1 package ExtUtils::Liblist;
3 @ISA = qw(ExtUtils::Liblist::Kid File::Spec);
8 opendir my $dir, $_[0];
9 grep /$rex/, readdir $dir;
12 sub file_name_is_absolute {
15 'File::Spec'->file_name_is_absolute(@_);
19 package ExtUtils::Liblist::Kid;
21 # This kid package is to be used by MakeMaker. It will not work if
22 # $self is not a Makemaker.
25 # Broken out of MakeMaker from version 4.11
27 our $VERSION = substr q$Revision: 1.25 $, 10;
34 if ($^O eq 'VMS') { return &_vms_ext; }
35 elsif($^O eq 'MSWin32') { return &_win32_ext; }
36 else { return &_unix_os2_ext; }
40 my($self,$potential_libs, $verbose) = @_;
41 if ($^O =~ 'os2' and $Config{perllibs}) {
42 # Dynamic libraries are not transitive, so we may need including
43 # the libraries linked against perl.dll again.
45 $potential_libs .= " " if $potential_libs;
46 $potential_libs .= $Config{perllibs};
48 return ("", "", "", "") unless $potential_libs;
49 warn "Potential libraries are '$potential_libs':\n" if $verbose;
51 my($so) = $Config{'so'};
52 my($libs) = $Config{'perllibs'};
53 my $Config_libext = $Config{lib_ext} || ".a";
56 # compute $extralibs, $bsloadlibs and $ldloadlibs from
58 # this is a rewrite of Andy Dougherty's extliblist in perl
60 my(@searchpath); # from "-L/path" entries in $potential_libs
61 my(@libpath) = split " ", $Config{'libpth'};
62 my(@ldloadlibs, @bsloadlibs, @extralibs, @ld_run_path, %ld_run_path_seen);
63 my($fullname, $thislib, $thispth, @fullname);
64 my($pwd) = cwd(); # from Cwd.pm
67 foreach $thislib (split ' ', $potential_libs){
69 # Handle possible linker path arguments.
70 if ($thislib =~ s/^(-[LR])//){ # save path flag type
73 warn "$ptype$thislib ignored, directory does not exist\n"
77 unless ($self->file_name_is_absolute($thislib)) {
78 warn "Warning: $ptype$thislib changed to $ptype$pwd/$thislib\n";
79 $thislib = $self->catdir($pwd,$thislib);
81 push(@searchpath, $thislib);
82 push(@extralibs, "$ptype$thislib");
83 push(@ldloadlibs, "$ptype$thislib");
87 # Handle possible library arguments.
88 unless ($thislib =~ s/^-l//){
89 warn "Unrecognized argument in LIBS ignored: '$thislib'\n";
94 foreach $thispth (@searchpath, @libpath){
96 # Try to find the full name of the library. We need this to
97 # determine whether it's a dynamically-loadable library or not.
98 # This tends to be subject to various os-specific quirks.
99 # For gcc-2.6.2 on linux (March 1995), DLD can not load
100 # .sa libraries, with the exception of libm.sa, so we
101 # deliberately skip them.
103 $self->lsdir($thispth,"^\Qlib$thislib.$so.\E[0-9]+")){
104 # Take care that libfoo.so.10 wins against libfoo.so.9.
105 # Compare two libraries to find the most recent version
106 # number. E.g. if you have libfoo.so.9.0.7 and
107 # libfoo.so.10.1, first convert all digits into two
108 # decimal places. Then we'll add ".00" to the shorter
109 # strings so that we're comparing strings of equal length
110 # Thus we'll compare libfoo.so.09.07.00 with
111 # libfoo.so.10.01.00. Some libraries might have letters
112 # in the version. We don't know what they mean, but will
113 # try to skip them gracefully -- we'll set any letter to
114 # '0'. Finally, sort in reverse so we can take the
117 #TODO: iterate through the directory instead of sorting
119 $fullname = "$thispth/" .
