This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
[win32] merge change#687 from maintbranch
[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
fb73857a 15$VERSION = $VERSION = "1.03"; # avoid typo warning
dc848c6f 16
8e07c86e 17require Config;
8e07c86e 18
dc848c6f
PP
19require AutoLoader;
20*AUTOLOAD = \&AutoLoader::AUTOLOAD;
8e07c86e 21
fb73857a
PP
22# The following require can't be removed during maintenance
23# releases, sadly, because of the risk of buggy code that does
24# require Carp; Carp::croak "..."; without brackets dying
25# if Carp hasn't been loaded in earlier compile time. :-(
26# We'll let those bugs get found on the development track.
27require Carp if $] < 5.00450;
28
29
8e07c86e
AD
30# enable debug/trace messages from DynaLoader perl code
31$dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
32
ff7f3c60
NIS
33#
34# Flags to alter dl_load_file behaviour. Assigned bits:
35# 0x01 make symbols available for linking later dl_load_file's.
36# (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
f86702cc 37# (ignored under VMS; effect is built-in to image linking)
ff7f3c60
NIS
38#
39# This is called as a class method $module->dl_load_flags. The
40# definition here will be inherited and result on "default" loading
41# behaviour unless a sub-class of DynaLoader defines its own version.
42#
43
44sub dl_load_flags { 0x00 }
45
46#
47
d404d5bf
PP
48($dl_dlext, $dlsrc)
49 = @Config::Config{'dlext', 'dlsrc'};
8e07c86e
AD
50
51# Some systems need special handling to expand file specifications
52# (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
53# See dl_expandspec() for more details. Should be harmless but
54# inefficient to define on systems that don't need it.
d404d5bf 55$do_expand = $Is_VMS = $^O eq 'VMS';
8e07c86e
AD
56
57@dl_require_symbols = (); # names of symbols we need
58@dl_resolve_using = (); # names of files to link with
59@dl_library_path = (); # path to look for files
ff7f3c60
NIS
60@dl_librefs = (); # things we have loaded
61@dl_modules = (); # Modules we have loaded
8e07c86e
AD
62
63# This is a fix to support DLD's unfortunate desire to relink -lc
64@dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
65
66# Initialise @dl_library_path with the 'standard' library path
67# for this platform as determined by Configure
68push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
69
70# Add to @dl_library_path any extra directories we can gather from
71# environment variables. So far LD_LIBRARY_PATH is the only known
72# variable used for this purpose. Others may be added later.
73push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
74 if $ENV{LD_LIBRARY_PATH};
75
76
77# No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
54d6a3b3 78boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
8e07c86e
AD
79
80
81if ($dl_debug) {
82 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
83 print STDERR "DynaLoader not linked into this perl\n"
84 unless defined(&boot_DynaLoader);
85}
86
871; # End of main code
88
89
fb73857a
PP
90sub croak { require Carp; Carp::croak(@_) }
91
8e07c86e
AD
92# The bootstrap function cannot be autoloaded (without complications)
93# so we define it here:
94
95sub bootstrap {
96 # use local vars to enable $module.bs script to edit values
97 local(@args) = @_;
98 local($module) = $args[0];
99 local(@dirs, $file);
100
fb73857a
PP
101 unless ($module) {
102 require Carp;
103 Carp::confess("Usage: DynaLoader::bootstrap(module)");
104 }
8e07c86e
AD
105
106 # A common error on platforms which don't support dynamic loading.
107 # Since it's fatal and potentially confusing we give a detailed message.
fb73857a 108 croak("Can't load module $module, dynamic loading not available in this perl.\n".
8e07c86e
AD
109 " (You may need to build a new perl executable which either supports\n".
110 " dynamic loading or has the $module module statically linked into it.)\n")
111 unless defined(&dl_load_file);
112
113 my @modparts = split(/::/,$module);
114 my $modfname = $modparts[-1];
115
116 # Some systems have restrictions on files names for DLL's etc.
