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 $XS_VERSION);
32 $VERSION = '1.05'; # avoid typo warning
34 # See http://rt.perl.org/rt3//Public/Bug/Display.html?id=32539
35 # for why we need this. Basically any embedded code will have 1.05 hard-coded
36 # in it as the XS_VERSION to check against. If a shared libperl is upgraded,
37 # then it will pull in a newer DynaLoader.pm file, because the shared libperl
38 # provides the paths for @INC. The file in @INC provides the
39 # $DynaLoader::XS_VERSION that the existing embedded code checks against, so
40 # we must keep this value constant, else bootstrap_DynaLoader will croak()
41 # Whilst moving bootstrap_DynaLoader to the shared libperl is the correct
42 # long-term fix, it doesn't help current installations, as they're still
43 # going to find the boot_DynaLoader linked to them (with its hard-coded 1.05)
44 # (It's found via a passed in function pointer in the xsinit parameter to
45 # perl_parse, and in turn that is typically the static function xs_init
46 # defined in the same place as the caller to perl_parse, and at the same time,
47 # so compiled in and installed as binaries now deployed.)
51 *AUTOLOAD = \&AutoLoader::AUTOLOAD;
55 # The following require can't be removed during maintenance
56 # releases, sadly, because of the risk of buggy code that does
57 # require Carp; Carp::croak "..."; without brackets dying
58 # if Carp hasn't been loaded in earlier compile time. :-(
59 # We'll let those bugs get found on the development track.
60 require Carp if $] < 5.00450;
62 # enable debug/trace messages from DynaLoader perl code
63 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
66 # Flags to alter dl_load_file behaviour. Assigned bits:
67 # 0x01 make symbols available for linking later dl_load_file's.
68 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
69 # (ignored under VMS; effect is built-in to image linking)
71 # This is called as a class method $module->dl_load_flags. The
72 # definition here will be inherited and result on "default" loading
73 # behaviour unless a sub-class of DynaLoader defines its own version.
76 sub dl_load_flags { 0x00 }
79 # = @Config::Config{'dlext', 'dlsrc'};
82 print OUT " (\$dl_dlext, \$dlsrc) = (",
83 to_string($Config::Config{'dlext'}), ",",
84 to_string($Config::Config{'dlsrc'}), ")\n;" ;
88 # Some systems need special handling to expand file specifications
89 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
90 # See dl_expandspec() for more details. Should be harmless but
91 # inefficient to define on systems that don't need it.
92 $Is_VMS = $^O eq 'VMS';
94 $Is_MacOS = $^O eq 'MacOS';
97 $Mac_FS = eval { require Mac::FileSpec::Unixish } if $Is_MacOS;
99 @dl_require_symbols = (); # names of symbols we need
100 @dl_resolve_using = (); # names of files to link with
101 @dl_library_path = (); # path to look for files
103 #XSLoader.pm may have added elements before we were required
104 #@dl_shared_objects = (); # shared objects for symbols we have
105 #@dl_librefs = (); # things we have loaded
106 #@dl_modules = (); # Modules we have loaded
108 # This is a fix to support DLD's unfortunate desire to relink -lc
109 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
113 my $cfg_dl_library_path = <<'EOT';
114 push(@dl_library_path, split(' ', $Config::Config{libpth}));
117 sub dquoted_comma_list {
118 join(", ", map {qq("$_")} @_);
121 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
122 eval $cfg_dl_library_path;
123 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
124 my $dl_library_path = dquoted_comma_list(@dl_library_path);
126 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
128 \@dl_library_path = ($dl_library_path);
135 # Initialise \@dl_library_path with the 'standard' library path
136 # for this platform as determined by Configure.
