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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 | |
73c78b0a |
15 | use vars qw($VERSION @ISA) ; |
16 | |
8e07c86e |
17 | require Carp; |
18 | require Config; |
19 | require AutoLoader; |
20 | |
21 | @ISA=qw(AutoLoader); |
22 | |
376006fe |
23 | $VERSION = "1.01" ; |
8e07c86e |
24 | |
25 | sub import { } # override import inherited from AutoLoader |
26 | |
27 | # enable debug/trace messages from DynaLoader perl code |
28 | $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug; |
29 | |
ff7f3c60 |
30 | # |
31 | # Flags to alter dl_load_file behaviour. Assigned bits: |
32 | # 0x01 make symbols available for linking later dl_load_file's. |
33 | # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL)) |
f86702cc |
34 | # (ignored under VMS; effect is built-in to image linking) |
ff7f3c60 |
35 | # |
36 | # This is called as a class method $module->dl_load_flags. The |
37 | # definition here will be inherited and result on "default" loading |
38 | # behaviour unless a sub-class of DynaLoader defines its own version. |
39 | # |
40 | |
41 | sub dl_load_flags { 0x00 } |
42 | |
43 | # |
44 | |
d404d5bf |
45 | ($dl_dlext, $dlsrc) |
46 | = @Config::Config{'dlext', 'dlsrc'}; |
8e07c86e |
47 | |
48 | # Some systems need special handling to expand file specifications |
49 | # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>) |
50 | # See dl_expandspec() for more details. Should be harmless but |
51 | # inefficient to define on systems that don't need it. |
d404d5bf |
52 | $do_expand = $Is_VMS = $^O eq 'VMS'; |
8e07c86e |
53 | |
54 | @dl_require_symbols = (); # names of symbols we need |
55 | @dl_resolve_using = (); # names of files to link with |
56 | @dl_library_path = (); # path to look for files |
ff7f3c60 |
57 | @dl_librefs = (); # things we have loaded |
58 | @dl_modules = (); # Modules we have loaded |
8e07c86e |
59 | |
60 | # This is a fix to support DLD's unfortunate desire to relink -lc |
61 | @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs"; |
62 | |
63 | # Initialise @dl_library_path with the 'standard' library path |
64 | # for this platform as determined by Configure |
65 | push(@dl_library_path, split(' ',$Config::Config{'libpth'})); |
66 | |
67 | # Add to @dl_library_path any extra directories we can gather from |
68 | # environment variables. So far LD_LIBRARY_PATH is the only known |
69 | # variable used for this purpose. Others may be added later. |
70 | push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH})) |
71 | if $ENV{LD_LIBRARY_PATH}; |
72 | |
73 | |
74 | # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here. |
54d6a3b3 |
75 | boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader); |
8e07c86e |
76 | |
77 | |
78 | if ($dl_debug) { |
79 | print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n"; |
80 | print STDERR "DynaLoader not linked into this perl\n" |
81 | unless defined(&boot_DynaLoader); |
82 | } |
83 | |
84 | 1; # End of main code |
85 | |
86 | |
87 | # The bootstrap function cannot be autoloaded (without complications) |
88 | # so we define it here: |
89 | |
90 | sub bootstrap { |
91 | # use local vars to enable $module.bs script to edit values |
92 | local(@args) = @_; |
93 | local($module) = $args[0]; |
94 | local(@dirs, $file); |
95 | |
4633a7c4 |
96 | Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module; |
8e07c86e |
97 | |
98 | # A common error on platforms which don't support dynamic loading. |
99 | # Since it's fatal and potentially confusing we give a detailed message. |
100 | Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n". |
101 | " (You may need to build a new perl executable which either supports\n". |
102 | " dynamic loading or has the $module module statically linked into it.)\n") |
103 | unless defined(&dl_load_file); |
104 | |
105 | my @modparts = split(/::/,$module); |
106 | my $modfname = $modparts[-1]; |
107 | |