117 # mod2fname returns appropriate file base name (typically truncated)
118 # It may also edit @modparts if required.
119 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
120
121 my $modpname = join('/',@modparts);
122
123 print STDERR "DynaLoader::bootstrap for $module ",
124 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
125
126 foreach (@INC) {
54d6a3b3 127 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
8e07c86e
AD
128 my $dir = "$_/auto/$modpname";
129 next unless -d $dir; # skip over uninteresting directories
130
131 # check for common cases to avoid autoload of dl_findfile
fb73857a
PP
132 my $try = "$dir/$modfname.$dl_dlext";
133 last if $file = ($do_expand) ? dl_expandspec($try) : (-f $try && $try);
8e07c86e
AD
134
135 # no luck here, save dir for possible later dl_findfile search
fb73857a 136 push @dirs, $dir;
8e07c86e
AD
137 }
138 # last resort, let dl_findfile have a go in all known locations
fb73857a 139 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
8e07c86e 140
fb73857a
PP
141 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
142 unless $file; # wording similar to error from 'require'
8e07c86e
AD
143
144 my $bootname = "boot_$module";
145 $bootname =~ s/\W/_/g;
146 @dl_require_symbols = ($bootname);
147
148 # Execute optional '.bootstrap' perl script for this module.
149 # The .bs file can be used to configure @dl_resolve_using etc to
150 # match the needs of the individual module on this architecture.
151 my $bs = $file;
152 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
153 if (-s $bs) { # only read file if it's not empty
d404d5bf 154 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
8e07c86e
AD
155 eval { do $bs; };
156 warn "$bs: $@\n" if $@;
157 }
158
159 # Many dynamic extension loading problems will appear to come from
160 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
161 # Often these errors are actually occurring in the initialisation
162 # C code of the extension XS file. Perl reports the error as being
163 # in this perl code simply because this was the last perl code
164 # it executed.
165
ff7f3c60 166 my $libref = dl_load_file($file, $module->dl_load_flags) or
fb73857a 167 croak("Can't load '$file' for module $module: ".dl_error()."\n");
8e07c86e 168
ff7f3c60
NIS
169 push(@dl_librefs,$libref); # record loaded object
170
8e07c86e 171 my @unresolved = dl_undef_symbols();
fb73857a
PP
172 if (@unresolved) {
173 require Carp;
174 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
175 }
8e07c86e
AD
176
177 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
fb73857a 178 croak("Can't find '$bootname' symbol in $file\n");
8e07c86e
AD
179
180 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
181
ff7f3c60
NIS
182 push(@dl_modules, $module); # record loaded module
183
8e07c86e
AD
184 # See comment block above
185 &$xs(@args);
186}
187
188
fb73857a
PP
189#sub _check_file { # private utility to handle dl_expandspec vs -f tests
190# my($file) = @_;
191# return $file if (!$do_expand && -f $file); # the common case
192# return $file if ( $do_expand && ($file=dl_expandspec($file)));
193# return undef;
194#}
8e07c86e
AD
195
196
197# Let autosplit and the autoloader deal with these functions:
198__END__
199
200
201sub dl_findfile {
202 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
203 # This function does not automatically consider the architecture
204 # or the perl library auto directories.
