[win32] minor cleanup
[p5sagit/p5-mst-13.2.git] / lib / ExtUtils / Liblist.pm
CommitLineData
005c1a0e 1package ExtUtils::Liblist;
8a1da95f 2use vars qw($VERSION);
005c1a0e 3# Broken out of MakeMaker from version 4.11
4
84902520 5$VERSION = substr q$Revision: 1.25 $, 10;
f1387719 6
005c1a0e 7use Config;
8f1aa56b 8use Cwd 'cwd';
4633a7c4 9use File::Basename;
10
005c1a0e 11sub ext {
3e3baf6d 12 if ($^O eq 'VMS') { return &_vms_ext; }
13 elsif($^O eq 'MSWin32') { return &_win32_ext; }
14 else { return &_unix_os2_ext; }
55497cff 15}
16
17sub _unix_os2_ext {
e611f912 18 my($self,$potential_libs, $verbose) = @_;
f1387719 19 if ($^O =~ 'os2' and $Config{libs}) {
4e68a208 20 # Dynamic libraries are not transitive, so we may need including
21 # the libraries linked against perl.dll again.
22
23 $potential_libs .= " " if $potential_libs;
24 $potential_libs .= $Config{libs};
25 }
4633a7c4 26 return ("", "", "", "") unless $potential_libs;
fb73857a 27 warn "Potential libraries are '$potential_libs':\n" if $verbose;
005c1a0e 28
29 my($so) = $Config{'so'};
30 my($libs) = $Config{'libs'};
55497cff 31 my $Config_libext = $Config{lib_ext} || ".a";
32
005c1a0e 33
34 # compute $extralibs, $bsloadlibs and $ldloadlibs from
35 # $potential_libs
36 # this is a rewrite of Andy Dougherty's extliblist in perl
005c1a0e 37
38 my(@searchpath); # from "-L/path" entries in $potential_libs
39 my(@libpath) = split " ", $Config{'libpth'};
4633a7c4 40 my(@ldloadlibs, @bsloadlibs, @extralibs, @ld_run_path, %ld_run_path_seen);
005c1a0e 41 my($fullname, $thislib, $thispth, @fullname);
8f1aa56b 42 my($pwd) = cwd(); # from Cwd.pm
005c1a0e 43 my($found) = 0;
44
45 foreach $thislib (split ' ', $potential_libs){
46
47 # Handle possible linker path arguments.
48 if ($thislib =~ s/^(-[LR])//){ # save path flag type
49 my($ptype) = $1;
50 unless (-d $thislib){
fb73857a 51 warn "$ptype$thislib ignored, directory does not exist\n"
e611f912 52 if $verbose;
005c1a0e 53 next;
54 }
f1387719 55 unless ($self->file_name_is_absolute($thislib)) {
fb73857a 56 warn "Warning: $ptype$thislib changed to $ptype$pwd/$thislib\n";
f1387719 57 $thislib = $self->catdir($pwd,$thislib);
005c1a0e 58 }
59 push(@searchpath, $thislib);
60 push(@extralibs, "$ptype$thislib");
61 push(@ldloadlibs, "$ptype$thislib");
62 next;
63 }
64
65 # Handle possible library arguments.
66 unless ($thislib =~ s/^-l//){
fb73857a 67 warn "Unrecognized argument in LIBS ignored: '$thislib'\n";
005c1a0e 68 next;
69 }
70
71 my($found_lib)=0;
72 foreach $thispth (@searchpath, @libpath){
73
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.
4e1fac24 80 if (@fullname =
81 $self->lsdir($thispth,"^\Qlib$thislib.$so.\E[0-9]+")){
005c1a0e 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
93 # first element.
94
95 #TODO: iterate through the directory instead of sorting
96
97 $fullname = "$thispth/" .
