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';
81 $Mac_FS = eval { require Mac::FileSpec::Unixish } if $Is_MacOS;
83 @dl_require_symbols = (); # names of symbols we need
84 @dl_resolve_using = (); # names of files to link with
85 @dl_library_path = (); # path to look for files
87 #XSLoader.pm may have added elements before we were required
88 #@dl_librefs = (); # things we have loaded
89 #@dl_modules = (); # Modules we have loaded
91 # This is a fix to support DLD's unfortunate desire to relink -lc
92 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
96 my $cfg_dl_library_path = <<'EOT';
97 push(@dl_library_path, split(' ', $Config::Config{libpth}));
100 sub dquoted_comma_list {
101 join(", ", map {qq("$_")} @_);
104 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
105 eval $cfg_dl_library_path;
106 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
107 my $dl_library_path = dquoted_comma_list(@dl_library_path);
109 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
111 \@dl_library_path = ($dl_library_path);
118 # Initialise \@dl_library_path with the 'standard' library path
119 # for this platform as determined by Configure.
127 my $ldlibpthname_defined;
130 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
131 $ldlibpthname = $Config::Config{ldlibpthname};
132 $ldlibpthname_defined = defined $Config::Config{ldlibpthname} ? 1 : 0;
133 $pthsep = $Config::Config{path_sep};
136 $ldlibpthname = q($Config::Config{ldlibpthname});
137 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
138 $pthsep = q($Config::Config{path_sep});
140 my \$ldlibpthname = $ldlibpthname;
141 my \$ldlibpthname_defined = $ldlibpthname_defined;
142 my \$pthsep = $pthsep;
147 my $env_dl_library_path = <<'EOT';
148 if ($ldlibpthname_defined &&
149 exists $ENV{$ldlibpthname}) {
150 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
153 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
155 if ($ldlibpthname_defined &&
156 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
157 exists $ENV{LD_LIBRARY_PATH}) {
158 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
162 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
163 eval $env_dl_library_path;
167 # Add to \@dl_library_path any extra directories we can gather from environment
175 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
176 my $dl_library_path = dquoted_comma_list(@dl_library_path);
178 # The below \@dl_library_path has been expanded (%Config, %ENV)
179 # in Perl build time.
181 \@dl_library_path = ($dl_library_path);
187 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
188 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
189 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
193 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
194 print STDERR "DynaLoader not linked into this perl\n"
195 unless defined(&boot_DynaLoader);
198 1; # End of main code
201 sub croak { require Carp; Carp::croak(@_) }
203 sub bootstrap_inherit {
205 local *isa = *{"$module\::ISA"};
206 local @isa = (@isa, 'DynaLoader');
207 # Cannot goto due to delocalization. Will report errors on a wrong line?
211 # The bootstrap function cannot be autoloaded (without complications)
212 # so we define it here:
215 # use local vars to enable $module.bs script to edit values
217 local($module) = $args[0];
222 Carp::confess("Usage: DynaLoader::bootstrap(module)");
225 # A common error on platforms which don't support dynamic loading.
226 # Since it's fatal and potentially confusing we give a detailed message.
227 croak("Can't load module $module, dynamic loading not available in this perl.\n".
228 " (You may need to build a new perl executable which either supports\n".
229 " dynamic loading or has the $module module statically linked into it.)\n")
230 unless defined(&dl_load_file);
232 my @modparts = split(/::/,$module);
233 my $modfname = $modparts[-1];
235 # Some systems have restrictions on files names for DLL's etc.
236 # mod2fname returns appropriate file base name (typically truncated)
237 # It may also edit @modparts if required.
