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
83 @dl_librefs = (); # things we have loaded
84 @dl_modules = (); # Modules we have loaded
86 # This is a fix to support DLD's unfortunate desire to relink -lc
87 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
91 my $cfg_dl_library_path = <<'EOT';
92 push(@dl_library_path, split(' ', $Config::Config{libpth}));
95 sub dquoted_comma_list {
96 join(", ", map {qq("$_")} @_);
99 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
100 eval $cfg_dl_library_path;
101 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
102 my $dl_library_path = dquoted_comma_list(@dl_library_path);
104 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
106 \@dl_library_path = ($dl_library_path);
113 # Initialise \@dl_library_path with the 'standard' library path
114 # for this platform as determined by Configure.
122 my $ldlibpthname_defined;
125 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
126 $ldlibpthname = $Config::Config{ldlibpthname};
127 $ldlibpthname_defined = defined $Config::Config{ldlibpthname} ? 1 : 0;
128 $pthsep = $Config::Config{path_sep};
131 $ldlibpthname = q($Config::Config{ldlibpthname});
132 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
133 $pthsep = q($Config::Config{path_sep});
135 my \$ldlibpthname = $ldlibpthname;
136 my \$ldlibpthname_defined = $ldlibpthname_defined;
137 my \$pthsep = $pthsep;
142 my $env_dl_library_path = <<'EOT';
143 if ($ldlibpthname_defined &&
144 exists $ENV{$ldlibpthname}) {
145 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
148 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
150 if ($ldlibpthname_defined &&
151 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
152 exists $ENV{LD_LIBRARY_PATH}) {
153 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
157 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
158 eval $env_dl_library_path;
162 # Add to \@dl_library_path any extra directories we can gather from environment
170 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
171 my $dl_library_path = dquoted_comma_list(@dl_library_path);
173 # The below \@dl_library_path has been expanded (%Config, %ENV)
174 # in Perl build time.
176 \@dl_library_path = ($dl_library_path);
182 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
183 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
184 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
188 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
189 print STDERR "DynaLoader not linked into this perl\n"
190 unless defined(&boot_DynaLoader);
193 1; # End of main code
196 sub croak { require Carp; Carp::croak(@_) }
198 sub bootstrap_inherit {
200 local *isa = *{"$module\::ISA"};
201 local @isa = (@isa, 'DynaLoader');
202 # Cannot goto due to delocalization. Will report errors on a wrong line?
206 # The bootstrap function cannot be autoloaded (without complications)
207 # so we define it here:
210 # use local vars to enable $module.bs script to edit values
212 local($module) = $args[0];
217 Carp::confess("Usage: DynaLoader::bootstrap(module)");
220 # A common error on platforms which don't support dynamic loading.
221 # Since it's fatal and potentially confusing we give a detailed message.
222 croak("Can't load module $module, dynamic loading not available in this perl.\n".
223 " (You may need to build a new perl executable which either supports\n".
224 " dynamic loading or has the $module module statically linked into it.)\n")
225 unless defined(&dl_load_file);
227 my @modparts = split(/::/,$module);
228 my $modfname = $modparts[-1];
230 # Some systems have restrictions on files names for DLL's etc.
231 # mod2fname returns appropriate file base name (typically truncated)
232 # It may also edit @modparts if required.
233 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
235 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
237 print STDERR "DynaLoader::bootstrap for $module ",
239 ? "(:auto:$modpname:$modfname.$dl_dlext)\n" :
240 "(auto/$modpname/$modfname.$dl_dlext)\n")
244 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
248 $dir = "$_:auto:$modpname";
250 $dir = "$_/auto/$modpname";
252 next unless -d $dir; # skip over uninteresting directories
254 # check for common cases to avoid autoload of dl_findfile
255 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
256 last if $file = ($do_expand) ? dl_expandspec($try) : (-f $try && $try);
258 # no luck here, save dir for possible later dl_findfile search
261 # last resort, let dl_findfile have a go in all known locations
262 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
264 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
265 unless $file; # wording similar to error from 'require'
267 $file = uc($file) if $Is_VMS && $Config::Config{d_vms_case_sensitive_symbols};
268 my $bootname = "boot_$module";
269 $bootname =~ s/\W/_/g;
270 @dl_require_symbols = ($bootname);
272 # Execute optional '.bootstrap' perl script for this module.
