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)
101 # (ignored under Android; the linker always uses RTLD_LOCAL)
103 # This is called as a class method $module->dl_load_flags. The
104 # definition here will be inherited and result on "default" loading
105 # behaviour unless a sub-class of DynaLoader defines its own version.
108 sub dl_load_flags { 0x00 }
112 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
113 print OUT "(\$dl_dlext, \$dl_so, \$dlsrc) = (",
114 to_string($Config{'dlext'}), ",",
115 to_string($Config{'so'}), ",",
116 to_string($Config{'dlsrc'}), ")\n;" ;
120 ($dl_dlext, $dl_so, $dlsrc) = @Config::Config{qw(dlext so dlsrc)};
124 print OUT expand_os_specific(<<'EOT');
127 # Some systems need special handling to expand file specifications
128 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
129 # See dl_expandspec() for more details. Should be harmless but
130 # inefficient to define on systems that don't need it.
131 $Is_VMS = $^O eq 'VMS';
133 $do_expand = <<$^O-eq-VMS>>1<<|$^O-eq-VMS>>0<</$^O-eq-VMS>>;
135 @dl_require_symbols = (); # names of symbols we need
136 @dl_resolve_using = (); # names of files to link with
137 @dl_library_path = (); # path to look for files
139 #XSLoader.pm may have added elements before we were required
140 #@dl_shared_objects = (); # shared objects for symbols we have
141 #@dl_librefs = (); # things we have loaded
142 #@dl_modules = (); # Modules we have loaded
144 # This is a fix to support DLD's unfortunate desire to relink -lc
145 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
149 my $cfg_dl_library_path = <<'EOT';
150 push(@dl_library_path, split(' ', $Config::Config{libpth}));
153 sub dquoted_comma_list {
154 join(", ", map {'"'.quotemeta($_).'"'} @_);
157 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
158 eval $cfg_dl_library_path;
159 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
160 my $dl_library_path = dquoted_comma_list(@dl_library_path);
162 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
164 \@dl_library_path = ($dl_library_path);
171 # Initialise \@dl_library_path with the 'standard' library path
172 # for this platform as determined by Configure.
180 my $ldlibpthname_defined;
183 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
184 $ldlibpthname = to_string($Config::Config{ldlibpthname});
185 $ldlibpthname_defined = to_string(defined $Config::Config{ldlibpthname} ? 1 : 0);
186 $pthsep = to_string($Config::Config{path_sep});
189 $ldlibpthname = q($Config::Config{ldlibpthname});
190 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
191 $pthsep = q($Config::Config{path_sep});
194 my \$ldlibpthname = $ldlibpthname;
195 my \$ldlibpthname_defined = $ldlibpthname_defined;
196 my \$pthsep = $pthsep;
200 my $env_dl_library_path = <<'EOT';
201 if ($ldlibpthname_defined &&
202 exists $ENV{$ldlibpthname}) {
203 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
206 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
208 if ($ldlibpthname_defined &&
209 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
210 exists $ENV{LD_LIBRARY_PATH}) {
211 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
215 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
216 eval $env_dl_library_path;
220 # Add to \@dl_library_path any extra directories we can gather from environment
228 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
229 my $dl_library_path = dquoted_comma_list(@dl_library_path);
231 # The below \@dl_library_path has been expanded (%Config, %ENV)
232 # in Perl build time.
234 \@dl_library_path = ($dl_library_path);
239 if ( $Config::Config{d_libname_unique} ) {
240 printf OUT <<'EOT', length($Config::Config{dlext}) + 1;
244 my $name_max = 255; # No easy way to get this here
246 my $libname = "PL_" . join("__", @$parts);
248 return $libname if (length($libname)+$so_len) <= $name_max;
250 # It's too darned big, so we need to go strip. We use the same
251 # algorithm as xsubpp does. First, strip out doubled __
252 $libname =~ s/__/_/g;
253 return $libname if (length($libname)+$so_len) <= $name_max;
255 # Strip duplicate letters
256 1 while $libname =~ s/(.)\1/\U$1/i;
257 return $libname if (length($libname)+$so_len) <= $name_max;
259 # Still too long. Truncate.