120 (sort { my($ma) = $a;
122 $ma =~ tr/A-Za-z/0/s;
123 $ma =~ s/\b(\d)\b/0$1/g;
124 $mb =~ tr/A-Za-z/0/s;
125 $mb =~ s/\b(\d)\b/0$1/g;
126 while (length($ma) < length($mb)) { $ma .= ".00"; }
127 while (length($mb) < length($ma)) { $mb .= ".00"; }
128 # Comparison deliberately backwards
129 $mb cmp $ma;} @fullname)[0];
130 } elsif (-f ($fullname="$thispth/lib$thislib.$so")
131 && (($Config{'dlsrc'} ne "dl_dld.xs") || ($thislib eq "m"))){
132 } elsif (-f ($fullname="$thispth/lib${thislib}_s$Config_libext")
133 && (! $Config{'archname'} =~ /RM\d\d\d-svr4/)
134 && ($thislib .= "_s") ){ # we must explicitly use _s version
135 } elsif (-f ($fullname="$thispth/lib$thislib$Config_libext")){
136 } elsif (-f ($fullname="$thispth/$thislib$Config_libext")){
137 } elsif (-f ($fullname="$thispth/Slib$thislib$Config_libext")){
138 } elsif ($^O eq 'dgux'
139 && -l ($fullname="$thispth/lib$thislib$Config_libext")
140 && readlink($fullname) =~ /^elink:/s) {
141 # Some of DG's libraries look like misconnected symbolic
142 # links, but development tools can follow them. (They
145 # libm.a -> elink:${SDE_PATH:-/usr}/sde/\
146 # ${TARGET_BINARY_INTERFACE:-m88kdgux}/usr/lib/libm.a
148 # , the compilation tools expand the environment variables.)
150 warn "$thislib not found in $thispth\n" if $verbose;
153 warn "'-l$thislib' found at $fullname\n" if $verbose;
154 my($fullnamedir) = dirname($fullname);
155 push @ld_run_path, $fullnamedir unless $ld_run_path_seen{$fullnamedir}++;
159 # Now update library lists
161 # what do we know about this library...
162 my $is_dyna = ($fullname !~ /\Q$Config_libext\E\z/);
163 my $in_perl = ($libs =~ /\B-l\Q$ {thislib}\E\b/s);
165 # Do not add it into the list if it is already linked in
166 # with the main perl executable.
167 # We have to special-case the NeXT, because math and ndbm
168 # are both in libsys_s
170 ($Config{'osname'} eq 'next' &&
171 ($thislib eq 'm' || $thislib eq 'ndbm')) ){
172 push(@extralibs, "-l$thislib");
175 # We might be able to load this archive file dynamically
176 if ( ($Config{'dlsrc'} =~ /dl_next/ && $Config{'osvers'} lt '4_0')
177 || ($Config{'dlsrc'} =~ /dl_dld/) )
179 # We push -l$thislib instead of $fullname because
180 # it avoids hardwiring a fixed path into the .bs file.
181 # Mkbootstrap will automatically add dl_findfile() to
182 # the .bs file if it sees a name in the -l format.
183 # USE THIS, when dl_findfile() is fixed:
184 # push(@bsloadlibs, "-l$thislib");
185 # OLD USE WAS while checking results against old_extliblist
186 push(@bsloadlibs, "$fullname");
189 # For SunOS4, do not add in this shared library if
190 # it is already linked in the main perl executable
191 push(@ldloadlibs, "-l$thislib")
192 unless ($in_perl and $^O eq 'sunos');
194 push(@ldloadlibs, "-l$thislib");
197 last; # found one here so don't bother looking further
199 warn "Note (probably harmless): "
200 ."No library found for -l$thislib\n"
203 return ('','','','') unless $found;
204 ("@extralibs", "@bsloadlibs", "@ldloadlibs",join(":",@ld_run_path));
209 require Text::ParseWords;
211 my($self, $potential_libs, $verbose) = @_;
213 # If user did not supply a list, we punt.
