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a0d0e21e |
1 | package DynaLoader; |
2 | |
8e07c86e |
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 | |
dc848c6f |
15 | use vars qw($VERSION); |
16 | |
17 | $VERSION = "1.02"; |
73c78b0a |
18 | |
8e07c86e |
19 | require Carp; |
20 | require Config; |
8e07c86e |
21 | |
dc848c6f |
22 | require AutoLoader; |
23 | *AUTOLOAD = \&AutoLoader::AUTOLOAD; |
8e07c86e |
24 | |
25 | # enable debug/trace messages from DynaLoader perl code |
26 | $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug; |
27 | |
ff7f3c60 |
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) |
ff7f3c60 |
33 | # |
34 | # This is called as a class method $module->dl_load_flags. The |
35 | # definition here will be inherited and result on "default" loading |
36 | # behaviour unless a sub-class of DynaLoader defines its own version. |
37 | # |
38 | |
39 | sub dl_load_flags { 0x00 } |
40 | |
41 | # |
42 | |
d404d5bf |
43 | ($dl_dlext, $dlsrc) |
44 | = @Config::Config{'dlext', 'dlsrc'}; |
8e07c86e |
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'; |
8e07c86e |
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 |
ff7f3c60 |
55 | @dl_librefs = (); # things we have loaded |
56 | @dl_modules = (); # Modules we have loaded |
8e07c86e |
57 | |
58 | # This is a fix to support DLD's unfortunate desire to relink -lc |
59 | @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs"; |
60 | |
61 | # Initialise @dl_library_path with the 'standard' library path |
62 | # for this platform as determined by Configure |
63 | push(@dl_library_path, split(' ',$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. |
68 | push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH})) |
69 | if $ENV{LD_LIBRARY_PATH}; |
70 | |
71 | |
72 | # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here. |
54d6a3b3 |
73 | boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader); |
8e07c86e |
74 | |
75 | |
76 | if ($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 | |
82 | 1; # End of main code |
83 | |
84 | |
85 | # The bootstrap function cannot be autoloaded (without complications) |
86 | # so we define it here: |
87 | |
88 | sub 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; |
8e07c86e |
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; |
8e07c86e |
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)") |
8e07c86e |
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; |
8e07c86e |
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 $module: ".dl_error()."\n"); |
8e07c86e |
157 | |
ff7f3c60 |
158 | push(@dl_librefs,$libref); # record loaded object |
159 | |
8e07c86e |
160 | my @unresolved = dl_undef_symbols(); |
4633a7c4 |
161 | Carp::carp("Undefined symbols present after loading $file: @unresolved\n") |
8e07c86e |
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"); |
8e07c86e |
166 | |
167 | my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file); |
168 | |
ff7f3c60 |
169 | push(@dl_modules, $module); # record loaded module |
170 | |
8e07c86e |
171 | # See comment block above |
172 | &$xs(@args); |
173 | } |
174 | |
175 | |
176 | sub _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 | |
188 | sub 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 |
8e07c86e |
196 | my $dl_so = $Config::Config{'so'}; # suffix for shared libraries |
197 | |
198 | print STDERR "dl_findfile(@args)\n" if $dl_debug; |
199 | |
200 | # accumulate directories but process files as they appear |
201 | arg: foreach(@args) { |
202 | # Special fast case: full filepath requires no search |
54d6a3b3 |
203 | if ($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) { |
8e07c86e |
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; } |
8e07c86e |
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; |
8e07c86e |
235 | push(@names,"$_.$dl_so") unless m/\.$dl_so$/o; |
236 | push(@names,"lib$_.$dl_so") unless m:/:; |
8e07c86e |
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; |
8e07c86e |
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 $found[0] unless wantarray; |
261 | @found; |
262 | } |
263 | |
264 | |
265 | sub dl_expandspec { |
266 | my($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"); |
8e07c86e |
283 | } else { |
284 | return undef unless -f $file; |
285 | } |
286 | print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug; |
287 | $file; |
288 | } |
289 | |
ff7f3c60 |
290 | sub 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 | |
3b35bae3 |
301 | =head1 NAME |
302 | |
303 | DynaLoader - Dynamically load C libraries into Perl code |
304 | |
ff7f3c60 |
305 | dl_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 |
3b35bae3 |
306 | |