205 my (@args) = @_;
206 my (@dirs, $dir); # which directories to search
207 my (@found); # full paths to real files we have found
d404d5bf 208 my $dl_ext= $Config::Config{'dlext'}; # suffix for perl extensions
8e07c86e
AD
209 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
210
211 print STDERR "dl_findfile(@args)\n" if $dl_debug;
212
213 # accumulate directories but process files as they appear
214 arg: foreach(@args) {
215 # Special fast case: full filepath requires no search
54d6a3b3
PP
216 if ($Is_VMS && m%[:>/\]]% && -f $_) {
217 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
218 last arg unless wantarray;
219 next;
220 }
221 elsif (m:/: && -f $_ && !$do_expand) {
8e07c86e
AD
222 push(@found,$_);
223 last arg unless wantarray;
224 next;
225 }
226
227 # Deal with directories first:
228 # Using a -L prefix is the preferred option (faster and more robust)
229 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
230
231 # Otherwise we try to try to spot directories by a heuristic
232 # (this is a more complicated issue than it first appears)
233 if (m:/: && -d $_) { push(@dirs, $_); next; }
234
235 # VMS: we may be using native VMS directry syntax instead of
236 # Unix emulation, so check this as well
54d6a3b3 237 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
8e07c86e
AD
238
239 # Only files should get this far...
240 my(@names, $name); # what filenames to look for
241 if (m:-l: ) { # convert -lname to appropriate library name
242 s/-l//;
243 push(@names,"lib$_.$dl_so");
244 push(@names,"lib$_.a");
245 } else { # Umm, a bare name. Try various alternatives:
246 # these should be ordered with the most likely first
d404d5bf 247 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
8e07c86e
AD
248 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
249 push(@names,"lib$_.$dl_so") unless m:/:;
8e07c86e
AD
250 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
251 push(@names, $_);
252 }
253 foreach $dir (@dirs, @dl_library_path) {
254 next unless -d $dir;
54d6a3b3 255 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
8e07c86e
AD
256 foreach $name (@names) {
257 my($file) = "$dir/$name";
258 print STDERR " checking in $dir for $name\n" if $dl_debug;
fb73857a
PP
259 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
260 #$file = _check_file($file);
8e07c86e
AD
261 if ($file) {
262 push(@found, $file);
263 next arg; # no need to look any further
264 }
265 }
266 }
267 }
268 if ($dl_debug) {
269 foreach(@dirs) {
270 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
271 }
272 print STDERR "dl_findfile found: @found\n";
273 }
274 return $found[0] unless wantarray;
275 @found;
276}
277
278
279sub dl_expandspec {
280 my($spec) = @_;
281 # Optional function invoked if DynaLoader.pm sets $do_expand.
282 # Most systems do not require or use this function.
283 # Some systems may implement it in the dl_*.xs file in which case
284 # this autoload version will not be called but is harmless.
285
286 # This function is designed to deal with systems which treat some
287 # 'filenames' in a special way. For example VMS 'Logical Names'
288 # (something like unix environment variables - but different).
289 # This function should recognise such names and expand them into
290 # full file paths.
291 # Must return undef if $spec is invalid or file does not exist.
292
293 my $file = $spec; # default output to input
294
d404d5bf 295 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
fb73857a 296 require Carp;
4633a7c4 297 Carp::croak("dl_expandspec: should be defined in XS file!\n");
8e07c86e
AD
298 } else {
299 return undef unless -f $file;
300 }
301 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
302 $file;
303}
304
ff7f3c60
NIS
305sub dl_find_symbol_anywhere
306{
307 my $sym = shift;
308 my $libref;
309 foreach $libref (@dl_librefs) {
310 my $symref = dl_find_symbol($libref,$sym);
311 return $symref if $symref;
312 }
313 return undef;
314}
8e07c86e 315
3b35bae3
AD
316=head1 NAME
317
318DynaLoader - Dynamically load C libraries into Perl code
319
ff7f3c60 320dl_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
AD
321
322=head1 SYNOPSIS
323
8e07c86e 324 package YourPackage;
3b35bae3 325 require DynaLoader;
c2960299 326 @ISA = qw(... DynaLoader ...);
8e07c86e 327 bootstrap YourPackage;
3b35bae3 328
ff7f3c60
NIS
329 # optional method for 'global' loading
330 sub dl_load_flags { 0x01 }
331
3b35bae3
AD
332
333=head1 DESCRIPTION
334
c2960299 335This document defines a standard generic interface to the dynamic
3b35bae3
AD
336linking mechanisms available on many platforms. Its primary purpose is
337to implement automatic dynamic loading of Perl modules.