238 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
240 # Truncate the module name to 8.3 format for NetWare
241 if (($^O eq 'NetWare') && (length($modfname) > 8)) {
242 $modfname = substr($modfname, 0, 8);
245 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
247 print STDERR "DynaLoader::bootstrap for $module ",
249 ? "(:auto:$modpname:$modfname.$dl_dlext)\n" :
250 "(auto/$modpname/$modfname.$dl_dlext)\n")
254 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
258 if ($Mac_FS && ! -d $path) {
259 $path = Mac::FileSpec::Unixish::nativize($path);
261 $path .= ":" unless /:$/;
262 $dir = "${path}auto:$modpname";
264 $dir = "$_/auto/$modpname";
267 next unless -d $dir; # skip over uninteresting directories
269 # check for common cases to avoid autoload of dl_findfile
270 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
271 last if $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
273 # no luck here, save dir for possible later dl_findfile search
276 # last resort, let dl_findfile have a go in all known locations
277 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
279 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
280 unless $file; # wording similar to error from 'require'
282 $file = uc($file) if $Is_VMS && $Config::Config{d_vms_case_sensitive_symbols};
283 my $bootname = "boot_$module";
284 $bootname =~ s/\W/_/g;
285 @dl_require_symbols = ($bootname);
287 # Execute optional '.bootstrap' perl script for this module.
288 # The .bs file can be used to configure @dl_resolve_using etc to
289 # match the needs of the individual module on this architecture.
291 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
292 if (-s $bs) { # only read file if it's not empty
293 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
295 warn "$bs: $@\n" if $@;
300 if ($^O eq 'darwin') {
301 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
302 goto boot; #extension library has already been loaded, e.g. darwin
306 # Many dynamic extension loading problems will appear to come from
307 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
308 # Often these errors are actually occurring in the initialisation
309 # C code of the extension XS file. Perl reports the error as being
310 # in this perl code simply because this was the last perl code
313 my $libref = dl_load_file($file, $module->dl_load_flags) or
314 croak("Can't load '$file' for module $module: ".dl_error());
316 push(@dl_librefs,$libref); # record loaded object
318 my @unresolved = dl_undef_symbols();
321 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
324 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
325 croak("Can't find '$bootname' symbol in $file\n");
327 push(@dl_modules, $module); # record loaded module
330 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
332 # See comment block above
337 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
339 # return $file if (!$do_expand && -f $file); # the common case
340 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
345 # Let autosplit and the autoloader deal with these functions:
350 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
351 # This function does not automatically consider the architecture
352 # or the perl library auto directories.
354 my (@dirs, $dir); # which directories to search
355 my (@found); # full paths to real files we have found
358 print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
359 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
360 print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
361 "; # \$Config::Config{'so'} suffix for shared libraries\n";
365 print STDERR "dl_findfile(@args)\n" if $dl_debug;
367 # accumulate directories but process files as they appear
368 arg: foreach(@args) {
369 # Special fast case: full filepath requires no search
370 if ($Is_VMS && m%[:>/\]]% && -f $_) {
371 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
372 last arg unless wantarray;
378 last arg unless wantarray;
381 elsif (m:/: && -f $_ && !$do_expand) {
383 last arg unless wantarray;
387 # Deal with directories first:
388 # Using a -L prefix is the preferred option (faster and more robust)
389 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
392 # Otherwise we try to try to spot directories by a heuristic
393 # (this is a more complicated issue than it first appears)
394 if (m/:/ && -d $_) { push(@dirs, $_); next; }
395 # Only files should get this far...
396 my(@names, $name); # what filenames to look for
399 foreach $dir (@dirs, @dl_library_path) {
401 $dir =~ s/^([^:]+)$/:$1/;
403 foreach $name (@names) {
404 my($file) = "$dir:$name";
405 print STDERR " checking in $dir for $name\n" if $dl_debug;
408 next arg; # no need to look any further
415 # Otherwise we try to try to spot directories by a heuristic
416 # (this is a more complicated issue than it first appears)
417 if (m:/: && -d $_) { push(@dirs, $_); next; }
419 # VMS: we may be using native VMS directory syntax instead of
420 # Unix emulation, so check this as well
421 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
423 # Only files should get this far...
