C<ExtUtils::Liblist::ext($self, $potential_libs, $verbose);>
512 This utility takes a list of libraries in the form C<-llib1 -llib2
513 -llib3> and prints out lines suitable for inclusion in an extension
514 Makefile. Extra library paths may be included with the form
515 C<-L/another/path> this will affect the searches for all subsequent
518 It returns an array of four scalar values: EXTRALIBS, BSLOADLIBS,
519 LDLOADLIBS, and LD_RUN_PATH. Some of these don't mean anything
520 on VMS and Win32. See the details about those platform specifics
523 Dependent libraries can be linked in one of three ways:
527 =item * For static extensions
529 by the ld command when the perl binary is linked with the extension
530 library. See EXTRALIBS below.
532 =item * For dynamic extensions
534 by the ld command when the shared object is built/linked. See
537 =item * For dynamic extensions
539 by the DynaLoader when the shared object is loaded. See BSLOADLIBS
546 List of libraries that need to be linked with when linking a perl
547 binary which includes this extension Only those libraries that
548 actually exist are included. These are written to a file and used
551 =head2 LDLOADLIBS and LD_RUN_PATH
553 List of those libraries which can or must be linked into the shared
554 library when created using ld. These may be static or dynamic
555 libraries. LD_RUN_PATH is a colon separated list of the directories
556 in LDLOADLIBS. It is passed as an environment variable to the process
557 that links the shared library.
561 List of those libraries that are needed but can be linked in
562 dynamically at run time on this platform. SunOS/Solaris does not need
563 this because ld records the information (from LDLOADLIBS) into the
564 object file. This list is used to create a .bs (bootstrap) file.
568 This module deals with a lot of system dependencies and has quite a
569 few architecture specific B<if>s in the code.
571 =head2 VMS implementation
573 The version of ext() which is executed under VMS differs from the
574 Unix-OS/2 version in several respects:
580 Input library and path specifications are accepted with or without the
581 C<-l> and C<-L> prefices used by Unix linkers. If neither prefix is
582 present, a token is considered a directory to search if it is in fact
583 a directory, and a library to search for otherwise. Authors who wish
584 their extensions to be portable to Unix or OS/2 should use the Unix
585 prefixes, since the Unix-OS/2 version of ext() requires them.
589 Wherever possible, shareable images are preferred to object libraries,
590 and object libraries to plain object files. In accordance with VMS
591 naming conventions, ext() looks for files named I<lib>shr and I<lib>rtl;
592 it also looks for I<lib>lib and libI<lib> to accomodate Unix conventions
593 used in some ported software.
597 For each library that is found, an appropriate directive for a linker options
598 file is generated. The return values are space-separated strings of
599 these directives, rather than elements used on the linker command line.
603 LDLOADLIBS contains both the libraries found based on C<$potential_libs> and
604 the CRTLs, if any, specified in Config.pm. EXTRALIBS contains just those
605 libraries found based on C<$potential_libs>. BSLOADLIBS and LD_RUN_PATH
610 In addition, an attempt is made to recognize several common Unix library
611 names, and filter them out or convert them to their VMS equivalents, as
614 In general, the VMS version of ext() should properly handle input from
615 extensions originally designed for a Unix or VMS environment. If you
616 encounter problems, or discover cases where the search could be improved,
619 =head2 Win32 implementation
621 The version of ext() which is executed under Win32 differs from the
622 Unix-OS/2 version in several respects:
628 If C<$potential_libs> is empty, the return value will be empty.
629 Otherwise, the libraries specified by C<$Config{libs}> (see Config.pm)
630 will be appended to the list of C<$potential_libs>. The libraries
631 will be searched for in the directories specified in C<$potential_libs>,
632 C<$Config{libpth}>, and in C<$Config{installarchlib}/CORE>.
633 For each library that is found, a space-separated list of fully qualified
634 library pathnames is generated.
638 Input library and path specifications are accepted with or without the
639 C<-l> and C<-L> prefices used by Unix linkers.
641 An entry of the form C<-La:\foo> specifies the C<a:\foo> directory to look
642 for the libraries that follow.
