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 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
240 if (($^O eq 'NetWare') && (length($modfname) > 8)) {
241 $modfname = substr($modfname, 0, 8);
244 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
246 print STDERR "DynaLoader::bootstrap for $module ",
248 ? "(:auto:$modpname:$modfname.$dl_dlext)\n" :
249 "(auto/$modpname/$modfname.$dl_dlext)\n")
253 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
257 if ($Mac_FS && ! -d $path) {
258 $path = Mac::FileSpec::Unixish::nativize($path);
260 $path .= ":" unless /:$/;
261 $dir = "${path}auto:$modpname";
263 $dir = "$_/auto/$modpname";
265 if ($^O ne 'NetWare') {
266 next unless -d $dir; # skip over uninteresting directories
269 next if -f $dir; # skip over uninteresting directories
272 # check for common cases to avoid autoload of dl_findfile
273 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
274 if ($^O ne 'NetWare') {
275 last if $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
278 last if $file = ($do_expand) ? dl_expandspec($try) : ($try);
281 # no luck here, save dir for possible later dl_findfile search
284 # last resort, let dl_findfile have a go in all known locations
285 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
287 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
288 unless $file; # wording similar to error from 'require'
290 $file = uc($file) if $Is_VMS && $Config::Config{d_vms_case_sensitive_symbols};
291 my $bootname = "boot_$module";
292 $bootname =~ s/\W/_/g;
293 @dl_require_symbols = ($bootname);
295 # Execute optional '.bootstrap' perl script for this module.
296 # The .bs file can be used to configure @dl_resolve_using etc to
297 # match the needs of the individual module on this architecture.
299 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
300 if (-s $bs) { # only read file if it's not empty
301 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
303 warn "$bs: $@\n" if $@;
308 if ($^O eq 'darwin') {
309 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
310 goto boot; #extension library has already been loaded, e.g. darwin
314 # Many dynamic extension loading problems will appear to come from
315 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
316 # Often these errors are actually occurring in the initialisation
317 # C code of the extension XS file. Perl reports the error as being
318 # in this perl code simply because this was the last perl code
321 my $libref = dl_load_file($file, $module->dl_load_flags) or
322 croak("Can't load '$file' for module $module: ".dl_error());
324 push(@dl_librefs,$libref); # record loaded object
326 my @unresolved = dl_undef_symbols();
329 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
332 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
333 croak("Can't find '$bootname' symbol in $file\n");
335 push(@dl_modules, $module); # record loaded module
338 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
340 # See comment block above
345 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
347 # return $file if (!$do_expand && -f $file); # the common case
348 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
353 # Let autosplit and the autoloader deal with these functions:
358 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
359 # This function does not automatically consider the architecture
360 # or the perl library auto directories.
362 my (@dirs, $dir); # which directories to search
363 my (@found); # full paths to real files we have found
366 print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
367 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
368 print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
369 "; # \$Config::Config{'so'} suffix for shared libraries\n";
373 print STDERR "dl_findfile(@args)\n" if $dl_debug;
375 # accumulate directories but process files as they appear
376 arg: foreach(@args) {
377 # Special fast case: full filepath requires no search
378 if ($Is_VMS && m%[:>/\]]% && -f $_) {
379 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
380 last arg unless wantarray;
386 last arg unless wantarray;
389 elsif (m:/: && -f $_ && !$do_expand) {
391 last arg unless wantarray;
395 # Deal with directories first:
396 # Using a -L prefix is the preferred option (faster and more robust)
397 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
400 # Otherwise we try to try to spot directories by a heuristic
401 # (this is a more complicated issue than it first appears)
402 if (m/:/ && -d $_) { push(@dirs, $_); next; }
403 # Only files should get this far...
404 my(@names, $name); # what filenames to look for
407 foreach $dir (@dirs, @dl_library_path) {
409 $dir =~ s/^([^:]+)$/:$1/;
411 foreach $name (@names) {
412 my($file) = "$dir:$name";
413 print STDERR " checking in $dir for $name\n" if $dl_debug;
416 next arg; # no need to look any further
423 # Otherwise we try to try to spot directories by a heuristic
424 # (this is a more complicated issue than it first appears)
425 if (m:/: && -d $_) { push(@dirs, $_); next; }
427 # VMS: we may be using native VMS directory syntax instead of
428 # Unix emulation, so check this as well
429 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
431 # Only files should get this far...