424 my(@names, $name); # what filenames to look for
425 if (m:-l: ) { # convert -lname to appropriate library name
427 push(@names,"lib$_.$dl_so");
428 push(@names,"lib$_.a");
429 } else { # Umm, a bare name. Try various alternatives:
430 # these should be ordered with the most likely first
431 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
432 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
433 push(@names,"lib$_.$dl_so") unless m:/:;
434 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
437 foreach $dir (@dirs, @dl_library_path) {
439 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
440 foreach $name (@names) {
441 my($file) = "$dir/$name";
442 print STDERR " checking in $dir for $name\n" if $dl_debug;
443 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
444 #$file = _check_file($file);
447 next arg; # no need to look any further
454 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
456 print STDERR "dl_findfile found: @found\n";
458 return $found[0] unless wantarray;
465 # Optional function invoked if DynaLoader.pm sets $do_expand.
466 # Most systems do not require or use this function.
467 # Some systems may implement it in the dl_*.xs file in which case
468 # this autoload version will not be called but is harmless.
470 # This function is designed to deal with systems which treat some
471 # 'filenames' in a special way. For example VMS 'Logical Names'
472 # (something like unix environment variables - but different).
473 # This function should recognise such names and expand them into
475 # Must return undef if $spec is invalid or file does not exist.
477 my $file = $spec; # default output to input
479 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
481 Carp::croak("dl_expandspec: should be defined in XS file!\n");
483 return undef unless -f $file;
485 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
489 sub dl_find_symbol_anywhere
493 foreach $libref (@dl_librefs) {
494 my $symref = dl_find_symbol($libref,$sym);
495 return $symref if $symref;
502 DynaLoader - Dynamically load C libraries into Perl code
504 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_unload_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
510 @ISA = qw(... DynaLoader ...);
511 bootstrap YourPackage;
513 # optional method for 'global' loading
514 sub dl_load_flags { 0x01 }
519 This document defines a standard generic interface to the dynamic
520 linking mechanisms available on many platforms. Its primary purpose is
521 to implement automatic dynamic loading of Perl modules.
523 This document serves as both a specification for anyone wishing to
524 implement the DynaLoader for a new platform and as a guide for
525 anyone wishing to use the DynaLoader directly in an application.
527 The DynaLoader is designed to be a very simple high-level
528 interface that is sufficiently general to cover the requirements
529 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
531 It is also hoped that the interface will cover the needs of OS/2, NT
532 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
534 It must be stressed that the DynaLoader, by itself, is practically
535 useless for accessing non-Perl libraries because it provides almost no
536 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
537 library function or supplying arguments. A C::DynaLib module
538 is available from CPAN sites which performs that function for some
539 common system types. And since the year 2000, there's also Inline::C,
540 a module that allows you to write Perl subroutines in C. Also available
541 from your local CPAN site.
543 DynaLoader Interface Summary
552 bootstrap($modulename) Perl
553 @filepaths = dl_findfile(@names) Perl
554 $flags = $modulename->dl_load_flags Perl
555 $symref = dl_find_symbol_anywhere($symbol) Perl
557 $libref = dl_load_file($filename, $flags) C
558 $status = dl_unload_file($libref) C
559 $symref = dl_find_symbol($libref, $symbol) C
560 @symbols = dl_undef_symbols() C
561 dl_install_xsub($name, $symref [, $filename]) C
562 $message = dl_error C
566 =item @dl_library_path
568 The standard/default list of directories in which dl_findfile() will
569 search for libraries etc. Directories are searched in order:
570 $dl_library_path[0], [1], ... etc
572 @dl_library_path is initialised to hold the list of 'normal' directories
573 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
574 ensure portability across a wide range of platforms.
576 @dl_library_path should also be initialised with any other directories
577 that can be determined from the environment at runtime (such as
578 LD_LIBRARY_PATH for SunOS).
580 After initialisation @dl_library_path can be manipulated by an
581 application using push and unshift before calling dl_findfile().
582 Unshift can be used to add directories to the front of the search order
583 either to save search time or to override libraries with the same name
584 in the 'normal' directories.
586 The load function that dl_load_file() calls may require an absolute
587 pathname. The dl_findfile() function and @dl_library_path can be
588 used to search for and return the absolute pathname for the
589 library/object that you wish to load.
591 =item @dl_resolve_using
593 A list of additional libraries or other shared objects which can be
594 used to resolve any undefined symbols that might be generated by a
595 later call to load_file().