108 | # Some systems have restrictions on files names for DLL's etc. |
109 | # mod2fname returns appropriate file base name (typically truncated) |
110 | # It may also edit @modparts if required. |
111 | $modfname = &mod2fname(\@modparts) if defined &mod2fname; |
112 | |
113 | my $modpname = join('/',@modparts); |
114 | |
115 | print STDERR "DynaLoader::bootstrap for $module ", |
116 | "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug; |
117 | |
118 | foreach (@INC) { |
54d6a3b3 |
119 | chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS; |
8e07c86e |
120 | my $dir = "$_/auto/$modpname"; |
121 | next unless -d $dir; # skip over uninteresting directories |
122 | |
123 | # check for common cases to avoid autoload of dl_findfile |
124 | last if ($file=_check_file("$dir/$modfname.$dl_dlext")); |
125 | |
126 | # no luck here, save dir for possible later dl_findfile search |
127 | push(@dirs, "-L$dir"); |
128 | } |
129 | # last resort, let dl_findfile have a go in all known locations |
130 | $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file; |
131 | |
4633a7c4 |
132 | Carp::croak("Can't find loadable object for module $module in \@INC (@INC)") |
8e07c86e |
133 | unless $file; |
134 | |
135 | my $bootname = "boot_$module"; |
136 | $bootname =~ s/\W/_/g; |
137 | @dl_require_symbols = ($bootname); |
138 | |
139 | # Execute optional '.bootstrap' perl script for this module. |
140 | # The .bs file can be used to configure @dl_resolve_using etc to |
141 | # match the needs of the individual module on this architecture. |
142 | my $bs = $file; |
143 | $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library |
144 | if (-s $bs) { # only read file if it's not empty |
d404d5bf |
145 | print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug; |
8e07c86e |
146 | eval { do $bs; }; |
147 | warn "$bs: $@\n" if $@; |
148 | } |
149 | |
150 | # Many dynamic extension loading problems will appear to come from |
151 | # this section of code: XYZ failed at line 123 of DynaLoader.pm. |
152 | # Often these errors are actually occurring in the initialisation |
153 | # C code of the extension XS file. Perl reports the error as being |
154 | # in this perl code simply because this was the last perl code |
155 | # it executed. |
156 | |
ff7f3c60 |
157 | my $libref = dl_load_file($file, $module->dl_load_flags) or |
4633a7c4 |
158 | Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n"); |
8e07c86e |
159 | |
ff7f3c60 |
160 | push(@dl_librefs,$libref); # record loaded object |
161 | |
8e07c86e |
162 | my @unresolved = dl_undef_symbols(); |
4633a7c4 |
163 | Carp::carp("Undefined symbols present after loading $file: @unresolved\n") |
8e07c86e |
164 | if @unresolved; |
165 | |
166 | my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or |
4633a7c4 |
167 | Carp::croak("Can't find '$bootname' symbol in $file\n"); |
8e07c86e |
168 | |
169 | my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file); |
170 | |
ff7f3c60 |
171 | push(@dl_modules, $module); # record loaded module |
172 | |
8e07c86e |
173 | # See comment block above |
174 | &$xs(@args); |
175 | } |
176 | |
177 | |
178 | sub _check_file { # private utility to handle dl_expandspec vs -f tests |
179 | my($file) = @_; |
180 | return $file if (!$do_expand && -f $file); # the common case |
181 | return $file if ( $do_expand && ($file=dl_expandspec($file))); |
182 | return undef; |
183 | } |
184 | |
185 | |
186 | # Let autosplit and the autoloader deal with these functions: |
187 | __END__ |
188 | |
189 | |
190 | sub dl_findfile { |
191 | # Read ext/DynaLoader/DynaLoader.doc for detailed information. |
192 | # This function does not automatically consider the architecture |
193 | # or the perl library auto directories. |
194 | my (@args) = @_; |
195 | my (@dirs, $dir); # which directories to search |
196 | my (@found); # full paths to real files we have found |
d404d5bf |
197 | my $dl_ext= $Config::Config{'dlext'}; # suffix for perl extensions |
8e07c86e |