432 my(@names, $name); # what filenames to look for
433 if (m:-l: ) { # convert -lname to appropriate library name
435 push(@names,"lib$_.$dl_so");
436 push(@names,"lib$_.a");
437 } else { # Umm, a bare name. Try various alternatives:
438 # these should be ordered with the most likely first
439 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
440 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
441 push(@names,"lib$_.$dl_so") unless m:/:;
442 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
445 foreach $dir (@dirs, @dl_library_path) {
447 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
448 foreach $name (@names) {
449 my($file) = "$dir/$name";
450 print STDERR " checking in $dir for $name\n" if $dl_debug;
451 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
452 #$file = _check_file($file);
455 next arg; # no need to look any further
462 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
464 print STDERR "dl_findfile found: @found\n";
466 return $found[0] unless wantarray;
473 # Optional function invoked if DynaLoader.pm sets $do_expand.
474 # Most systems do not require or use this function.
475 # Some systems may implement it in the dl_*.xs file in which case
476 # this autoload version will not be called but is harmless.
478 # This function is designed to deal with systems which treat some
479 # 'filenames' in a special way. For example VMS 'Logical Names'
480 # (something like unix environment variables - but different).
481 # This function should recognise such names and expand them into
483 # Must return undef if $spec is invalid or file does not exist.
485 my $file = $spec; # default output to input
487 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
489 Carp::croak("dl_expandspec: should be defined in XS file!\n");
491 return undef unless -f $file;
493 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
497 sub dl_find_symbol_anywhere
501 foreach $libref (@dl_librefs) {
502 my $symref = dl_find_symbol($libref,$sym);
503 return $symref if $symref;
510 DynaLoader - Dynamically load C libraries into Perl code
512 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_unload_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
518 @ISA = qw(... DynaLoader ...);
519 bootstrap YourPackage;
521 # optional method for 'global' loading
522 sub dl_load_flags { 0x01 }
527 This document defines a standard generic interface to the dynamic
528 linking mechanisms available on many platforms. Its primary purpose is
529 to implement automatic dynamic loading of Perl modules.
531 This document serves as both a specification for anyone wishing to
532 implement the DynaLoader for a new platform and as a guide for
533 anyone wishing to use the DynaLoader directly in an application.
535 The DynaLoader is designed to be a very simple high-level
536 interface that is sufficiently general to cover the requirements
537 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
539 It is also hoped that the interface will cover the needs of OS/2, NT
540 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
542 It must be stressed that the DynaLoader, by itself, is practically
543 useless for accessing non-Perl libraries because it provides almost no
544 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
545 library function or supplying arguments. A C::DynaLib module
546 is available from CPAN sites which performs that function for some
549 DynaLoader Interface Summary
558 bootstrap($modulename) Perl
559 @filepaths = dl_findfile(@names) Perl
560 $flags = $modulename->dl_load_flags Perl
561 $symref = dl_find_symbol_anywhere($symbol) Perl
563 $libref = dl_load_file($filename, $flags) C
564 $status = dl_unload_file($libref) C
565 $symref = dl_find_symbol($libref, $symbol) C
566 @symbols = dl_undef_symbols() C
567 dl_install_xsub($name, $symref [, $filename]) C
568 $message = dl_error C
572 =item @dl_library_path
574 The standard/default list of directories in which dl_findfile() will
575 search for libraries etc. Directories are searched in order:
576 $dl_library_path[0], [1], ... etc
578 @dl_library_path is initialised to hold the list of 'normal' directories
579 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
580 ensure portability across a wide range of platforms.
582 @dl_library_path should also be initialised with any other directories
583 that can be determined from the environment at runtime (such as
584 LD_LIBRARY_PATH for SunOS).
586 After initialisation @dl_library_path can be manipulated by an
587 application using push and unshift before calling dl_findfile().
588 Unshift can be used to add directories to the front of the search order
589 either to save search time or to override libraries with the same name
590 in the 'normal' directories.
592 The load function that dl_load_file() calls may require an absolute
593 pathname. The dl_findfile() function and @dl_library_path can be
594 used to search for and return the absolute pathname for the
595 library/object that you wish to load.
