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
92 *AUTOLOAD = \&AutoLoader::AUTOLOAD;
96 # enable debug/trace messages from DynaLoader perl code
97 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
100 # Flags to alter dl_load_file behaviour. Assigned bits:
101 # 0x01 make symbols available for linking later dl_load_file's.
102 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
103 # (ignored under VMS; effect is built-in to image linking)
105 # This is called as a class method $module->dl_load_flags. The
106 # definition here will be inherited and result on "default" loading
107 # behaviour unless a sub-class of DynaLoader defines its own version.
110 sub dl_load_flags { 0x00 }
114 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
115 print OUT "(\$dl_dlext, \$dl_so, \$dlsrc) = (",
116 to_string($Config{'dlext'}), ",",
117 to_string($Config{'so'}), ",",
118 to_string($Config{'dlsrc'}), ")\n;" ;
122 ($dl_dlext, $dl_so, $dlsrc) = @Config::Config{qw(dlext so dlsrc)};
126 print OUT expand_os_specific(<<'EOT');
129 # Some systems need special handling to expand file specifications
130 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
131 # See dl_expandspec() for more details. Should be harmless but
132 # inefficient to define on systems that don't need it.
133 $Is_VMS = $^O eq 'VMS';
135 $do_expand = <<$^O-eq-VMS>>1<<|$^O-eq-VMS>>0<</$^O-eq-VMS>>;
139 $Mac_FS = eval { require Mac::FileSpec::Unixish };
142 @dl_require_symbols = (); # names of symbols we need
143 @dl_resolve_using = (); # names of files to link with
144 @dl_library_path = (); # path to look for files
146 #XSLoader.pm may have added elements before we were required
147 #@dl_shared_objects = (); # shared objects for symbols we have
148 #@dl_librefs = (); # things we have loaded
149 #@dl_modules = (); # Modules we have loaded
151 # This is a fix to support DLD's unfortunate desire to relink -lc
152 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
156 my $cfg_dl_library_path = <<'EOT';
157 push(@dl_library_path, split(' ', $Config::Config{libpth}));
160 sub dquoted_comma_list {
161 join(", ", map {'"'.quotemeta($_).'"'} @_);
164 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
165 eval $cfg_dl_library_path;
166 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
167 my $dl_library_path = dquoted_comma_list(@dl_library_path);
169 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
171 \@dl_library_path = ($dl_library_path);
178 # Initialise \@dl_library_path with the 'standard' library path
179 # for this platform as determined by Configure.
187 my $ldlibpthname_defined;
190 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
191 $ldlibpthname = to_string($Config::Config{ldlibpthname});
192 $ldlibpthname_defined = to_string(defined $Config::Config{ldlibpthname} ? 1 : 0);
193 $pthsep = to_string($Config::Config{path_sep});
196 $ldlibpthname = q($Config::Config{ldlibpthname});
197 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
198 $pthsep = q($Config::Config{path_sep});
201 my \$ldlibpthname = $ldlibpthname;
202 my \$ldlibpthname_defined = $ldlibpthname_defined;
203 my \$pthsep = $pthsep;
207 my $env_dl_library_path = <<'EOT';
208 if ($ldlibpthname_defined &&
209 exists $ENV{$ldlibpthname}) {
210 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
213 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
215 if ($ldlibpthname_defined &&
216 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
217 exists $ENV{LD_LIBRARY_PATH}) {
218 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
222 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
223 eval $env_dl_library_path;
227 # Add to \@dl_library_path any extra directories we can gather from environment
235 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
236 my $dl_library_path = dquoted_comma_list(@dl_library_path);
238 # The below \@dl_library_path has been expanded (%Config, %ENV)
239 # in Perl build time.
