This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Auto-generated from global.sym and interp.sym.
[perl5.git] / ext / DynaLoader / DynaLoader.pm
CommitLineData
a0d0e21e
LW
1package DynaLoader;
2
8e07c86e
AD
3# And Gandalf said: 'Many folk like to know beforehand what is to
4# be set on the table; but those who have laboured to prepare the
5# feast like to keep their secret; for wonder makes the words of
6# praise louder.'
7
8# (Quote from Tolkien sugested by Anno Siegel.)
9#
10# See pod text at end of file for documentation.
11# See also ext/DynaLoader/README in source tree for other information.
12#
13# Tim.Bunce@ig.co.uk, August 1994
14
15require Carp;
16require Config;
17require AutoLoader;
18
19@ISA=qw(AutoLoader);
20
21
22sub import { } # override import inherited from AutoLoader
23
24# enable debug/trace messages from DynaLoader perl code
25$dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
26
27($dl_dlext, $dlsrc, $osname)
28 = @Config::Config{'dlext', 'dlsrc', 'osname'};
29
30# Some systems need special handling to expand file specifications
31# (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
32# See dl_expandspec() for more details. Should be harmless but
33# inefficient to define on systems that don't need it.
34$do_expand = ($osname eq 'VMS');
35
36@dl_require_symbols = (); # names of symbols we need
37@dl_resolve_using = (); # names of files to link with
38@dl_library_path = (); # path to look for files
39
40# This is a fix to support DLD's unfortunate desire to relink -lc
41@dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
42
43# Initialise @dl_library_path with the 'standard' library path
44# for this platform as determined by Configure
45push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
46
47# Add to @dl_library_path any extra directories we can gather from
48# environment variables. So far LD_LIBRARY_PATH is the only known
49# variable used for this purpose. Others may be added later.
50push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
51 if $ENV{LD_LIBRARY_PATH};
52
53
54# No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
55boot_DynaLoader() if defined(&boot_DynaLoader);
56
57
58if ($dl_debug) {
59 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
60 print STDERR "DynaLoader not linked into this perl\n"
61 unless defined(&boot_DynaLoader);
62}
63
641; # End of main code
65
66
67# The bootstrap function cannot be autoloaded (without complications)
68# so we define it here:
69
70sub bootstrap {
71 # use local vars to enable $module.bs script to edit values
72 local(@args) = @_;
73 local($module) = $args[0];
74 local(@dirs, $file);
75
4633a7c4 76 Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module;
8e07c86e
AD
77
78 # A common error on platforms which don't support dynamic loading.
79 # Since it's fatal and potentially confusing we give a detailed message.
80 Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n".
81 " (You may need to build a new perl executable which either supports\n".
82 " dynamic loading or has the $module module statically linked into it.)\n")
83 unless defined(&dl_load_file);
84
85 my @modparts = split(/::/,$module);
86 my $modfname = $modparts[-1];
87
88 # Some systems have restrictions on files names for DLL's etc.
89 # mod2fname returns appropriate file base name (typically truncated)
90 # It may also edit @modparts if required.
91 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
92
93 my $modpname = join('/',@modparts);
94
95 print STDERR "DynaLoader::bootstrap for $module ",
96 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
97
98 foreach (@INC) {
99 my $dir = "$_/auto/$modpname";
100 next unless -d $dir; # skip over uninteresting directories
101
102 # check for common cases to avoid autoload of dl_findfile
103 last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
104
105 # no luck here, save dir for possible later dl_findfile search
106 push(@dirs, "-L$dir");
107 }
108 # last resort, let dl_findfile have a go in all known locations
109 $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
110
4633a7c4 111 Carp::croak("Can't find loadable object for module $module in \@INC (@INC)")
8e07c86e
AD
112 unless $file;
113
114 my $bootname = "boot_$module";
115 $bootname =~ s/\W/_/g;
116 @dl_require_symbols = ($bootname);
117
118 # Execute optional '.bootstrap' perl script for this module.
119 # The .bs file can be used to configure @dl_resolve_using etc to
120 # match the needs of the individual module on this architecture.
121 my $bs = $file;
122 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
123 if (-s $bs) { # only read file if it's not empty
124 print STDERR "BS: $bs ($osname, $dlsrc)\n" if $dl_debug;
125 eval { do $bs; };
126 warn "$bs: $@\n" if $@;
127 }
128
129 # Many dynamic extension loading problems will appear to come from
130 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
131 # Often these errors are actually occurring in the initialisation
132 # C code of the extension XS file. Perl reports the error as being
133 # in this perl code simply because this was the last perl code
134 # it executed.