260 $libname = substr($libname, 0, $name_max - $so_len);
266 # following long string contains $^O-specific stuff, which is factored out
267 print OUT expand_os_specific(<<'EOT');
268 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
269 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
270 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
274 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
275 print STDERR "DynaLoader not linked into this perl\n"
276 unless defined(&boot_DynaLoader);
279 1; # End of main code
282 sub croak { require Carp; Carp::croak(@_) }
284 sub bootstrap_inherit {
286 local *isa = *{"$module\::ISA"};
287 local @isa = (@isa, 'DynaLoader');
288 # Cannot goto due to delocalization. Will report errors on a wrong line?
293 # use local vars to enable $module.bs script to edit values
295 local($module) = $args[0];
300 Carp::confess("Usage: DynaLoader::bootstrap(module)");
303 # A common error on platforms which don't support dynamic loading.
304 # Since it's fatal and potentially confusing we give a detailed message.
305 croak("Can't load module $module, dynamic loading not available in this perl.\n".
306 " (You may need to build a new perl executable which either supports\n".
307 " dynamic loading or has the $module module statically linked into it.)\n")
308 unless defined(&dl_load_file);
312 # Can dynaload, but cannot dynaload Perl modules...
313 die 'Dynaloaded Perl modules are not available in this build of Perl' if $OS2::is_static;
316 my @modparts = split(/::/,$module);
317 my $modfname = $modparts[-1];
319 # Some systems have restrictions on files names for DLL's etc.
320 # mod2fname returns appropriate file base name (typically truncated)
321 # It may also edit @modparts if required.
322 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
325 # Truncate the module name to 8.3 format for NetWare
326 if ((length($modfname) > 8)) {
327 $modfname = substr($modfname, 0, 8);
331 my $modpname = join('/',@modparts);
333 print STDERR "DynaLoader::bootstrap for $module ",
334 "(auto/$modpname/$modfname.$dl_dlext)\n"
338 <<$^O-eq-VMS>>chop($_ = VMS::Filespec::unixpath($_));<</$^O-eq-VMS>>
339 my $dir = "$_/auto/$modpname";
341 next unless -d $dir; # skip over uninteresting directories
343 # check for common cases to avoid autoload of dl_findfile
344 my $try = "$dir/$modfname.$dl_dlext";
345 last if $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
347 # no luck here, save dir for possible later dl_findfile search
350 # last resort, let dl_findfile have a go in all known locations
351 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
353 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
354 unless $file; # wording similar to error from 'require'
356 <<$^O-eq-VMS>>$file = uc($file) if $Config::Config{d_vms_case_sensitive_symbols};<</$^O-eq-VMS>>
357 my $bootname = "boot_$module";
358 $bootname =~ s/\W/_/g;
359 @dl_require_symbols = ($bootname);
361 # Execute optional '.bootstrap' perl script for this module.
362 # The .bs file can be used to configure @dl_resolve_using etc to
363 # match the needs of the individual module on this architecture.
365 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
366 if (-s $bs) { # only read file if it's not empty
367 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
369 warn "$bs: $@\n" if $@;
375 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
376 goto boot; #extension library has already been loaded, e.g. darwin
380 # Many dynamic extension loading problems will appear to come from
381 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
382 # Often these errors are actually occurring in the initialisation
383 # C code of the extension XS file. Perl reports the error as being
384 # in this perl code simply because this was the last perl code
387 my $flags = $module->dl_load_flags;
389 # See the note above regarding the linker.