241 \@dl_library_path = ($dl_library_path);
247 # following long string contains $^O-specific stuff, which is factored out
248 print OUT expand_os_specific(<<'EOT');
249 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
250 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
251 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
255 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
256 print STDERR "DynaLoader not linked into this perl\n"
257 unless defined(&boot_DynaLoader);
260 1; # End of main code
263 sub croak { require Carp; Carp::croak(@_) }
265 sub bootstrap_inherit {
267 local *isa = *{"$module\::ISA"};
268 local @isa = (@isa, 'DynaLoader');
269 # Cannot goto due to delocalization. Will report errors on a wrong line?
273 # The bootstrap function cannot be autoloaded (without complications)
274 # so we define it here:
277 # use local vars to enable $module.bs script to edit values
279 local($module) = $args[0];
284 Carp::confess("Usage: DynaLoader::bootstrap(module)");
287 # A common error on platforms which don't support dynamic loading.
288 # Since it's fatal and potentially confusing we give a detailed message.
289 croak("Can't load module $module, dynamic loading not available in this perl.\n".
290 " (You may need to build a new perl executable which either supports\n".
291 " dynamic loading or has the $module module statically linked into it.)\n")
292 unless defined(&dl_load_file);
296 # Can dynaload, but cannot dynaload Perl modules...
297 die 'Dynaloaded Perl modules are not available in this build of Perl' if $OS2::is_static;
300 my @modparts = split(/::/,$module);
301 my $modfname = $modparts[-1];
303 # Some systems have restrictions on files names for DLL's etc.
304 # mod2fname returns appropriate file base name (typically truncated)
305 # It may also edit @modparts if required.
306 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
309 # Truncate the module name to 8.3 format for NetWare
310 if ((length($modfname) > 8)) {
311 $modfname = substr($modfname, 0, 8);
315 my $modpname = join(<<$^O-eq-MacOS>>':'<<|$^O-eq-MacOS>>'/'<</$^O-eq-MacOS>>,@modparts);
317 print STDERR "DynaLoader::bootstrap for $module ",
318 <<$^O-eq-MacOS>> "(:auto:$modpname:$modfname.$dl_dlext)\n"
319 <<|$^O-eq-MacOS>>"(auto/$modpname/$modfname.$dl_dlext)\n"<</$^O-eq-MacOS>>
323 <<$^O-eq-VMS>>chop($_ = VMS::Filespec::unixpath($_));<</$^O-eq-VMS>>
326 if ($Mac_FS && ! -d $path) {
327 $path = Mac::FileSpec::Unixish::nativize($path);
329 $path .= ":" unless /:$/;
330 my $dir = "${path}auto:$modpname";
332 my $dir = "$_/auto/$modpname";
335 next unless -d $dir; # skip over uninteresting directories
337 # check for common cases to avoid autoload of dl_findfile
338 my $try = <<$^O-eq-MacOS>> "$dir:$modfname.$dl_dlext" <<|$^O-eq-MacOS>> "$dir/$modfname.$dl_dlext"<</$^O-eq-MacOS>>;
339 last if $file = <<$^O-eq-VMS>>($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
340 <<|$^O-eq-VMS>>(-f $try) && $try;
343 # no luck here, save dir for possible later dl_findfile search
346 # last resort, let dl_findfile have a go in all known locations
347 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
349 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
350 unless $file; # wording similar to error from 'require'
352 <<$^O-eq-VMS>>$file = uc($file) if $Config::Config{d_vms_case_sensitive_symbols};<</$^O-eq-VMS>>
353 my $bootname = "boot_$module";
354 $bootname =~ s/\W/_/g;
355 @dl_require_symbols = ($bootname);
357 # Execute optional '.bootstrap' perl script for this module.
358 # The .bs file can be used to configure @dl_resolve_using etc to
359 # match the needs of the individual module on this architecture.
