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[perl5.git] / ext / DynaLoader / DynaLoader.pm
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1package DynaLoader;
2
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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
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15use vars qw($VERSION);
16
17$VERSION = "1.02";
73c78b0a 18
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19require Carp;
20require Config;
8e07c86e 21
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22require AutoLoader;
23*AUTOLOAD = \&AutoLoader::AUTOLOAD;
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24
25# enable debug/trace messages from DynaLoader perl code
26$dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
27
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28#
29# Flags to alter dl_load_file behaviour. Assigned bits:
30# 0x01 make symbols available for linking later dl_load_file's.
31# (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
f86702cc 32# (ignored under VMS; effect is built-in to image linking)
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33#
34# This is called as a class method $module->dl_load_flags. The
35# definition here will be inherited and result on "default" loading
36# behaviour unless a sub-class of DynaLoader defines its own version.
37#
38
39sub dl_load_flags { 0x00 }
40
41#
42
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43($dl_dlext, $dlsrc)
44 = @Config::Config{'dlext', 'dlsrc'};
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45
46# Some systems need special handling to expand file specifications
47# (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
48# See dl_expandspec() for more details. Should be harmless but
49# inefficient to define on systems that don't need it.
d404d5bf 50$do_expand = $Is_VMS = $^O eq 'VMS';
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51
52@dl_require_symbols = (); # names of symbols we need
53@dl_resolve_using = (); # names of files to link with
54@dl_library_path = (); # path to look for files
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55@dl_librefs = (); # things we have loaded
56@dl_modules = (); # Modules we have loaded
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57
58# This is a fix to support DLD's unfortunate desire to relink -lc
59@dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
60
61# Initialise @dl_library_path with the 'standard' library path
62# for this platform as determined by Configure
63push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
64
65# Add to @dl_library_path any extra directories we can gather from
66# environment variables. So far LD_LIBRARY_PATH is the only known
67# variable used for this purpose. Others may be added later.
68push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
69 if $ENV{LD_LIBRARY_PATH};
70
71
72# No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
54d6a3b3 73boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
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74
75
76if ($dl_debug) {
77 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
78 print STDERR "DynaLoader not linked into this perl\n"
79 unless defined(&boot_DynaLoader);
80}
81
821; # End of main code
83
84
85# The bootstrap function cannot be autoloaded (without complications)
86# so we define it here:
87
88sub bootstrap {
89 # use local vars to enable $module.bs script to edit values
90 local(@args) = @_;
91 local($module) = $args[0];
92 local(@dirs, $file);
93
4633a7c4 94 Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module;
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95
96 # A common error on platforms which don't support dynamic loading.
97 # Since it's fatal and potentially confusing we give a detailed message.
98 Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n".
99 " (You may need to build a new perl executable which either supports\n".
100 " dynamic loading or has the $module module statically linked into it.)\n")
101 unless defined(&dl_load_file);
102
103 my @modparts = split(/::/,$module);
104 my $modfname = $modparts[-1];
105
106 # Some systems have restrictions on files names for DLL's etc.
107 # mod2fname returns appropriate file base name (typically truncated)
108 # It may also edit @modparts if required.
109 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
110
111 my $modpname = join('/',@modparts);
112
113 print STDERR "DynaLoader::bootstrap for $module ",
114 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
115
116 foreach (@INC) {
54d6a3b3 117 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
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118 my $dir = "$_/auto/$modpname";
119 next unless -d $dir; # skip over uninteresting directories
120
121 # check for common cases to avoid autoload of dl_findfile
122 last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
123
124 # no luck here, save dir for possible later dl_findfile search
125 push(@dirs, "-L$dir");
126 }
127 # last resort, let dl_findfile have a go in all known locations
128 $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
129
4633a7c4 130 Carp::croak("Can't find loadable object for module $module in \@INC (@INC)")
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131 unless $file;
132
133 my $bootname = "boot_$module";
134 $bootname =~ s/\W/_/g;
135 @dl_require_symbols = ($bootname);
136
137 # Execute optional '.bootstrap' perl script for this module.
138 # The .bs file can be used to configure @dl_resolve_using etc to
139 # match the needs of the individual module on this architecture.
