10 unlink "DynaLoader.pm" if -f "DynaLoader.pm";
11 open OUT, ">DynaLoader.pm" or die $!;
14 # Generated from DynaLoader.pm.PL
18 # And Gandalf said: 'Many folk like to know beforehand what is to
19 # be set on the table; but those who have laboured to prepare the
20 # feast like to keep their secret; for wonder makes the words of
23 # (Quote from Tolkien suggested by Anno Siegel.)
25 # See pod text at end of file for documentation.
26 # See also ext/DynaLoader/README in source tree for other information.
28 # Tim.Bunce@ig.co.uk, August 1994
30 use vars qw($VERSION *AUTOLOAD);
32 $VERSION = 1.04; # avoid typo warning
35 *AUTOLOAD = \&AutoLoader::AUTOLOAD;
39 # The following require can't be removed during maintenance
40 # releases, sadly, because of the risk of buggy code that does
41 # require Carp; Carp::croak "..."; without brackets dying
42 # if Carp hasn't been loaded in earlier compile time. :-(
43 # We'll let those bugs get found on the development track.
44 require Carp if $] < 5.00450;
46 # enable debug/trace messages from DynaLoader perl code
47 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
50 # Flags to alter dl_load_file behaviour. Assigned bits:
51 # 0x01 make symbols available for linking later dl_load_file's.
52 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
53 # (ignored under VMS; effect is built-in to image linking)
55 # This is called as a class method $module->dl_load_flags. The
56 # definition here will be inherited and result on "default" loading
57 # behaviour unless a sub-class of DynaLoader defines its own version.
60 sub dl_load_flags { 0x00 }
63 # = @Config::Config{'dlext', 'dlsrc'};
66 print OUT " (\$dl_dlext, \$dlsrc) = (",
67 to_string($Config::Config{'dlext'}), ",",
68 to_string($Config::Config{'dlsrc'}), ")\n;" ;
72 # Some systems need special handling to expand file specifications
73 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
74 # See dl_expandspec() for more details. Should be harmless but
75 # inefficient to define on systems that don't need it.
76 $Is_VMS = $^O eq 'VMS';
78 $Is_MacOS = $^O eq 'MacOS';
80 @dl_require_symbols = (); # names of symbols we need
81 @dl_resolve_using = (); # names of files to link with
82 @dl_library_path = (); # path to look for files
84 #XSLoader.pm may have added elements before we were required
85 #@dl_librefs = (); # things we have loaded
86 #@dl_modules = (); # Modules we have loaded
88 # This is a fix to support DLD's unfortunate desire to relink -lc
89 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
93 my $cfg_dl_library_path = <<'EOT';
94 push(@dl_library_path, split(' ', $Config::Config{libpth}));
97 sub dquoted_comma_list {
98 join(", ", map {qq("$_")} @_);
101 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
102 eval $cfg_dl_library_path;
103 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
104 my $dl_library_path = dquoted_comma_list(@dl_library_path);
106 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
108 \@dl_library_path = ($dl_library_path);
115 # Initialise \@dl_library_path with the 'standard' library path
116 # for this platform as determined by Configure.
124 my $ldlibpthname_defined;
127 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
128 $ldlibpthname = $Config::Config{ldlibpthname};
129 $ldlibpthname_defined = defined $Config::Config{ldlibpthname} ? 1 : 0;
130 $pthsep = $Config::Config{path_sep};
133 $ldlibpthname = q($Config::Config{ldlibpthname});
134 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
135 $pthsep = q($Config::Config{path_sep});
137 my \$ldlibpthname = $ldlibpthname;
138 my \$ldlibpthname_defined = $ldlibpthname_defined;
139 my \$pthsep = $pthsep;
144 my $env_dl_library_path = <<'EOT';
145 if ($ldlibpthname_defined &&
146 exists $ENV{$ldlibpthname}) {
147 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
150 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
152 if ($ldlibpthname_defined &&
153 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
154 exists $ENV{LD_LIBRARY_PATH}) {
155 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
159 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
160 eval $env_dl_library_path;
164 # Add to \@dl_library_path any extra directories we can gather from environment
172 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
173 my $dl_library_path = dquoted_comma_list(@dl_library_path);
175 # The below \@dl_library_path has been expanded (%Config, %ENV)
176 # in Perl build time.
