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 = '1.05'; # 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_shared_objects = (); # shared objects for symbols we have
89 #@dl_librefs = (); # things we have loaded
90 #@dl_modules = (); # Modules we have loaded
92 # This is a fix to support DLD's unfortunate desire to relink -lc
93 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
97 my $cfg_dl_library_path = <<'EOT';
98 push(@dl_library_path, split(' ', $Config::Config{libpth}));
101 sub dquoted_comma_list {
102 join(", ", map {qq("$_")} @_);
105 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
106 eval $cfg_dl_library_path;
107 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
108 my $dl_library_path = dquoted_comma_list(@dl_library_path);
110 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
112 \@dl_library_path = ($dl_library_path);
119 # Initialise \@dl_library_path with the 'standard' library path
120 # for this platform as determined by Configure.
128 my $ldlibpthname_defined;
131 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
132 $ldlibpthname = $Config::Config{ldlibpthname};
133 $ldlibpthname_defined = defined $Config::Config{ldlibpthname} ? 1 : 0;
134 $pthsep = $Config::Config{path_sep};
137 $ldlibpthname = q($Config::Config{ldlibpthname});
138 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
139 $pthsep = q($Config::Config{path_sep});
141 my \$ldlibpthname = $ldlibpthname;
142 my \$ldlibpthname_defined = $ldlibpthname_defined;
143 my \$pthsep = $pthsep;
148 my $env_dl_library_path = <<'EOT';
149 if ($ldlibpthname_defined &&
150 exists $ENV{$ldlibpthname}) {
151 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
154 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
156 if ($ldlibpthname_defined &&
157 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
158 exists $ENV{LD_LIBRARY_PATH}) {
159 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
163 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
164 eval $env_dl_library_path;
168 # Add to \@dl_library_path any extra directories we can gather from environment
176 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
177 my $dl_library_path = dquoted_comma_list(@dl_library_path);
179 # The below \@dl_library_path has been expanded (%Config, %ENV)
180 # in Perl build time.
182 \@dl_library_path = ($dl_library_path);
188 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
189 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
190 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
194 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
195 print STDERR "DynaLoader not linked into this perl\n"
196 unless defined(&boot_DynaLoader);
199 1; # End of main code
202 sub croak { require Carp; Carp::croak(@_) }
204 sub bootstrap_inherit {
206 local *isa = *{"$module\::ISA"};
207 local @isa = (@isa, 'DynaLoader');
208 # Cannot goto due to delocalization. Will report errors on a wrong line?
212 # The bootstrap function cannot be autoloaded (without complications)
213 # so we define it here:
216 # use local vars to enable $module.bs script to edit values
218 local($module) = $args[0];
223 Carp::confess("Usage: DynaLoader::bootstrap(module)");
226 # A common error on platforms which don't support dynamic loading.
227 # Since it's fatal and potentially confusing we give a detailed message.
228 croak("Can't load module $module, dynamic loading not available in this perl.\n".
229 " (You may need to build a new perl executable which either supports\n".
230 " dynamic loading or has the $module module statically linked into it.)\n")
231 unless defined(&dl_load_file);
235 print OUT <<'EOT' if $^O eq 'os2';
236 # Can dynaload, but cannot dynaload Perl modules...
237 die 'Dynaloaded Perl modules are not available in this build of Perl' if $OS2::is_static;
242 my @modparts = split(/::/,$module);
243 my $modfname = $modparts[-1];
245 # Some systems have restrictions on files names for DLL's etc.
246 # mod2fname returns appropriate file base name (typically truncated)
247 # It may also edit @modparts if required.