597 This is only required on some platforms which do not handle dependent
598 libraries automatically. For example the Socket Perl extension
599 library (F<auto/Socket/Socket.so>) contains references to many socket
600 functions which need to be resolved when it's loaded. Most platforms
601 will automatically know where to find the 'dependent' library (e.g.,
602 F</usr/lib/libsocket.so>). A few platforms need to be told the
603 location of the dependent library explicitly. Use @dl_resolve_using
608 @dl_resolve_using = dl_findfile('-lsocket');
610 =item @dl_require_symbols
612 A list of one or more symbol names that are in the library/object file
613 to be dynamically loaded. This is only required on some platforms.
617 An array of the handles returned by successful calls to dl_load_file(),
618 made by bootstrap, in the order in which they were loaded.
619 Can be used with dl_find_symbol() to look for a symbol in any of
624 An array of module (package) names that have been bootstrap'ed.
630 $message = dl_error();
632 Error message text from the last failed DynaLoader function. Note
633 that, similar to errno in unix, a successful function call does not
636 Implementations should detect the error as soon as it occurs in any of
637 the other functions and save the corresponding message for later
638 retrieval. This will avoid problems on some platforms (such as SunOS)
639 where the error message is very temporary (e.g., dlerror()).
643 Internal debugging messages are enabled when $dl_debug is set true.
644 Currently setting $dl_debug only affects the Perl side of the
645 DynaLoader. These messages should help an application developer to
646 resolve any DynaLoader usage problems.
648 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
650 For the DynaLoader developer/porter there is a similar debugging
651 variable added to the C code (see dlutils.c) and enabled if Perl was
652 built with the B<-DDEBUGGING> flag. This can also be set via the
653 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
660 @filepaths = dl_findfile(@names)
662 Determine the full paths (including file suffix) of one or more
663 loadable files given their generic names and optionally one or more
664 directories. Searches directories in @dl_library_path by default and
665 returns an empty list if no files were found.
667 Names can be specified in a variety of platform independent forms. Any
668 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
669 an appropriate suffix for the platform.
671 If a name does not already have a suitable prefix and/or suffix then
672 the corresponding file will be searched for by trying combinations of
673 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
676 If any directories are included in @names they are searched before
677 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
678 names are treated as filenames to be searched for.
680 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
684 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
687 =item dl_expandspec()
691 $filepath = dl_expandspec($spec)
693 Some unusual systems, such as VMS, require special filename handling in
694 order to deal with symbolic names for files (i.e., VMS's Logical Names).
696 To support these systems a dl_expandspec() function can be implemented
697 either in the F<dl_*.xs> file or code can be added to the autoloadable
698 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
705 $libref = dl_load_file($filename, $flags)
707 Dynamically load $filename, which must be the path to a shared object
708 or library. An opaque 'library reference' is returned as a handle for
709 the loaded object. Returns undef on error.
711 The $flags argument to alters dl_load_file behaviour.
714 0x01 make symbols available for linking later dl_load_file's.
715 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
716 (ignored under VMS; this is a normal part of image linking)
718 (On systems that provide a handle for the loaded object such as SunOS
719 and HPUX, $libref will be that handle. On other systems $libref will
720 typically be $filename or a pointer to a buffer containing $filename.
721 The application should not examine or alter $libref in any way.)
723 This is the function that does the real work. It should use the
724 current values of @dl_require_symbols and @dl_resolve_using if required.
726 SunOS: dlopen($filename)
727 HP-UX: shl_load($filename)
728 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
729 NeXT: rld_load($filename, @dl_resolve_using)
730 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
732 (The dlopen() function is also used by Solaris and some versions of
733 Linux, and is a common choice when providing a "wrapper" on other
734 mechanisms as is done in the OS/2 port.)
736 =item dl_unload_file()
740 $status = dl_unload_file($libref)
742 Dynamically unload $libref, which must be an opaque 'library reference' as
743 returned from dl_load_file. Returns one on success and zero on failure.
745 This function is optional and may not necessarily be provided on all platforms.
746 If it is defined, it is called automatically when the interpreter exits for
747 every shared object or library loaded by DynaLoader::bootstrap. All such
748 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
749 loads the libraries. The files are unloaded in last-in, first-out order.