392 my $libref = dl_load_file($file, $flags) or
393 croak("Can't load '$file' for module $module: ".dl_error());
395 push(@dl_librefs,$libref); # record loaded object
397 my @unresolved = dl_undef_symbols();
400 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
403 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
404 croak("Can't find '$bootname' symbol in $file\n");
406 push(@dl_modules, $module); # record loaded module
409 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
411 # See comment block above
413 push(@dl_shared_objects, $file); # record files loaded
419 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
420 # This function does not automatically consider the architecture
421 # or the perl library auto directories.
423 my (@dirs, $dir); # which directories to search
424 my (@found); # full paths to real files we have found
425 #my $dl_ext= <<=to_string($Config::Config{'dlext'})>>; # $Config::Config{'dlext'} suffix for perl extensions
426 #my $dl_so = <<=to_string($Config::Config{'so'})>>; # $Config::Config{'so'} suffix for shared libraries
428 print STDERR "dl_findfile(@args)\n" if $dl_debug;
430 # accumulate directories but process files as they appear
431 arg: foreach(@args) {
432 # Special fast case: full filepath requires no search
434 if (m%[:>/\]]% && -f $_) {
435 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
436 last arg unless wantarray;
443 last arg unless wantarray;
448 # Deal with directories first:
449 # Using a -L prefix is the preferred option (faster and more robust)
450 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
452 # Otherwise we try to try to spot directories by a heuristic
453 # (this is a more complicated issue than it first appears)
454 if (m:/: && -d $_) { push(@dirs, $_); next; }
457 # VMS: we may be using native VMS directory syntax instead of
458 # Unix emulation, so check this as well
459 if (/[:>\]]/ && -d $_) { push(@dirs, $_); next; }
462 # Only files should get this far...
463 my(@names, $name); # what filenames to look for
464 if (m:-l: ) { # convert -lname to appropriate library name
466 push(@names,"lib$_.$dl_so");
467 push(@names,"lib$_.a");
468 } else { # Umm, a bare name. Try various alternatives:
469 # these should be ordered with the most likely first
470 push(@names,"$_.$dl_dlext") unless m/\.$dl_dlext$/o;
471 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
473 push(@names,"cyg$_.$dl_so") unless m:/:;
475 push(@names,"lib$_.$dl_so") unless m:/:;
476 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
482 if ($0 =~ /^([a-z]):/i) {
484 @dirs = map { "$drive:$_" } @dirs;
485 @dl_library_path = map { "$drive:$_" } @dl_library_path;
488 foreach $dir (@dirs, @dl_library_path) {
491 chop($dir = VMS::Filespec::unixpath($dir));
493 foreach $name (@names) {
494 my($file) = "$dir$dirsep$name";
495 print STDERR " checking in $dir for $name\n" if $dl_debug;
496 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
497 #$file = _check_file($file);
500 next arg; # no need to look any further
507 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
509 print STDERR "dl_findfile found: @found\n";
511 return $found[0] unless wantarray;
517 # dl_expandspec should be defined in dl_vms.xs
521 # Optional function invoked if DynaLoader.pm sets $do_expand.
522 # Most systems do not require or use this function.
523 # Some systems may implement it in the dl_*.xs file in which case
524 # this Perl version should be excluded at build time.
526 # This function is designed to deal with systems which treat some
527 # 'filenames' in a special way. For example VMS 'Logical Names'
528 # (something like unix environment variables - but different).
529 # This function should recognise such names and expand them into
531 # Must return undef if $spec is invalid or file does not exist.
533 my $file = $spec; # default output to input
535 return undef unless -f $file;
536 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
541 sub dl_find_symbol_anywhere
545 foreach $libref (@dl_librefs) {
546 my $symref = dl_find_symbol($libref,$sym);
547 return $symref if $symref;
556 DynaLoader - Dynamically load C libraries into Perl code
562 @ISA = qw(... DynaLoader ...);
563 bootstrap YourPackage;
565 # optional method for 'global' loading
566 sub dl_load_flags { 0x01 }
571 This document defines a standard generic interface to the dynamic
572 linking mechanisms available on many platforms. Its primary purpose is
573 to implement automatic dynamic loading of Perl modules.