307 | =head1 SYNOPSIS |
308 | |
8e07c86e |
309 | package YourPackage; |
3b35bae3 |
310 | require DynaLoader; |
c2960299 |
311 | @ISA = qw(... DynaLoader ...); |
8e07c86e |
312 | bootstrap YourPackage; |
3b35bae3 |
313 | |
ff7f3c60 |
314 | # optional method for 'global' loading |
315 | sub dl_load_flags { 0x01 } |
316 | |
3b35bae3 |
317 | |
318 | =head1 DESCRIPTION |
319 | |
c2960299 |
320 | This document defines a standard generic interface to the dynamic |
3b35bae3 |
321 | linking mechanisms available on many platforms. Its primary purpose is |
322 | to implement automatic dynamic loading of Perl modules. |
323 | |
c2960299 |
324 | This document serves as both a specification for anyone wishing to |
325 | implement the DynaLoader for a new platform and as a guide for |
326 | anyone wishing to use the DynaLoader directly in an application. |
327 | |
3b35bae3 |
328 | The DynaLoader is designed to be a very simple high-level |
329 | interface that is sufficiently general to cover the requirements |
330 | of SunOS, HP-UX, NeXT, Linux, VMS and other platforms. |
331 | |
c2960299 |
332 | It is also hoped that the interface will cover the needs of OS/2, NT |
333 | etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime). |
3b35bae3 |
334 | |
335 | It must be stressed that the DynaLoader, by itself, is practically |
336 | useless for accessing non-Perl libraries because it provides almost no |
337 | Perl-to-C 'glue'. There is, for example, no mechanism for calling a C |
338 | library function or supplying arguments. It is anticipated that any |
339 | glue that may be developed in the future will be implemented in a |
340 | separate dynamically loaded module. |
341 | |
342 | DynaLoader Interface Summary |
343 | |
344 | @dl_library_path |
345 | @dl_resolve_using |
346 | @dl_require_symbols |
347 | $dl_debug |
ff7f3c60 |
348 | @dl_librefs |
349 | @dl_modules |
3b35bae3 |
350 | Implemented in: |
351 | bootstrap($modulename) Perl |
352 | @filepaths = dl_findfile(@names) Perl |
ff7f3c60 |
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 |
3b35bae3 |
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 | |
366 | The standard/default list of directories in which dl_findfile() will |
367 | search 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 |
372 | ensure portability across a wide range of platforms. |
373 | |
374 | @dl_library_path should also be initialised with any other directories |
375 | that can be determined from the environment at runtime (such as |
376 | LD_LIBRARY_PATH for SunOS). |
377 | |
378 | After initialisation @dl_library_path can be manipulated by an |
379 | application using push and unshift before calling dl_findfile(). |
380 | Unshift can be used to add directories to the front of the search order |
381 | either to save search time or to override libraries with the same name |
382 | in the 'normal' directories. |
383 | |
384 | The load function that dl_load_file() calls may require an absolute |
385 | pathname. The dl_findfile() function and @dl_library_path can be |
386 | used to search for and return the absolute pathname for the |
387 | library/object that you wish to load. |
388 | |
389 | =item @dl_resolve_using |
390 | |
391 | A list of additional libraries or other shared objects which can be |
392 | used to resolve any undefined symbols that might be generated by a |
393 | later call to load_file(). |
394 | |
395 | This is only required on some platforms which do not handle dependent |
396 | libraries automatically. For example the Socket Perl extension library |
397 | (F<auto/Socket/Socket.so>) contains references to many socket functions |
398 | which need to be resolved when it's loaded. Most platforms will |
399 | automatically know where to find the 'dependent' library (e.g., |
400 | F</usr/lib/libsocket.so>). A few platforms need to to be told the location |
401 | of the dependent library explicitly. Use @dl_resolve_using for this. |
402 | |
403 | Example usage: |
404 | |
405 | @dl_resolve_using = dl_findfile('-lsocket'); |
406 | |
407 | =item @dl_require_symbols |
408 | |
409 | A list of one or more symbol names that are in the library/object file |
410 | to be dynamically loaded. This is only required on some platforms. |
411 | |
ff7f3c60 |
412 | =item @dl_librefs |
413 | |
414 | An array of the handles returned by successful calls to dl_load_file(), |
415 | made by bootstrap, in the order in which they were loaded. |
416 | Can be used with dl_find_symbol() to look for a symbol in any of |
417 | the loaded files. |
418 | |
419 | =item @dl_modules |
420 | |
421 | An array of module (package) names that have been bootstrap'ed. |
422 | |
3b35bae3 |
423 | =item dl_error() |