361 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
362 if (-s $bs) { # only read file if it's not empty
363 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
365 warn "$bs: $@\n" if $@;
371 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
372 goto boot; #extension library has already been loaded, e.g. darwin
376 # Many dynamic extension loading problems will appear to come from
377 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
378 # Often these errors are actually occurring in the initialisation
379 # C code of the extension XS file. Perl reports the error as being
380 # in this perl code simply because this was the last perl code
383 my $libref = dl_load_file($file, $module->dl_load_flags) or
384 croak("Can't load '$file' for module $module: ".dl_error());
386 push(@dl_librefs,$libref); # record loaded object
388 my @unresolved = dl_undef_symbols();
391 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
394 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
395 croak("Can't find '$bootname' symbol in $file\n");
397 push(@dl_modules, $module); # record loaded module
400 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
402 # See comment block above
404 push(@dl_shared_objects, $file); # record files loaded
410 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
412 # return $file if (!$do_expand && -f $file); # the common case
413 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
418 # Let autosplit and the autoloader deal with these functions:
423 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
424 # This function does not automatically consider the architecture
425 # or the perl library auto directories.
427 my (@dirs, $dir); # which directories to search
428 my (@found); # full paths to real files we have found
429 #my $dl_ext= <<=to_string($Config::Config{'dlext'})>>; # $Config::Config{'dlext'} suffix for perl extensions
430 #my $dl_so = <<=to_string($Config::Config{'so'})>>; # $Config::Config{'so'} suffix for shared libraries
432 print STDERR "dl_findfile(@args)\n" if $dl_debug;
434 # accumulate directories but process files as they appear
435 arg: foreach(@args) {
436 # Special fast case: full filepath requires no search
438 if (m%[:>/\]]% && -f $_) {
439 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
440 last arg unless wantarray;
447 last arg unless wantarray;
453 last arg unless wantarray;
458 # Deal with directories first:
459 # Using a -L prefix is the preferred option (faster and more robust)
460 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
463 # Otherwise we try to try to spot directories by a heuristic
464 # (this is a more complicated issue than it first appears)
465 if (m/:/ && -d $_) { push(@dirs, $_); next; }
466 # Only files should get this far...
467 my(@names, $name); # what filenames to look for
470 foreach $dir (@dirs, @dl_library_path) {
472 $dir =~ s/^([^:]+)$/:$1/;
474 foreach $name (@names) {
475 my($file) = "$dir:$name";
476 print STDERR " checking in $dir for $name\n" if $dl_debug;
479 next arg; # no need to look any further
486 # Otherwise we try to try to spot directories by a heuristic
487 # (this is a more complicated issue than it first appears)
488 if (m:/: && -d $_) { push(@dirs, $_); next; }
491 # VMS: we may be using native VMS directory syntax instead of
492 # Unix emulation, so check this as well
493 if (/[:>\]]/ && -d $_) { push(@dirs, $_); next; }
496 # Only files should get this far...
497 my(@names, $name); # what filenames to look for
498 if (m:-l: ) { # convert -lname to appropriate library name
500 push(@names,"lib$_.$dl_so");
501 push(@names,"lib$_.a");
502 } else { # Umm, a bare name. Try various alternatives:
503 # these should be ordered with the most likely first
504 push(@names,"$_.$dl_dlext") unless m/\.$dl_dlext$/o;
505 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
506 push(@names,"lib$_.$dl_so") unless m:/:;
507 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
513 if ($0 =~ /^([a-z]):/i) {
515 @dirs = map { "$drive:$_" } @dirs;
516 @dl_library_path = map { "$drive:$_" } @dl_library_path;
519 foreach $dir (@dirs, @dl_library_path) {
522 chop($dir = VMS::Filespec::unixpath($dir));
524 foreach $name (@names) {
525 my($file) = "$dir$dirsep$name";
526 print STDERR " checking in $dir for $name\n" if $dl_debug;
527 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
528 #$file = _check_file($file);
531 next arg; # no need to look any further
538 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
540 print STDERR "dl_findfile found: @found\n";
542 return $found[0] unless wantarray;
549 # Optional function invoked if DynaLoader.pm sets $do_expand.
550 # Most systems do not require or use this function.
551 # Some systems may implement it in the dl_*.xs file in which case
552 # this autoload version will not be called but is harmless.