198 | my $dl_so = $Config::Config{'so'}; # suffix for shared libraries |
199 | |
200 | print STDERR "dl_findfile(@args)\n" if $dl_debug; |
201 | |
202 | # accumulate directories but process files as they appear |
203 | arg: foreach(@args) { |
204 | # Special fast case: full filepath requires no search |
54d6a3b3 |
205 | if ($Is_VMS && m%[:>/\]]% && -f $_) { |
206 | push(@found,dl_expandspec(VMS::Filespec::vmsify($_))); |
207 | last arg unless wantarray; |
208 | next; |
209 | } |
210 | elsif (m:/: && -f $_ && !$do_expand) { |
8e07c86e |
211 | push(@found,$_); |
212 | last arg unless wantarray; |
213 | next; |
214 | } |
215 | |
216 | # Deal with directories first: |
217 | # Using a -L prefix is the preferred option (faster and more robust) |
218 | if (m:^-L:) { s/^-L//; push(@dirs, $_); next; } |
219 | |
220 | # Otherwise we try to try to spot directories by a heuristic |
221 | # (this is a more complicated issue than it first appears) |
222 | if (m:/: && -d $_) { push(@dirs, $_); next; } |
223 | |
224 | # VMS: we may be using native VMS directry syntax instead of |
225 | # Unix emulation, so check this as well |
54d6a3b3 |
226 | if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; } |
8e07c86e |
227 | |
228 | # Only files should get this far... |
229 | my(@names, $name); # what filenames to look for |
230 | if (m:-l: ) { # convert -lname to appropriate library name |
231 | s/-l//; |
232 | push(@names,"lib$_.$dl_so"); |
233 | push(@names,"lib$_.a"); |
234 | } else { # Umm, a bare name. Try various alternatives: |
235 | # these should be ordered with the most likely first |
d404d5bf |
236 | push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o; |
8e07c86e |
237 | push(@names,"$_.$dl_so") unless m/\.$dl_so$/o; |
238 | push(@names,"lib$_.$dl_so") unless m:/:; |
8e07c86e |
239 | push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs"; |
240 | push(@names, $_); |
241 | } |
242 | foreach $dir (@dirs, @dl_library_path) { |
243 | next unless -d $dir; |
54d6a3b3 |
244 | chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS; |
8e07c86e |
245 | foreach $name (@names) { |
246 | my($file) = "$dir/$name"; |
247 | print STDERR " checking in $dir for $name\n" if $dl_debug; |
248 | $file = _check_file($file); |
249 | if ($file) { |
250 | push(@found, $file); |
251 | next arg; # no need to look any further |
252 | } |
253 | } |
254 | } |
255 | } |
256 | if ($dl_debug) { |
257 | foreach(@dirs) { |
258 | print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_; |
259 | } |
260 | print STDERR "dl_findfile found: @found\n"; |
261 | } |
262 | return $found[0] unless wantarray; |
263 | @found; |
264 | } |
265 | |
266 | |
267 | sub dl_expandspec { |
268 | my($spec) = @_; |
269 | # Optional function invoked if DynaLoader.pm sets $do_expand. |
270 | # Most systems do not require or use this function. |
271 | # Some systems may implement it in the dl_*.xs file in which case |
272 | # this autoload version will not be called but is harmless. |
273 | |
274 | # This function is designed to deal with systems which treat some |
275 | # 'filenames' in a special way. For example VMS 'Logical Names' |
276 | # (something like unix environment variables - but different). |
277 | # This function should recognise such names and expand them into |
278 | # full file paths. |
279 | # Must return undef if $spec is invalid or file does not exist. |
280 | |
281 | my $file = $spec; # default output to input |
282 | |
d404d5bf |
283 | if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs |
4633a7c4 |
284 | Carp::croak("dl_expandspec: should be defined in XS file!\n"); |
8e07c86e |
285 | } else { |
286 | return undef unless -f $file; |
287 | } |
288 | print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug; |
289 | $file; |
290 | } |
291 | |
ff7f3c60 |
292 | sub dl_find_symbol_anywhere |
293 | { |
294 | my $sym = shift; |
295 | my $libref; |
296 | foreach $libref (@dl_librefs) { |
297 | my $symref = dl_find_symbol($libref,$sym); |