644 An entry of the form C<-lfoo> specifies the library C<foo>, which may be
645 spelled differently depending on what kind of compiler you are using. If
646 you are using GCC, it gets translated to C<libfoo.a>, but for other win32
647 compilers, it becomes C<foo.lib>. If no files are found by those translated
648 names, one more attempt is made to find them using either C<foo.a> or
649 C<libfoo.lib>, depending on whether GCC or some other win32 compiler is
650 being used, respectively.
652 If neither the C<-L> or C<-l> prefix is present in an entry, the entry is
653 considered a directory to search if it is in fact a directory, and a
654 library to search for otherwise. The C<$Config{lib_ext}> suffix will
655 be appended to any entries that are not directories and don't already have
658 Note that the C<-L> and <-l> prefixes are B<not required>, but authors
659 who wish their extensions to be portable to Unix or OS/2 should use the
660 prefixes, since the Unix-OS/2 version of ext() requires them.
664 Entries cannot be plain object files, as many Win32 compilers will
665 not handle object files in the place of libraries.
669 Entries in C<$potential_libs> beginning with a colon and followed by
670 alphanumeric characters are treated as flags. Unknown flags will be ignored.
672 An entry that matches C</:nodefault/i> disables the appending of default
673 libraries found in C<$Config{libs}> (this should be only needed very rarely).
675 An entry that matches C</:nosearch/i> disables all searching for
676 the libraries specified after it. Translation of C<-Lfoo> and
677 C<-lfoo> still happens as appropriate (depending on compiler being used,
678 as reflected by C<$Config{cc}>), but the entries are not verified to be
679 valid files or directories.
681 An entry that matches C</:search/i> reenables searching for
682 the libraries specified after it. You can put it at the end to
683 enable searching for default libraries specified by C<$Config{libs}>.
687 The libraries specified may be a mixture of static libraries and
688 import libraries (to link with DLLs). Since both kinds are used
689 pretty transparently on the win32 platform, we do not attempt to
690 distinguish between them.
694 LDLOADLIBS and EXTRALIBS are always identical under Win32, and BSLOADLIBS
695 and LD_RUN_PATH are always empty (this may change in future).
699 You must make sure that any paths and path components are properly
700 surrounded with double-quotes if they contain spaces. For example,
701 C<$potential_libs> could be (literally):
703 "-Lc:\Program Files\vc\lib" msvcrt.lib "la test\foo bar.lib"
705 Note how the first and last entries are protected by quotes in order
706 to protect the spaces.
710 Since this module is most often used only indirectly from extension
711 C<Makefile.PL> files, here is an example C<Makefile.PL> entry to add
712 a library to the build process for an extension:
716 When using GCC, that entry specifies that MakeMaker should first look
717 for C<libgl.a> (followed by C<gl.a>) in all the locations specified by
720 When using a compiler other than GCC, the above entry will search for
721 C<gl.lib> (followed by C<libgl.lib>).
723 If the library happens to be in a location not in C<$Config{libpth}>,
726 LIBS => ['-Lc:\gllibs -lgl']
728 Here is a less often used example:
730 LIBS => ['-lgl', ':nosearch -Ld:\mesalibs -lmesa -luser32']
732 This specifies a search for library C<gl> as before. If that search
733 fails to find the library, it looks at the next item in the list. The
734 C<:nosearch> flag will prevent searching for the libraries that follow,
735 so it simply returns the value as C<-Ld:\mesalibs -lmesa -luser32>,
736 since GCC can use that value as is with its linker.
738 When using the Visual C compiler, the second item is returned as
739 C<-libpath:d:\mesalibs mesa.lib user32.lib>.
741 When using the Borland compiler, the second item is returned as
742 C<-Ld:\mesalibs mesa.lib user32.lib>, and MakeMaker takes care of
743 moving the C<-Ld:\mesalibs> to the correct place in the linker
751 L<ExtUtils::MakeMaker>