135
136 my $libref = dl_load_file($file) or
4633a7c4 137 Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n");
8e07c86e
AD
138
139 my @unresolved = dl_undef_symbols();
4633a7c4 140 Carp::carp("Undefined symbols present after loading $file: @unresolved\n")
8e07c86e
AD
141 if @unresolved;
142
143 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
4633a7c4 144 Carp::croak("Can't find '$bootname' symbol in $file\n");
8e07c86e
AD
145
146 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
147
148 # See comment block above
149 &$xs(@args);
150}
151
152
153sub _check_file { # private utility to handle dl_expandspec vs -f tests
154 my($file) = @_;
155 return $file if (!$do_expand && -f $file); # the common case
156 return $file if ( $do_expand && ($file=dl_expandspec($file)));
157 return undef;
158}
159
160
161# Let autosplit and the autoloader deal with these functions:
162__END__
163
164
165sub dl_findfile {
166 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
167 # This function does not automatically consider the architecture
168 # or the perl library auto directories.
169 my (@args) = @_;
170 my (@dirs, $dir); # which directories to search
171 my (@found); # full paths to real files we have found
172 my $vms = ($osname eq 'VMS');
173 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
174
175 print STDERR "dl_findfile(@args)\n" if $dl_debug;
176
177 # accumulate directories but process files as they appear
178 arg: foreach(@args) {
179 # Special fast case: full filepath requires no search
180 if (m:/: && -f $_ && !$do_expand) {
181 push(@found,$_);
182 last arg unless wantarray;
183 next;
184 }
185
186 # Deal with directories first:
187 # Using a -L prefix is the preferred option (faster and more robust)
188 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
189
190 # Otherwise we try to try to spot directories by a heuristic
191 # (this is a more complicated issue than it first appears)
192 if (m:/: && -d $_) { push(@dirs, $_); next; }
193
194 # VMS: we may be using native VMS directry syntax instead of
195 # Unix emulation, so check this as well
196 if ($vms && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
197
198 # Only files should get this far...
199 my(@names, $name); # what filenames to look for
200 if (m:-l: ) { # convert -lname to appropriate library name
201 s/-l//;
202 push(@names,"lib$_.$dl_so");
203 push(@names,"lib$_.a");
204 } else { # Umm, a bare name. Try various alternatives:
205 # these should be ordered with the most likely first
206 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
207 push(@names,"lib$_.$dl_so") unless m:/:;
208 push(@names,"$_.o") unless m/\.(o|$dl_so)$/o;
209 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
210 push(@names, $_);
211 }
212 foreach $dir (@dirs, @dl_library_path) {
213 next unless -d $dir;
214 foreach $name (@names) {
215 my($file) = "$dir/$name";
216 print STDERR " checking in $dir for $name\n" if $dl_debug;
217 $file = _check_file($file);
218 if ($file) {
219 push(@found, $file);
220 next arg; # no need to look any further
221 }
222 }
223 }
224 }
225 if ($dl_debug) {
226 foreach(@dirs) {
227 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
228 }
229 print STDERR "dl_findfile found: @found\n";
230 }
231 return $found[0] unless wantarray;
232 @found;
233}
234
235
236sub dl_expandspec {
237 my($spec) = @_;
238 # Optional function invoked if DynaLoader.pm sets $do_expand.
239 # Most systems do not require or use this function.
240 # Some systems may implement it in the dl_*.xs file in which case
241 # this autoload version will not be called but is harmless.
242
243 # This function is designed to deal with systems which treat some
244 # 'filenames' in a special way. For example VMS 'Logical Names'
245 # (something like unix environment variables - but different).
246 # This function should recognise such names and expand them into
247 # full file paths.
248 # Must return undef if $spec is invalid or file does not exist.
249
250 my $file = $spec; # default output to input
251
252 if ($osname eq 'VMS') { # dl_expandspec should be defined in dl_vms.xs
4633a7c4 253 Carp::croak("dl_expandspec: should be defined in XS file!\n");
8e07c86e
AD
254 } else {
255 return undef unless -f $file;
256 }
257 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
258 $file;
259}
260
261
3b35bae3
AD
262=head1 NAME
263
264DynaLoader - Dynamically load C libraries into Perl code
265
266dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_undef_symbols(), dl_install_xsub(), boostrap() - routines used by DynaLoader modules
267
268=head1 SYNOPSIS
269
8e07c86e 270 package YourPackage;
3b35bae3 271 require DynaLoader;
c2960299 272 @ISA = qw(... DynaLoader ...);
8e07c86e 273 bootstrap YourPackage;
3b35bae3
AD
274
275
276=head1 DESCRIPTION
277
c2960299 278This document defines a standard generic interface to the dynamic
3b35bae3
AD
279linking mechanisms available on many platforms. Its primary purpose is
280to implement automatic dynamic loading of Perl modules.