338
c2960299
AD
339This document serves as both a specification for anyone wishing to
340implement the DynaLoader for a new platform and as a guide for
341anyone wishing to use the DynaLoader directly in an application.
342
3b35bae3
AD
343The DynaLoader is designed to be a very simple high-level
344interface that is sufficiently general to cover the requirements
345of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
346
c2960299
AD
347It is also hoped that the interface will cover the needs of OS/2, NT
348etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
3b35bae3
AD
349
350It must be stressed that the DynaLoader, by itself, is practically
351useless for accessing non-Perl libraries because it provides almost no
352Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
90248788
TB
353library function or supplying arguments. A ExtUtils::DynaLib module
354is available from CPAN sites which performs that function for some
355common system types.
3b35bae3
AD
356
357DynaLoader Interface Summary
358
359 @dl_library_path
360 @dl_resolve_using
361 @dl_require_symbols
362 $dl_debug
ff7f3c60
NIS
363 @dl_librefs
364 @dl_modules
3b35bae3
AD
365 Implemented in:
366 bootstrap($modulename) Perl
367 @filepaths = dl_findfile(@names) Perl
ff7f3c60
NIS
368 $flags = $modulename->dl_load_flags Perl
369 $symref = dl_find_symbol_anywhere($symbol) Perl
3b35bae3 370
ff7f3c60 371 $libref = dl_load_file($filename, $flags) C
3b35bae3
AD
372 $symref = dl_find_symbol($libref, $symbol) C
373 @symbols = dl_undef_symbols() C
374 dl_install_xsub($name, $symref [, $filename]) C
375 $message = dl_error C
376
377=over 4
378
379=item @dl_library_path
380
381The standard/default list of directories in which dl_findfile() will
382search for libraries etc. Directories are searched in order:
383$dl_library_path[0], [1], ... etc
384
385@dl_library_path is initialised to hold the list of 'normal' directories
386(F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
387ensure portability across a wide range of platforms.
388
389@dl_library_path should also be initialised with any other directories
390that can be determined from the environment at runtime (such as
391LD_LIBRARY_PATH for SunOS).
392
393After initialisation @dl_library_path can be manipulated by an
394application using push and unshift before calling dl_findfile().
395Unshift can be used to add directories to the front of the search order
396either to save search time or to override libraries with the same name
397in the 'normal' directories.
398
399The load function that dl_load_file() calls may require an absolute
400pathname. The dl_findfile() function and @dl_library_path can be
401used to search for and return the absolute pathname for the
402library/object that you wish to load.
403
404=item @dl_resolve_using
405
406A list of additional libraries or other shared objects which can be
407used to resolve any undefined symbols that might be generated by a
408later call to load_file().
409
410This is only required on some platforms which do not handle dependent
7a2e2cd6
PP
411libraries automatically. For example the Socket Perl extension
412library (F<auto/Socket/Socket.so>) contains references to many socket
413functions which need to be resolved when it's loaded. Most platforms
414will automatically know where to find the 'dependent' library (e.g.,
415F</usr/lib/libsocket.so>). A few platforms need to be told the
416location of the dependent library explicitly. Use @dl_resolve_using
417for this.
3b35bae3
AD
418
419Example usage:
420
421 @dl_resolve_using = dl_findfile('-lsocket');
422
423=item @dl_require_symbols
424
425A list of one or more symbol names that are in the library/object file
426to be dynamically loaded. This is only required on some platforms.
427
ff7f3c60
NIS
428=item @dl_librefs
429
430An array of the handles returned by successful calls to dl_load_file(),
431made by bootstrap, in the order in which they were loaded.
432Can be used with dl_find_symbol() to look for a symbol in any of
433the loaded files.
434
435=item @dl_modules
436
437An array of module (package) names that have been bootstrap'ed.