178 \@dl_library_path = ($dl_library_path);
184 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
185 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
186 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
190 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
191 print STDERR "DynaLoader not linked into this perl\n"
192 unless defined(&boot_DynaLoader);
195 1; # End of main code
198 sub croak { require Carp; Carp::croak(@_) }
200 sub bootstrap_inherit {
202 local *isa = *{"$module\::ISA"};
203 local @isa = (@isa, 'DynaLoader');
204 # Cannot goto due to delocalization. Will report errors on a wrong line?
208 # The bootstrap function cannot be autoloaded (without complications)
209 # so we define it here:
212 # use local vars to enable $module.bs script to edit values
214 local($module) = $args[0];
219 Carp::confess("Usage: DynaLoader::bootstrap(module)");
222 # A common error on platforms which don't support dynamic loading.
223 # Since it's fatal and potentially confusing we give a detailed message.
224 croak("Can't load module $module, dynamic loading not available in this perl.\n".
225 " (You may need to build a new perl executable which either supports\n".
226 " dynamic loading or has the $module module statically linked into it.)\n")
227 unless defined(&dl_load_file);
229 my @modparts = split(/::/,$module);
230 my $modfname = $modparts[-1];
232 # Some systems have restrictions on files names for DLL's etc.
233 # mod2fname returns appropriate file base name (typically truncated)
234 # It may also edit @modparts if required.
235 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
237 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
239 print STDERR "DynaLoader::bootstrap for $module ",
241 ? "(:auto:$modpname:$modfname.$dl_dlext)\n" :
242 "(auto/$modpname/$modfname.$dl_dlext)\n")
246 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
249 $_ .= ":" unless /:$/;
250 $dir = "${_}auto:$modpname";
252 $dir = "$_/auto/$modpname";
254 next unless -d $dir; # skip over uninteresting directories
256 # check for common cases to avoid autoload of dl_findfile
257 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
258 last if $file = ($do_expand) ? dl_expandspec($try) : (-f $try && $try);
260 # no luck here, save dir for possible later dl_findfile search
263 # last resort, let dl_findfile have a go in all known locations
264 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
266 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
267 unless $file; # wording similar to error from 'require'
269 $file = uc($file) if $Is_VMS && $Config::Config{d_vms_case_sensitive_symbols};
270 my $bootname = "boot_$module";
271 $bootname =~ s/\W/_/g;
272 @dl_require_symbols = ($bootname);
274 # Execute optional '.bootstrap' perl script for this module.
275 # The .bs file can be used to configure @dl_resolve_using etc to
276 # match the needs of the individual module on this architecture.
278 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
279 if (-s $bs) { # only read file if it's not empty
280 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
282 warn "$bs: $@\n" if $@;
285 # Many dynamic extension loading problems will appear to come from
286 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
287 # Often these errors are actually occurring in the initialisation
288 # C code of the extension XS file. Perl reports the error as being
289 # in this perl code simply because this was the last perl code
292 my $libref = dl_load_file($file, $module->dl_load_flags) or
293 croak("Can't load '$file' for module $module: ".dl_error());
295 push(@dl_librefs,$libref); # record loaded object
297 my @unresolved = dl_undef_symbols();
300 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
303 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
304 croak("Can't find '$bootname' symbol in $file\n");
306 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
308 push(@dl_modules, $module); # record loaded module
310 # See comment block above
315 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
317 # return $file if (!$do_expand && -f $file); # the common case
318 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
323 # Let autosplit and the autoloader deal with these functions:
328 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
329 # This function does not automatically consider the architecture
330 # or the perl library auto directories.
332 my (@dirs, $dir); # which directories to search
333 my (@found); # full paths to real files we have found
336 print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
337 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
338 print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
339 "; # \$Config::Config{'so'} suffix for shared libraries\n";
343 print STDERR "dl_findfile(@args)\n" if $dl_debug;
345 # accumulate directories but process files as they appear
346 arg: foreach(@args) {
347 # Special fast case: full filepath requires no search
348 if ($Is_VMS && m%[:>/\]]% && -f $_) {
349 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
350 last arg unless wantarray;
356 last arg unless wantarray;
359 elsif (m:/: && -f $_ && !$do_expand) {
361 last arg unless wantarray;
365 # Deal with directories first:
366 # Using a -L prefix is the preferred option (faster and more robust)
367 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
370 # Otherwise we try to try to spot directories by a heuristic
371 # (this is a more complicated issue than it first appears)
372 if (m/:/ && -d $_) { push(@dirs, $_); next; }
373 # Only files should get this far...