424 | |
425 | Syntax: |
426 | |
427 | $message = dl_error(); |
428 | |
429 | Error message text from the last failed DynaLoader function. Note |
430 | that, similar to errno in unix, a successful function call does not |
431 | reset this message. |
432 | |
433 | Implementations should detect the error as soon as it occurs in any of |
434 | the other functions and save the corresponding message for later |
435 | retrieval. This will avoid problems on some platforms (such as SunOS) |
436 | where the error message is very temporary (e.g., dlerror()). |
437 | |
438 | =item $dl_debug |
439 | |
440 | Internal debugging messages are enabled when $dl_debug is set true. |
441 | Currently setting $dl_debug only affects the Perl side of the |
442 | DynaLoader. These messages should help an application developer to |
443 | resolve any DynaLoader usage problems. |
444 | |
445 | $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined. |
446 | |
447 | For the DynaLoader developer/porter there is a similar debugging |
448 | variable added to the C code (see dlutils.c) and enabled if Perl was |
449 | built with the B<-DDEBUGGING> flag. This can also be set via the |
450 | PERL_DL_DEBUG environment variable. Set to 1 for minimal information or |
451 | higher for more. |
452 | |
453 | =item dl_findfile() |
454 | |
455 | Syntax: |
456 | |
457 | @filepaths = dl_findfile(@names) |
458 | |
459 | Determine the full paths (including file suffix) of one or more |
460 | loadable files given their generic names and optionally one or more |
461 | directories. Searches directories in @dl_library_path by default and |
462 | returns an empty list if no files were found. |
463 | |
464 | Names can be specified in a variety of platform independent forms. Any |
465 | names in the form B<-lname> are converted into F<libname.*>, where F<.*> is |
466 | an appropriate suffix for the platform. |
467 | |
468 | If a name does not already have a suitable prefix and/or suffix then |
469 | the corresponding file will be searched for by trying combinations of |
470 | prefix and suffix appropriate to the platform: "$name.o", "lib$name.*" |
471 | and "$name". |
472 | |
473 | If any directories are included in @names they are searched before |
c2960299 |
474 | @dl_library_path. Directories may be specified as B<-Ldir>. Any other |
475 | names are treated as filenames to be searched for. |
3b35bae3 |
476 | |
477 | Using arguments of the form C<-Ldir> and C<-lname> is recommended. |
478 | |
479 | Example: |
480 | |
481 | @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix)); |
482 | |
483 | |
484 | =item dl_expandspec() |
485 | |
486 | Syntax: |
487 | |
488 | $filepath = dl_expandspec($spec) |
489 | |
490 | Some unusual systems, such as VMS, require special filename handling in |
491 | order to deal with symbolic names for files (i.e., VMS's Logical Names). |
492 | |
493 | To support these systems a dl_expandspec() function can be implemented |
494 | either in the F<dl_*.xs> file or code can be added to the autoloadable |
c2960299 |
495 | dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for |
496 | more information. |
3b35bae3 |
497 | |
498 | =item dl_load_file() |
499 | |
500 | Syntax: |
501 | |
ff7f3c60 |
502 | $libref = dl_load_file($filename, $flags) |
3b35bae3 |
503 | |
504 | Dynamically load $filename, which must be the path to a shared object |
505 | or library. An opaque 'library reference' is returned as a handle for |
506 | the loaded object. Returns undef on error. |
507 | |
ff7f3c60 |
508 | The $flags argument to alters dl_load_file behaviour. |
509 | Assigned 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 | |
3b35bae3 |
515 | (On systems that provide a handle for the loaded object such as SunOS |
516 | and HPUX, $libref will be that handle. On other systems $libref will |
517 | typically be $filename or a pointer to a buffer containing $filename. |
518 | The application should not examine or alter $libref in any way.) |
519 | |
ff7f3c60 |
520 | This is the function that does the real work. It should use the |
521 | current values of @dl_require_symbols and @dl_resolve_using if required. |
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522 | |
523 | SunOS: dlopen($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 |
530 | Linux, and is a common choice when providing a "wrapper" on other |
531 | mechanisms as is done in the OS/2 port.) |
532 | |
533 | =item dl_loadflags() |
534 | |
535 | Syntax: |
536 | |
537 | $flags = dl_loadflags $modulename; |
538 | |
539 | Designed 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 |
541 | DynaLoader itself returns 0, which produces standard behavior from |
