11 # subroutine expand_os_specific expands $^O-specific preprocessing information
12 # so that it will not be re-calculated at runtime in Dynaloader.pm
14 # Syntax of preprocessor should be kept extremely simple:
15 # - directives are in double angle brackets <<...>>
16 # - <<=string>> will be just evaluated
17 # - for $^O-specific there are two forms:
20 # this directive should be closed with respectively
23 # construct <<|$^O-ne-osname>> means #else
24 # nested <<$^O...>>-constructs are allowed but nested values must be for
27 # -- added by VKON, 03-10-2004 to separate $^O-specific between OSes
28 # (so that Win32 never checks for $^O eq 'VMS' for example)
30 # The $^O tests test both for $^O and for $Config{osname}.
31 # The latter is better for some for cross-compilation setups.
33 sub expand_os_specific {
37 s/<<\$\^O-(eq|ne)-(\w+)>>(.*?)<<\/\$\^O-\1-\2>>/
38 my ($op, $os, $expr) = ($1,$2,$3);
39 if ($op ne 'eq' and $op ne 'ne') {die "wrong eq-ne arg in $&"};
40 if ($expr =~ m[^(.*?)<<\|\$\^O-$op-$os>>(.*?)$]s) {
42 my ($if,$el) = ($1,$2);
43 if (($op eq 'eq' and ($^O eq $os || $Config{osname} eq $os)) || ($op eq 'ne' and ($^O ne $os || $Config{osname} ne $os))) {
52 if (($op eq 'eq' and ($^O eq $os || $Config{osname} eq $os)) || ($op eq 'ne' and ($^O ne $os || $Config{osname} ne $os))) {
60 if (/<<(=|\$\^O-)/) {die "bad <<\$^O-eq/ne-osname>> expression.".
61 " Unclosed brackets?";
67 unlink "DynaLoader.pm" if -f "DynaLoader.pm";
68 open OUT, ">DynaLoader.pm" or die $!;
71 # Generated from DynaLoader_pm.PL
75 # And Gandalf said: 'Many folk like to know beforehand what is to
76 # be set on the table; but those who have laboured to prepare the
77 # feast like to keep their secret; for wonder makes the words of
80 # (Quote from Tolkien suggested by Anno Siegel.)
82 # See pod text at end of file for documentation.
83 # See also ext/DynaLoader/README in source tree for other information.
85 # Tim.Bunce@ig.co.uk, August 1994
93 # enable debug/trace messages from DynaLoader perl code
94 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
97 # Flags to alter dl_load_file behaviour. Assigned bits:
98 # 0x01 make symbols available for linking later dl_load_file's.
99 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
100 # (ignored under VMS; effect is built-in to image linking)
102 # This is called as a class method $module->dl_load_flags. The
103 # definition here will be inherited and result on "default" loading
104 # behaviour unless a sub-class of DynaLoader defines its own version.
107 sub dl_load_flags { 0x00 }
111 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
112 print OUT "(\$dl_dlext, \$dl_so, \$dlsrc) = (",
113 to_string($Config{'dlext'}), ",",
114 to_string($Config{'so'}), ",",
115 to_string($Config{'dlsrc'}), ")\n;" ;
119 ($dl_dlext, $dl_so, $dlsrc) = @Config::Config{qw(dlext so dlsrc)};
123 print OUT expand_os_specific(<<'EOT');
126 # Some systems need special handling to expand file specifications
127 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
128 # See dl_expandspec() for more details. Should be harmless but
129 # inefficient to define on systems that don't need it.