214 # (caller should probably use the list in $Config{libs})
215 return ("", "", "", "") unless $potential_libs;
217 my $cc = $Config{cc};
218 my $VC = 1 if $cc =~ /^cl/i;
219 my $BC = 1 if $cc =~ /^bcc/i;
220 my $GC = 1 if $cc =~ /^gcc/i;
221 my $so = $Config{'so'};
222 my $libs = $Config{'perllibs'};
223 my $libpth = $Config{'libpth'};
224 my $libext = $Config{'lib_ext'} || ".lib";
226 if ($libs and $potential_libs !~ /:nodefault/i) {
227 # If Config.pm defines a set of default libs, we always
228 # tack them on to the user-supplied list, unless the user
229 # specified :nodefault
231 $potential_libs .= " " if $potential_libs;
232 $potential_libs .= $libs;
234 warn "Potential libraries are '$potential_libs':\n" if $verbose;
236 # normalize to forward slashes
238 $potential_libs =~ s,\\,/,g;
240 # compute $extralibs from $potential_libs
242 my @searchpath; # from "-L/path" in $potential_libs
243 my @libpath = Text::ParseWords::quotewords('\s+', 0, $libpth);
245 my $pwd = cwd(); # from Cwd.pm
249 my($fullname, $thislib, $thispth);
251 # add "$Config{installarchlib}/CORE" to default search path
252 push @libpath, "$Config{installarchlib}/CORE";
254 if ($VC and exists $ENV{LIB} and $ENV{LIB}) {
255 push @libpath, split /;/, $ENV{LIB};
258 foreach (Text::ParseWords::quotewords('\s+', 0, $potential_libs)){
262 # see if entry is a flag
264 $search = 0 if lc eq ':nosearch';
265 $search = 1 if lc eq ':search';
266 warn "Ignoring unknown flag '$thislib'\n"
267 if $verbose and !/^:(no)?(search|default)$/i;
271 # if searching is disabled, do compiler-specific translations
273 s/^-l(.+)$/$1.lib/ unless $GC;
274 s/^-L/-libpath:/ if $VC;
275 push(@extralibs, $_);
280 # handle possible linker path arguments
281 if (s/^-L// and not -d) {
282 warn "$thislib ignored, directory does not exist\n"
287 unless ($self->file_name_is_absolute($_)) {
288 warn "Warning: '$thislib' changed to '-L$pwd/$_'\n";
289 $_ = $self->catdir($pwd,$_);
291 push(@searchpath, $_);
295 # handle possible library arguments
296 if (s/^-l// and $GC and !/^lib/i) {
299 $_ .= $libext if !/\Q$libext\E$/i;
304 # look for the file itself
306 warn "'$thislib' found as '$_'\n" if $verbose;
308 push(@extralibs, $_);
313 foreach $thispth (@searchpath, @libpath){
314 unless (-f ($fullname="$thispth\\$_")) {
315 warn "'$thislib' not found as '$fullname'\n" if $verbose;
318 warn "'$thislib' found as '$fullname'\n" if $verbose;
321 push(@extralibs, $fullname);
325 # do another pass with (or without) leading 'lib' if they used -l
326 if (!$found_lib and $thislib =~ /^-l/ and !$secondpass++) {
328 goto LOOKAGAIN if s/^lib//i;
337 warn "Note (probably harmless): "
338 ."No library found for '$thislib'\n"
343 return ('','','','') unless $found;
345 # make sure paths with spaces are properly quoted
346 @extralibs = map { (/\s/ && !/^".*"$/) ? qq["$_"] : $_ } @extralibs;
347 $lib = join(' ',@extralibs);
349 # normalize back to backward slashes (to help braindead tools)
350 # XXX this may break equally braindead GNU tools that don't understand
351 # backslashes, either. Seems like one can't win here. Cursed be CP/M.