542 | dl_load_file(). |
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543 | |
544 | =item dl_find_symbol() |
545 | |
546 | Syntax: |
547 | |
548 | $symref = dl_find_symbol($libref, $symbol) |
549 | |
550 | Return the address of the symbol $symbol or C<undef> if not found. If the |
551 | target system has separate functions to search for symbols of different |
552 | types then dl_find_symbol() should search for function symbols first and |
553 | then other types. |
554 | |
555 | The exact manner in which the address is returned in $symref is not |
556 | currently defined. The only initial requirement is that $symref can |
557 | be passed to, and understood by, dl_install_xsub(). |
558 | |
559 | SunOS: dlsym($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 | |
568 | Syntax: |
569 | |
570 | $symref = dl_find_symbol_anywhere($symbol) |
571 | |
572 | Applies dl_find_symbol() to the members of @dl_librefs and returns |
573 | the first match found. |
574 | |
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575 | =item dl_undef_symbols() |
576 | |
577 | Example |
578 | |
579 | @symbols = dl_undef_symbols() |
580 | |
581 | Return a list of symbol names which remain undefined after load_file(). |
582 | Returns C<()> if not known. Don't worry if your platform does not provide |
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583 | a mechanism for this. Most do not need it and hence do not provide it, |
584 | they just return an empty list. |
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585 | |
586 | |
587 | =item dl_install_xsub() |
588 | |
589 | Syntax: |
590 | |
591 | dl_install_xsub($perl_name, $symref [, $filename]) |
592 | |
593 | Create a new Perl external subroutine named $perl_name using $symref as |
594 | a pointer to the function which implements the routine. This is simply |
595 | a direct call to newXSUB(). Returns a reference to the installed |
596 | function. |
597 | |
598 | The $filename parameter is used by Perl to identify the source file for |
599 | the function if required by die(), caller() or the debugger. If |
600 | $filename is not defined then "DynaLoader" will be used. |
601 | |
602 | |
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603 | =item bootstrap() |
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604 | |
605 | Syntax: |
606 | |
607 | bootstrap($module) |
608 | |
609 | This is the normal entry point for automatic dynamic loading in Perl. |
610 | |
611 | It performs the following actions: |
612 | |
613 | =over 8 |
614 | |
615 | =item * |
616 | |
617 | locates an auto/$module directory by searching @INC |
618 | |
619 | =item * |
620 | |
621 | uses dl_findfile() to determine the filename to load |
622 | |
623 | =item * |
624 | |
625 | sets @dl_require_symbols to C<("boot_$module")> |
626 | |
627 | =item * |
628 | |
629 | executes an F<auto/$module/$module.bs> file if it exists |
630 | (typically used to add to @dl_resolve_using any files which |
631 | are required to load the module on the current platform) |
632 | |
633 | =item * |
634 | |
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635 | calls dl_load_flags() to determine how to load the file. |
636 | |
637 | =item * |
638 | |
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639 | calls dl_load_file() to load the file |
640 | |
641 | =item * |
642 | |
643 | calls dl_undef_symbols() and warns if any symbols are undefined |
644 | |
645 | =item * |
646 | |
647 | calls dl_find_symbol() for "boot_$module" |
648 | |
649 | =item * |
650 | |
651 | calls dl_install_xsub() to install it as "${module}::bootstrap" |
652 | |
653 | =item * |
654 | |
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655 | calls &{"${module}::bootstrap"} to bootstrap the module (actually |
656 | it 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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665 | Tim Bunce, 11 August 1994. |
666 | |
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667 | This interface is based on the work and comments of (in no particular |
668 | order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno |
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669 | Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others. |
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670 | |
671 | Larry Wall designed the elegant inherited bootstrap mechanism and |
672 | implemented the first Perl 5 dynamic loader using it. |
673 | |
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674 | Solaris global loading added by Nick Ing-Simmons with design/coding |
675 | assistance from Tim Bunce, January 1996. |
676 | |
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677 | =cut |