597 =item @dl_resolve_using
599 A list of additional libraries or other shared objects which can be
600 used to resolve any undefined symbols that might be generated by a
601 later call to load_file().
603 This is only required on some platforms which do not handle dependent
604 libraries automatically. For example the Socket Perl extension
605 library (F<auto/Socket/Socket.so>) contains references to many socket
606 functions which need to be resolved when it's loaded. Most platforms
607 will automatically know where to find the 'dependent' library (e.g.,
608 F</usr/lib/libsocket.so>). A few platforms need to be told the
609 location of the dependent library explicitly. Use @dl_resolve_using
614 @dl_resolve_using = dl_findfile('-lsocket');
616 =item @dl_require_symbols
618 A list of one or more symbol names that are in the library/object file
619 to be dynamically loaded. This is only required on some platforms.
623 An array of the handles returned by successful calls to dl_load_file(),
624 made by bootstrap, in the order in which they were loaded.
625 Can be used with dl_find_symbol() to look for a symbol in any of
630 An array of module (package) names that have been bootstrap'ed.
636 $message = dl_error();
638 Error message text from the last failed DynaLoader function. Note
639 that, similar to errno in unix, a successful function call does not
642 Implementations should detect the error as soon as it occurs in any of
643 the other functions and save the corresponding message for later
644 retrieval. This will avoid problems on some platforms (such as SunOS)
645 where the error message is very temporary (e.g., dlerror()).
649 Internal debugging messages are enabled when $dl_debug is set true.
650 Currently setting $dl_debug only affects the Perl side of the
651 DynaLoader. These messages should help an application developer to
652 resolve any DynaLoader usage problems.
654 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
656 For the DynaLoader developer/porter there is a similar debugging
657 variable added to the C code (see dlutils.c) and enabled if Perl was
658 built with the B<-DDEBUGGING> flag. This can also be set via the
659 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
666 @filepaths = dl_findfile(@names)
668 Determine the full paths (including file suffix) of one or more
669 loadable files given their generic names and optionally one or more
670 directories. Searches directories in @dl_library_path by default and
671 returns an empty list if no files were found.
673 Names can be specified in a variety of platform independent forms. Any
674 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
675 an appropriate suffix for the platform.
677 If a name does not already have a suitable prefix and/or suffix then
678 the corresponding file will be searched for by trying combinations of
679 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
682 If any directories are included in @names they are searched before
683 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
684 names are treated as filenames to be searched for.
686 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
690 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
693 =item dl_expandspec()
697 $filepath = dl_expandspec($spec)
699 Some unusual systems, such as VMS, require special filename handling in
700 order to deal with symbolic names for files (i.e., VMS's Logical Names).
702 To support these systems a dl_expandspec() function can be implemented
703 either in the F<dl_*.xs> file or code can be added to the autoloadable
704 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
711 $libref = dl_load_file($filename, $flags)
713 Dynamically load $filename, which must be the path to a shared object
714 or library. An opaque 'library reference' is returned as a handle for
715 the loaded object. Returns undef on error.
717 The $flags argument to alters dl_load_file behaviour.
720 0x01 make symbols available for linking later dl_load_file's.
721 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
722 (ignored under VMS; this is a normal part of image linking)
724 (On systems that provide a handle for the loaded object such as SunOS
725 and HPUX, $libref will be that handle. On other systems $libref will
726 typically be $filename or a pointer to a buffer containing $filename.
727 The application should not examine or alter $libref in any way.)
729 This is the function that does the real work. It should use the
730 current values of @dl_require_symbols and @dl_resolve_using if required.
732 SunOS: dlopen($filename)
733 HP-UX: shl_load($filename)
734 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
735 NeXT: rld_load($filename, @dl_resolve_using)
736 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
738 (The dlopen() function is also used by Solaris and some versions of
739 Linux, and is a common choice when providing a "wrapper" on other
740 mechanisms as is done in the OS/2 port.)
742 =item dl_unload_file()
746 $status = dl_unload_file($libref)
748 Dynamically unload $libref, which must be an opaque 'library reference' as
749 returned from dl_load_file. Returns one on success and zero on failure.