130 $Is_VMS = $^O eq 'VMS';
132 $do_expand = <<$^O-eq-VMS>>1<<|$^O-eq-VMS>>0<</$^O-eq-VMS>>;
134 @dl_require_symbols = (); # names of symbols we need
135 @dl_resolve_using = (); # names of files to link with
136 @dl_library_path = (); # path to look for files
138 #XSLoader.pm may have added elements before we were required
139 #@dl_shared_objects = (); # shared objects for symbols we have
140 #@dl_librefs = (); # things we have loaded
141 #@dl_modules = (); # Modules we have loaded
143 # This is a fix to support DLD's unfortunate desire to relink -lc
144 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
148 my $cfg_dl_library_path = <<'EOT';
149 push(@dl_library_path, split(' ', $Config::Config{libpth}));
152 sub dquoted_comma_list {
153 join(", ", map {'"'.quotemeta($_).'"'} @_);
156 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
157 eval $cfg_dl_library_path;
158 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
159 my $dl_library_path = dquoted_comma_list(@dl_library_path);
161 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
163 \@dl_library_path = ($dl_library_path);
170 # Initialise \@dl_library_path with the 'standard' library path
171 # for this platform as determined by Configure.
179 my $ldlibpthname_defined;
182 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
183 $ldlibpthname = to_string($Config::Config{ldlibpthname});
184 $ldlibpthname_defined = to_string(defined $Config::Config{ldlibpthname} ? 1 : 0);
185 $pthsep = to_string($Config::Config{path_sep});
188 $ldlibpthname = q($Config::Config{ldlibpthname});
189 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
190 $pthsep = q($Config::Config{path_sep});
193 my \$ldlibpthname = $ldlibpthname;
194 my \$ldlibpthname_defined = $ldlibpthname_defined;
195 my \$pthsep = $pthsep;
199 my $env_dl_library_path = <<'EOT';
200 if ($ldlibpthname_defined &&
201 exists $ENV{$ldlibpthname}) {
202 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
205 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
207 if ($ldlibpthname_defined &&
208 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
209 exists $ENV{LD_LIBRARY_PATH}) {
210 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
214 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
215 eval $env_dl_library_path;
219 # Add to \@dl_library_path any extra directories we can gather from environment
227 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
228 my $dl_library_path = dquoted_comma_list(@dl_library_path);
230 # The below \@dl_library_path has been expanded (%Config, %ENV)
231 # in Perl build time.
233 \@dl_library_path = ($dl_library_path);
239 # following long string contains $^O-specific stuff, which is factored out
240 print OUT expand_os_specific(<<'EOT');
241 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
242 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
243 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
247 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
248 print STDERR "DynaLoader not linked into this perl\n"
249 unless defined(&boot_DynaLoader);
252 1; # End of main code
255 sub croak { require Carp; Carp::croak(@_) }
257 sub bootstrap_inherit {
259 local *isa = *{"$module\::ISA"};
260 local @isa = (@isa, 'DynaLoader');
261 # Cannot goto due to delocalization. Will report errors on a wrong line?
266 # use local vars to enable $module.bs script to edit values
268 local($module) = $args[0];
273 Carp::confess("Usage: DynaLoader::bootstrap(module)");
276 # A common error on platforms which don't support dynamic loading.
277 # Since it's fatal and potentially confusing we give a detailed message.
278 croak("Can't load module $module, dynamic loading not available in this perl.\n".
279 " (You may need to build a new perl executable which either supports\n".
280 " dynamic loading or has the $module module statically linked into it.)\n")
281 unless defined(&dl_load_file);
285 # Can dynaload, but cannot dynaload Perl modules...
286 die 'Dynaloaded Perl modules are not available in this build of Perl' if $OS2::is_static;
289 my @modparts = split(/::/,$module);
290 my $modfname = $modparts[-1];
292 # Some systems have restrictions on files names for DLL's etc.
293 # mod2fname returns appropriate file base name (typically truncated)
294 # It may also edit @modparts if required.
295 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
298 # Truncate the module name to 8.3 format for NetWare
299 if ((length($modfname) > 8)) {
300 $modfname = substr($modfname, 0, 8);
304 my $modpname = join('/',@modparts);
306 print STDERR "DynaLoader::bootstrap for $module ",
307 "(auto/$modpname/$modfname.$dl_dlext)\n"
311 <<$^O-eq-VMS>>chop($_ = VMS::Filespec::unixpath($_));<</$^O-eq-VMS>>
312 my $dir = "$_/auto/$modpname";
314 next unless -d $dir; # skip over uninteresting directories
316 # check for common cases to avoid autoload of dl_findfile
317 my $try = "$dir/$modfname.$dl_dlext";
318 last if $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
320 # no luck here, save dir for possible later dl_findfile search
323 # last resort, let dl_findfile have a go in all known locations
324 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
326 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
327 unless $file; # wording similar to error from 'require'
329 <<$^O-eq-VMS>>$file = uc($file) if $Config::Config{d_vms_case_sensitive_symbols};<</$^O-eq-VMS>>
330 my $bootname = "boot_$module";
331 $bootname =~ s/\W/_/g;
332 @dl_require_symbols = ($bootname);
334 # Execute optional '.bootstrap' perl script for this module.