144 my $ldlibpthname_defined;
147 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
148 $ldlibpthname = $Config::Config{ldlibpthname};
149 $ldlibpthname_defined = defined $Config::Config{ldlibpthname} ? 1 : 0;
150 $pthsep = $Config::Config{path_sep};
153 $ldlibpthname = q($Config::Config{ldlibpthname});
154 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
155 $pthsep = q($Config::Config{path_sep});
157 my \$ldlibpthname = $ldlibpthname;
158 my \$ldlibpthname_defined = $ldlibpthname_defined;
159 my \$pthsep = $pthsep;
164 my $env_dl_library_path = <<'EOT';
165 if ($ldlibpthname_defined &&
166 exists $ENV{$ldlibpthname}) {
167 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
170 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
172 if ($ldlibpthname_defined &&
173 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
174 exists $ENV{LD_LIBRARY_PATH}) {
175 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
179 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
180 eval $env_dl_library_path;
184 # Add to \@dl_library_path any extra directories we can gather from environment
192 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
193 my $dl_library_path = dquoted_comma_list(@dl_library_path);
195 # The below \@dl_library_path has been expanded (%Config, %ENV)
196 # in Perl build time.
198 \@dl_library_path = ($dl_library_path);
204 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
205 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
206 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
210 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
211 print STDERR "DynaLoader not linked into this perl\n"
212 unless defined(&boot_DynaLoader);
215 1; # End of main code
218 sub croak { require Carp; Carp::croak(@_) }
220 sub bootstrap_inherit {
222 local *isa = *{"$module\::ISA"};
223 local @isa = (@isa, 'DynaLoader');
224 # Cannot goto due to delocalization. Will report errors on a wrong line?
228 # The bootstrap function cannot be autoloaded (without complications)
229 # so we define it here:
232 # use local vars to enable $module.bs script to edit values
234 local($module) = $args[0];
239 Carp::confess("Usage: DynaLoader::bootstrap(module)");
242 # A common error on platforms which don't support dynamic loading.
243 # Since it's fatal and potentially confusing we give a detailed message.
244 croak("Can't load module $module, dynamic loading not available in this perl.\n".
245 " (You may need to build a new perl executable which either supports\n".
246 " dynamic loading or has the $module module statically linked into it.)\n")
247 unless defined(&dl_load_file);
251 print OUT <<'EOT' if $^O eq 'os2';
252 # Can dynaload, but cannot dynaload Perl modules...
253 die 'Dynaloaded Perl modules are not available in this build of Perl' if $OS2::is_static;
258 my @modparts = split(/::/,$module);
259 my $modfname = $modparts[-1];
261 # Some systems have restrictions on files names for DLL's etc.
262 # mod2fname returns appropriate file base name (typically truncated)
263 # It may also edit @modparts if required.
264 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
266 # Truncate the module name to 8.3 format for NetWare
267 if (($^O eq 'NetWare') && (length($modfname) > 8)) {
268 $modfname = substr($modfname, 0, 8);
271 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
273 print STDERR "DynaLoader::bootstrap for $module ",
275 ? "(:auto:$modpname:$modfname.$dl_dlext)\n" :
276 "(auto/$modpname/$modfname.$dl_dlext)\n")
280 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
284 if ($Mac_FS && ! -d $path) {
285 $path = Mac::FileSpec::Unixish::nativize($path);
287 $path .= ":" unless /:$/;
288 $dir = "${path}auto:$modpname";
290 $dir = "$_/auto/$modpname";
293 next unless -d $dir; # skip over uninteresting directories
295 # check for common cases to avoid autoload of dl_findfile
296 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
297 last if $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
299 # no luck here, save dir for possible later dl_findfile search
302 # last resort, let dl_findfile have a go in all known locations
303 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
305 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
306 unless $file; # wording similar to error from 'require'
308 $file = uc($file) if $Is_VMS && $Config::Config{d_vms_case_sensitive_symbols};
309 my $bootname = "boot_$module";
310 $bootname =~ s/\W/_/g;
311 @dl_require_symbols = ($bootname);
313 # Execute optional '.bootstrap' perl script for this module.