281
c2960299
AD
282This document serves as both a specification for anyone wishing to
283implement the DynaLoader for a new platform and as a guide for
284anyone wishing to use the DynaLoader directly in an application.
285
3b35bae3
AD
286The DynaLoader is designed to be a very simple high-level
287interface that is sufficiently general to cover the requirements
288of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
289
c2960299
AD
290It is also hoped that the interface will cover the needs of OS/2, NT
291etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
3b35bae3
AD
292
293It must be stressed that the DynaLoader, by itself, is practically
294useless for accessing non-Perl libraries because it provides almost no
295Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
296library function or supplying arguments. It is anticipated that any
297glue that may be developed in the future will be implemented in a
298separate dynamically loaded module.
299
300DynaLoader Interface Summary
301
302 @dl_library_path
303 @dl_resolve_using
304 @dl_require_symbols
305 $dl_debug
306 Implemented in:
307 bootstrap($modulename) Perl
308 @filepaths = dl_findfile(@names) Perl
309
310 $libref = dl_load_file($filename) C
311 $symref = dl_find_symbol($libref, $symbol) C
312 @symbols = dl_undef_symbols() C
313 dl_install_xsub($name, $symref [, $filename]) C
314 $message = dl_error C
315
316=over 4
317
318=item @dl_library_path
319
320The standard/default list of directories in which dl_findfile() will
321search for libraries etc. Directories are searched in order:
322$dl_library_path[0], [1], ... etc
323
324@dl_library_path is initialised to hold the list of 'normal' directories
325(F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
326ensure portability across a wide range of platforms.
327
328@dl_library_path should also be initialised with any other directories
329that can be determined from the environment at runtime (such as
330LD_LIBRARY_PATH for SunOS).
331
332After initialisation @dl_library_path can be manipulated by an
333application using push and unshift before calling dl_findfile().
334Unshift can be used to add directories to the front of the search order
335either to save search time or to override libraries with the same name
336in the 'normal' directories.
337
338The load function that dl_load_file() calls may require an absolute
339pathname. The dl_findfile() function and @dl_library_path can be
340used to search for and return the absolute pathname for the
341library/object that you wish to load.
342
343=item @dl_resolve_using
344
345A list of additional libraries or other shared objects which can be
346used to resolve any undefined symbols that might be generated by a
347later call to load_file().
348
349This is only required on some platforms which do not handle dependent
350libraries automatically. For example the Socket Perl extension library
351(F<auto/Socket/Socket.so>) contains references to many socket functions
352which need to be resolved when it's loaded. Most platforms will
353automatically know where to find the 'dependent' library (e.g.,
354F</usr/lib/libsocket.so>). A few platforms need to to be told the location
355of the dependent library explicitly. Use @dl_resolve_using for this.
356
357Example usage:
358
359 @dl_resolve_using = dl_findfile('-lsocket');
360
361=item @dl_require_symbols
362
363A list of one or more symbol names that are in the library/object file
364to be dynamically loaded. This is only required on some platforms.
365
366=item dl_error()
367
368Syntax:
369
370 $message = dl_error();
371
372Error message text from the last failed DynaLoader function. Note
373that, similar to errno in unix, a successful function call does not
374reset this message.
375
376Implementations should detect the error as soon as it occurs in any of
377the other functions and save the corresponding message for later
378retrieval. This will avoid problems on some platforms (such as SunOS)
379where the error message is very temporary (e.g., dlerror()).
380
381=item $dl_debug
382
383Internal debugging messages are enabled when $dl_debug is set true.
384Currently setting $dl_debug only affects the Perl side of the
385DynaLoader. These messages should help an application developer to
386resolve any DynaLoader usage problems.
387
388$dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
389
390For the DynaLoader developer/porter there is a similar debugging
391variable added to the C code (see dlutils.c) and enabled if Perl was
392built with the B<-DDEBUGGING> flag. This can also be set via the
393PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
394higher for more.
395
396=item dl_findfile()
397
398Syntax:
399
400 @filepaths = dl_findfile(@names)
401
402Determine the full paths (including file suffix) of one or more
403loadable files given their generic names and optionally one or more
404directories. Searches directories in @dl_library_path by default and
405returns an empty list if no files were found.
406
407Names can be specified in a variety of platform independent forms. Any
408names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
409an appropriate suffix for the platform.
410
411If a name does not already have a suitable prefix and/or suffix then
412the corresponding file will be searched for by trying combinations of
413prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
414and "$name".