298 | return $symref if $symref; |
299 | } |
300 | return undef; |
301 | } |
8e07c86e |
302 | |
3b35bae3 |
303 | =head1 NAME |
304 | |
305 | DynaLoader - Dynamically load C libraries into Perl code |
306 | |
ff7f3c60 |
307 | 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 |
308 | |
309 | =head1 SYNOPSIS |
310 | |
8e07c86e |
311 | package YourPackage; |
3b35bae3 |
312 | require DynaLoader; |
c2960299 |
313 | @ISA = qw(... DynaLoader ...); |
8e07c86e |
314 | bootstrap YourPackage; |
3b35bae3 |
315 | |
ff7f3c60 |
316 | # optional method for 'global' loading |
317 | sub dl_load_flags { 0x01 } |
318 | |
3b35bae3 |
319 | |
320 | =head1 DESCRIPTION |
321 | |
c2960299 |
322 | This document defines a standard generic interface to the dynamic |
3b35bae3 |
323 | linking mechanisms available on many platforms. Its primary purpose is |
324 | to implement automatic dynamic loading of Perl modules. |
325 | |
c2960299 |
326 | This document serves as both a specification for anyone wishing to |
327 | implement the DynaLoader for a new platform and as a guide for |
328 | anyone wishing to use the DynaLoader directly in an application. |
329 | |
3b35bae3 |
330 | The DynaLoader is designed to be a very simple high-level |
331 | interface that is sufficiently general to cover the requirements |
332 | of SunOS, HP-UX, NeXT, Linux, VMS and other platforms. |
333 | |
c2960299 |
334 | It is also hoped that the interface will cover the needs of OS/2, NT |
335 | etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime). |
3b35bae3 |
336 | |
337 | It must be stressed that the DynaLoader, by itself, is practically |
338 | useless for accessing non-Perl libraries because it provides almost no |
339 | Perl-to-C 'glue'. There is, for example, no mechanism for calling a C |
340 | library function or supplying arguments. It is anticipated that any |
341 | glue that may be developed in the future will be implemented in a |
342 | separate dynamically loaded module. |
343 | |
344 | DynaLoader Interface Summary |
345 | |
346 | @dl_library_path |
347 | @dl_resolve_using |
348 | @dl_require_symbols |
349 | $dl_debug |
ff7f3c60 |
350 | @dl_librefs |
351 | @dl_modules |
3b35bae3 |
352 | Implemented in: |
353 | bootstrap($modulename) Perl |
354 | @filepaths = dl_findfile(@names) Perl |
ff7f3c60 |
355 | $flags = $modulename->dl_load_flags Perl |
356 | $symref = dl_find_symbol_anywhere($symbol) Perl |
3b35bae3 |
357 | |
ff7f3c60 |
358 | $libref = dl_load_file($filename, $flags) C |
3b35bae3 |
359 | $symref = dl_find_symbol($libref, $symbol) C |
360 | @symbols = dl_undef_symbols() C |
361 | dl_install_xsub($name, $symref [, $filename]) C |
362 | $message = dl_error C |
363 | |
364 | =over 4 |
365 | |
366 | =item @dl_library_path |
367 | |
368 | The standard/default list of directories in which dl_findfile() will |
369 | search for libraries etc. Directories are searched in order: |
370 | $dl_library_path[0], [1], ... etc |
371 | |
372 | @dl_library_path is initialised to hold the list of 'normal' directories |
373 | (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should |
374 | ensure portability across a wide range of platforms. |
375 | |
376 | @dl_library_path should also be initialised with any other directories |
377 | that can be determined from the environment at runtime (such as |
378 | LD_LIBRARY_PATH for SunOS). |
379 | |
380 | After initialisation @dl_library_path can be manipulated by an |
381 | application using push and unshift before calling dl_findfile(). |
382 | Unshift can be used to add directories to the front of the search order |
383 | either to save search time or to override libraries with the same name |
384 | in the 'normal' directories. |
385 | |
386 | The load function that dl_load_file() calls may require an absolute |
387 | pathname. The dl_findfile() function and @dl_library_path can be |
388 | used to search for and return the absolute pathname for the |