314 # The .bs file can be used to configure @dl_resolve_using etc to
315 # match the needs of the individual module on this architecture.
317 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
318 if (-s $bs) { # only read file if it's not empty
319 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
321 warn "$bs: $@\n" if $@;
326 if ($^O eq 'darwin') {
327 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
328 goto boot; #extension library has already been loaded, e.g. darwin
332 # Many dynamic extension loading problems will appear to come from
333 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
334 # Often these errors are actually occurring in the initialisation
335 # C code of the extension XS file. Perl reports the error as being
336 # in this perl code simply because this was the last perl code
339 my $libref = dl_load_file($file, $module->dl_load_flags) or
340 croak("Can't load '$file' for module $module: ".dl_error());
342 push(@dl_librefs,$libref); # record loaded object
344 my @unresolved = dl_undef_symbols();
347 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
350 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
351 croak("Can't find '$bootname' symbol in $file\n");
353 push(@dl_modules, $module); # record loaded module
356 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
358 # See comment block above
360 push(@dl_shared_objects, $file); # record files loaded
366 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
368 # return $file if (!$do_expand && -f $file); # the common case
369 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
374 # Let autosplit and the autoloader deal with these functions:
379 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
380 # This function does not automatically consider the architecture
381 # or the perl library auto directories.
383 my (@dirs, $dir); # which directories to search
384 my (@found); # full paths to real files we have found
387 print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
388 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
389 print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
390 "; # \$Config::Config{'so'} suffix for shared libraries\n";
394 print STDERR "dl_findfile(@args)\n" if $dl_debug;
396 # accumulate directories but process files as they appear
397 arg: foreach(@args) {
398 # Special fast case: full filepath requires no search
399 if ($Is_VMS && m%[:>/\]]% && -f $_) {
400 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
401 last arg unless wantarray;
407 last arg unless wantarray;
410 elsif (m:/: && -f $_ && !$do_expand) {
412 last arg unless wantarray;
416 # Deal with directories first:
417 # Using a -L prefix is the preferred option (faster and more robust)
418 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
421 # Otherwise we try to try to spot directories by a heuristic
422 # (this is a more complicated issue than it first appears)
423 if (m/:/ && -d $_) { push(@dirs, $_); next; }
424 # Only files should get this far...
425 my(@names, $name); # what filenames to look for
428 foreach $dir (@dirs, @dl_library_path) {
430 $dir =~ s/^([^:]+)$/:$1/;
432 foreach $name (@names) {
433 my($file) = "$dir:$name";
434 print STDERR " checking in $dir for $name\n" if $dl_debug;
437 next arg; # no need to look any further
444 # Otherwise we try to try to spot directories by a heuristic
445 # (this is a more complicated issue than it first appears)
446 if (m:/: && -d $_) { push(@dirs, $_); next; }
448 # VMS: we may be using native VMS directory syntax instead of
449 # Unix emulation, so check this as well
450 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
452 # Only files should get this far...
453 my(@names, $name); # what filenames to look for
454 if (m:-l: ) { # convert -lname to appropriate library name
456 push(@names,"lib$_.$dl_so");
457 push(@names,"lib$_.a");
458 } else { # Umm, a bare name. Try various alternatives:
459 # these should be ordered with the most likely first
460 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
461 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
462 push(@names,"lib$_.$dl_so") unless m:/:;
463 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
466 foreach $dir (@dirs, @dl_library_path) {
468 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
469 foreach $name (@names) {
470 my($file) = "$dir/$name";
471 print STDERR " checking in $dir for $name\n" if $dl_debug;
472 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
473 #$file = _check_file($file);
476 next arg; # no need to look any further
483 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
485 print STDERR "dl_findfile found: @found\n";
487 return $found[0] unless wantarray;
494 # Optional function invoked if DynaLoader.pm sets $do_expand.
495 # Most systems do not require or use this function.
496 # Some systems may implement it in the dl_*.xs file in which case
497 # this autoload version will not be called but is harmless.