140 my $bs = $file;
141 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
142 if (-s $bs) { # only read file if it's not empty
d404d5bf 143 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
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144 eval { do $bs; };
145 warn "$bs: $@\n" if $@;
146 }
147
148 # Many dynamic extension loading problems will appear to come from
149 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
150 # Often these errors are actually occurring in the initialisation
151 # C code of the extension XS file. Perl reports the error as being
152 # in this perl code simply because this was the last perl code
153 # it executed.
154
ff7f3c60 155 my $libref = dl_load_file($file, $module->dl_load_flags) or
4633a7c4 156 Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n");
8e07c86e 157
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158 push(@dl_librefs,$libref); # record loaded object
159
8e07c86e 160 my @unresolved = dl_undef_symbols();
4633a7c4 161 Carp::carp("Undefined symbols present after loading $file: @unresolved\n")
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162 if @unresolved;
163
164 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
4633a7c4 165 Carp::croak("Can't find '$bootname' symbol in $file\n");
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166
167 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
168
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169 push(@dl_modules, $module); # record loaded module
170
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171 # See comment block above
172 &$xs(@args);
173}
174
175
176sub _check_file { # private utility to handle dl_expandspec vs -f tests
177 my($file) = @_;
178 return $file if (!$do_expand && -f $file); # the common case
179 return $file if ( $do_expand && ($file=dl_expandspec($file)));
180 return undef;
181}
182
183
184# Let autosplit and the autoloader deal with these functions:
185__END__
186
187
188sub dl_findfile {
189 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
190 # This function does not automatically consider the architecture
191 # or the perl library auto directories.
192 my (@args) = @_;
193 my (@dirs, $dir); # which directories to search
194 my (@found); # full paths to real files we have found
d404d5bf 195 my $dl_ext= $Config::Config{'dlext'}; # suffix for perl extensions
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196 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
197
198 print STDERR "dl_findfile(@args)\n" if $dl_debug;
199
200 # accumulate directories but process files as they appear
201 arg: foreach(@args) {
202 # Special fast case: full filepath requires no search
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203 if ($Is_VMS && m%[:>/\]]% && -f $_) {
204 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
205 last arg unless wantarray;
206 next;
207 }
208 elsif (m:/: && -f $_ && !$do_expand) {
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209 push(@found,$_);
210 last arg unless wantarray;
211 next;
212 }
213
214 # Deal with directories first:
215 # Using a -L prefix is the preferred option (faster and more robust)
216 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
217
218 # Otherwise we try to try to spot directories by a heuristic
219 # (this is a more complicated issue than it first appears)
220 if (m:/: && -d $_) { push(@dirs, $_); next; }
221
222 # VMS: we may be using native VMS directry syntax instead of
223 # Unix emulation, so check this as well
54d6a3b3 224 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
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225
226 # Only files should get this far...
227 my(@names, $name); # what filenames to look for
228 if (m:-l: ) { # convert -lname to appropriate library name
229 s/-l//;
230 push(@names,"lib$_.$dl_so");
231 push(@names,"lib$_.a");
232 } else { # Umm, a bare name. Try various alternatives:
233 # these should be ordered with the most likely first
d404d5bf 234 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
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235 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
236 push(@names,"lib$_.$dl_so") unless m:/:;
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237 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
238 push(@names, $_);
239 }
240 foreach $dir (@dirs, @dl_library_path) {
241 next unless -d $dir;
54d6a3b3 242 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
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243 foreach $name (@names) {
244 my($file) = "$dir/$name";
245 print STDERR " checking in $dir for $name\n" if $dl_debug;
246 $file = _check_file($file);
247 if ($file) {
248 push(@found, $file);
249 next arg; # no need to look any further
250 }
251 }
252 }
253 }
254 if ($dl_debug) {
255 foreach(@dirs) {
256 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
257 }
258 print STDERR "dl_findfile found: @found\n";
259 }
260 return $found[0] unless wantarray;
261 @found;
262}
263
264
265sub dl_expandspec {
266 my($spec) = @_;
267 # Optional function invoked if DynaLoader.pm sets $do_expand.