335 # The .bs file can be used to configure @dl_resolve_using etc to
336 # match the needs of the individual module on this architecture.
338 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
339 if (-s $bs) { # only read file if it's not empty
340 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
342 warn "$bs: $@\n" if $@;
348 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
349 goto boot; #extension library has already been loaded, e.g. darwin
353 # Many dynamic extension loading problems will appear to come from
354 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
355 # Often these errors are actually occurring in the initialisation
356 # C code of the extension XS file. Perl reports the error as being
357 # in this perl code simply because this was the last perl code
360 my $libref = dl_load_file($file, $module->dl_load_flags) or
361 croak("Can't load '$file' for module $module: ".dl_error());
363 push(@dl_librefs,$libref); # record loaded object
365 my @unresolved = dl_undef_symbols();
368 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
371 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
372 croak("Can't find '$bootname' symbol in $file\n");
374 push(@dl_modules, $module); # record loaded module
377 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
379 # See comment block above
381 push(@dl_shared_objects, $file); # record files loaded
387 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
388 # This function does not automatically consider the architecture
389 # or the perl library auto directories.
391 my (@dirs, $dir); # which directories to search
392 my (@found); # full paths to real files we have found
393 #my $dl_ext= <<=to_string($Config::Config{'dlext'})>>; # $Config::Config{'dlext'} suffix for perl extensions
394 #my $dl_so = <<=to_string($Config::Config{'so'})>>; # $Config::Config{'so'} suffix for shared libraries
396 print STDERR "dl_findfile(@args)\n" if $dl_debug;
398 # accumulate directories but process files as they appear
399 arg: foreach(@args) {
400 # Special fast case: full filepath requires no search
402 if (m%[:>/\]]% && -f $_) {
403 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
404 last arg unless wantarray;
411 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; }
420 # Otherwise we try to try to spot directories by a heuristic
421 # (this is a more complicated issue than it first appears)
422 if (m:/: && -d $_) { push(@dirs, $_); next; }
425 # VMS: we may be using native VMS directory syntax instead of
426 # Unix emulation, so check this as well
427 if (/[:>\]]/ && -d $_) { push(@dirs, $_); next; }
430 # Only files should get this far...
431 my(@names, $name); # what filenames to look for
432 if (m:-l: ) { # convert -lname to appropriate library name
434 push(@names,"lib$_.$dl_so");
435 push(@names,"lib$_.a");
436 } else { # Umm, a bare name. Try various alternatives:
437 # these should be ordered with the most likely first
438 push(@names,"$_.$dl_dlext") unless m/\.$dl_dlext$/o;
439 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
441 push(@names,"cyg$_.$dl_so") unless m:/:;
443 push(@names,"lib$_.$dl_so") unless m:/:;
444 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
450 if ($0 =~ /^([a-z]):/i) {
452 @dirs = map { "$drive:$_" } @dirs;
453 @dl_library_path = map { "$drive:$_" } @dl_library_path;
456 foreach $dir (@dirs, @dl_library_path) {
459 chop($dir = VMS::Filespec::unixpath($dir));
461 foreach $name (@names) {
462 my($file) = "$dir$dirsep$name";
463 print STDERR " checking in $dir for $name\n" if $dl_debug;
464 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
465 #$file = _check_file($file);
468 next arg; # no need to look any further
475 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
477 print STDERR "dl_findfile found: @found\n";
479 return $found[0] unless wantarray;
485 # dl_expandspec should be defined in dl_vms.xs
489 # Optional function invoked if DynaLoader.pm sets $do_expand.