273 # The .bs file can be used to configure @dl_resolve_using etc to
274 # match the needs of the individual module on this architecture.
276 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
277 if (-s $bs) { # only read file if it's not empty
278 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
280 warn "$bs: $@\n" if $@;
283 # Many dynamic extension loading problems will appear to come from
284 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
285 # Often these errors are actually occurring in the initialisation
286 # C code of the extension XS file. Perl reports the error as being
287 # in this perl code simply because this was the last perl code
290 my $libref = dl_load_file($file, $module->dl_load_flags) or
291 croak("Can't load '$file' for module $module: ".dl_error());
293 push(@dl_librefs,$libref); # record loaded object
295 my @unresolved = dl_undef_symbols();
298 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
301 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
302 croak("Can't find '$bootname' symbol in $file\n");
304 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
306 push(@dl_modules, $module); # record loaded module
308 # See comment block above
313 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
315 # return $file if (!$do_expand && -f $file); # the common case
316 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
321 # Let autosplit and the autoloader deal with these functions:
326 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
327 # This function does not automatically consider the architecture
328 # or the perl library auto directories.
330 my (@dirs, $dir); # which directories to search
331 my (@found); # full paths to real files we have found
334 print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
335 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
336 print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
337 "; # \$Config::Config{'so'} suffix for shared libraries\n";
341 print STDERR "dl_findfile(@args)\n" if $dl_debug;
343 # accumulate directories but process files as they appear
344 arg: foreach(@args) {
345 # Special fast case: full filepath requires no search
346 if ($Is_VMS && m%[:>/\]]% && -f $_) {
347 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
348 last arg unless wantarray;
354 last arg unless wantarray;
357 elsif (m:/: && -f $_ && !$do_expand) {
359 last arg unless wantarray;
363 # Deal with directories first:
364 # Using a -L prefix is the preferred option (faster and more robust)
365 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
368 # Otherwise we try to try to spot directories by a heuristic
369 # (this is a more complicated issue than it first appears)
370 if (m/:/ && -d $_) { push(@dirs, $_); next; }
371 # Only files should get this far...
372 my(@names, $name); # what filenames to look for
375 foreach $dir (@dirs, @dl_library_path) {
377 $dir =~ s/^([^:]+)$/:$1/;
379 foreach $name (@names) {
380 my($file) = "$dir:$name";
381 print STDERR " checking in $dir for $name\n" if $dl_debug;
384 next arg; # no need to look any further
391 # Otherwise we try to try to spot directories by a heuristic
392 # (this is a more complicated issue than it first appears)
393 if (m:/: && -d $_) { push(@dirs, $_); next; }
395 # VMS: we may be using native VMS directory syntax instead of
396 # Unix emulation, so check this as well
397 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
399 # Only files should get this far...
400 my(@names, $name); # what filenames to look for
401 if (m:-l: ) { # convert -lname to appropriate library name
403 push(@names,"lib$_.$dl_so");
404 push(@names,"lib$_.a");
405 } else { # Umm, a bare name. Try various alternatives:
406 # these should be ordered with the most likely first
407 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
408 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
409 push(@names,"lib$_.$dl_so") unless m:/:;
410 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
413 foreach $dir (@dirs, @dl_library_path) {
415 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
416 foreach $name (@names) {
417 my($file) = "$dir/$name";
418 print STDERR " checking in $dir for $name\n" if $dl_debug;
419 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
420 #$file = _check_file($file);
423 next arg; # no need to look any further
430 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
432 print STDERR "dl_findfile found: @found\n";
434 return $found[0] unless wantarray;
441 # Optional function invoked if DynaLoader.pm sets $do_expand.