98 (sort { my($ma) = $a;
99 my($mb) = $b;
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") || ($thislib eq "m"))){
4633a7c4 110 } elsif (-f ($fullname="$thispth/lib${thislib}_s$Config_libext")
005c1a0e 111 && ($thislib .= "_s") ){ # we must explicitly use _s version
4633a7c4 112 } elsif (-f ($fullname="$thispth/lib$thislib$Config_libext")){
864a5fa8 113 } elsif (-f ($fullname="$thispth/$thislib$Config_libext")){
4633a7c4 114 } elsif (-f ($fullname="$thispth/Slib$thislib$Config_libext")){
8f1aa56b 115 } elsif ($^O eq 'dgux'
c07a80fd 116 && -l ($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
120 # look like this:
121 #
122 # libm.a -> elink:${SDE_PATH:-/usr}/sde/\
123 # ${TARGET_BINARY_INTERFACE:-m88kdgux}/usr/lib/libm.a
124 #
125 # , the compilation tools expand the environment variables.)
005c1a0e 126 } else {
fb73857a 127 warn "$thislib not found in $thispth\n" if $verbose;
005c1a0e 128 next;
129 }
fb73857a 130 warn "'-l$thislib' found at $fullname\n" if $verbose;
4633a7c4 131 my($fullnamedir) = dirname($fullname);
132 push @ld_run_path, $fullnamedir unless $ld_run_path_seen{$fullnamedir}++;
005c1a0e 133 $found++;
134 $found_lib++;
135
136 # Now update library lists
137
138 # what do we know about this library...
4633a7c4 139 my $is_dyna = ($fullname !~ /\Q$Config_libext\E$/);
4e68a208 140 my $in_perl = ($libs =~ /\B-l\Q$ {thislib}\E\b/s);
005c1a0e 141
142 # Do not add it into the list if it is already linked in
143 # with the main perl executable.
974f612f 144 # We have to special-case the NeXT, because math and ndbm
145 # are both in libsys_s
005c1a0e 146 unless ($in_perl ||
974f612f 147 ($Config{'osname'} eq 'next' &&
148 ($thislib eq 'm' || $thislib eq 'ndbm')) ){
005c1a0e 149 push(@extralibs, "-l$thislib");
150 }
151
152 # We might be able to load this archive file dynamically
974f612f 153 if ( ($Config{'dlsrc'} =~ /dl_next/ && $Config{'osvers'} lt '4_0')
154 || ($Config{'dlsrc'} =~ /dl_dld/) )
155 {
005c1a0e 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, "$fullname");
164 } else {
165 if ($is_dyna){
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$thislib")
8f1aa56b 169 unless ($in_perl and $^O eq 'sunos');
005c1a0e 170 } else {
171 push(@ldloadlibs, "-l$thislib");
172 }
173 }
174 last; # found one here so don't bother looking further
175 }
fb73857a 176 warn "Note (probably harmless): "
f3d9a6ba 177 ."No library found for -l$thislib\n"
005c1a0e 178 unless $found_lib>0;
179 }
4633a7c4 180 return ('','','','') unless $found;
181 ("@extralibs", "@bsloadlibs", "@ldloadlibs",join(":",@ld_run_path));
005c1a0e 182}
183
3e3baf6d 184sub _win32_ext {
e611f912 185 my($self, $potential_libs, $verbose) = @_;
3e3baf6d 186
187 # If user did not supply a list, we punt.
188 # (caller should probably use the list in $Config{libs})
189 return ("", "", "", "") unless $potential_libs;
190
191 my($so) = $Config{'so'};
192 my($libs) = $Config{'libs'};
193 my($libpth) = $Config{'libpth'};
194 my($libext) = $Config{'lib_ext'} || ".lib";
195
196 if ($libs and $potential_libs !~ /:nodefault/i) {
197 # If Config.pm defines a set of default libs, we always
198 # tack them on to the user-supplied list, unless the user
199 # specified :nodefault
200
201 $potential_libs .= " " if $potential_libs;
202 $potential_libs .= $libs;
203 }
fb73857a 204 warn "Potential libraries are '$potential_libs':\n" if $verbose;
3e3baf6d 205
206 # compute $extralibs from $potential_libs
207
208 my(@searchpath); # from "-L/path" entries in $potential_libs
209 my(@libpath) = split " ", $libpth;
210 my(@extralibs);
211 my($fullname, $thislib, $thispth);
212 my($pwd) = cwd(); # from Cwd.pm
213 my($lib) = '';
214 my($found) = 0;
215
216 foreach $thislib (split ' ', $potential_libs){
217
218 # Handle possible linker path arguments.