354 warn "Result: $lib\n" if $verbose;
355 wantarray ? ($lib, '', $lib, '') : $lib;
360 my($self, $potential_libs,$verbose) = @_;
362 my($dbgqual) = $self->{OPTIMIZE} || $Config{'optimize'} ||
363 $self->{CCFLAS} || $Config{'ccflags'};
364 @crtls = ( ($dbgqual =~ m-/Debug-i ? $Config{'dbgprefix'} : '')
366 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'perllibs'});
367 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'libc'});
368 # In general, we pass through the basic libraries from %Config unchanged.
369 # The one exception is that if we're building in the Perl source tree, and
370 # a library spec could be resolved via a logical name, we go to some trouble
371 # to insure that the copy in the local tree is used, rather than one to
372 # which a system-wide logical may point.
373 if ($self->{PERL_SRC}) {
374 my($lib,$locspec,$type);
375 foreach $lib (@crtls) {
376 if (($locspec,$type) = $lib =~ m-^([\w$\-]+)(/\w+)?- and $locspec =~ /perl/i) {
377 if (lc $type eq '/share') { $locspec .= $Config{'exe_ext'}; }
378 elsif (lc $type eq '/library') { $locspec .= $Config{'lib_ext'}; }
379 else { $locspec .= $Config{'obj_ext'}; }
380 $locspec = $self->catfile($self->{PERL_SRC},$locspec);
381 $lib = "$locspec$type" if -e $locspec;
385 $crtlstr = @crtls ? join(' ',@crtls) : '';
387 unless ($potential_libs) {
388 warn "Result:\n\tEXTRALIBS: \n\tLDLOADLIBS: $crtlstr\n" if $verbose;
389 return ('', '', $crtlstr, '');
392 my(@dirs,@libs,$dir,$lib,%found,@fndlibs,$ldlib);
394 my($so,$lib_ext,$obj_ext) = @Config{'so','lib_ext','obj_ext'};
395 # List of common Unix library names and there VMS equivalents
396 # (VMS equivalent of '' indicates that the library is automatially
397 # searched by the linker, and should be skipped here.)
398 my %libmap = ( 'm' => '', 'f77' => '', 'F77' => '', 'V77' => '', 'c' => '',
399 'malloc' => '', 'crypt' => '', 'resolv' => '', 'c_s' => '',
400 'socket' => '', 'X11' => 'DECW$XLIBSHR',
401 'Xt' => 'DECW$XTSHR', 'Xm' => 'DECW$XMLIBSHR',
402 'Xmu' => 'DECW$XMULIBSHR');
403 if ($Config{'vms_cc_type'} ne 'decc') { $libmap{'curses'} = 'VAXCCURSE'; }
405 warn "Potential libraries are '$potential_libs'\n" if $verbose;
407 # First, sort out directories and library names in the input
408 foreach $lib (split ' ',$potential_libs) {
409 push(@dirs,$1), next if $lib =~ /^-L(.*)/;
410 push(@dirs,$lib), next if $lib =~ /[:>\]]$/;
411 push(@dirs,$lib), next if -d $lib;
412 push(@libs,$1), next if $lib =~ /^-l(.*)/;
415 push(@dirs,split(' ',$Config{'libpth'}));
417 # Now make sure we've got VMS-syntax absolute directory specs
418 # (We don't, however, check whether someone's hidden a relative
419 # path in a logical name.)