442 # Most systems do not require or use this function.
443 # Some systems may implement it in the dl_*.xs file in which case
444 # this autoload version will not be called but is harmless.
446 # This function is designed to deal with systems which treat some
447 # 'filenames' in a special way. For example VMS 'Logical Names'
448 # (something like unix environment variables - but different).
449 # This function should recognise such names and expand them into
451 # Must return undef if $spec is invalid or file does not exist.
453 my $file = $spec; # default output to input
455 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
457 Carp::croak("dl_expandspec: should be defined in XS file!\n");
459 return undef unless -f $file;
461 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
465 sub dl_find_symbol_anywhere
469 foreach $libref (@dl_librefs) {
470 my $symref = dl_find_symbol($libref,$sym);
471 return $symref if $symref;
478 DynaLoader - Dynamically load C libraries into Perl code
480 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_unload_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
486 @ISA = qw(... DynaLoader ...);
487 bootstrap YourPackage;
489 # optional method for 'global' loading
490 sub dl_load_flags { 0x01 }
495 This document defines a standard generic interface to the dynamic
496 linking mechanisms available on many platforms. Its primary purpose is
497 to implement automatic dynamic loading of Perl modules.
499 This document serves as both a specification for anyone wishing to
500 implement the DynaLoader for a new platform and as a guide for
501 anyone wishing to use the DynaLoader directly in an application.
503 The DynaLoader is designed to be a very simple high-level
504 interface that is sufficiently general to cover the requirements
505 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
507 It is also hoped that the interface will cover the needs of OS/2, NT
508 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
510 It must be stressed that the DynaLoader, by itself, is practically
511 useless for accessing non-Perl libraries because it provides almost no
512 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
513 library function or supplying arguments. A C::DynaLib module
514 is available from CPAN sites which performs that function for some
517 DynaLoader Interface Summary
526 bootstrap($modulename) Perl
527 @filepaths = dl_findfile(@names) Perl
528 $flags = $modulename->dl_load_flags Perl
529 $symref = dl_find_symbol_anywhere($symbol) Perl
531 $libref = dl_load_file($filename, $flags) C
532 $status = dl_unload_file($libref) C
533 $symref = dl_find_symbol($libref, $symbol) C
534 @symbols = dl_undef_symbols() C
535 dl_install_xsub($name, $symref [, $filename]) C
536 $message = dl_error C
540 =item @dl_library_path
542 The standard/default list of directories in which dl_findfile() will
543 search for libraries etc. Directories are searched in order:
544 $dl_library_path[0], [1], ... etc
546 @dl_library_path is initialised to hold the list of 'normal' directories
547 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
548 ensure portability across a wide range of platforms.
550 @dl_library_path should also be initialised with any other directories
551 that can be determined from the environment at runtime (such as
552 LD_LIBRARY_PATH for SunOS).
554 After initialisation @dl_library_path can be manipulated by an
555 application using push and unshift before calling dl_findfile().
556 Unshift can be used to add directories to the front of the search order
557 either to save search time or to override libraries with the same name
558 in the 'normal' directories.
560 The load function that dl_load_file() calls may require an absolute
561 pathname. The dl_findfile() function and @dl_library_path can be
562 used to search for and return the absolute pathname for the
563 library/object that you wish to load.
565 =item @dl_resolve_using
567 A list of additional libraries or other shared objects which can be
568 used to resolve any undefined symbols that might be generated by a
569 later call to load_file().
571 This is only required on some platforms which do not handle dependent
572 libraries automatically. For example the Socket Perl extension
573 library (F<auto/Socket/Socket.so>) contains references to many socket
574 functions which need to be resolved when it's loaded. Most platforms
575 will automatically know where to find the 'dependent' library (e.g.,
576 F</usr/lib/libsocket.so>). A few platforms need to be told the
577 location of the dependent library explicitly. Use @dl_resolve_using
582 @dl_resolve_using = dl_findfile('-lsocket');
584 =item @dl_require_symbols
586 A list of one or more symbol names that are in the library/object file
587 to be dynamically loaded. This is only required on some platforms.