219 if ($thislib =~ s/^-L// and not -d $thislib) {
fb73857a 220 warn "-L$thislib ignored, directory does not exist\n"
e611f912 221 if $verbose;
3e3baf6d 222 next;
223 }
224 elsif (-d $thislib) {
225 unless ($self->file_name_is_absolute($thislib)) {
fb73857a 226 warn "Warning: -L$thislib changed to -L$pwd/$thislib\n";
3e3baf6d 227 $thislib = $self->catdir($pwd,$thislib);
228 }
229 push(@searchpath, $thislib);
230 next;
231 }
232
233 # Handle possible library arguments.
2d7a9237 234 if ($thislib =~ s/^-l// and $thislib !~ /^lib/i) {
235 $thislib = "lib$thislib";
236 }
3e3baf6d 237 $thislib .= $libext if $thislib !~ /\Q$libext\E$/i;
238
239 my($found_lib)=0;
240 foreach $thispth (@searchpath, @libpath){
241 unless (-f ($fullname="$thispth\\$thislib")) {
fb73857a 242 warn "$thislib not found in $thispth\n" if $verbose;
3e3baf6d 243 next;
244 }
fb73857a 245 warn "'$thislib' found at $fullname\n" if $verbose;
3e3baf6d 246 $found++;
247 $found_lib++;
248 push(@extralibs, $fullname);
249 last;
250 }
fb73857a 251 warn "Note (probably harmless): "
3e3baf6d 252 ."No library found for '$thislib'\n"
253 unless $found_lib>0;
254 }
255 return ('','','','') unless $found;
256 $lib = join(' ',@extralibs);
fb73857a 257 warn "Result: $lib\n" if $verbose;
3e3baf6d 258 wantarray ? ($lib, '', $lib, '') : $lib;
259}
260
55497cff 261
262sub _vms_ext {
263 my($self, $potential_libs,$verbose) = @_;
09b7f37c 264 my(@crtls,$crtlstr);
265 my($dbgqual) = $self->{OPTIMIZE} || $Config{'optimize'} ||
266 $self->{CCFLAS} || $Config{'ccflags'};
267 @crtls = ( ($dbgqual =~ m-/Debug-i ? $Config{'dbgprefix'} : '')
268 . 'PerlShr/Share' );
269 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'libs'});
270 push(@crtls, grep { not /\(/ } split /\s+/, $Config{'libc'});
271 # In general, we pass through the basic libraries from %Config unchanged.
272 # The one exception is that if we're building in the Perl source tree, and
273 # a library spec could be resolved via a logical name, we go to some trouble
274 # to insure that the copy in the local tree is used, rather than one to
275 # which a system-wide logical may point.
276 if ($self->{PERL_SRC}) {
277 my($lib,$locspec,$type);
278 foreach $lib (@crtls) {
279 if (($locspec,$type) = $lib =~ m-^([\w$\-]+)(/\w+)?- and $locspec =~ /perl/i) {
280 if (lc $type eq '/share') { $locspec .= $Config{'exe_ext'}; }
281 elsif (lc $type eq '/library') { $locspec .= $Config{'lib_ext'}; }
282 else { $locspec .= $Config{'obj_ext'}; }
283 $locspec = $self->catfile($self->{PERL_SRC},$locspec);
284 $lib = "$locspec$type" if -e $locspec;
285 }
286 }
287 }
288 $crtlstr = @crtls ? join(' ',@crtls) : '';
55497cff 289
09b7f37c 290 unless ($potential_libs) {
291 warn "Result:\n\tEXTRALIBS: \n\tLDLOADLIBS: $crtlstr\n" if $verbose;
292 return ('', '', $crtlstr, '');
293 }
294
295 my(@dirs,@libs,$dir,$lib,%sh,%olb,%obj,$ldlib);
55497cff 296 my $cwd = cwd();
297 my($so,$lib_ext,$obj_ext) = @Config{'so','lib_ext','obj_ext'};
298 # List of common Unix library names and there VMS equivalents
299 # (VMS equivalent of '' indicates that the library is automatially
300 # searched by the linker, and should be skipped here.)