248 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
250 # Truncate the module name to 8.3 format for NetWare
251 if (($^O eq 'NetWare') && (length($modfname) > 8)) {
252 $modfname = substr($modfname, 0, 8);
255 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
257 print STDERR "DynaLoader::bootstrap for $module ",
259 ? "(:auto:$modpname:$modfname.$dl_dlext)\n" :
260 "(auto/$modpname/$modfname.$dl_dlext)\n")
264 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
268 if ($Mac_FS && ! -d $path) {
269 $path = Mac::FileSpec::Unixish::nativize($path);
271 $path .= ":" unless /:$/;
272 $dir = "${path}auto:$modpname";
274 $dir = "$_/auto/$modpname";
277 next unless -d $dir; # skip over uninteresting directories
279 # check for common cases to avoid autoload of dl_findfile
280 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
281 last if $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
283 # no luck here, save dir for possible later dl_findfile search
286 # last resort, let dl_findfile have a go in all known locations
287 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
289 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
290 unless $file; # wording similar to error from 'require'
292 $file = uc($file) if $Is_VMS && $Config::Config{d_vms_case_sensitive_symbols};
293 my $bootname = "boot_$module";
294 $bootname =~ s/\W/_/g;
295 @dl_require_symbols = ($bootname);
297 # Execute optional '.bootstrap' perl script for this module.
298 # The .bs file can be used to configure @dl_resolve_using etc to
299 # match the needs of the individual module on this architecture.
301 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
302 if (-s $bs) { # only read file if it's not empty
303 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
305 warn "$bs: $@\n" if $@;
310 if ($^O eq 'darwin') {
311 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
312 goto boot; #extension library has already been loaded, e.g. darwin
316 # Many dynamic extension loading problems will appear to come from
317 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
318 # Often these errors are actually occurring in the initialisation
319 # C code of the extension XS file. Perl reports the error as being
320 # in this perl code simply because this was the last perl code
323 my $libref = dl_load_file($file, $module->dl_load_flags) or
324 croak("Can't load '$file' for module $module: ".dl_error());
326 push(@dl_librefs,$libref); # record loaded object
328 my @unresolved = dl_undef_symbols();
331 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
334 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
335 croak("Can't find '$bootname' symbol in $file\n");
337 push(@dl_modules, $module); # record loaded module
340 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
342 # See comment block above
344 push(@dl_shared_objects, $file); # record files loaded
350 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
352 # return $file if (!$do_expand && -f $file); # the common case
353 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
358 # Let autosplit and the autoloader deal with these functions:
363 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
364 # This function does not automatically consider the architecture
365 # or the perl library auto directories.
367 my (@dirs, $dir); # which directories to search
368 my (@found); # full paths to real files we have found
371 print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
372 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
373 print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
374 "; # \$Config::Config{'so'} suffix for shared libraries\n";
378 print STDERR "dl_findfile(@args)\n" if $dl_debug;
380 # accumulate directories but process files as they appear
381 arg: foreach(@args) {
382 # Special fast case: full filepath requires no search
383 if ($Is_VMS && m%[:>/\]]% && -f $_) {
384 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
385 last arg unless wantarray;
391 last arg unless wantarray;
394 elsif (m:/: && -f $_ && !$do_expand) {
396 last arg unless wantarray;
400 # Deal with directories first:
401 # Using a -L prefix is the preferred option (faster and more robust)
402 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
405 # Otherwise we try to try to spot directories by a heuristic
406 # (this is a more complicated issue than it first appears)
407 if (m/:/ && -d $_) { push(@dirs, $_); next; }
408 # Only files should get this far...
409 my(@names, $name); # what filenames to look for
412 foreach $dir (@dirs, @dl_library_path) {
414 $dir =~ s/^([^:]+)$/:$1/;
416 foreach $name (@names) {
417 my($file) = "$dir:$name";
418 print STDERR " checking in $dir for $name\n" if $dl_debug;
421 next arg; # no need to look any further
428 # Otherwise we try to try to spot directories by a heuristic
429 # (this is a more complicated issue than it first appears)
430 if (m:/: && -d $_) { push(@dirs, $_); next; }
432 # VMS: we may be using native VMS directory syntax instead of
433 # Unix emulation, so check this as well
434 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
436 # Only files should get this far...