499 # This function is designed to deal with systems which treat some
500 # 'filenames' in a special way. For example VMS 'Logical Names'
501 # (something like unix environment variables - but different).
502 # This function should recognise such names and expand them into
504 # Must return undef if $spec is invalid or file does not exist.
506 my $file = $spec; # default output to input
508 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
510 Carp::croak("dl_expandspec: should be defined in XS file!\n");
512 return undef unless -f $file;
514 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
518 sub dl_find_symbol_anywhere
522 foreach $libref (@dl_librefs) {
523 my $symref = dl_find_symbol($libref,$sym);
524 return $symref if $symref;
531 DynaLoader - Dynamically load C libraries into Perl code
537 @ISA = qw(... DynaLoader ...);
538 bootstrap YourPackage;
540 # optional method for 'global' loading
541 sub dl_load_flags { 0x01 }
546 This document defines a standard generic interface to the dynamic
547 linking mechanisms available on many platforms. Its primary purpose is
548 to implement automatic dynamic loading of Perl modules.
550 This document serves as both a specification for anyone wishing to
551 implement the DynaLoader for a new platform and as a guide for
552 anyone wishing to use the DynaLoader directly in an application.
554 The DynaLoader is designed to be a very simple high-level
555 interface that is sufficiently general to cover the requirements
556 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
558 It is also hoped that the interface will cover the needs of OS/2, NT
559 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
561 It must be stressed that the DynaLoader, by itself, is practically
562 useless for accessing non-Perl libraries because it provides almost no
563 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
564 library function or supplying arguments. A C::DynaLib module
565 is available from CPAN sites which performs that function for some
566 common system types. And since the year 2000, there's also Inline::C,
567 a module that allows you to write Perl subroutines in C. Also available
568 from your local CPAN site.
570 DynaLoader Interface Summary
580 bootstrap($modulename) Perl
581 @filepaths = dl_findfile(@names) Perl
582 $flags = $modulename->dl_load_flags Perl
583 $symref = dl_find_symbol_anywhere($symbol) Perl
585 $libref = dl_load_file($filename, $flags) C
586 $status = dl_unload_file($libref) C
587 $symref = dl_find_symbol($libref, $symbol) C
588 @symbols = dl_undef_symbols() C
589 dl_install_xsub($name, $symref [, $filename]) C
590 $message = dl_error C
594 =item @dl_library_path
596 The standard/default list of directories in which dl_findfile() will
597 search for libraries etc. Directories are searched in order:
598 $dl_library_path[0], [1], ... etc
600 @dl_library_path is initialised to hold the list of 'normal' directories
601 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
602 ensure portability across a wide range of platforms.
604 @dl_library_path should also be initialised with any other directories
605 that can be determined from the environment at runtime (such as
606 LD_LIBRARY_PATH for SunOS).
608 After initialisation @dl_library_path can be manipulated by an
609 application using push and unshift before calling dl_findfile().
610 Unshift can be used to add directories to the front of the search order
611 either to save search time or to override libraries with the same name
612 in the 'normal' directories.
614 The load function that dl_load_file() calls may require an absolute
615 pathname. The dl_findfile() function and @dl_library_path can be
616 used to search for and return the absolute pathname for the
617 library/object that you wish to load.
619 =item @dl_resolve_using
621 A list of additional libraries or other shared objects which can be
622 used to resolve any undefined symbols that might be generated by a
623 later call to load_file().
625 This is only required on some platforms which do not handle dependent
626 libraries automatically. For example the Socket Perl extension
627 library (F<auto/Socket/Socket.so>) contains references to many socket
628 functions which need to be resolved when it's loaded. Most platforms
629 will automatically know where to find the 'dependent' library (e.g.,
630 F</usr/lib/libsocket.so>). A few platforms need to be told the
631 location of the dependent library explicitly. Use @dl_resolve_using
636 @dl_resolve_using = dl_findfile('-lsocket');
638 =item @dl_require_symbols
640 A list of one or more symbol names that are in the library/object file
641 to be dynamically loaded. This is only required on some platforms.