268 # Most systems do not require or use this function.
269 # Some systems may implement it in the dl_*.xs file in which case
270 # this autoload version will not be called but is harmless.
271
272 # This function is designed to deal with systems which treat some
273 # 'filenames' in a special way. For example VMS 'Logical Names'
274 # (something like unix environment variables - but different).
275 # This function should recognise such names and expand them into
276 # full file paths.
277 # Must return undef if $spec is invalid or file does not exist.
278
279 my $file = $spec; # default output to input
280
d404d5bf 281 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
4633a7c4 282 Carp::croak("dl_expandspec: should be defined in XS file!\n");
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283 } else {
284 return undef unless -f $file;
285 }
286 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
287 $file;
288}
289
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290sub dl_find_symbol_anywhere
291{
292 my $sym = shift;
293 my $libref;
294 foreach $libref (@dl_librefs) {
295 my $symref = dl_find_symbol($libref,$sym);
296 return $symref if $symref;
297 }
298 return undef;
299}
8e07c86e 300
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301=head1 NAME
302
303DynaLoader - Dynamically load C libraries into Perl code
304
ff7f3c60 305dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
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306
307=head1 SYNOPSIS
308
8e07c86e 309 package YourPackage;
3b35bae3 310 require DynaLoader;
c2960299 311 @ISA = qw(... DynaLoader ...);
8e07c86e 312 bootstrap YourPackage;
3b35bae3 313
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314 # optional method for 'global' loading
315 sub dl_load_flags { 0x01 }
316
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317
318=head1 DESCRIPTION
319
c2960299 320This document defines a standard generic interface to the dynamic
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321linking mechanisms available on many platforms. Its primary purpose is
322to implement automatic dynamic loading of Perl modules.
323
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324This document serves as both a specification for anyone wishing to
325implement the DynaLoader for a new platform and as a guide for
326anyone wishing to use the DynaLoader directly in an application.
327
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328The DynaLoader is designed to be a very simple high-level
329interface that is sufficiently general to cover the requirements
330of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
331
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332It is also hoped that the interface will cover the needs of OS/2, NT
333etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
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334
335It must be stressed that the DynaLoader, by itself, is practically
336useless for accessing non-Perl libraries because it provides almost no
337Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
338library function or supplying arguments. It is anticipated that any
339glue that may be developed in the future will be implemented in a
340separate dynamically loaded module.
341
342DynaLoader Interface Summary
343
344 @dl_library_path
345 @dl_resolve_using
346 @dl_require_symbols
347 $dl_debug
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348 @dl_librefs
349 @dl_modules
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350 Implemented in:
351 bootstrap($modulename) Perl
352 @filepaths = dl_findfile(@names) Perl
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353 $flags = $modulename->dl_load_flags Perl
354 $symref = dl_find_symbol_anywhere($symbol) Perl
3b35bae3 355
ff7f3c60 356 $libref = dl_load_file($filename, $flags) C
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357 $symref = dl_find_symbol($libref, $symbol) C
358 @symbols = dl_undef_symbols() C
359 dl_install_xsub($name, $symref [, $filename]) C
360 $message = dl_error C
361
362=over 4
363
364=item @dl_library_path
365
366The standard/default list of directories in which dl_findfile() will
367search for libraries etc. Directories are searched in order:
368$dl_library_path[0], [1], ... etc
369
370@dl_library_path is initialised to hold the list of 'normal' directories
371(F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
372ensure portability across a wide range of platforms.
373
374@dl_library_path should also be initialised with any other directories
375that can be determined from the environment at runtime (such as
376LD_LIBRARY_PATH for SunOS).
377
378After initialisation @dl_library_path can be manipulated by an
379application using push and unshift before calling dl_findfile().
380Unshift can be used to add directories to the front of the search order
381either to save search time or to override libraries with the same name
382in the 'normal' directories.
383
384The load function that dl_load_file() calls may require an absolute
385pathname. The dl_findfile() function and @dl_library_path can be
386used to search for and return the absolute pathname for the
387library/object that you wish to load.
388
389=item @dl_resolve_using
390
391A list of additional libraries or other shared objects which can be
392used to resolve any undefined symbols that might be generated by a
393later call to load_file().