490 # Most systems do not require or use this function.
491 # Some systems may implement it in the dl_*.xs file in which case
492 # this Perl version should be excluded at build time.
494 # This function is designed to deal with systems which treat some
495 # 'filenames' in a special way. For example VMS 'Logical Names'
496 # (something like unix environment variables - but different).
497 # This function should recognise such names and expand them into
499 # Must return undef if $spec is invalid or file does not exist.
501 my $file = $spec; # default output to input
503 return undef unless -f $file;
504 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
509 sub dl_find_symbol_anywhere
513 foreach $libref (@dl_librefs) {
514 my $symref = dl_find_symbol($libref,$sym);
515 return $symref if $symref;
524 DynaLoader - Dynamically load C libraries into Perl code
530 @ISA = qw(... DynaLoader ...);
531 bootstrap YourPackage;
533 # optional method for 'global' loading
534 sub dl_load_flags { 0x01 }
539 This document defines a standard generic interface to the dynamic
540 linking mechanisms available on many platforms. Its primary purpose is
541 to implement automatic dynamic loading of Perl modules.
543 This document serves as both a specification for anyone wishing to
544 implement the DynaLoader for a new platform and as a guide for
545 anyone wishing to use the DynaLoader directly in an application.
547 The DynaLoader is designed to be a very simple high-level
548 interface that is sufficiently general to cover the requirements
549 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
551 It is also hoped that the interface will cover the needs of OS/2, NT
552 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
554 It must be stressed that the DynaLoader, by itself, is practically
555 useless for accessing non-Perl libraries because it provides almost no
556 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
557 library function or supplying arguments. A C::DynaLib module
558 is available from CPAN sites which performs that function for some
559 common system types. And since the year 2000, there's also Inline::C,
560 a module that allows you to write Perl subroutines in C. Also available
561 from your local CPAN site.
563 DynaLoader Interface Summary
573 bootstrap($modulename) Perl
574 @filepaths = dl_findfile(@names) Perl
575 $flags = $modulename->dl_load_flags Perl
576 $symref = dl_find_symbol_anywhere($symbol) Perl
578 $libref = dl_load_file($filename, $flags) C
579 $status = dl_unload_file($libref) C
580 $symref = dl_find_symbol($libref, $symbol) C
581 @symbols = dl_undef_symbols() C
582 dl_install_xsub($name, $symref [, $filename]) C
583 $message = dl_error C
587 =item @dl_library_path
589 The standard/default list of directories in which dl_findfile() will
590 search for libraries etc. Directories are searched in order:
591 $dl_library_path[0], [1], ... etc
593 @dl_library_path is initialised to hold the list of 'normal' directories
594 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
595 ensure portability across a wide range of platforms.
597 @dl_library_path should also be initialised with any other directories
598 that can be determined from the environment at runtime (such as
599 LD_LIBRARY_PATH for SunOS).
601 After initialisation @dl_library_path can be manipulated by an
602 application using push and unshift before calling dl_findfile().
603 Unshift can be used to add directories to the front of the search order
604 either to save search time or to override libraries with the same name
605 in the 'normal' directories.
607 The load function that dl_load_file() calls may require an absolute
608 pathname. The dl_findfile() function and @dl_library_path can be
609 used to search for and return the absolute pathname for the
610 library/object that you wish to load.
612 =item @dl_resolve_using
614 A list of additional libraries or other shared objects which can be
615 used to resolve any undefined symbols that might be generated by a
616 later call to load_file().
618 This is only required on some platforms which do not handle dependent
619 libraries automatically. For example the Socket Perl extension
620 library (F<auto/Socket/Socket.so>) contains references to many socket
621 functions which need to be resolved when it's loaded. Most platforms
622 will automatically know where to find the 'dependent' library (e.g.,
623 F</usr/lib/libsocket.so>). A few platforms need to be told the
624 location of the dependent library explicitly. Use @dl_resolve_using
629 @dl_resolve_using = dl_findfile('-lsocket');
631 =item @dl_require_symbols
633 A list of one or more symbol names that are in the library/object file
634 to be dynamically loaded. This is only required on some platforms.