591 An array of the handles returned by successful calls to dl_load_file(),
592 made by bootstrap, in the order in which they were loaded.
593 Can be used with dl_find_symbol() to look for a symbol in any of
598 An array of module (package) names that have been bootstrap'ed.
604 $message = dl_error();
606 Error message text from the last failed DynaLoader function. Note
607 that, similar to errno in unix, a successful function call does not
610 Implementations should detect the error as soon as it occurs in any of
611 the other functions and save the corresponding message for later
612 retrieval. This will avoid problems on some platforms (such as SunOS)
613 where the error message is very temporary (e.g., dlerror()).
617 Internal debugging messages are enabled when $dl_debug is set true.
618 Currently setting $dl_debug only affects the Perl side of the
619 DynaLoader. These messages should help an application developer to
620 resolve any DynaLoader usage problems.
622 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
624 For the DynaLoader developer/porter there is a similar debugging
625 variable added to the C code (see dlutils.c) and enabled if Perl was
626 built with the B<-DDEBUGGING> flag. This can also be set via the
627 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
634 @filepaths = dl_findfile(@names)
636 Determine the full paths (including file suffix) of one or more
637 loadable files given their generic names and optionally one or more
638 directories. Searches directories in @dl_library_path by default and
639 returns an empty list if no files were found.
641 Names can be specified in a variety of platform independent forms. Any
642 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
643 an appropriate suffix for the platform.
645 If a name does not already have a suitable prefix and/or suffix then
646 the corresponding file will be searched for by trying combinations of
647 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
650 If any directories are included in @names they are searched before
651 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
652 names are treated as filenames to be searched for.
654 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
658 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
661 =item dl_expandspec()
665 $filepath = dl_expandspec($spec)
667 Some unusual systems, such as VMS, require special filename handling in
668 order to deal with symbolic names for files (i.e., VMS's Logical Names).
670 To support these systems a dl_expandspec() function can be implemented
671 either in the F<dl_*.xs> file or code can be added to the autoloadable
672 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
679 $libref = dl_load_file($filename, $flags)
681 Dynamically load $filename, which must be the path to a shared object
682 or library. An opaque 'library reference' is returned as a handle for
683 the loaded object. Returns undef on error.
685 The $flags argument to alters dl_load_file behaviour.
688 0x01 make symbols available for linking later dl_load_file's.
689 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
690 (ignored under VMS; this is a normal part of image linking)
692 (On systems that provide a handle for the loaded object such as SunOS
693 and HPUX, $libref will be that handle. On other systems $libref will
694 typically be $filename or a pointer to a buffer containing $filename.
695 The application should not examine or alter $libref in any way.)
697 This is the function that does the real work. It should use the
698 current values of @dl_require_symbols and @dl_resolve_using if required.
700 SunOS: dlopen($filename)
701 HP-UX: shl_load($filename)
702 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
703 NeXT: rld_load($filename, @dl_resolve_using)
704 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
706 (The dlopen() function is also used by Solaris and some versions of
707 Linux, and is a common choice when providing a "wrapper" on other
708 mechanisms as is done in the OS/2 port.)
710 =item dl_unload_file()
714 $status = dl_unload_file($libref)
716 Dynamically unload $libref, which must be an opaque 'library reference' as
717 returned from dl_load_file. Returns one on success and zero on failure.
719 This function is optional and may not necessarily be provided on all platforms.
720 If it is defined, it is called automatically when the interpreter exits for
721 every shared object or library loaded by DynaLoader::bootstrap. All such
722 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
723 loads the libraries. The files are unloaded in last-in, first-out order.