394
395This is only required on some platforms which do not handle dependent
396libraries automatically. For example the Socket Perl extension library
397(F<auto/Socket/Socket.so>) contains references to many socket functions
398which need to be resolved when it's loaded. Most platforms will
399automatically know where to find the 'dependent' library (e.g.,
400F</usr/lib/libsocket.so>). A few platforms need to to be told the location
401of the dependent library explicitly. Use @dl_resolve_using for this.
402
403Example usage:
404
405 @dl_resolve_using = dl_findfile('-lsocket');
406
407=item @dl_require_symbols
408
409A list of one or more symbol names that are in the library/object file
410to be dynamically loaded. This is only required on some platforms.
411
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412=item @dl_librefs
413
414An array of the handles returned by successful calls to dl_load_file(),
415made by bootstrap, in the order in which they were loaded.
416Can be used with dl_find_symbol() to look for a symbol in any of
417the loaded files.
418
419=item @dl_modules
420
421An array of module (package) names that have been bootstrap'ed.
422
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423=item dl_error()
424
425Syntax:
426
427 $message = dl_error();
428
429Error message text from the last failed DynaLoader function. Note
430that, similar to errno in unix, a successful function call does not
431reset this message.
432
433Implementations should detect the error as soon as it occurs in any of
434the other functions and save the corresponding message for later
435retrieval. This will avoid problems on some platforms (such as SunOS)
436where the error message is very temporary (e.g., dlerror()).
437
438=item $dl_debug
439
440Internal debugging messages are enabled when $dl_debug is set true.
441Currently setting $dl_debug only affects the Perl side of the
442DynaLoader. These messages should help an application developer to
443resolve any DynaLoader usage problems.
444
445$dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
446
447For the DynaLoader developer/porter there is a similar debugging
448variable added to the C code (see dlutils.c) and enabled if Perl was
449built with the B<-DDEBUGGING> flag. This can also be set via the
450PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
451higher for more.
452
453=item dl_findfile()
454
455Syntax:
456
457 @filepaths = dl_findfile(@names)
458
459Determine the full paths (including file suffix) of one or more
460loadable files given their generic names and optionally one or more
461directories. Searches directories in @dl_library_path by default and
462returns an empty list if no files were found.
463
464Names can be specified in a variety of platform independent forms. Any
465names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
466an appropriate suffix for the platform.
467
468If a name does not already have a suitable prefix and/or suffix then
469the corresponding file will be searched for by trying combinations of
470prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
471and "$name".
472
473If any directories are included in @names they are searched before
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474@dl_library_path. Directories may be specified as B<-Ldir>. Any other
475names are treated as filenames to be searched for.
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476
477Using arguments of the form C<-Ldir> and C<-lname> is recommended.
478
479Example:
480
481 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
482
483
484=item dl_expandspec()
485
486Syntax:
487
488 $filepath = dl_expandspec($spec)
489
490Some unusual systems, such as VMS, require special filename handling in
491order to deal with symbolic names for files (i.e., VMS's Logical Names).
492
493To support these systems a dl_expandspec() function can be implemented
494either in the F<dl_*.xs> file or code can be added to the autoloadable
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495dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
496more information.
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497
498=item dl_load_file()
499
500Syntax:
501
ff7f3c60 502 $libref = dl_load_file($filename, $flags)
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503
504Dynamically load $filename, which must be the path to a shared object
505or library. An opaque 'library reference' is returned as a handle for
506the loaded object. Returns undef on error.
507
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508The $flags argument to alters dl_load_file behaviour.
509Assigned bits:
510
511 0x01 make symbols available for linking later dl_load_file's.
512 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
f86702cc 513 (ignored under VMS; this is a normal part of image linking)
ff7f3c60 514
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515(On systems that provide a handle for the loaded object such as SunOS
516and HPUX, $libref will be that handle. On other systems $libref will
517typically be $filename or a pointer to a buffer containing $filename.
518The application should not examine or alter $libref in any way.)
519
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520This is the function that does the real work. It should use the
521current values of @dl_require_symbols and @dl_resolve_using if required.