751 This unloading is usually necessary when embedding a shared-object perl (e.g.
752 one configured with -Duseshrplib) within a larger application, and the perl
753 interpreter is created and destroyed several times within the lifetime of the
754 application. In this case it is possible that the system dynamic linker will
755 unload and then subsequently reload the shared libperl without relocating any
756 references to it from any files DynaLoaded by the previous incarnation of the
757 interpreter. As a result, any shared objects opened by DynaLoader may point to
758 a now invalid 'ghost' of the libperl shared object, causing apparently random
759 memory corruption and crashes. This behaviour is most commonly seen when using
760 Apache and mod_perl built with the APXS mechanism.
762 SunOS: dlclose($libref)
768 (The dlclose() function is also used by Solaris and some versions of
769 Linux, and is a common choice when providing a "wrapper" on other
770 mechanisms as is done in the OS/2 port.)
772 =item dl_load_flags()
776 $flags = dl_load_flags $modulename;
778 Designed to be a method call, and to be overridden by a derived class
779 (i.e. a class which has DynaLoader in its @ISA). The definition in
780 DynaLoader itself returns 0, which produces standard behavior from
783 =item dl_find_symbol()
787 $symref = dl_find_symbol($libref, $symbol)
789 Return the address of the symbol $symbol or C<undef> if not found. If the
790 target system has separate functions to search for symbols of different
791 types then dl_find_symbol() should search for function symbols first and
794 The exact manner in which the address is returned in $symref is not
795 currently defined. The only initial requirement is that $symref can
796 be passed to, and understood by, dl_install_xsub().
798 SunOS: dlsym($libref, $symbol)
799 HP-UX: shl_findsym($libref, $symbol)
800 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
801 NeXT: rld_lookup("_$symbol")
802 VMS: lib$find_image_symbol($libref,$symbol)
805 =item dl_find_symbol_anywhere()
809 $symref = dl_find_symbol_anywhere($symbol)
811 Applies dl_find_symbol() to the members of @dl_librefs and returns
812 the first match found.
814 =item dl_undef_symbols()
818 @symbols = dl_undef_symbols()
820 Return a list of symbol names which remain undefined after load_file().
821 Returns C<()> if not known. Don't worry if your platform does not provide
822 a mechanism for this. Most do not need it and hence do not provide it,
823 they just return an empty list.
826 =item dl_install_xsub()
830 dl_install_xsub($perl_name, $symref [, $filename])
832 Create a new Perl external subroutine named $perl_name using $symref as
833 a pointer to the function which implements the routine. This is simply
834 a direct call to newXSUB(). Returns a reference to the installed
837 The $filename parameter is used by Perl to identify the source file for
838 the function if required by die(), caller() or the debugger. If
839 $filename is not defined then "DynaLoader" will be used.
848 This is the normal entry point for automatic dynamic loading in Perl.
850 It performs the following actions:
856 locates an auto/$module directory by searching @INC
860 uses dl_findfile() to determine the filename to load
864 sets @dl_require_symbols to C<("boot_$module")>
868 executes an F<auto/$module/$module.bs> file if it exists
869 (typically used to add to @dl_resolve_using any files which
870 are required to load the module on the current platform)
874 calls dl_load_flags() to determine how to load the file.
878 calls dl_load_file() to load the file
882 calls dl_undef_symbols() and warns if any symbols are undefined
886 calls dl_find_symbol() for "boot_$module"
890 calls dl_install_xsub() to install it as "${module}::bootstrap"
894 calls &{"${module}::bootstrap"} to bootstrap the module (actually
895 it uses the function reference returned by dl_install_xsub for speed)
904 Tim Bunce, 11 August 1994.
906 This interface is based on the work and comments of (in no particular
907 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
908 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
910 Larry Wall designed the elegant inherited bootstrap mechanism and
911 implemented the first Perl 5 dynamic loader using it.
913 Solaris global loading added by Nick Ing-Simmons with design/coding
914 assistance from Tim Bunce, January 1996.