645 An array of the handles returned by successful calls to dl_load_file(),
646 made by bootstrap, in the order in which they were loaded.
647 Can be used with dl_find_symbol() to look for a symbol in any of
652 An array of module (package) names that have been bootstrap'ed.
654 =item @dl_shared_objects
656 An array of file names for the shared objects that were loaded.
662 $message = dl_error();
664 Error message text from the last failed DynaLoader function. Note
665 that, similar to errno in unix, a successful function call does not
668 Implementations should detect the error as soon as it occurs in any of
669 the other functions and save the corresponding message for later
670 retrieval. This will avoid problems on some platforms (such as SunOS)
671 where the error message is very temporary (e.g., dlerror()).
675 Internal debugging messages are enabled when $dl_debug is set true.
676 Currently setting $dl_debug only affects the Perl side of the
677 DynaLoader. These messages should help an application developer to
678 resolve any DynaLoader usage problems.
680 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
682 For the DynaLoader developer/porter there is a similar debugging
683 variable added to the C code (see dlutils.c) and enabled if Perl was
684 built with the B<-DDEBUGGING> flag. This can also be set via the
685 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
692 @filepaths = dl_findfile(@names)
694 Determine the full paths (including file suffix) of one or more
695 loadable files given their generic names and optionally one or more
696 directories. Searches directories in @dl_library_path by default and
697 returns an empty list if no files were found.
699 Names can be specified in a variety of platform independent forms. Any
700 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
701 an appropriate suffix for the platform.
703 If a name does not already have a suitable prefix and/or suffix then
704 the corresponding file will be searched for by trying combinations of
705 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
708 If any directories are included in @names they are searched before
709 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
710 names are treated as filenames to be searched for.
712 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
716 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
719 =item dl_expandspec()
723 $filepath = dl_expandspec($spec)
725 Some unusual systems, such as VMS, require special filename handling in
726 order to deal with symbolic names for files (i.e., VMS's Logical Names).
728 To support these systems a dl_expandspec() function can be implemented
729 either in the F<dl_*.xs> file or code can be added to the autoloadable
730 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
737 $libref = dl_load_file($filename, $flags)
739 Dynamically load $filename, which must be the path to a shared object
740 or library. An opaque 'library reference' is returned as a handle for
741 the loaded object. Returns undef on error.
743 The $flags argument to alters dl_load_file behaviour.
746 0x01 make symbols available for linking later dl_load_file's.
747 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
748 (ignored under VMS; this is a normal part of image linking)
750 (On systems that provide a handle for the loaded object such as SunOS
751 and HPUX, $libref will be that handle. On other systems $libref will
752 typically be $filename or a pointer to a buffer containing $filename.
753 The application should not examine or alter $libref in any way.)
755 This is the function that does the real work. It should use the
756 current values of @dl_require_symbols and @dl_resolve_using if required.
758 SunOS: dlopen($filename)
759 HP-UX: shl_load($filename)
760 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
761 NeXT: rld_load($filename, @dl_resolve_using)
762 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
764 (The dlopen() function is also used by Solaris and some versions of
765 Linux, and is a common choice when providing a "wrapper" on other
766 mechanisms as is done in the OS/2 port.)
768 =item dl_unload_file()
772 $status = dl_unload_file($libref)
774 Dynamically unload $libref, which must be an opaque 'library reference' as
775 returned from dl_load_file. Returns one on success and zero on failure.
777 This function is optional and may not necessarily be provided on all platforms.
778 If it is defined, it is called automatically when the interpreter exits for
779 every shared object or library loaded by DynaLoader::bootstrap. All such
780 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
781 loads the libraries. The files are unloaded in last-in, first-out order.