437 my(@names, $name); # what filenames to look for
438 if (m:-l: ) { # convert -lname to appropriate library name
440 push(@names,"lib$_.$dl_so");
441 push(@names,"lib$_.a");
442 } else { # Umm, a bare name. Try various alternatives:
443 # these should be ordered with the most likely first
444 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
445 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
446 push(@names,"lib$_.$dl_so") unless m:/:;
447 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
450 foreach $dir (@dirs, @dl_library_path) {
452 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
453 foreach $name (@names) {
454 my($file) = "$dir/$name";
455 print STDERR " checking in $dir for $name\n" if $dl_debug;
456 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
457 #$file = _check_file($file);
460 next arg; # no need to look any further
467 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
469 print STDERR "dl_findfile found: @found\n";
471 return $found[0] unless wantarray;
478 # Optional function invoked if DynaLoader.pm sets $do_expand.
479 # Most systems do not require or use this function.
480 # Some systems may implement it in the dl_*.xs file in which case
481 # this autoload version will not be called but is harmless.
483 # This function is designed to deal with systems which treat some
484 # 'filenames' in a special way. For example VMS 'Logical Names'
485 # (something like unix environment variables - but different).
486 # This function should recognise such names and expand them into
488 # Must return undef if $spec is invalid or file does not exist.
490 my $file = $spec; # default output to input
492 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
494 Carp::croak("dl_expandspec: should be defined in XS file!\n");
496 return undef unless -f $file;
498 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
502 sub dl_find_symbol_anywhere
506 foreach $libref (@dl_librefs) {
507 my $symref = dl_find_symbol($libref,$sym);
508 return $symref if $symref;
515 DynaLoader - Dynamically load C libraries into Perl code
521 @ISA = qw(... DynaLoader ...);
522 bootstrap YourPackage;
524 # optional method for 'global' loading
525 sub dl_load_flags { 0x01 }
530 This document defines a standard generic interface to the dynamic
531 linking mechanisms available on many platforms. Its primary purpose is
532 to implement automatic dynamic loading of Perl modules.
534 This document serves as both a specification for anyone wishing to
535 implement the DynaLoader for a new platform and as a guide for
536 anyone wishing to use the DynaLoader directly in an application.
538 The DynaLoader is designed to be a very simple high-level
539 interface that is sufficiently general to cover the requirements
540 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
542 It is also hoped that the interface will cover the needs of OS/2, NT
543 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
545 It must be stressed that the DynaLoader, by itself, is practically
546 useless for accessing non-Perl libraries because it provides almost no
547 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
548 library function or supplying arguments. A C::DynaLib module
549 is available from CPAN sites which performs that function for some
550 common system types. And since the year 2000, there's also Inline::C,
551 a module that allows you to write Perl subroutines in C. Also available
552 from your local CPAN site.
554 DynaLoader Interface Summary
564 bootstrap($modulename) Perl
565 @filepaths = dl_findfile(@names) Perl
566 $flags = $modulename->dl_load_flags Perl
567 $symref = dl_find_symbol_anywhere($symbol) Perl
569 $libref = dl_load_file($filename, $flags) C
570 $status = dl_unload_file($libref) C
571 $symref = dl_find_symbol($libref, $symbol) C
572 @symbols = dl_undef_symbols() C
573 dl_install_xsub($name, $symref [, $filename]) C
574 $message = dl_error C
578 =item @dl_library_path
580 The standard/default list of directories in which dl_findfile() will
581 search for libraries etc. Directories are searched in order:
582 $dl_library_path[0], [1], ... etc
584 @dl_library_path is initialised to hold the list of 'normal' directories
585 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
586 ensure portability across a wide range of platforms.
588 @dl_library_path should also be initialised with any other directories
589 that can be determined from the environment at runtime (such as
590 LD_LIBRARY_PATH for SunOS).
592 After initialisation @dl_library_path can be manipulated by an
593 application using push and unshift before calling dl_findfile().
594 Unshift can be used to add directories to the front of the search order
595 either to save search time or to override libraries with the same name
596 in the 'normal' directories.
598 The load function that dl_load_file() calls may require an absolute
599 pathname. The dl_findfile() function and @dl_library_path can be
600 used to search for and return the absolute pathname for the
601 library/object that you wish to load.
603 =item @dl_resolve_using
605 A list of additional libraries or other shared objects which can be
606 used to resolve any undefined symbols that might be generated by a
607 later call to load_file().