554 # This function is designed to deal with systems which treat some
555 # 'filenames' in a special way. For example VMS 'Logical Names'
556 # (something like unix environment variables - but different).
557 # This function should recognise such names and expand them into
559 # Must return undef if $spec is invalid or file does not exist.
561 my $file = $spec; # default output to input
564 # dl_expandspec should be defined in dl_vms.xs
566 Carp::croak("dl_expandspec: should be defined in XS file!\n");
568 return undef unless -f $file;
570 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
574 sub dl_find_symbol_anywhere
578 foreach $libref (@dl_librefs) {
579 my $symref = dl_find_symbol($libref,$sym);
580 return $symref if $symref;
587 DynaLoader - Dynamically load C libraries into Perl code
593 @ISA = qw(... DynaLoader ...);
594 bootstrap YourPackage;
596 # optional method for 'global' loading
597 sub dl_load_flags { 0x01 }
602 This document defines a standard generic interface to the dynamic
603 linking mechanisms available on many platforms. Its primary purpose is
604 to implement automatic dynamic loading of Perl modules.
606 This document serves as both a specification for anyone wishing to
607 implement the DynaLoader for a new platform and as a guide for
608 anyone wishing to use the DynaLoader directly in an application.
610 The DynaLoader is designed to be a very simple high-level
611 interface that is sufficiently general to cover the requirements
612 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
614 It is also hoped that the interface will cover the needs of OS/2, NT
615 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
617 It must be stressed that the DynaLoader, by itself, is practically
618 useless for accessing non-Perl libraries because it provides almost no
619 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
620 library function or supplying arguments. A C::DynaLib module
621 is available from CPAN sites which performs that function for some
622 common system types. And since the year 2000, there's also Inline::C,
623 a module that allows you to write Perl subroutines in C. Also available
624 from your local CPAN site.
626 DynaLoader Interface Summary
636 bootstrap($modulename) Perl
637 @filepaths = dl_findfile(@names) Perl
638 $flags = $modulename->dl_load_flags Perl
639 $symref = dl_find_symbol_anywhere($symbol) Perl
641 $libref = dl_load_file($filename, $flags) C
642 $status = dl_unload_file($libref) C
643 $symref = dl_find_symbol($libref, $symbol) C
644 @symbols = dl_undef_symbols() C
645 dl_install_xsub($name, $symref [, $filename]) C
646 $message = dl_error C
650 =item @dl_library_path
652 The standard/default list of directories in which dl_findfile() will
653 search for libraries etc. Directories are searched in order:
654 $dl_library_path[0], [1], ... etc
656 @dl_library_path is initialised to hold the list of 'normal' directories
657 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
658 ensure portability across a wide range of platforms.
660 @dl_library_path should also be initialised with any other directories
661 that can be determined from the environment at runtime (such as
662 LD_LIBRARY_PATH for SunOS).
664 After initialisation @dl_library_path can be manipulated by an
665 application using push and unshift before calling dl_findfile().
666 Unshift can be used to add directories to the front of the search order
667 either to save search time or to override libraries with the same name
668 in the 'normal' directories.
670 The load function that dl_load_file() calls may require an absolute
671 pathname. The dl_findfile() function and @dl_library_path can be
672 used to search for and return the absolute pathname for the
673 library/object that you wish to load.
675 =item @dl_resolve_using
677 A list of additional libraries or other shared objects which can be
678 used to resolve any undefined symbols that might be generated by a
679 later call to load_file().
681 This is only required on some platforms which do not handle dependent
682 libraries automatically. For example the Socket Perl extension
683 library (F<auto/Socket/Socket.so>) contains references to many socket
684 functions which need to be resolved when it's loaded. Most platforms
685 will automatically know where to find the 'dependent' library (e.g.,
686 F</usr/lib/libsocket.so>). A few platforms need to be told the
687 location of the dependent library explicitly. Use @dl_resolve_using
692 @dl_resolve_using = dl_findfile('-lsocket');
694 =item @dl_require_symbols
696 A list of one or more symbol names that are in the library/object file
697 to be dynamically loaded. This is only required on some platforms.