783 This unloading is usually necessary when embedding a shared-object perl (e.g.
784 one configured with -Duseshrplib) within a larger application, and the perl
785 interpreter is created and destroyed several times within the lifetime of the
786 application. In this case it is possible that the system dynamic linker will
787 unload and then subsequently reload the shared libperl without relocating any
788 references to it from any files DynaLoaded by the previous incarnation of the
789 interpreter. As a result, any shared objects opened by DynaLoader may point to
790 a now invalid 'ghost' of the libperl shared object, causing apparently random
791 memory corruption and crashes. This behaviour is most commonly seen when using
792 Apache and mod_perl built with the APXS mechanism.
794 SunOS: dlclose($libref)
800 (The dlclose() function is also used by Solaris and some versions of
801 Linux, and is a common choice when providing a "wrapper" on other
802 mechanisms as is done in the OS/2 port.)
804 =item dl_load_flags()
808 $flags = dl_load_flags $modulename;
810 Designed to be a method call, and to be overridden by a derived class
811 (i.e. a class which has DynaLoader in its @ISA). The definition in
812 DynaLoader itself returns 0, which produces standard behavior from
815 =item dl_find_symbol()
819 $symref = dl_find_symbol($libref, $symbol)
821 Return the address of the symbol $symbol or C<undef> if not found. If the
822 target system has separate functions to search for symbols of different
823 types then dl_find_symbol() should search for function symbols first and
826 The exact manner in which the address is returned in $symref is not
827 currently defined. The only initial requirement is that $symref can
828 be passed to, and understood by, dl_install_xsub().
830 SunOS: dlsym($libref, $symbol)
831 HP-UX: shl_findsym($libref, $symbol)
832 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
833 NeXT: rld_lookup("_$symbol")
834 VMS: lib$find_image_symbol($libref,$symbol)
837 =item dl_find_symbol_anywhere()
841 $symref = dl_find_symbol_anywhere($symbol)
843 Applies dl_find_symbol() to the members of @dl_librefs and returns
844 the first match found.
846 =item dl_undef_symbols()
850 @symbols = dl_undef_symbols()
852 Return a list of symbol names which remain undefined after load_file().
853 Returns C<()> if not known. Don't worry if your platform does not provide
854 a mechanism for this. Most do not need it and hence do not provide it,
855 they just return an empty list.
858 =item dl_install_xsub()
862 dl_install_xsub($perl_name, $symref [, $filename])
864 Create a new Perl external subroutine named $perl_name using $symref as
865 a pointer to the function which implements the routine. This is simply
866 a direct call to newXSUB(). Returns a reference to the installed
869 The $filename parameter is used by Perl to identify the source file for
870 the function if required by die(), caller() or the debugger. If
871 $filename is not defined then "DynaLoader" will be used.
880 This is the normal entry point for automatic dynamic loading in Perl.
882 It performs the following actions:
888 locates an auto/$module directory by searching @INC
892 uses dl_findfile() to determine the filename to load
896 sets @dl_require_symbols to C<("boot_$module")>
900 executes an F<auto/$module/$module.bs> file if it exists
901 (typically used to add to @dl_resolve_using any files which
902 are required to load the module on the current platform)
906 calls dl_load_flags() to determine how to load the file.
910 calls dl_load_file() to load the file
914 calls dl_undef_symbols() and warns if any symbols are undefined
918 calls dl_find_symbol() for "boot_$module"
922 calls dl_install_xsub() to install it as "${module}::bootstrap"
926 calls &{"${module}::bootstrap"} to bootstrap the module (actually
927 it uses the function reference returned by dl_install_xsub for speed)
936 Tim Bunce, 11 August 1994.
938 This interface is based on the work and comments of (in no particular
939 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
940 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
942 Larry Wall designed the elegant inherited bootstrap mechanism and
943 implemented the first Perl 5 dynamic loader using it.
945 Solaris global loading added by Nick Ing-Simmons with design/coding
946 assistance from Tim Bunce, January 1996.