638 An array of the handles returned by successful calls to dl_load_file(),
639 made by bootstrap, in the order in which they were loaded.
640 Can be used with dl_find_symbol() to look for a symbol in any of
645 An array of module (package) names that have been bootstrap'ed.
647 =item @dl_shared_objects
649 An array of file names for the shared objects that were loaded.
655 $message = dl_error();
657 Error message text from the last failed DynaLoader function. Note
658 that, similar to errno in unix, a successful function call does not
661 Implementations should detect the error as soon as it occurs in any of
662 the other functions and save the corresponding message for later
663 retrieval. This will avoid problems on some platforms (such as SunOS)
664 where the error message is very temporary (e.g., dlerror()).
668 Internal debugging messages are enabled when $dl_debug is set true.
669 Currently setting $dl_debug only affects the Perl side of the
670 DynaLoader. These messages should help an application developer to
671 resolve any DynaLoader usage problems.
673 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
675 For the DynaLoader developer/porter there is a similar debugging
676 variable added to the C code (see dlutils.c) and enabled if Perl was
677 built with the B<-DDEBUGGING> flag. This can also be set via the
678 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
685 @filepaths = dl_findfile(@names)
687 Determine the full paths (including file suffix) of one or more
688 loadable files given their generic names and optionally one or more
689 directories. Searches directories in @dl_library_path by default and
690 returns an empty list if no files were found.
692 Names can be specified in a variety of platform independent forms. Any
693 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
694 an appropriate suffix for the platform.
696 If a name does not already have a suitable prefix and/or suffix then
697 the corresponding file will be searched for by trying combinations of
698 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
701 If any directories are included in @names they are searched before
702 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
703 names are treated as filenames to be searched for.
705 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
709 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
712 =item dl_expandspec()
716 $filepath = dl_expandspec($spec)
718 Some unusual systems, such as VMS, require special filename handling in
719 order to deal with symbolic names for files (i.e., VMS's Logical Names).
721 To support these systems a dl_expandspec() function can be implemented
722 either in the F<dl_*.xs> file or code can be added to the dl_expandspec()
723 function in F<DynaLoader.pm>. See F<DynaLoader_pm.PL> for more information.
729 $libref = dl_load_file($filename, $flags)
731 Dynamically load $filename, which must be the path to a shared object
732 or library. An opaque 'library reference' is returned as a handle for
733 the loaded object. Returns undef on error.
735 The $flags argument to alters dl_load_file behaviour.
738 0x01 make symbols available for linking later dl_load_file's.
739 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
740 (ignored under VMS; this is a normal part of image linking)
742 (On systems that provide a handle for the loaded object such as SunOS
743 and HPUX, $libref will be that handle. On other systems $libref will
744 typically be $filename or a pointer to a buffer containing $filename.
745 The application should not examine or alter $libref in any way.)
747 This is the function that does the real work. It should use the
748 current values of @dl_require_symbols and @dl_resolve_using if required.
750 SunOS: dlopen($filename)
751 HP-UX: shl_load($filename)
752 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
753 NeXT: rld_load($filename, @dl_resolve_using)
754 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
756 (The dlopen() function is also used by Solaris and some versions of
757 Linux, and is a common choice when providing a "wrapper" on other
758 mechanisms as is done in the OS/2 port.)
760 =item dl_unload_file()
764 $status = dl_unload_file($libref)
766 Dynamically unload $libref, which must be an opaque 'library reference' as
767 returned from dl_load_file. Returns one on success and zero on failure.
769 This function is optional and may not necessarily be provided on all platforms.
770 If it is defined, it is called automatically when the interpreter exits for
771 every shared object or library loaded by DynaLoader::bootstrap. All such
772 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
773 loads the libraries. The files are unloaded in last-in, first-out order.