575 This document serves as both a specification for anyone wishing to
576 implement the DynaLoader for a new platform and as a guide for
577 anyone wishing to use the DynaLoader directly in an application.
579 The DynaLoader is designed to be a very simple high-level
580 interface that is sufficiently general to cover the requirements
581 of SunOS, HP-UX, Linux, VMS and other platforms.
583 It is also hoped that the interface will cover the needs of OS/2, NT
584 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
586 It must be stressed that the DynaLoader, by itself, is practically
587 useless for accessing non-Perl libraries because it provides almost no
588 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
589 library function or supplying arguments. A C::DynaLib module
590 is available from CPAN sites which performs that function for some
591 common system types. And since the year 2000, there's also Inline::C,
592 a module that allows you to write Perl subroutines in C. Also available
593 from your local CPAN site.
595 DynaLoader Interface Summary
606 bootstrap($modulename) Perl
607 @filepaths = dl_findfile(@names) Perl
608 $flags = $modulename->dl_load_flags Perl
609 $symref = dl_find_symbol_anywhere($symbol) Perl
611 $libref = dl_load_file($filename, $flags) C
612 $status = dl_unload_file($libref) C
613 $symref = dl_find_symbol($libref, $symbol) C
614 @symbols = dl_undef_symbols() C
615 dl_install_xsub($name, $symref [, $filename]) C
616 $message = dl_error C
620 =item @dl_library_path
622 The standard/default list of directories in which dl_findfile() will
623 search for libraries etc. Directories are searched in order:
624 $dl_library_path[0], [1], ... etc
626 @dl_library_path is initialised to hold the list of 'normal' directories
627 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
628 ensure portability across a wide range of platforms.
630 @dl_library_path should also be initialised with any other directories
631 that can be determined from the environment at runtime (such as
632 LD_LIBRARY_PATH for SunOS).
634 After initialisation @dl_library_path can be manipulated by an
635 application using push and unshift before calling dl_findfile().
636 Unshift can be used to add directories to the front of the search order
637 either to save search time or to override libraries with the same name
638 in the 'normal' directories.
640 The load function that dl_load_file() calls may require an absolute
641 pathname. The dl_findfile() function and @dl_library_path can be
642 used to search for and return the absolute pathname for the
643 library/object that you wish to load.
645 =item @dl_resolve_using
647 A list of additional libraries or other shared objects which can be
648 used to resolve any undefined symbols that might be generated by a
649 later call to load_file().
651 This is only required on some platforms which do not handle dependent
652 libraries automatically. For example the Socket Perl extension
653 library (F<auto/Socket/Socket.so>) contains references to many socket
654 functions which need to be resolved when it's loaded. Most platforms
655 will automatically know where to find the 'dependent' library (e.g.,
656 F</usr/lib/libsocket.so>). A few platforms need to be told the
657 location of the dependent library explicitly. Use @dl_resolve_using
662 @dl_resolve_using = dl_findfile('-lsocket');
664 =item @dl_require_symbols
666 A list of one or more symbol names that are in the library/object file
667 to be dynamically loaded. This is only required on some platforms.
671 An array of the handles returned by successful calls to dl_load_file(),
672 made by bootstrap, in the order in which they were loaded.
673 Can be used with dl_find_symbol() to look for a symbol in any of
678 An array of module (package) names that have been bootstrap'ed.
680 =item @dl_shared_objects
682 An array of file names for the shared objects that were loaded.
688 $message = dl_error();
690 Error message text from the last failed DynaLoader function. Note
691 that, similar to errno in unix, a successful function call does not
694 Implementations should detect the error as soon as it occurs in any of
695 the other functions and save the corresponding message for later
696 retrieval. This will avoid problems on some platforms (such as SunOS)
697 where the error message is very temporary (e.g., dlerror()).