374 my(@names, $name); # what filenames to look for
377 foreach $dir (@dirs, @dl_library_path) {
379 $dir =~ s/^([^:]+)$/:$1/;
381 foreach $name (@names) {
382 my($file) = "$dir:$name";
383 print STDERR " checking in $dir for $name\n" if $dl_debug;
386 next arg; # no need to look any further
393 # Otherwise we try to try to spot directories by a heuristic
394 # (this is a more complicated issue than it first appears)
395 if (m:/: && -d $_) { push(@dirs, $_); next; }
397 # VMS: we may be using native VMS directory syntax instead of
398 # Unix emulation, so check this as well
399 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
401 # Only files should get this far...
402 my(@names, $name); # what filenames to look for
403 if (m:-l: ) { # convert -lname to appropriate library name
405 push(@names,"lib$_.$dl_so");
406 push(@names,"lib$_.a");
407 } else { # Umm, a bare name. Try various alternatives:
408 # these should be ordered with the most likely first
409 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
410 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
411 push(@names,"lib$_.$dl_so") unless m:/:;
412 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
415 foreach $dir (@dirs, @dl_library_path) {
417 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
418 foreach $name (@names) {
419 my($file) = "$dir/$name";
420 print STDERR " checking in $dir for $name\n" if $dl_debug;
421 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
422 #$file = _check_file($file);
425 next arg; # no need to look any further
432 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
434 print STDERR "dl_findfile found: @found\n";
436 return $found[0] unless wantarray;
443 # Optional function invoked if DynaLoader.pm sets $do_expand.
444 # Most systems do not require or use this function.
445 # Some systems may implement it in the dl_*.xs file in which case
446 # this autoload version will not be called but is harmless.
448 # This function is designed to deal with systems which treat some
449 # 'filenames' in a special way. For example VMS 'Logical Names'
450 # (something like unix environment variables - but different).
451 # This function should recognise such names and expand them into
453 # Must return undef if $spec is invalid or file does not exist.
455 my $file = $spec; # default output to input
457 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
459 Carp::croak("dl_expandspec: should be defined in XS file!\n");
461 return undef unless -f $file;
463 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
467 sub dl_find_symbol_anywhere
471 foreach $libref (@dl_librefs) {
472 my $symref = dl_find_symbol($libref,$sym);
473 return $symref if $symref;
480 DynaLoader - Dynamically load C libraries into Perl code
482 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_unload_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
488 @ISA = qw(... DynaLoader ...);
489 bootstrap YourPackage;
491 # optional method for 'global' loading
492 sub dl_load_flags { 0x01 }
497 This document defines a standard generic interface to the dynamic
498 linking mechanisms available on many platforms. Its primary purpose is
499 to implement automatic dynamic loading of Perl modules.
501 This document serves as both a specification for anyone wishing to
502 implement the DynaLoader for a new platform and as a guide for
503 anyone wishing to use the DynaLoader directly in an application.
505 The DynaLoader is designed to be a very simple high-level
506 interface that is sufficiently general to cover the requirements
507 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
509 It is also hoped that the interface will cover the needs of OS/2, NT
510 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
512 It must be stressed that the DynaLoader, by itself, is practically
513 useless for accessing non-Perl libraries because it provides almost no
514 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
515 library function or supplying arguments. A C::DynaLib module
516 is available from CPAN sites which performs that function for some
519 DynaLoader Interface Summary
528 bootstrap($modulename) Perl
529 @filepaths = dl_findfile(@names) Perl
530 $flags = $modulename->dl_load_flags Perl
531 $symref = dl_find_symbol_anywhere($symbol) Perl
533 $libref = dl_load_file($filename, $flags) C
534 $status = dl_unload_file($libref) C
535 $symref = dl_find_symbol($libref, $symbol) C
536 @symbols = dl_undef_symbols() C
537 dl_install_xsub($name, $symref [, $filename]) C
538 $message = dl_error C
542 =item @dl_library_path
544 The standard/default list of directories in which dl_findfile() will
545 search for libraries etc. Directories are searched in order:
546 $dl_library_path[0], [1], ... etc
548 @dl_library_path is initialised to hold the list of 'normal' directories
549 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
550 ensure portability across a wide range of platforms.