701 An array of the handles returned by successful calls to dl_load_file(),
702 made by bootstrap, in the order in which they were loaded.
703 Can be used with dl_find_symbol() to look for a symbol in any of
708 An array of module (package) names that have been bootstrap'ed.
710 =item @dl_shared_objects
712 An array of file names for the shared objects that were loaded.
718 $message = dl_error();
720 Error message text from the last failed DynaLoader function. Note
721 that, similar to errno in unix, a successful function call does not
724 Implementations should detect the error as soon as it occurs in any of
725 the other functions and save the corresponding message for later
726 retrieval. This will avoid problems on some platforms (such as SunOS)
727 where the error message is very temporary (e.g., dlerror()).
731 Internal debugging messages are enabled when $dl_debug is set true.
732 Currently setting $dl_debug only affects the Perl side of the
733 DynaLoader. These messages should help an application developer to
734 resolve any DynaLoader usage problems.
736 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
738 For the DynaLoader developer/porter there is a similar debugging
739 variable added to the C code (see dlutils.c) and enabled if Perl was
740 built with the B<-DDEBUGGING> flag. This can also be set via the
741 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
748 @filepaths = dl_findfile(@names)
750 Determine the full paths (including file suffix) of one or more
751 loadable files given their generic names and optionally one or more
752 directories. Searches directories in @dl_library_path by default and
753 returns an empty list if no files were found.
755 Names can be specified in a variety of platform independent forms. Any
756 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
757 an appropriate suffix for the platform.
759 If a name does not already have a suitable prefix and/or suffix then
760 the corresponding file will be searched for by trying combinations of
761 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
764 If any directories are included in @names they are searched before
765 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
766 names are treated as filenames to be searched for.
768 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
772 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
775 =item dl_expandspec()
779 $filepath = dl_expandspec($spec)
781 Some unusual systems, such as VMS, require special filename handling in
782 order to deal with symbolic names for files (i.e., VMS's Logical Names).
784 To support these systems a dl_expandspec() function can be implemented
785 either in the F<dl_*.xs> file or code can be added to the autoloadable
786 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
793 $libref = dl_load_file($filename, $flags)
795 Dynamically load $filename, which must be the path to a shared object
796 or library. An opaque 'library reference' is returned as a handle for
797 the loaded object. Returns undef on error.
799 The $flags argument to alters dl_load_file behaviour.
802 0x01 make symbols available for linking later dl_load_file's.
803 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
804 (ignored under VMS; this is a normal part of image linking)
806 (On systems that provide a handle for the loaded object such as SunOS
807 and HPUX, $libref will be that handle. On other systems $libref will
808 typically be $filename or a pointer to a buffer containing $filename.
809 The application should not examine or alter $libref in any way.)
811 This is the function that does the real work. It should use the
812 current values of @dl_require_symbols and @dl_resolve_using if required.
814 SunOS: dlopen($filename)
815 HP-UX: shl_load($filename)
816 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
817 NeXT: rld_load($filename, @dl_resolve_using)
818 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
820 (The dlopen() function is also used by Solaris and some versions of
821 Linux, and is a common choice when providing a "wrapper" on other
822 mechanisms as is done in the OS/2 port.)
824 =item dl_unload_file()
828 $status = dl_unload_file($libref)
830 Dynamically unload $libref, which must be an opaque 'library reference' as
831 returned from dl_load_file. Returns one on success and zero on failure.
833 This function is optional and may not necessarily be provided on all platforms.
834 If it is defined, it is called automatically when the interpreter exits for
835 every shared object or library loaded by DynaLoader::bootstrap. All such
836 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
837 loads the libraries. The files are unloaded in last-in, first-out order.