438
3b35bae3
AD
439=item dl_error()
440
441Syntax:
442
443 $message = dl_error();
444
445Error message text from the last failed DynaLoader function. Note
446that, similar to errno in unix, a successful function call does not
447reset this message.
448
449Implementations should detect the error as soon as it occurs in any of
450the other functions and save the corresponding message for later
451retrieval. This will avoid problems on some platforms (such as SunOS)
452where the error message is very temporary (e.g., dlerror()).
453
454=item $dl_debug
455
456Internal debugging messages are enabled when $dl_debug is set true.
457Currently setting $dl_debug only affects the Perl side of the
458DynaLoader. These messages should help an application developer to
459resolve any DynaLoader usage problems.
460
461$dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
462
463For the DynaLoader developer/porter there is a similar debugging
464variable added to the C code (see dlutils.c) and enabled if Perl was
465built with the B<-DDEBUGGING> flag. This can also be set via the
466PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
467higher for more.
468
469=item dl_findfile()
470
471Syntax:
472
473 @filepaths = dl_findfile(@names)
474
475Determine the full paths (including file suffix) of one or more
476loadable files given their generic names and optionally one or more
477directories. Searches directories in @dl_library_path by default and
478returns an empty list if no files were found.
479
480Names can be specified in a variety of platform independent forms. Any
481names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
482an appropriate suffix for the platform.
483
484If a name does not already have a suitable prefix and/or suffix then
485the corresponding file will be searched for by trying combinations of
486prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
487and "$name".
488
489If any directories are included in @names they are searched before
c2960299
AD
490@dl_library_path. Directories may be specified as B<-Ldir>. Any other
491names are treated as filenames to be searched for.
3b35bae3
AD
492
493Using arguments of the form C<-Ldir> and C<-lname> is recommended.
494
495Example:
496
497 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
498
499
500=item dl_expandspec()
501
502Syntax:
503
504 $filepath = dl_expandspec($spec)
505
506Some unusual systems, such as VMS, require special filename handling in
507order to deal with symbolic names for files (i.e., VMS's Logical Names).
508
509To support these systems a dl_expandspec() function can be implemented
510either in the F<dl_*.xs> file or code can be added to the autoloadable
c2960299
AD
511dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
512more information.
3b35bae3
AD
513
514=item dl_load_file()
515
516Syntax:
517
ff7f3c60 518 $libref = dl_load_file($filename, $flags)
3b35bae3
AD
519
520Dynamically load $filename, which must be the path to a shared object
521or library. An opaque 'library reference' is returned as a handle for
522the loaded object. Returns undef on error.
523
ff7f3c60
NIS
524The $flags argument to alters dl_load_file behaviour.
525Assigned bits:
526
527 0x01 make symbols available for linking later dl_load_file's.
528 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
f86702cc 529 (ignored under VMS; this is a normal part of image linking)
ff7f3c60 530
3b35bae3
AD
531(On systems that provide a handle for the loaded object such as SunOS
532and HPUX, $libref will be that handle. On other systems $libref will
533typically be $filename or a pointer to a buffer containing $filename.
534The application should not examine or alter $libref in any way.)
535
ff7f3c60
NIS
536This is the function that does the real work. It should use the
537current values of @dl_require_symbols and @dl_resolve_using if required.
3b35bae3
AD
538
539 SunOS: dlopen($filename)
540 HP-UX: shl_load($filename)
541 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
542 NeXT: rld_load($filename, @dl_resolve_using)
543 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
544
ff7f3c60
NIS
545(The dlopen() function is also used by Solaris and some versions of
546Linux, and is a common choice when providing a "wrapper" on other
547mechanisms as is done in the OS/2 port.)
548
549=item dl_loadflags()
550
551Syntax:
552
553 $flags = dl_loadflags $modulename;
554
555Designed to be a method call, and to be overridden by a derived class
556(i.e. a class which has DynaLoader in its @ISA). The definition in
557DynaLoader itself returns 0, which produces standard behavior from
558dl_load_file().