701 Internal debugging messages are enabled when $dl_debug is set true.
702 Currently setting $dl_debug only affects the Perl side of the
703 DynaLoader. These messages should help an application developer to
704 resolve any DynaLoader usage problems.
706 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
708 For the DynaLoader developer/porter there is a similar debugging
709 variable added to the C code (see dlutils.c) and enabled if Perl was
710 built with the B<-DDEBUGGING> flag. This can also be set via the
711 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
716 When specified (localised) in a module's F<.pm> file, indicates the extension
717 which the module's loadable object will have. For example:
719 local $DynaLoader::dl_dlext = 'unusual_ext';
721 would indicate that the module's loadable object has an extension of
722 C<unusual_ext> instead of the more usual C<$Config{dlext}>. NOTE: This also
723 requires that the module's F<Makefile.PL> specify (in C<WriteMakefile()>):
725 DLEXT => 'unusual_ext',
731 @filepaths = dl_findfile(@names)
733 Determine the full paths (including file suffix) of one or more
734 loadable files given their generic names and optionally one or more
735 directories. Searches directories in @dl_library_path by default and
736 returns an empty list if no files were found.
738 Names can be specified in a variety of platform independent forms. Any
739 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
740 an appropriate suffix for the platform.
742 If a name does not already have a suitable prefix and/or suffix then
743 the corresponding file will be searched for by trying combinations of
744 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
747 If any directories are included in @names they are searched before
748 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
749 names are treated as filenames to be searched for.
751 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
755 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
758 =item dl_expandspec()
762 $filepath = dl_expandspec($spec)
764 Some unusual systems, such as VMS, require special filename handling in
765 order to deal with symbolic names for files (i.e., VMS's Logical Names).
767 To support these systems a dl_expandspec() function can be implemented
768 either in the F<dl_*.xs> file or code can be added to the dl_expandspec()
769 function in F<DynaLoader.pm>. See F<DynaLoader_pm.PL> for more information.
775 $libref = dl_load_file($filename, $flags)
777 Dynamically load $filename, which must be the path to a shared object
778 or library. An opaque 'library reference' is returned as a handle for
779 the loaded object. Returns undef on error.
781 The $flags argument to alters dl_load_file behaviour.
784 0x01 make symbols available for linking later dl_load_file's.
785 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
786 (ignored under VMS; this is a normal part of image linking)
788 (On systems that provide a handle for the loaded object such as SunOS
789 and HPUX, $libref will be that handle. On other systems $libref will
790 typically be $filename or a pointer to a buffer containing $filename.
791 The application should not examine or alter $libref in any way.)
793 This is the function that does the real work. It should use the
794 current values of @dl_require_symbols and @dl_resolve_using if required.
796 SunOS: dlopen($filename)
797 HP-UX: shl_load($filename)
798 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
799 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
801 (The dlopen() function is also used by Solaris and some versions of
802 Linux, and is a common choice when providing a "wrapper" on other
803 mechanisms as is done in the OS/2 port.)
805 =item dl_unload_file()
809 $status = dl_unload_file($libref)
811 Dynamically unload $libref, which must be an opaque 'library reference' as
812 returned from dl_load_file. Returns one on success and zero on failure.
813 This function is optional and may not necessarily be provided on all platforms.
815 If it is defined and perl is compiled with the C macro C<DL_UNLOAD_ALL_AT_EXIT>
816 defined, then it is called automatically when the interpreter exits for
817 every shared object or library loaded by DynaLoader::bootstrap. All such
818 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
819 loads the libraries. The files are unloaded in last-in, first-out order.