389 | library/object that you wish to load. |
390 | |
391 | =item @dl_resolve_using |
392 | |
393 | A list of additional libraries or other shared objects which can be |
394 | used to resolve any undefined symbols that might be generated by a |
395 | later call to load_file(). |
396 | |
397 | This is only required on some platforms which do not handle dependent |
398 | libraries automatically. For example the Socket Perl extension library |
399 | (F<auto/Socket/Socket.so>) contains references to many socket functions |
400 | which need to be resolved when it's loaded. Most platforms will |
401 | automatically know where to find the 'dependent' library (e.g., |
402 | F</usr/lib/libsocket.so>). A few platforms need to to be told the location |
403 | of the dependent library explicitly. Use @dl_resolve_using for this. |
404 | |
405 | Example usage: |
406 | |
407 | @dl_resolve_using = dl_findfile('-lsocket'); |
408 | |
409 | =item @dl_require_symbols |
410 | |
411 | A list of one or more symbol names that are in the library/object file |
412 | to be dynamically loaded. This is only required on some platforms. |
413 | |
ff7f3c60 |
414 | =item @dl_librefs |
415 | |
416 | An array of the handles returned by successful calls to dl_load_file(), |
417 | made by bootstrap, in the order in which they were loaded. |
418 | Can be used with dl_find_symbol() to look for a symbol in any of |
419 | the loaded files. |
420 | |
421 | =item @dl_modules |
422 | |
423 | An array of module (package) names that have been bootstrap'ed. |
424 | |
3b35bae3 |
425 | =item dl_error() |
426 | |
427 | Syntax: |
428 | |
429 | $message = dl_error(); |
430 | |
431 | Error message text from the last failed DynaLoader function. Note |
432 | that, similar to errno in unix, a successful function call does not |
433 | reset this message. |
434 | |
435 | Implementations should detect the error as soon as it occurs in any of |
436 | the other functions and save the corresponding message for later |
437 | retrieval. This will avoid problems on some platforms (such as SunOS) |
438 | where the error message is very temporary (e.g., dlerror()). |
439 | |
440 | =item $dl_debug |
441 | |
442 | Internal debugging messages are enabled when $dl_debug is set true. |
443 | Currently setting $dl_debug only affects the Perl side of the |
444 | DynaLoader. These messages should help an application developer to |
445 | resolve any DynaLoader usage problems. |
446 | |
447 | $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined. |
448 | |
449 | For the DynaLoader developer/porter there is a similar debugging |
450 | variable added to the C code (see dlutils.c) and enabled if Perl was |
451 | built with the B<-DDEBUGGING> flag. This can also be set via the |
452 | PERL_DL_DEBUG environment variable. Set to 1 for minimal information or |
453 | higher for more. |
454 | |
455 | =item dl_findfile() |
456 | |
457 | Syntax: |
458 | |
459 | @filepaths = dl_findfile(@names) |
460 | |
461 | Determine the full paths (including file suffix) of one or more |
462 | loadable files given their generic names and optionally one or more |
463 | directories. Searches directories in @dl_library_path by default and |
464 | returns an empty list if no files were found. |
465 | |
466 | Names can be specified in a variety of platform independent forms. Any |
467 | names in the form B<-lname> are converted into F<libname.*>, where F<.*> is |
468 | an appropriate suffix for the platform. |
469 | |
470 | If a name does not already have a suitable prefix and/or suffix then |
471 | the corresponding file will be searched for by trying combinations of |
472 | prefix and suffix appropriate to the platform: "$name.o", "lib$name.*" |
473 | and "$name". |
474 | |
475 | If any directories are included in @names they are searched before |
c2960299 |
476 | @dl_library_path. Directories may be specified as B<-Ldir>. Any other |
477 | names are treated as filenames to be searched for. |
3b35bae3 |