301 my %libmap = ( 'm' => '', 'f77' => '', 'F77' => '', 'V77' => '', 'c' => '',
302 'malloc' => '', 'crypt' => '', 'resolv' => '', 'c_s' => '',
303 'socket' => '', 'X11' => 'DECW$XLIBSHR',
304 'Xt' => 'DECW$XTSHR', 'Xm' => 'DECW$XMLIBSHR',
305 'Xmu' => 'DECW$XMULIBSHR');
306 if ($Config{'vms_cc_type'} ne 'decc') { $libmap{'curses'} = 'VAXCCURSE'; }
307
fb73857a 308 warn "Potential libraries are '$potential_libs'\n" if $verbose;
55497cff 309
310 # First, sort out directories and library names in the input
311 foreach $lib (split ' ',$potential_libs) {
312 push(@dirs,$1), next if $lib =~ /^-L(.*)/;
313 push(@dirs,$lib), next if $lib =~ /[:>\]]$/;
314 push(@dirs,$lib), next if -d $lib;
315 push(@libs,$1), next if $lib =~ /^-l(.*)/;
316 push(@libs,$lib);
317 }
318 push(@dirs,split(' ',$Config{'libpth'}));
319
320 # Now make sure we've got VMS-syntax absolute directory specs
321 # (We don't, however, check whether someone's hidden a relative
322 # path in a logical name.)
323 foreach $dir (@dirs) {
324 unless (-d $dir) {
fb73857a 325 warn "Skipping nonexistent Directory $dir\n" if $verbose > 1;
55497cff 326 $dir = '';
327 next;
328 }
fb73857a 329 warn "Resolving directory $dir\n" if $verbose;
55497cff 330 if ($self->file_name_is_absolute($dir)) { $dir = $self->fixpath($dir,1); }
331 else { $dir = $self->catdir($cwd,$dir); }
332 }
333 @dirs = grep { length($_) } @dirs;
334 unshift(@dirs,''); # Check each $lib without additions first
335
336 LIB: foreach $lib (@libs) {
337 if (exists $libmap{$lib}) {
338 next unless length $libmap{$lib};
339 $lib = $libmap{$lib};
340 }
341
342 my(@variants,$variant,$name,$test,$cand);
343 my($ctype) = '';
344
345 # If we don't have a file type, consider it a possibly abbreviated name and
346 # check for common variants. We try these first to grab libraries before
347 # a like-named executable image (e.g. -lperl resolves to perlshr.exe
348 # before perl.exe).
349 if ($lib !~ /\.[^:>\]]*$/) {
350 push(@variants,"${lib}shr","${lib}rtl","${lib}lib");
351 push(@variants,"lib$lib") if $lib !~ /[:>\]]/;
352 }
353 push(@variants,$lib);
fb73857a 354 warn "Looking for $lib\n" if $verbose;
55497cff 355 foreach $variant (@variants) {
356 foreach $dir (@dirs) {
357 my($type);
358
359 $name = "$dir$variant";
fb73857a 360 warn "\tChecking $name\n" if $verbose > 2;
55497cff 361 if (-f ($test = VMS::Filespec::rmsexpand($name))) {
362 # It's got its own suffix, so we'll have to figure out the type
363 if ($test =~ /(?:$so|exe)$/i) { $type = 'sh'; }
364 elsif ($test =~ /(?:$lib_ext|olb)$/i) { $type = 'olb'; }
365 elsif ($test =~ /(?:$obj_ext|obj)$/i) {
fb73857a 366 warn "Note (probably harmless): "
f3d9a6ba 367 ."Plain object file $test found in library list\n";
55497cff 368 $type = 'obj';
369 }
370 else {
fb73857a 371 warn "Note (probably harmless): "
f3d9a6ba 372 ."Unknown library type for $test; assuming shared\n";
55497cff 373 $type = 'sh';
374 }
375 }
376 elsif (-f ($test = VMS::Filespec::rmsexpand($name,$so)) or
377 -f ($test = VMS::Filespec::rmsexpand($name,'.exe'))) {
378 $type = 'sh';
379 $name = $test unless $test =~ /exe;?\d*$/i;
380 }
381 elsif (not length($ctype) and # If we've got a lib already, don't bother
382 ( -f ($test = VMS::Filespec::rmsexpand($name,$lib_ext)) or
383 -f ($test = VMS::Filespec::rmsexpand($name,'.olb')))) {
384 $type = 'olb';