839 This unloading is usually necessary when embedding a shared-object perl (e.g.
840 one configured with -Duseshrplib) within a larger application, and the perl
841 interpreter is created and destroyed several times within the lifetime of the
842 application. In this case it is possible that the system dynamic linker will
843 unload and then subsequently reload the shared libperl without relocating any
844 references to it from any files DynaLoaded by the previous incarnation of the
845 interpreter. As a result, any shared objects opened by DynaLoader may point to
846 a now invalid 'ghost' of the libperl shared object, causing apparently random
847 memory corruption and crashes. This behaviour is most commonly seen when using
848 Apache and mod_perl built with the APXS mechanism.
850 SunOS: dlclose($libref)
856 (The dlclose() function is also used by Solaris and some versions of
857 Linux, and is a common choice when providing a "wrapper" on other
858 mechanisms as is done in the OS/2 port.)
860 =item dl_load_flags()
864 $flags = dl_load_flags $modulename;
866 Designed to be a method call, and to be overridden by a derived class
867 (i.e. a class which has DynaLoader in its @ISA). The definition in
868 DynaLoader itself returns 0, which produces standard behavior from
871 =item dl_find_symbol()
875 $symref = dl_find_symbol($libref, $symbol)
877 Return the address of the symbol $symbol or C<undef> if not found. If the
878 target system has separate functions to search for symbols of different
879 types then dl_find_symbol() should search for function symbols first and
882 The exact manner in which the address is returned in $symref is not
883 currently defined. The only initial requirement is that $symref can
884 be passed to, and understood by, dl_install_xsub().
886 SunOS: dlsym($libref, $symbol)
887 HP-UX: shl_findsym($libref, $symbol)
888 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
889 NeXT: rld_lookup("_$symbol")
890 VMS: lib$find_image_symbol($libref,$symbol)
893 =item dl_find_symbol_anywhere()
897 $symref = dl_find_symbol_anywhere($symbol)
899 Applies dl_find_symbol() to the members of @dl_librefs and returns
900 the first match found.
902 =item dl_undef_symbols()
906 @symbols = dl_undef_symbols()
908 Return a list of symbol names which remain undefined after load_file().
909 Returns C<()> if not known. Don't worry if your platform does not provide
910 a mechanism for this. Most do not need it and hence do not provide it,
911 they just return an empty list.
914 =item dl_install_xsub()
918 dl_install_xsub($perl_name, $symref [, $filename])
920 Create a new Perl external subroutine named $perl_name using $symref as
921 a pointer to the function which implements the routine. This is simply
922 a direct call to newXSUB(). Returns a reference to the installed
925 The $filename parameter is used by Perl to identify the source file for
926 the function if required by die(), caller() or the debugger. If
927 $filename is not defined then "DynaLoader" will be used.
936 This is the normal entry point for automatic dynamic loading in Perl.
938 It performs the following actions:
944 locates an auto/$module directory by searching @INC
948 uses dl_findfile() to determine the filename to load
952 sets @dl_require_symbols to C<("boot_$module")>
956 executes an F<auto/$module/$module.bs> file if it exists
957 (typically used to add to @dl_resolve_using any files which
958 are required to load the module on the current platform)
962 calls dl_load_flags() to determine how to load the file.
966 calls dl_load_file() to load the file
970 calls dl_undef_symbols() and warns if any symbols are undefined
974 calls dl_find_symbol() for "boot_$module"
978 calls dl_install_xsub() to install it as "${module}::bootstrap"
982 calls &{"${module}::bootstrap"} to bootstrap the module (actually
983 it uses the function reference returned by dl_install_xsub for speed)
992 Tim Bunce, 11 August 1994.
994 This interface is based on the work and comments of (in no particular
995 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
996 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
998 Larry Wall designed the elegant inherited bootstrap mechanism and
999 implemented the first Perl 5 dynamic loader using it.
1001 Solaris global loading added by Nick Ing-Simmons with design/coding
1002 assistance from Tim Bunce, January 1996.
1007 close OUT or die $!;