609 This is only required on some platforms which do not handle dependent
610 libraries automatically. For example the Socket Perl extension
611 library (F<auto/Socket/Socket.so>) contains references to many socket
612 functions which need to be resolved when it's loaded. Most platforms
613 will automatically know where to find the 'dependent' library (e.g.,
614 F</usr/lib/libsocket.so>). A few platforms need to be told the
615 location of the dependent library explicitly. Use @dl_resolve_using
620 @dl_resolve_using = dl_findfile('-lsocket');
622 =item @dl_require_symbols
624 A list of one or more symbol names that are in the library/object file
625 to be dynamically loaded. This is only required on some platforms.
629 An array of the handles returned by successful calls to dl_load_file(),
630 made by bootstrap, in the order in which they were loaded.
631 Can be used with dl_find_symbol() to look for a symbol in any of
636 An array of module (package) names that have been bootstrap'ed.
638 =item @dl_shared_objects
640 An array of file names for the shared objects that were loaded.
646 $message = dl_error();
648 Error message text from the last failed DynaLoader function. Note
649 that, similar to errno in unix, a successful function call does not
652 Implementations should detect the error as soon as it occurs in any of
653 the other functions and save the corresponding message for later
654 retrieval. This will avoid problems on some platforms (such as SunOS)
655 where the error message is very temporary (e.g., dlerror()).
659 Internal debugging messages are enabled when $dl_debug is set true.
660 Currently setting $dl_debug only affects the Perl side of the
661 DynaLoader. These messages should help an application developer to
662 resolve any DynaLoader usage problems.
664 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
666 For the DynaLoader developer/porter there is a similar debugging
667 variable added to the C code (see dlutils.c) and enabled if Perl was
668 built with the B<-DDEBUGGING> flag. This can also be set via the
669 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
676 @filepaths = dl_findfile(@names)
678 Determine the full paths (including file suffix) of one or more
679 loadable files given their generic names and optionally one or more
680 directories. Searches directories in @dl_library_path by default and
681 returns an empty list if no files were found.
683 Names can be specified in a variety of platform independent forms. Any
684 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
685 an appropriate suffix for the platform.
687 If a name does not already have a suitable prefix and/or suffix then
688 the corresponding file will be searched for by trying combinations of
689 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
692 If any directories are included in @names they are searched before
693 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
694 names are treated as filenames to be searched for.
696 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
700 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
703 =item dl_expandspec()
707 $filepath = dl_expandspec($spec)
709 Some unusual systems, such as VMS, require special filename handling in
710 order to deal with symbolic names for files (i.e., VMS's Logical Names).
712 To support these systems a dl_expandspec() function can be implemented
713 either in the F<dl_*.xs> file or code can be added to the autoloadable
714 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
721 $libref = dl_load_file($filename, $flags)
723 Dynamically load $filename, which must be the path to a shared object
724 or library. An opaque 'library reference' is returned as a handle for
725 the loaded object. Returns undef on error.
727 The $flags argument to alters dl_load_file behaviour.
730 0x01 make symbols available for linking later dl_load_file's.
731 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
732 (ignored under VMS; this is a normal part of image linking)
734 (On systems that provide a handle for the loaded object such as SunOS
735 and HPUX, $libref will be that handle. On other systems $libref will
736 typically be $filename or a pointer to a buffer containing $filename.
737 The application should not examine or alter $libref in any way.)
739 This is the function that does the real work. It should use the
740 current values of @dl_require_symbols and @dl_resolve_using if required.
742 SunOS: dlopen($filename)
743 HP-UX: shl_load($filename)
744 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
745 NeXT: rld_load($filename, @dl_resolve_using)
746 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
748 (The dlopen() function is also used by Solaris and some versions of
749 Linux, and is a common choice when providing a "wrapper" on other
750 mechanisms as is done in the OS/2 port.)
752 =item dl_unload_file()
756 $status = dl_unload_file($libref)
758 Dynamically unload $libref, which must be an opaque 'library reference' as
759 returned from dl_load_file. Returns one on success and zero on failure.