478 | |
479 | Using arguments of the form C<-Ldir> and C<-lname> is recommended. |
480 | |
481 | Example: |
482 | |
483 | @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix)); |
484 | |
485 | |
486 | =item dl_expandspec() |
487 | |
488 | Syntax: |
489 | |
490 | $filepath = dl_expandspec($spec) |
491 | |
492 | Some unusual systems, such as VMS, require special filename handling in |
493 | order to deal with symbolic names for files (i.e., VMS's Logical Names). |
494 | |
495 | To support these systems a dl_expandspec() function can be implemented |
496 | either in the F<dl_*.xs> file or code can be added to the autoloadable |
c2960299 |
497 | dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for |
498 | more information. |
3b35bae3 |
499 | |
500 | =item dl_load_file() |
501 | |
502 | Syntax: |
503 | |
ff7f3c60 |
504 | $libref = dl_load_file($filename, $flags) |
3b35bae3 |
505 | |
506 | Dynamically load $filename, which must be the path to a shared object |
507 | or library. An opaque 'library reference' is returned as a handle for |
508 | the loaded object. Returns undef on error. |
509 | |
ff7f3c60 |
510 | The $flags argument to alters dl_load_file behaviour. |
511 | Assigned bits: |
512 | |
513 | 0x01 make symbols available for linking later dl_load_file's. |
514 | (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL)) |
f86702cc |
515 | (ignored under VMS; this is a normal part of image linking) |
ff7f3c60 |
516 | |
3b35bae3 |
517 | (On systems that provide a handle for the loaded object such as SunOS |
518 | and HPUX, $libref will be that handle. On other systems $libref will |
519 | typically be $filename or a pointer to a buffer containing $filename. |
520 | The application should not examine or alter $libref in any way.) |
521 | |
ff7f3c60 |
522 | This is the function that does the real work. It should use the |
523 | current values of @dl_require_symbols and @dl_resolve_using if required. |
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524 | |
525 | SunOS: dlopen($filename) |
526 | HP-UX: shl_load($filename) |
527 | Linux: dld_create_reference(@dl_require_symbols); dld_link($filename) |
528 | NeXT: rld_load($filename, @dl_resolve_using) |
529 | VMS: lib$find_image_symbol($filename,$dl_require_symbols[0]) |
530 | |
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531 | (The dlopen() function is also used by Solaris and some versions of |
532 | Linux, and is a common choice when providing a "wrapper" on other |
533 | mechanisms as is done in the OS/2 port.) |
534 | |
535 | =item dl_loadflags() |
536 | |
537 | Syntax: |
538 | |
539 | $flags = dl_loadflags $modulename; |
540 | |
541 | Designed to be a method call, and to be overridden by a derived class |
542 | (i.e. a class which has DynaLoader in its @ISA). The definition in |
543 | DynaLoader itself returns 0, which produces standard behavior from |
544 | dl_load_file(). |
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545 | |
546 | =item dl_find_symbol() |
547 | |
548 | Syntax: |
549 | |
550 | $symref = dl_find_symbol($libref, $symbol) |
551 | |
552 | Return the address of the symbol $symbol or C<undef> if not found. If the |
553 | target system has separate functions to search for symbols of different |
554 | types then dl_find_symbol() should search for function symbols first and |
555 | then other types. |
556 | |
557 | The exact manner in which the address is returned in $symref is not |
558 | currently defined. The only initial requirement is that $symref can |
559 | be passed to, and understood by, dl_install_xsub(). |
560 | |
561 | SunOS: dlsym($libref, $symbol) |
562 | HP-UX: shl_findsym($libref, $symbol) |
563 | Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol) |
564 | NeXT: rld_lookup("_$symbol") |
565 | VMS: lib$find_image_symbol($libref,$symbol) |
566 | |
567 | |
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568 | =item dl_find_symbol_anywhere() |
569 | |
570 | Syntax: |
571 | |