725 This unloading is usually necessary when embedding a shared-object perl (e.g.
726 one configured with -Duseshrplib) within a larger application, and the perl
727 interpreter is created and destroyed several times within the lifetime of the
728 application. In this case it is possible that the system dynamic linker will
729 unload and then subsequently reload the shared libperl without relocating any
730 references to it from any files DynaLoaded by the previous incarnation of the
731 interpreter. As a result, any shared objects opened by DynaLoader may point to
732 a now invalid 'ghost' of the libperl shared object, causing apparently random
733 memory corruption and crashes. This behaviour is most commonly seen when using
734 Apache and mod_perl built with the APXS mechanism.
736 SunOS: dlclose($libref)
742 (The dlclose() function is also used by Solaris and some versions of
743 Linux, and is a common choice when providing a "wrapper" on other
744 mechanisms as is done in the OS/2 port.)
750 $flags = dl_loadflags $modulename;
752 Designed to be a method call, and to be overridden by a derived class
753 (i.e. a class which has DynaLoader in its @ISA). The definition in
754 DynaLoader itself returns 0, which produces standard behavior from
757 =item dl_find_symbol()
761 $symref = dl_find_symbol($libref, $symbol)
763 Return the address of the symbol $symbol or C<undef> if not found. If the
764 target system has separate functions to search for symbols of different
765 types then dl_find_symbol() should search for function symbols first and
768 The exact manner in which the address is returned in $symref is not
769 currently defined. The only initial requirement is that $symref can
770 be passed to, and understood by, dl_install_xsub().
772 SunOS: dlsym($libref, $symbol)
773 HP-UX: shl_findsym($libref, $symbol)
774 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
775 NeXT: rld_lookup("_$symbol")
776 VMS: lib$find_image_symbol($libref,$symbol)
779 =item dl_find_symbol_anywhere()
783 $symref = dl_find_symbol_anywhere($symbol)
785 Applies dl_find_symbol() to the members of @dl_librefs and returns
786 the first match found.
788 =item dl_undef_symbols()
792 @symbols = dl_undef_symbols()
794 Return a list of symbol names which remain undefined after load_file().
795 Returns C<()> if not known. Don't worry if your platform does not provide
796 a mechanism for this. Most do not need it and hence do not provide it,
797 they just return an empty list.
800 =item dl_install_xsub()
804 dl_install_xsub($perl_name, $symref [, $filename])
806 Create a new Perl external subroutine named $perl_name using $symref as
807 a pointer to the function which implements the routine. This is simply
808 a direct call to newXSUB(). Returns a reference to the installed
811 The $filename parameter is used by Perl to identify the source file for
812 the function if required by die(), caller() or the debugger. If
813 $filename is not defined then "DynaLoader" will be used.
822 This is the normal entry point for automatic dynamic loading in Perl.
824 It performs the following actions:
830 locates an auto/$module directory by searching @INC
834 uses dl_findfile() to determine the filename to load
838 sets @dl_require_symbols to C<("boot_$module")>
842 executes an F<auto/$module/$module.bs> file if it exists
843 (typically used to add to @dl_resolve_using any files which
844 are required to load the module on the current platform)
848 calls dl_load_flags() to determine how to load the file.
852 calls dl_load_file() to load the file
856 calls dl_undef_symbols() and warns if any symbols are undefined
860 calls dl_find_symbol() for "boot_$module"
864 calls dl_install_xsub() to install it as "${module}::bootstrap"
868 calls &{"${module}::bootstrap"} to bootstrap the module (actually
869 it uses the function reference returned by dl_install_xsub for speed)
878 Tim Bunce, 11 August 1994.
880 This interface is based on the work and comments of (in no particular
881 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
882 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
884 Larry Wall designed the elegant inherited bootstrap mechanism and
885 implemented the first Perl 5 dynamic loader using it.
887 Solaris global loading added by Nick Ing-Simmons with design/coding
888 assistance from Tim Bunce, January 1996.