385 $name = $test unless $test =~ /olb;?\d*$/i;
386 }
387 elsif (not length($ctype) and # If we've got a lib already, don't bother
388 ( -f ($test = VMS::Filespec::rmsexpand($name,$obj_ext)) or
389 -f ($test = VMS::Filespec::rmsexpand($name,'.obj')))) {
fb73857a 390 warn "Note (probably harmless): "
f3d9a6ba 391 ."Plain object file $test found in library list\n";
55497cff 392 $type = 'obj';
393 $name = $test unless $test =~ /obj;?\d*$/i;
394 }
395 if (defined $type) {
396 $ctype = $type; $cand = $name;
397 last if $ctype eq 'sh';
398 }
399 }
400 if ($ctype) {
401 eval '$' . $ctype . "{'$cand'}++";
402 die "Error recording library: $@" if $@;
fb73857a 403 warn "\tFound as $cand (really $test), type $ctype\n" if $verbose > 1;
55497cff 404 next LIB;
405 }
406 }
fb73857a 407 warn "Note (probably harmless): "
f3d9a6ba 408 ."No library found for $lib\n";
55497cff 409 }
410
411 @libs = sort keys %obj;
412 # This has to precede any other CRTLs, so just make it first
413 if ($olb{VAXCCURSE}) {
414 push(@libs,"$olb{VAXCCURSE}/Library");
415 delete $olb{VAXCCURSE};
416 }
417 push(@libs, map { "$_/Library" } sort keys %olb);
418 push(@libs, map { "$_/Share" } sort keys %sh);
419 $lib = join(' ',@libs);
09b7f37c 420
421 $ldlib = $crtlstr ? "$lib $crtlstr" : $lib;
422 warn "Result:\n\tEXTRALIBS: $lib\n\tLDLOADLIBS: $ldlib\n" if $verbose;
423 wantarray ? ($lib, '', $ldlib, '') : $lib;
55497cff 424}
425
005c1a0e 4261;
c2e89b3d 427
864a5fa8 428__END__
cb1a09d0 429
864a5fa8 430=head1 NAME
431
432ExtUtils::Liblist - determine libraries to use and how to use them
433
434=head1 SYNOPSIS
435
436C<require ExtUtils::Liblist;>
437
e611f912 438C<ExtUtils::Liblist::ext($self, $potential_libs, $verbose);>
864a5fa8 439
440=head1 DESCRIPTION
441
442This utility takes a list of libraries in the form C<-llib1 -llib2
443-llib3> and prints out lines suitable for inclusion in an extension
444Makefile. Extra library paths may be included with the form
445C<-L/another/path> this will affect the searches for all subsequent
446libraries.
447
448It returns an array of four scalar values: EXTRALIBS, BSLOADLIBS,
3e3baf6d 449LDLOADLIBS, and LD_RUN_PATH. Some of these don't mean anything
450on VMS and Win32. See the details about those platform specifics
451below.
864a5fa8 452
453Dependent libraries can be linked in one of three ways:
454
455=over 2
456
457=item * For static extensions
458
459by the ld command when the perl binary is linked with the extension
460library. See EXTRALIBS below.
461
462=item * For dynamic extensions
463
464by the ld command when the shared object is built/linked. See
465LDLOADLIBS below.
466
467=item * For dynamic extensions
468
469by the DynaLoader when the shared object is loaded. See BSLOADLIBS
470below.
471
472=back
473
474=head2 EXTRALIBS
475
476List of libraries that need to be linked with when linking a perl
477binary which includes this extension Only those libraries that
478actually exist are included. These are written to a file and used
479when linking perl.
480
481=head2 LDLOADLIBS and LD_RUN_PATH
482
483List of those libraries which can or must be linked into the shared
484library when created using ld. These may be static or dynamic
485libraries. LD_RUN_PATH is a colon separated list of the directories
486in LDLOADLIBS. It is passed as an environment variable to the process
487that links the shared library.