552 @dl_library_path should also be initialised with any other directories
553 that can be determined from the environment at runtime (such as
554 LD_LIBRARY_PATH for SunOS).
556 After initialisation @dl_library_path can be manipulated by an
557 application using push and unshift before calling dl_findfile().
558 Unshift can be used to add directories to the front of the search order
559 either to save search time or to override libraries with the same name
560 in the 'normal' directories.
562 The load function that dl_load_file() calls may require an absolute
563 pathname. The dl_findfile() function and @dl_library_path can be
564 used to search for and return the absolute pathname for the
565 library/object that you wish to load.
567 =item @dl_resolve_using
569 A list of additional libraries or other shared objects which can be
570 used to resolve any undefined symbols that might be generated by a
571 later call to load_file().
573 This is only required on some platforms which do not handle dependent
574 libraries automatically. For example the Socket Perl extension
575 library (F<auto/Socket/Socket.so>) contains references to many socket
576 functions which need to be resolved when it's loaded. Most platforms
577 will automatically know where to find the 'dependent' library (e.g.,
578 F</usr/lib/libsocket.so>). A few platforms need to be told the
579 location of the dependent library explicitly. Use @dl_resolve_using
584 @dl_resolve_using = dl_findfile('-lsocket');
586 =item @dl_require_symbols
588 A list of one or more symbol names that are in the library/object file
589 to be dynamically loaded. This is only required on some platforms.
593 An array of the handles returned by successful calls to dl_load_file(),
594 made by bootstrap, in the order in which they were loaded.
595 Can be used with dl_find_symbol() to look for a symbol in any of
600 An array of module (package) names that have been bootstrap'ed.
606 $message = dl_error();
608 Error message text from the last failed DynaLoader function. Note
609 that, similar to errno in unix, a successful function call does not
612 Implementations should detect the error as soon as it occurs in any of
613 the other functions and save the corresponding message for later
614 retrieval. This will avoid problems on some platforms (such as SunOS)
615 where the error message is very temporary (e.g., dlerror()).
619 Internal debugging messages are enabled when $dl_debug is set true.
620 Currently setting $dl_debug only affects the Perl side of the
621 DynaLoader. These messages should help an application developer to
622 resolve any DynaLoader usage problems.
624 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
626 For the DynaLoader developer/porter there is a similar debugging
627 variable added to the C code (see dlutils.c) and enabled if Perl was
628 built with the B<-DDEBUGGING> flag. This can also be set via the
629 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
636 @filepaths = dl_findfile(@names)
638 Determine the full paths (including file suffix) of one or more
639 loadable files given their generic names and optionally one or more
640 directories. Searches directories in @dl_library_path by default and
641 returns an empty list if no files were found.
643 Names can be specified in a variety of platform independent forms. Any
644 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
645 an appropriate suffix for the platform.
647 If a name does not already have a suitable prefix and/or suffix then
648 the corresponding file will be searched for by trying combinations of
649 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
652 If any directories are included in @names they are searched before
653 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
654 names are treated as filenames to be searched for.
656 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
660 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
663 =item dl_expandspec()
667 $filepath = dl_expandspec($spec)
669 Some unusual systems, such as VMS, require special filename handling in
670 order to deal with symbolic names for files (i.e., VMS's Logical Names).
672 To support these systems a dl_expandspec() function can be implemented
673 either in the F<dl_*.xs> file or code can be added to the autoloadable
674 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
681 $libref = dl_load_file($filename, $flags)
683 Dynamically load $filename, which must be the path to a shared object
684 or library. An opaque 'library reference' is returned as a handle for
685 the loaded object. Returns undef on error.
687 The $flags argument to alters dl_load_file behaviour.
690 0x01 make symbols available for linking later dl_load_file's.
691 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
692 (ignored under VMS; this is a normal part of image linking)
694 (On systems that provide a handle for the loaded object such as SunOS
695 and HPUX, $libref will be that handle. On other systems $libref will
696 typically be $filename or a pointer to a buffer containing $filename.
697 The application should not examine or alter $libref in any way.)
699 This is the function that does the real work. It should use the
700 current values of @dl_require_symbols and @dl_resolve_using if required.
702 SunOS: dlopen($filename)
703 HP-UX: shl_load($filename)
704 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
705 NeXT: rld_load($filename, @dl_resolve_using)
706 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
708 (The dlopen() function is also used by Solaris and some versions of
709 Linux, and is a common choice when providing a "wrapper" on other
710 mechanisms as is done in the OS/2 port.)