775 This unloading is usually necessary when embedding a shared-object perl (e.g.
776 one configured with -Duseshrplib) within a larger application, and the perl
777 interpreter is created and destroyed several times within the lifetime of the
778 application. In this case it is possible that the system dynamic linker will
779 unload and then subsequently reload the shared libperl without relocating any
780 references to it from any files DynaLoaded by the previous incarnation of the
781 interpreter. As a result, any shared objects opened by DynaLoader may point to
782 a now invalid 'ghost' of the libperl shared object, causing apparently random
783 memory corruption and crashes. This behaviour is most commonly seen when using
784 Apache and mod_perl built with the APXS mechanism.
786 SunOS: dlclose($libref)
792 (The dlclose() function is also used by Solaris and some versions of
793 Linux, and is a common choice when providing a "wrapper" on other
794 mechanisms as is done in the OS/2 port.)
796 =item dl_load_flags()
800 $flags = dl_load_flags $modulename;
802 Designed to be a method call, and to be overridden by a derived class
803 (i.e. a class which has DynaLoader in its @ISA). The definition in
804 DynaLoader itself returns 0, which produces standard behavior from
807 =item dl_find_symbol()
811 $symref = dl_find_symbol($libref, $symbol)
813 Return the address of the symbol $symbol or C<undef> if not found. If the
814 target system has separate functions to search for symbols of different
815 types then dl_find_symbol() should search for function symbols first and
818 The exact manner in which the address is returned in $symref is not
819 currently defined. The only initial requirement is that $symref can
820 be passed to, and understood by, dl_install_xsub().
822 SunOS: dlsym($libref, $symbol)
823 HP-UX: shl_findsym($libref, $symbol)
824 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
825 NeXT: rld_lookup("_$symbol")
826 VMS: lib$find_image_symbol($libref,$symbol)
829 =item dl_find_symbol_anywhere()
833 $symref = dl_find_symbol_anywhere($symbol)
835 Applies dl_find_symbol() to the members of @dl_librefs and returns
836 the first match found.
838 =item dl_undef_symbols()
842 @symbols = dl_undef_symbols()
844 Return a list of symbol names which remain undefined after load_file().
845 Returns C<()> if not known. Don't worry if your platform does not provide
846 a mechanism for this. Most do not need it and hence do not provide it,
847 they just return an empty list.
850 =item dl_install_xsub()
854 dl_install_xsub($perl_name, $symref [, $filename])
856 Create a new Perl external subroutine named $perl_name using $symref as
857 a pointer to the function which implements the routine. This is simply
858 a direct call to newXSUB(). Returns a reference to the installed
861 The $filename parameter is used by Perl to identify the source file for
862 the function if required by die(), caller() or the debugger. If
863 $filename is not defined then "DynaLoader" will be used.
870 bootstrap($module [...])
872 This is the normal entry point for automatic dynamic loading in Perl.
874 It performs the following actions:
880 locates an auto/$module directory by searching @INC
884 uses dl_findfile() to determine the filename to load
888 sets @dl_require_symbols to C<("boot_$module")>
892 executes an F<auto/$module/$module.bs> file if it exists
893 (typically used to add to @dl_resolve_using any files which
894 are required to load the module on the current platform)
898 calls dl_load_flags() to determine how to load the file.
902 calls dl_load_file() to load the file
906 calls dl_undef_symbols() and warns if any symbols are undefined
910 calls dl_find_symbol() for "boot_$module"
914 calls dl_install_xsub() to install it as "${module}::bootstrap"
918 calls &{"${module}::bootstrap"} to bootstrap the module (actually
919 it uses the function reference returned by dl_install_xsub for speed)
923 All arguments to bootstrap() are passed to the module's bootstrap function.
924 The default code generated by F<xsubpp> expects $module [, $version]
925 If the optional $version argument is not given, it defaults to
926 C<$XS_VERSION // $VERSION> in the module's symbol table. The default code
927 compares the Perl-space version with the version of the compiled XS code,
928 and croaks with an error if they do not match.
935 Tim Bunce, 11 August 1994.
937 This interface is based on the work and comments of (in no particular
938 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
939 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
941 Larry Wall designed the elegant inherited bootstrap mechanism and
942 implemented the first Perl 5 dynamic loader using it.
944 Solaris global loading added by Nick Ing-Simmons with design/coding
945 assistance from Tim Bunce, January 1996.