572 | $symref = dl_find_symbol_anywhere($symbol) |
573 | |
574 | Applies dl_find_symbol() to the members of @dl_librefs and returns |
575 | the first match found. |
576 | |
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577 | =item dl_undef_symbols() |
578 | |
579 | Example |
580 | |
581 | @symbols = dl_undef_symbols() |
582 | |
583 | Return a list of symbol names which remain undefined after load_file(). |
584 | Returns C<()> if not known. Don't worry if your platform does not provide |
c2960299 |
585 | a mechanism for this. Most do not need it and hence do not provide it, |
586 | they just return an empty list. |
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587 | |
588 | |
589 | =item dl_install_xsub() |
590 | |
591 | Syntax: |
592 | |
593 | dl_install_xsub($perl_name, $symref [, $filename]) |
594 | |
595 | Create a new Perl external subroutine named $perl_name using $symref as |
596 | a pointer to the function which implements the routine. This is simply |
597 | a direct call to newXSUB(). Returns a reference to the installed |
598 | function. |
599 | |
600 | The $filename parameter is used by Perl to identify the source file for |
601 | the function if required by die(), caller() or the debugger. If |
602 | $filename is not defined then "DynaLoader" will be used. |
603 | |
604 | |
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605 | =item bootstrap() |
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606 | |
607 | Syntax: |
608 | |
609 | bootstrap($module) |
610 | |
611 | This is the normal entry point for automatic dynamic loading in Perl. |
612 | |
613 | It performs the following actions: |
614 | |
615 | =over 8 |
616 | |
617 | =item * |
618 | |
619 | locates an auto/$module directory by searching @INC |
620 | |
621 | =item * |
622 | |
623 | uses dl_findfile() to determine the filename to load |
624 | |
625 | =item * |
626 | |
627 | sets @dl_require_symbols to C<("boot_$module")> |
628 | |
629 | =item * |
630 | |
631 | executes an F<auto/$module/$module.bs> file if it exists |
632 | (typically used to add to @dl_resolve_using any files which |
633 | are required to load the module on the current platform) |
634 | |
635 | =item * |
636 | |
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637 | calls dl_load_flags() to determine how to load the file. |
638 | |
639 | =item * |
640 | |
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641 | calls dl_load_file() to load the file |
642 | |
643 | =item * |
644 | |
645 | calls dl_undef_symbols() and warns if any symbols are undefined |
646 | |
647 | =item * |
648 | |
649 | calls dl_find_symbol() for "boot_$module" |
650 | |
651 | =item * |
652 | |
653 | calls dl_install_xsub() to install it as "${module}::bootstrap" |
654 | |
655 | =item * |
656 | |
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657 | calls &{"${module}::bootstrap"} to bootstrap the module (actually |
658 | it uses the function reference returned by dl_install_xsub for speed) |
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659 | |
660 | =back |
661 | |
662 | =back |
663 | |
664 | |
665 | =head1 AUTHOR |
666 | |
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667 | Tim Bunce, 11 August 1994. |
668 | |
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669 | This interface is based on the work and comments of (in no particular |
670 | order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno |
c2960299 |
671 | Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others. |
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672 | |
673 | Larry Wall designed the elegant inherited bootstrap mechanism and |
674 | implemented the first Perl 5 dynamic loader using it. |
675 | |
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676 | Solaris global loading added by Nick Ing-Simmons with design/coding |
677 | assistance from Tim Bunce, January 1996. |
678 | |
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679 | =cut |