821 This unloading is usually necessary when embedding a shared-object perl (e.g.
822 one configured with -Duseshrplib) within a larger application, and the perl
823 interpreter is created and destroyed several times within the lifetime of the
824 application. In this case it is possible that the system dynamic linker will
825 unload and then subsequently reload the shared libperl without relocating any
826 references to it from any files DynaLoaded by the previous incarnation of the
827 interpreter. As a result, any shared objects opened by DynaLoader may point to
828 a now invalid 'ghost' of the libperl shared object, causing apparently random
829 memory corruption and crashes. This behaviour is most commonly seen when using
830 Apache and mod_perl built with the APXS mechanism.
832 SunOS: dlclose($libref)
837 (The dlclose() function is also used by Solaris and some versions of
838 Linux, and is a common choice when providing a "wrapper" on other
839 mechanisms as is done in the OS/2 port.)
841 =item dl_load_flags()
845 $flags = dl_load_flags $modulename;
847 Designed to be a method call, and to be overridden by a derived class
848 (i.e. a class which has DynaLoader in its @ISA). The definition in
849 DynaLoader itself returns 0, which produces standard behavior from
852 =item dl_find_symbol()
856 $symref = dl_find_symbol($libref, $symbol)
858 Return the address of the symbol $symbol or C<undef> if not found. If the
859 target system has separate functions to search for symbols of different
860 types then dl_find_symbol() should search for function symbols first and
863 The exact manner in which the address is returned in $symref is not
864 currently defined. The only initial requirement is that $symref can
865 be passed to, and understood by, dl_install_xsub().
867 SunOS: dlsym($libref, $symbol)
868 HP-UX: shl_findsym($libref, $symbol)
869 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
870 VMS: lib$find_image_symbol($libref,$symbol)
873 =item dl_find_symbol_anywhere()
877 $symref = dl_find_symbol_anywhere($symbol)
879 Applies dl_find_symbol() to the members of @dl_librefs and returns
880 the first match found.
882 =item dl_undef_symbols()
886 @symbols = dl_undef_symbols()
888 Return a list of symbol names which remain undefined after load_file().
889 Returns C<()> if not known. Don't worry if your platform does not provide
890 a mechanism for this. Most do not need it and hence do not provide it,
891 they just return an empty list.
894 =item dl_install_xsub()
898 dl_install_xsub($perl_name, $symref [, $filename])
900 Create a new Perl external subroutine named $perl_name using $symref as
901 a pointer to the function which implements the routine. This is simply
902 a direct call to newXS()/newXS_flags(). Returns a reference to the installed
905 The $filename parameter is used by Perl to identify the source file for
906 the function if required by die(), caller() or the debugger. If
907 $filename is not defined then "DynaLoader" will be used.
914 bootstrap($module [...])
916 This is the normal entry point for automatic dynamic loading in Perl.
918 It performs the following actions:
924 locates an auto/$module directory by searching @INC
928 uses dl_findfile() to determine the filename to load
932 sets @dl_require_symbols to C<("boot_$module")>
936 executes an F<auto/$module/$module.bs> file if it exists
937 (typically used to add to @dl_resolve_using any files which
938 are required to load the module on the current platform)
942 calls dl_load_flags() to determine how to load the file.
946 calls dl_load_file() to load the file
950 calls dl_undef_symbols() and warns if any symbols are undefined
954 calls dl_find_symbol() for "boot_$module"
958 calls dl_install_xsub() to install it as "${module}::bootstrap"
962 calls &{"${module}::bootstrap"} to bootstrap the module (actually
963 it uses the function reference returned by dl_install_xsub for speed)
967 All arguments to bootstrap() are passed to the module's bootstrap function.
968 The default code generated by F<xsubpp> expects $module [, $version]
969 If the optional $version argument is not given, it defaults to
970 C<$XS_VERSION // $VERSION> in the module's symbol table. The default code
971 compares the Perl-space version with the version of the compiled XS code,
972 and croaks with an error if they do not match.
979 Tim Bunce, 11 August 1994.
981 This interface is based on the work and comments of (in no particular
982 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
983 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
985 Larry Wall designed the elegant inherited bootstrap mechanism and
986 implemented the first Perl 5 dynamic loader using it.
988 Solaris global loading added by Nick Ing-Simmons with design/coding
989 assistance from Tim Bunce, January 1996.