420 foreach $dir (@dirs) {
422 warn "Skipping nonexistent Directory $dir\n" if $verbose > 1;
426 warn "Resolving directory $dir\n" if $verbose;
427 if ($self->file_name_is_absolute($dir)) { $dir = $self->fixpath($dir,1); }
428 else { $dir = $self->catdir($cwd,$dir); }
430 @dirs = grep { length($_) } @dirs;
431 unshift(@dirs,''); # Check each $lib without additions first
433 LIB: foreach $lib (@libs) {
434 if (exists $libmap{$lib}) {
435 next unless length $libmap{$lib};
436 $lib = $libmap{$lib};
439 my(@variants,$variant,$name,$test,$cand);
442 # If we don't have a file type, consider it a possibly abbreviated name and
443 # check for common variants. We try these first to grab libraries before
444 # a like-named executable image (e.g. -lperl resolves to perlshr.exe
446 if ($lib !~ /\.[^:>\]]*$/) {
447 push(@variants,"${lib}shr","${lib}rtl","${lib}lib");
448 push(@variants,"lib$lib") if $lib !~ /[:>\]]/;
450 push(@variants,$lib);
451 warn "Looking for $lib\n" if $verbose;
452 foreach $variant (@variants) {
453 foreach $dir (@dirs) {
456 $name = "$dir$variant";
457 warn "\tChecking $name\n" if $verbose > 2;
458 if (-f ($test = VMS::Filespec::rmsexpand($name))) {
459 # It's got its own suffix, so we'll have to figure out the type
460 if ($test =~ /(?:$so|exe)$/i) { $type = 'SHR'; }
461 elsif ($test =~ /(?:$lib_ext|olb)$/i) { $type = 'OLB'; }
462 elsif ($test =~ /(?:$obj_ext|obj)$/i) {
463 warn "Note (probably harmless): "
464 ."Plain object file $test found in library list\n";
468 warn "Note (probably harmless): "
469 ."Unknown library type for $test; assuming shared\n";
473 elsif (-f ($test = VMS::Filespec::rmsexpand($name,$so)) or
474 -f ($test = VMS::Filespec::rmsexpand($name,'.exe'))) {
476 $name = $test unless $test =~ /exe;?\d*$/i;
478 elsif (not length($ctype) and # If we've got a lib already, don't bother
479 ( -f ($test = VMS::Filespec::rmsexpand($name,$lib_ext)) or
480 -f ($test = VMS::Filespec::rmsexpand($name,'.olb')))) {
482 $name = $test unless $test =~ /olb;?\d*$/i;
484 elsif (not length($ctype) and # If we've got a lib already, don't bother
485 ( -f ($test = VMS::Filespec::rmsexpand($name,$obj_ext)) or
486 -f ($test = VMS::Filespec::rmsexpand($name,'.obj')))) {
487 warn "Note (probably harmless): "
488 ."Plain object file $test found in library list\n";
490 $name = $test unless $test =~ /obj;?\d*$/i;
493 $ctype = $type; $cand = $name;
494 last if $ctype eq 'SHR';
498 # This has to precede any other CRTLs, so just make it first
499 if ($cand eq 'VAXCCURSE') { unshift @{$found{$ctype}}, $cand; }
500 else { push @{$found{$ctype}}, $cand; }
501 warn "\tFound as $cand (really $test), type $ctype\n" if $verbose > 1;
505 warn "Note (probably harmless): "
506 ."No library found for $lib\n";
509 push @fndlibs, @{$found{OBJ}} if exists $found{OBJ};
510 push @fndlibs, map { "$_/Library" } @{$found{OLB}} if exists $found{OLB};
511 push @fndlibs, map { "$_/Share" } @{$found{SHR}} if exists $found{SHR};
512 $lib = join(' ',@fndlibs);
514 $ldlib = $crtlstr ? "$lib $crtlstr" : $lib;
515 warn "Result:\n\tEXTRALIBS: $lib\n\tLDLOADLIBS: $ldlib\n" if $verbose;
516 wantarray ? ($lib, '', $ldlib, '') : $lib;
525 ExtUtils::Liblist - determine libraries to use and how to use them
529 C<require ExtUtils::Liblist;>
531 C<ExtUtils::Liblist::ext($self, $potential_libs, $verbose);>
535 This utility takes a list of libraries in the form C<-llib1 -llib2
536 -llib3> and prints out lines suitable for inclusion in an extension
537 Makefile. Extra library paths may be included with the form
538 C<-L/another/path> this will affect the searches for all subsequent
541 It returns an array of four scalar values: EXTRALIBS, BSLOADLIBS,
542 LDLOADLIBS, and LD_RUN_PATH. Some of these don't mean anything
543 on VMS and Win32. See the details about those platform specifics
546 Dependent libraries can be linked in one of three ways:
550 =item * For static extensions
552 by the ld command when the perl binary is linked with the extension
553 library. See EXTRALIBS below.