3b35bae3
AD
559
560=item dl_find_symbol()
561
562Syntax:
563
564 $symref = dl_find_symbol($libref, $symbol)
565
566Return the address of the symbol $symbol or C<undef> if not found. If the
567target system has separate functions to search for symbols of different
568types then dl_find_symbol() should search for function symbols first and
569then other types.
570
571The exact manner in which the address is returned in $symref is not
572currently defined. The only initial requirement is that $symref can
573be passed to, and understood by, dl_install_xsub().
574
575 SunOS: dlsym($libref, $symbol)
576 HP-UX: shl_findsym($libref, $symbol)
577 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
578 NeXT: rld_lookup("_$symbol")
579 VMS: lib$find_image_symbol($libref,$symbol)
580
581
ff7f3c60
NIS
582=item dl_find_symbol_anywhere()
583
584Syntax:
585
586 $symref = dl_find_symbol_anywhere($symbol)
587
588Applies dl_find_symbol() to the members of @dl_librefs and returns
589the first match found.
590
3b35bae3
AD
591=item dl_undef_symbols()
592
593Example
594
595 @symbols = dl_undef_symbols()
596
597Return a list of symbol names which remain undefined after load_file().
598Returns C<()> if not known. Don't worry if your platform does not provide
c2960299
AD
599a mechanism for this. Most do not need it and hence do not provide it,
600they just return an empty list.
3b35bae3
AD
601
602
603=item dl_install_xsub()
604
605Syntax:
606
607 dl_install_xsub($perl_name, $symref [, $filename])
608
609Create a new Perl external subroutine named $perl_name using $symref as
610a pointer to the function which implements the routine. This is simply
611a direct call to newXSUB(). Returns a reference to the installed
612function.
613
614The $filename parameter is used by Perl to identify the source file for
615the function if required by die(), caller() or the debugger. If
616$filename is not defined then "DynaLoader" will be used.
617
618
1fef88e7 619=item bootstrap()
3b35bae3
AD
620
621Syntax:
622
623bootstrap($module)
624
625This is the normal entry point for automatic dynamic loading in Perl.
626
627It performs the following actions:
628
629=over 8
630
631=item *
632
633locates an auto/$module directory by searching @INC
634
635=item *
636
637uses dl_findfile() to determine the filename to load
638
639=item *
640
641sets @dl_require_symbols to C<("boot_$module")>
642
643=item *
644
645executes an F<auto/$module/$module.bs> file if it exists
646(typically used to add to @dl_resolve_using any files which
647are required to load the module on the current platform)
648
649=item *
650
ff7f3c60
NIS
651calls dl_load_flags() to determine how to load the file.
652
653=item *
654
3b35bae3
AD
655calls dl_load_file() to load the file
656
657=item *
658
659calls dl_undef_symbols() and warns if any symbols are undefined
660
661=item *
662
663calls dl_find_symbol() for "boot_$module"
664
665=item *
666
667calls dl_install_xsub() to install it as "${module}::bootstrap"
668
669=item *
670
8e07c86e
AD
671calls &{"${module}::bootstrap"} to bootstrap the module (actually
672it uses the function reference returned by dl_install_xsub for speed)
3b35bae3
AD
673
674=back
675
676=back
677
678
679=head1 AUTHOR
680
c2960299
AD
681Tim Bunce, 11 August 1994.
682
3b35bae3
AD
683This interface is based on the work and comments of (in no particular
684order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
c2960299 685Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
3b35bae3
AD
686
687Larry Wall designed the elegant inherited bootstrap mechanism and
688implemented the first Perl 5 dynamic loader using it.
689
ff7f3c60
NIS
690Solaris global loading added by Nick Ing-Simmons with design/coding
691assistance from Tim Bunce, January 1996.
692
3b35bae3 693=cut