761 This function is optional and may not necessarily be provided on all platforms.
762 If it is defined, it is called automatically when the interpreter exits for
763 every shared object or library loaded by DynaLoader::bootstrap. All such
764 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
765 loads the libraries. The files are unloaded in last-in, first-out order.
767 This unloading is usually necessary when embedding a shared-object perl (e.g.
768 one configured with -Duseshrplib) within a larger application, and the perl
769 interpreter is created and destroyed several times within the lifetime of the
770 application. In this case it is possible that the system dynamic linker will
771 unload and then subsequently reload the shared libperl without relocating any
772 references to it from any files DynaLoaded by the previous incarnation of the
773 interpreter. As a result, any shared objects opened by DynaLoader may point to
774 a now invalid 'ghost' of the libperl shared object, causing apparently random
775 memory corruption and crashes. This behaviour is most commonly seen when using
776 Apache and mod_perl built with the APXS mechanism.
778 SunOS: dlclose($libref)
784 (The dlclose() function is also used by Solaris and some versions of
785 Linux, and is a common choice when providing a "wrapper" on other
786 mechanisms as is done in the OS/2 port.)
788 =item dl_load_flags()
792 $flags = dl_load_flags $modulename;
794 Designed to be a method call, and to be overridden by a derived class
795 (i.e. a class which has DynaLoader in its @ISA). The definition in
796 DynaLoader itself returns 0, which produces standard behavior from
799 =item dl_find_symbol()
803 $symref = dl_find_symbol($libref, $symbol)
805 Return the address of the symbol $symbol or C<undef> if not found. If the
806 target system has separate functions to search for symbols of different
807 types then dl_find_symbol() should search for function symbols first and
810 The exact manner in which the address is returned in $symref is not
811 currently defined. The only initial requirement is that $symref can
812 be passed to, and understood by, dl_install_xsub().
814 SunOS: dlsym($libref, $symbol)
815 HP-UX: shl_findsym($libref, $symbol)
816 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
817 NeXT: rld_lookup("_$symbol")
818 VMS: lib$find_image_symbol($libref,$symbol)
821 =item dl_find_symbol_anywhere()
825 $symref = dl_find_symbol_anywhere($symbol)
827 Applies dl_find_symbol() to the members of @dl_librefs and returns
828 the first match found.
830 =item dl_undef_symbols()
834 @symbols = dl_undef_symbols()
836 Return a list of symbol names which remain undefined after load_file().
837 Returns C<()> if not known. Don't worry if your platform does not provide
838 a mechanism for this. Most do not need it and hence do not provide it,
839 they just return an empty list.
842 =item dl_install_xsub()
846 dl_install_xsub($perl_name, $symref [, $filename])
848 Create a new Perl external subroutine named $perl_name using $symref as
849 a pointer to the function which implements the routine. This is simply
850 a direct call to newXSUB(). Returns a reference to the installed
853 The $filename parameter is used by Perl to identify the source file for
854 the function if required by die(), caller() or the debugger. If
855 $filename is not defined then "DynaLoader" will be used.
864 This is the normal entry point for automatic dynamic loading in Perl.
866 It performs the following actions:
872 locates an auto/$module directory by searching @INC
876 uses dl_findfile() to determine the filename to load
880 sets @dl_require_symbols to C<("boot_$module")>
884 executes an F<auto/$module/$module.bs> file if it exists
885 (typically used to add to @dl_resolve_using any files which
886 are required to load the module on the current platform)
890 calls dl_load_flags() to determine how to load the file.
894 calls dl_load_file() to load the file
898 calls dl_undef_symbols() and warns if any symbols are undefined
902 calls dl_find_symbol() for "boot_$module"
906 calls dl_install_xsub() to install it as "${module}::bootstrap"
910 calls &{"${module}::bootstrap"} to bootstrap the module (actually
911 it uses the function reference returned by dl_install_xsub for speed)
920 Tim Bunce, 11 August 1994.
922 This interface is based on the work and comments of (in no particular
923 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
924 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
926 Larry Wall designed the elegant inherited bootstrap mechanism and
927 implemented the first Perl 5 dynamic loader using it.
929 Solaris global loading added by Nick Ing-Simmons with design/coding
930 assistance from Tim Bunce, January 1996.