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522
523 SunOS: dlopen($filename)
524 HP-UX: shl_load($filename)
525 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
526 NeXT: rld_load($filename, @dl_resolve_using)
527 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
528
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529(The dlopen() function is also used by Solaris and some versions of
530Linux, and is a common choice when providing a "wrapper" on other
531mechanisms as is done in the OS/2 port.)
532
533=item dl_loadflags()
534
535Syntax:
536
537 $flags = dl_loadflags $modulename;
538
539Designed to be a method call, and to be overridden by a derived class
540(i.e. a class which has DynaLoader in its @ISA). The definition in
541DynaLoader itself returns 0, which produces standard behavior from
542dl_load_file().
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543
544=item dl_find_symbol()
545
546Syntax:
547
548 $symref = dl_find_symbol($libref, $symbol)
549
550Return the address of the symbol $symbol or C<undef> if not found. If the
551target system has separate functions to search for symbols of different
552types then dl_find_symbol() should search for function symbols first and
553then other types.
554
555The exact manner in which the address is returned in $symref is not
556currently defined. The only initial requirement is that $symref can
557be passed to, and understood by, dl_install_xsub().
558
559 SunOS: dlsym($libref, $symbol)
560 HP-UX: shl_findsym($libref, $symbol)
561 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
562 NeXT: rld_lookup("_$symbol")
563 VMS: lib$find_image_symbol($libref,$symbol)
564
565
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566=item dl_find_symbol_anywhere()
567
568Syntax:
569
570 $symref = dl_find_symbol_anywhere($symbol)
571
572Applies dl_find_symbol() to the members of @dl_librefs and returns
573the first match found.
574
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575=item dl_undef_symbols()
576
577Example
578
579 @symbols = dl_undef_symbols()
580
581Return a list of symbol names which remain undefined after load_file().
582Returns C<()> if not known. Don't worry if your platform does not provide
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583a mechanism for this. Most do not need it and hence do not provide it,
584they just return an empty list.
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585
586
587=item dl_install_xsub()
588
589Syntax:
590
591 dl_install_xsub($perl_name, $symref [, $filename])
592
593Create a new Perl external subroutine named $perl_name using $symref as
594a pointer to the function which implements the routine. This is simply
595a direct call to newXSUB(). Returns a reference to the installed
596function.
597
598The $filename parameter is used by Perl to identify the source file for
599the function if required by die(), caller() or the debugger. If
600$filename is not defined then "DynaLoader" will be used.
601
602
1fef88e7 603=item bootstrap()
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604
605Syntax:
606
607bootstrap($module)
608
609This is the normal entry point for automatic dynamic loading in Perl.
610
611It performs the following actions:
612
613=over 8
614
615=item *
616
617locates an auto/$module directory by searching @INC
618
619=item *
620
621uses dl_findfile() to determine the filename to load
622
623=item *
624
625sets @dl_require_symbols to C<("boot_$module")>
626
627=item *
628
629executes an F<auto/$module/$module.bs> file if it exists
630(typically used to add to @dl_resolve_using any files which
631are required to load the module on the current platform)
632
633=item *
634
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635calls dl_load_flags() to determine how to load the file.
636
637=item *
638
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639calls dl_load_file() to load the file
640
641=item *
642
643calls dl_undef_symbols() and warns if any symbols are undefined
644
645=item *
646
647calls dl_find_symbol() for "boot_$module"
648
649=item *
650
651calls dl_install_xsub() to install it as "${module}::bootstrap"
652
653=item *
654
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655calls &{"${module}::bootstrap"} to bootstrap the module (actually
656it uses the function reference returned by dl_install_xsub for speed)
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657
658=back
659
660=back
661
662
663=head1 AUTHOR
664
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665Tim Bunce, 11 August 1994.
666
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667This interface is based on the work and comments of (in no particular
668order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
c2960299 669Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
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670
671Larry Wall designed the elegant inherited bootstrap mechanism and
672implemented the first Perl 5 dynamic loader using it.
673
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674Solaris global loading added by Nick Ing-Simmons with design/coding
675assistance from Tim Bunce, January 1996.
676
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