415
416If any directories are included in @names they are searched before
c2960299
AD
417@dl_library_path. Directories may be specified as B<-Ldir>. Any other
418names are treated as filenames to be searched for.
3b35bae3
AD
419
420Using arguments of the form C<-Ldir> and C<-lname> is recommended.
421
422Example:
423
424 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
425
426
427=item dl_expandspec()
428
429Syntax:
430
431 $filepath = dl_expandspec($spec)
432
433Some unusual systems, such as VMS, require special filename handling in
434order to deal with symbolic names for files (i.e., VMS's Logical Names).
435
436To support these systems a dl_expandspec() function can be implemented
437either in the F<dl_*.xs> file or code can be added to the autoloadable
c2960299
AD
438dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
439more information.
3b35bae3
AD
440
441=item dl_load_file()
442
443Syntax:
444
445 $libref = dl_load_file($filename)
446
447Dynamically load $filename, which must be the path to a shared object
448or library. An opaque 'library reference' is returned as a handle for
449the loaded object. Returns undef on error.
450
451(On systems that provide a handle for the loaded object such as SunOS
452and HPUX, $libref will be that handle. On other systems $libref will
453typically be $filename or a pointer to a buffer containing $filename.
454The application should not examine or alter $libref in any way.)
455
456This is function that does the real work. It should use the current
457values of @dl_require_symbols and @dl_resolve_using if required.
458
459 SunOS: dlopen($filename)
460 HP-UX: shl_load($filename)
461 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
462 NeXT: rld_load($filename, @dl_resolve_using)
463 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
464
465
466=item dl_find_symbol()
467
468Syntax:
469
470 $symref = dl_find_symbol($libref, $symbol)
471
472Return the address of the symbol $symbol or C<undef> if not found. If the
473target system has separate functions to search for symbols of different
474types then dl_find_symbol() should search for function symbols first and
475then other types.
476
477The exact manner in which the address is returned in $symref is not
478currently defined. The only initial requirement is that $symref can
479be passed to, and understood by, dl_install_xsub().
480
481 SunOS: dlsym($libref, $symbol)
482 HP-UX: shl_findsym($libref, $symbol)
483 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
484 NeXT: rld_lookup("_$symbol")
485 VMS: lib$find_image_symbol($libref,$symbol)
486
487
488=item dl_undef_symbols()
489
490Example
491
492 @symbols = dl_undef_symbols()
493
494Return a list of symbol names which remain undefined after load_file().
495Returns C<()> if not known. Don't worry if your platform does not provide
c2960299
AD
496a mechanism for this. Most do not need it and hence do not provide it,
497they just return an empty list.
3b35bae3
AD
498
499
500=item dl_install_xsub()
501
502Syntax:
503
504 dl_install_xsub($perl_name, $symref [, $filename])
505
506Create a new Perl external subroutine named $perl_name using $symref as
507a pointer to the function which implements the routine. This is simply
508a direct call to newXSUB(). Returns a reference to the installed
509function.
510
511The $filename parameter is used by Perl to identify the source file for
512the function if required by die(), caller() or the debugger. If
513$filename is not defined then "DynaLoader" will be used.
514
515
516=item boostrap()
517
518Syntax:
519
520bootstrap($module)
521
522This is the normal entry point for automatic dynamic loading in Perl.
523
524It performs the following actions:
525
526=over 8
527
528=item *
529
530locates an auto/$module directory by searching @INC
531
532=item *
533
534uses dl_findfile() to determine the filename to load
535
536=item *
537
538sets @dl_require_symbols to C<("boot_$module")>
539
540=item *
541
542executes an F<auto/$module/$module.bs> file if it exists
543(typically used to add to @dl_resolve_using any files which
544are required to load the module on the current platform)
545
546=item *
547
548calls dl_load_file() to load the file
549
550=item *
551
552calls dl_undef_symbols() and warns if any symbols are undefined
553
554=item *
555
556calls dl_find_symbol() for "boot_$module"
557
558=item *
559
560calls dl_install_xsub() to install it as "${module}::bootstrap"
561
562=item *
563
8e07c86e
AD
564calls &{"${module}::bootstrap"} to bootstrap the module (actually
565it uses the function reference returned by dl_install_xsub for speed)
3b35bae3
AD
566
567=back
568
569=back
570
571
572=head1 AUTHOR
573
c2960299
AD
574Tim Bunce, 11 August 1994.
575
3b35bae3
AD
576This interface is based on the work and comments of (in no particular
577order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
c2960299 578Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
3b35bae3
AD
579
580Larry Wall designed the elegant inherited bootstrap mechanism and
581implemented the first Perl 5 dynamic loader using it.
582
3b35bae3 583=cut