751 This function is optional and may not necessarily be provided on all platforms.
752 If it is defined, it is called automatically when the interpreter exits for
753 every shared object or library loaded by DynaLoader::bootstrap. All such
754 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
755 loads the libraries. The files are unloaded in last-in, first-out order.
757 This unloading is usually necessary when embedding a shared-object perl (e.g.
758 one configured with -Duseshrplib) within a larger application, and the perl
759 interpreter is created and destroyed several times within the lifetime of the
760 application. In this case it is possible that the system dynamic linker will
761 unload and then subsequently reload the shared libperl without relocating any
762 references to it from any files DynaLoaded by the previous incarnation of the
763 interpreter. As a result, any shared objects opened by DynaLoader may point to
764 a now invalid 'ghost' of the libperl shared object, causing apparently random
765 memory corruption and crashes. This behaviour is most commonly seen when using
766 Apache and mod_perl built with the APXS mechanism.
768 SunOS: dlclose($libref)
774 (The dlclose() function is also used by Solaris and some versions of
775 Linux, and is a common choice when providing a "wrapper" on other
776 mechanisms as is done in the OS/2 port.)
782 $flags = dl_loadflags $modulename;
784 Designed to be a method call, and to be overridden by a derived class
785 (i.e. a class which has DynaLoader in its @ISA). The definition in
786 DynaLoader itself returns 0, which produces standard behavior from
789 =item dl_find_symbol()
793 $symref = dl_find_symbol($libref, $symbol)
795 Return the address of the symbol $symbol or C<undef> if not found. If the
796 target system has separate functions to search for symbols of different
797 types then dl_find_symbol() should search for function symbols first and
800 The exact manner in which the address is returned in $symref is not
801 currently defined. The only initial requirement is that $symref can
802 be passed to, and understood by, dl_install_xsub().
804 SunOS: dlsym($libref, $symbol)
805 HP-UX: shl_findsym($libref, $symbol)
806 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
807 NeXT: rld_lookup("_$symbol")
808 VMS: lib$find_image_symbol($libref,$symbol)
811 =item dl_find_symbol_anywhere()
815 $symref = dl_find_symbol_anywhere($symbol)
817 Applies dl_find_symbol() to the members of @dl_librefs and returns
818 the first match found.
820 =item dl_undef_symbols()
824 @symbols = dl_undef_symbols()
826 Return a list of symbol names which remain undefined after load_file().
827 Returns C<()> if not known. Don't worry if your platform does not provide
828 a mechanism for this. Most do not need it and hence do not provide it,
829 they just return an empty list.
832 =item dl_install_xsub()
836 dl_install_xsub($perl_name, $symref [, $filename])
838 Create a new Perl external subroutine named $perl_name using $symref as
839 a pointer to the function which implements the routine. This is simply
840 a direct call to newXSUB(). Returns a reference to the installed
843 The $filename parameter is used by Perl to identify the source file for
844 the function if required by die(), caller() or the debugger. If
845 $filename is not defined then "DynaLoader" will be used.
854 This is the normal entry point for automatic dynamic loading in Perl.
856 It performs the following actions:
862 locates an auto/$module directory by searching @INC
866 uses dl_findfile() to determine the filename to load
870 sets @dl_require_symbols to C<("boot_$module")>
874 executes an F<auto/$module/$module.bs> file if it exists
875 (typically used to add to @dl_resolve_using any files which
876 are required to load the module on the current platform)
880 calls dl_load_flags() to determine how to load the file.
884 calls dl_load_file() to load the file
888 calls dl_undef_symbols() and warns if any symbols are undefined
892 calls dl_find_symbol() for "boot_$module"
896 calls dl_install_xsub() to install it as "${module}::bootstrap"
900 calls &{"${module}::bootstrap"} to bootstrap the module (actually
901 it uses the function reference returned by dl_install_xsub for speed)
910 Tim Bunce, 11 August 1994.
912 This interface is based on the work and comments of (in no particular
913 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
914 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
916 Larry Wall designed the elegant inherited bootstrap mechanism and
917 implemented the first Perl 5 dynamic loader using it.
919 Solaris global loading added by Nick Ing-Simmons with design/coding
920 assistance from Tim Bunce, January 1996.