555 =item * For dynamic extensions
557 by the ld command when the shared object is built/linked. See
560 =item * For dynamic extensions
562 by the DynaLoader when the shared object is loaded. See BSLOADLIBS
569 List of libraries that need to be linked with when linking a perl
570 binary which includes this extension. Only those libraries that
571 actually exist are included. These are written to a file and used
574 =head2 LDLOADLIBS and LD_RUN_PATH
576 List of those libraries which can or must be linked into the shared
577 library when created using ld. These may be static or dynamic
578 libraries. LD_RUN_PATH is a colon separated list of the directories
579 in LDLOADLIBS. It is passed as an environment variable to the process
580 that links the shared library.
584 List of those libraries that are needed but can be linked in
585 dynamically at run time on this platform. SunOS/Solaris does not need
586 this because ld records the information (from LDLOADLIBS) into the
587 object file. This list is used to create a .bs (bootstrap) file.
591 This module deals with a lot of system dependencies and has quite a
592 few architecture specific C<if>s in the code.
594 =head2 VMS implementation
596 The version of ext() which is executed under VMS differs from the
597 Unix-OS/2 version in several respects:
603 Input library and path specifications are accepted with or without the
604 C<-l> and C<-L> prefixes used by Unix linkers. If neither prefix is
605 present, a token is considered a directory to search if it is in fact
606 a directory, and a library to search for otherwise. Authors who wish
607 their extensions to be portable to Unix or OS/2 should use the Unix
608 prefixes, since the Unix-OS/2 version of ext() requires them.
612 Wherever possible, shareable images are preferred to object libraries,
613 and object libraries to plain object files. In accordance with VMS
614 naming conventions, ext() looks for files named I<lib>shr and I<lib>rtl;
615 it also looks for I<lib>lib and libI<lib> to accommodate Unix conventions
616 used in some ported software.
620 For each library that is found, an appropriate directive for a linker options
621 file is generated. The return values are space-separated strings of
622 these directives, rather than elements used on the linker command line.
626 LDLOADLIBS contains both the libraries found based on C<$potential_libs> and
627 the CRTLs, if any, specified in Config.pm. EXTRALIBS contains just those
628 libraries found based on C<$potential_libs>. BSLOADLIBS and LD_RUN_PATH
633 In addition, an attempt is made to recognize several common Unix library
634 names, and filter them out or convert them to their VMS equivalents, as
637 In general, the VMS version of ext() should properly handle input from
638 extensions originally designed for a Unix or VMS environment. If you
639 encounter problems, or discover cases where the search could be improved,
642 =head2 Win32 implementation
644 The version of ext() which is executed under Win32 differs from the
645 Unix-OS/2 version in several respects:
651 If C<$potential_libs> is empty, the return value will be empty.
652 Otherwise, the libraries specified by C<$Config{perllibs}> (see Config.pm)
653 will be appended to the list of C<$potential_libs>. The libraries
654 will be searched for in the directories specified in C<$potential_libs>,
655 C<$Config{libpth}>, and in C<$Config{installarchlib}/CORE>.
656 For each library that is found, a space-separated list of fully qualified
657 library pathnames is generated.
661 Input library and path specifications are accepted with or without the
662 C<-l> and C<-L> prefixes used by Unix linkers.
664 An entry of the form C<-La:\foo> specifies the C<a:\foo> directory to look
665 for the libraries that follow.