712 =item dl_unload_file()
716 $status = dl_unload_file($libref)
718 Dynamically unload $libref, which must be an opaque 'library reference' as
719 returned from dl_load_file. Returns one on success and zero on failure.
721 This function is optional and may not necessarily be provided on all platforms.
722 If it is defined, it is called automatically when the interpreter exits for
723 every shared object or library loaded by DynaLoader::bootstrap. All such
724 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
725 loads the libraries. The files are unloaded in last-in, first-out order.
727 This unloading is usually necessary when embedding a shared-object perl (e.g.
728 one configured with -Duseshrplib) within a larger application, and the perl
729 interpreter is created and destroyed several times within the lifetime of the
730 application. In this case it is possible that the system dynamic linker will
731 unload and then subsequently reload the shared libperl without relocating any
732 references to it from any files DynaLoaded by the previous incarnation of the
733 interpreter. As a result, any shared objects opened by DynaLoader may point to
734 a now invalid 'ghost' of the libperl shared object, causing apparently random
735 memory corruption and crashes. This behaviour is most commonly seen when using
736 Apache and mod_perl built with the APXS mechanism.
738 SunOS: dlclose($libref)
744 (The dlclose() function is also used by Solaris and some versions of
745 Linux, and is a common choice when providing a "wrapper" on other
746 mechanisms as is done in the OS/2 port.)
752 $flags = dl_loadflags $modulename;
754 Designed to be a method call, and to be overridden by a derived class
755 (i.e. a class which has DynaLoader in its @ISA). The definition in
756 DynaLoader itself returns 0, which produces standard behavior from
759 =item dl_find_symbol()
763 $symref = dl_find_symbol($libref, $symbol)
765 Return the address of the symbol $symbol or C<undef> if not found. If the
766 target system has separate functions to search for symbols of different
767 types then dl_find_symbol() should search for function symbols first and
770 The exact manner in which the address is returned in $symref is not
771 currently defined. The only initial requirement is that $symref can
772 be passed to, and understood by, dl_install_xsub().
774 SunOS: dlsym($libref, $symbol)
775 HP-UX: shl_findsym($libref, $symbol)
776 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
777 NeXT: rld_lookup("_$symbol")
778 VMS: lib$find_image_symbol($libref,$symbol)
781 =item dl_find_symbol_anywhere()
785 $symref = dl_find_symbol_anywhere($symbol)
787 Applies dl_find_symbol() to the members of @dl_librefs and returns
788 the first match found.
790 =item dl_undef_symbols()
794 @symbols = dl_undef_symbols()
796 Return a list of symbol names which remain undefined after load_file().
797 Returns C<()> if not known. Don't worry if your platform does not provide
798 a mechanism for this. Most do not need it and hence do not provide it,
799 they just return an empty list.
802 =item dl_install_xsub()
806 dl_install_xsub($perl_name, $symref [, $filename])
808 Create a new Perl external subroutine named $perl_name using $symref as
809 a pointer to the function which implements the routine. This is simply
810 a direct call to newXSUB(). Returns a reference to the installed
813 The $filename parameter is used by Perl to identify the source file for
814 the function if required by die(), caller() or the debugger. If
815 $filename is not defined then "DynaLoader" will be used.
824 This is the normal entry point for automatic dynamic loading in Perl.
826 It performs the following actions:
832 locates an auto/$module directory by searching @INC
836 uses dl_findfile() to determine the filename to load
840 sets @dl_require_symbols to C<("boot_$module")>
844 executes an F<auto/$module/$module.bs> file if it exists
845 (typically used to add to @dl_resolve_using any files which
846 are required to load the module on the current platform)
850 calls dl_load_flags() to determine how to load the file.
854 calls dl_load_file() to load the file
858 calls dl_undef_symbols() and warns if any symbols are undefined
862 calls dl_find_symbol() for "boot_$module"
866 calls dl_install_xsub() to install it as "${module}::bootstrap"
870 calls &{"${module}::bootstrap"} to bootstrap the module (actually
871 it uses the function reference returned by dl_install_xsub for speed)
880 Tim Bunce, 11 August 1994.
882 This interface is based on the work and comments of (in no particular
883 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
884 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
886 Larry Wall designed the elegant inherited bootstrap mechanism and
887 implemented the first Perl 5 dynamic loader using it.
889 Solaris global loading added by Nick Ing-Simmons with design/coding
890 assistance from Tim Bunce, January 1996.