488
489=head2 BSLOADLIBS
490
491List of those libraries that are needed but can be linked in
492dynamically at run time on this platform. SunOS/Solaris does not need
493this because ld records the information (from LDLOADLIBS) into the
494object file. This list is used to create a .bs (bootstrap) file.
495
496=head1 PORTABILITY
497
498This module deals with a lot of system dependencies and has quite a
499few architecture specific B<if>s in the code.
500
55497cff 501=head2 VMS implementation
502
503The version of ext() which is executed under VMS differs from the
504Unix-OS/2 version in several respects:
505
506=over 2
507
508=item *
509
510Input library and path specifications are accepted with or without the
511C<-l> and C<-L> prefices used by Unix linkers. If neither prefix is
512present, a token is considered a directory to search if it is in fact
513a directory, and a library to search for otherwise. Authors who wish
514their extensions to be portable to Unix or OS/2 should use the Unix
515prefixes, since the Unix-OS/2 version of ext() requires them.
516
517=item *
518
519Wherever possible, shareable images are preferred to object libraries,
520and object libraries to plain object files. In accordance with VMS
521naming conventions, ext() looks for files named I<lib>shr and I<lib>rtl;
522it also looks for I<lib>lib and libI<lib> to accomodate Unix conventions
523used in some ported software.
524
525=item *
526
527For each library that is found, an appropriate directive for a linker options
528file is generated. The return values are space-separated strings of
529these directives, rather than elements used on the linker command line.
530
531=item *
532
09b7f37c 533LDLOADLIBS contains both the libraries found based on C<$potential_libs> and
534the CRTLs, if any, specified in Config.pm. EXTRALIBS contains just those
535libraries found based on C<$potential_libs>. BSLOADLIBS and LD_RUN_PATH
536are always empty.
55497cff 537
538=back
539
540In addition, an attempt is made to recognize several common Unix library
541names, and filter them out or convert them to their VMS equivalents, as
542appropriate.
543
544In general, the VMS version of ext() should properly handle input from
545extensions originally designed for a Unix or VMS environment. If you
546encounter problems, or discover cases where the search could be improved,
547please let us know.
548
3e3baf6d 549=head2 Win32 implementation
550
551The version of ext() which is executed under Win32 differs from the
552Unix-OS/2 version in several respects:
553
554=over 2
555
556=item *
557
558Input library and path specifications are accepted with or without the
559C<-l> and C<-L> prefices used by Unix linkers. C<-lfoo> specifies the
2d7a9237 560library C<libfoo.lib> (unless C<foo> already starts with C<lib>), and
561C<-Ls:ome\dir> specifies a directory to look for the libraries that follow.
562If neither prefix is present, a token is considered a directory to search
563if it is in fact a directory, and a library to search for otherwise. The
564C<$Config{lib_ext}> suffix will be appended to any entries that are not
565directories and don't already have the suffix. Authors who wish their
566extensions to be portable to Unix or OS/2 should use the Unix prefixes,
567since the Unix-OS/2 version of ext() requires them.
3e3baf6d 568
569=item *
570
571Entries cannot be plain object files, as many Win32 compilers will
572not handle object files in the place of libraries.
573
574=item *
575
576If C<$potential_libs> is empty, the return value will be empty.
577Otherwise, the libraries specified by C<$Config{libs}> (see Config.pm)
578will be appended to the list of C<$potential_libs>. The libraries
579will be searched for in the directories specified in C<$potential_libs>
580as well as in C<$Config{libpth}>. For each library that is found, a
581space-separated list of fully qualified library pathnames is generated.
582You may specify an entry that matches C</:nodefault/i> in
583C<$potential_libs> to disable the appending of default libraries
584found in C<$Config{libs}> (this should be only needed very rarely).
585
586=item *
587
588The libraries specified may be a mixture of static libraries and
589import libraries (to link with DLLs). Since both kinds are used
590pretty transparently on the win32 platform, we do not attempt to
591distinguish between them.
592
593=item *
594
595LDLOADLIBS and EXTRALIBS are always identical under Win32, and BSLOADLIBS
596and LD_RUN_PATH are always empty (this may change in future).
597
598=back
599
600
864a5fa8 601=head1 SEE ALSO
602
603L<ExtUtils::MakeMaker>
604
605=cut
606