667 An entry of the form C<-lfoo> specifies the library C<foo>, which may be
668 spelled differently depending on what kind of compiler you are using. If
669 you are using GCC, it gets translated to C<libfoo.a>, but for other win32
670 compilers, it becomes C<foo.lib>. If no files are found by those translated
671 names, one more attempt is made to find them using either C<foo.a> or
672 C<libfoo.lib>, depending on whether GCC or some other win32 compiler is
673 being used, respectively.
675 If neither the C<-L> or C<-l> prefix is present in an entry, the entry is
676 considered a directory to search if it is in fact a directory, and a
677 library to search for otherwise. The C<$Config{lib_ext}> suffix will
678 be appended to any entries that are not directories and don't already have
681 Note that the C<-L> and C<-l> prefixes are B<not required>, but authors
682 who wish their extensions to be portable to Unix or OS/2 should use the
683 prefixes, since the Unix-OS/2 version of ext() requires them.
687 Entries cannot be plain object files, as many Win32 compilers will
688 not handle object files in the place of libraries.
692 Entries in C<$potential_libs> beginning with a colon and followed by
693 alphanumeric characters are treated as flags. Unknown flags will be ignored.
695 An entry that matches C</:nodefault/i> disables the appending of default
696 libraries found in C<$Config{perllibs}> (this should be only needed very rarely).
698 An entry that matches C</:nosearch/i> disables all searching for
699 the libraries specified after it. Translation of C<-Lfoo> and
700 C<-lfoo> still happens as appropriate (depending on compiler being used,
701 as reflected by C<$Config{cc}>), but the entries are not verified to be
702 valid files or directories.
704 An entry that matches C</:search/i> reenables searching for
705 the libraries specified after it. You can put it at the end to
706 enable searching for default libraries specified by C<$Config{perllibs}>.
710 The libraries specified may be a mixture of static libraries and
711 import libraries (to link with DLLs). Since both kinds are used
712 pretty transparently on the Win32 platform, we do not attempt to
713 distinguish between them.
717 LDLOADLIBS and EXTRALIBS are always identical under Win32, and BSLOADLIBS
718 and LD_RUN_PATH are always empty (this may change in future).
722 You must make sure that any paths and path components are properly
723 surrounded with double-quotes if they contain spaces. For example,
724 C<$potential_libs> could be (literally):
726 "-Lc:\Program Files\vc\lib" msvcrt.lib "la test\foo bar.lib"
728 Note how the first and last entries are protected by quotes in order
729 to protect the spaces.
733 Since this module is most often used only indirectly from extension
734 C<Makefile.PL> files, here is an example C<Makefile.PL> entry to add
735 a library to the build process for an extension:
739 When using GCC, that entry specifies that MakeMaker should first look
740 for C<libgl.a> (followed by C<gl.a>) in all the locations specified by
743 When using a compiler other than GCC, the above entry will search for
744 C<gl.lib> (followed by C<libgl.lib>).
746 If the library happens to be in a location not in C<$Config{libpth}>,
749 LIBS => ['-Lc:\gllibs -lgl']
751 Here is a less often used example:
753 LIBS => ['-lgl', ':nosearch -Ld:\mesalibs -lmesa -luser32']
755 This specifies a search for library C<gl> as before. If that search
756 fails to find the library, it looks at the next item in the list. The
757 C<:nosearch> flag will prevent searching for the libraries that follow,
758 so it simply returns the value as C<-Ld:\mesalibs -lmesa -luser32>,
759 since GCC can use that value as is with its linker.
761 When using the Visual C compiler, the second item is returned as
762 C<-libpath:d:\mesalibs mesa.lib user32.lib>.
764 When using the Borland compiler, the second item is returned as
765 C<-Ld:\mesalibs mesa.lib user32.lib>, and MakeMaker takes care of
766 moving the C<-Ld:\mesalibs> to the correct place in the linker
774 L<ExtUtils::MakeMaker>