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 $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
341 # no luck here, save dir for possible later dl_findfile search
344 # last resort, let dl_findfile have a go in all known locations
345 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
347 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
348 unless $file; # wording similar to error from 'require'
350 <<$^O-eq-VMS>>$file = uc($file) if $Config::Config{d_vms_case_sensitive_symbols};<</$^O-eq-VMS>>
351 my $bootname = "boot_$module";
352 $bootname =~ s/\W/_/g;
353 @dl_require_symbols = ($bootname);
355 # Execute optional '.bootstrap' perl script for this module.
356 # The .bs file can be used to configure @dl_resolve_using etc to
357 # match the needs of the individual module on this architecture.
359 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
360 if (-s $bs) { # only read file if it's not empty
361 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
363 warn "$bs: $@\n" if $@;
369 if ($boot_symbol_ref = dl_find_symbol(0, $bootname)) {
370 goto boot; #extension library has already been loaded, e.g. darwin
374 # Many dynamic extension loading problems will appear to come from
375 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
376 # Often these errors are actually occurring in the initialisation
377 # C code of the extension XS file. Perl reports the error as being
378 # in this perl code simply because this was the last perl code
381 my $libref = dl_load_file($file, $module->dl_load_flags) or
382 croak("Can't load '$file' for module $module: ".dl_error());
384 push(@dl_librefs,$libref); # record loaded object
386 my @unresolved = dl_undef_symbols();
389 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
392 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
393 croak("Can't find '$bootname' symbol in $file\n");
395 push(@dl_modules, $module); # record loaded module
398 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
400 # See comment block above
402 push(@dl_shared_objects, $file); # record files loaded
408 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
410 # return $file if (!$do_expand && -f $file); # the common case
411 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
416 # Let autosplit and the autoloader deal with these functions:
421 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
422 # This function does not automatically consider the architecture
423 # or the perl library auto directories.
425 my (@dirs, $dir); # which directories to search
426 my (@found); # full paths to real files we have found
427 #my $dl_ext= <<=to_string($Config::Config{'dlext'})>>; # $Config::Config{'dlext'} suffix for perl extensions
428 #my $dl_so = <<=to_string($Config::Config{'so'})>>; # $Config::Config{'so'} suffix for shared libraries
430 print STDERR "dl_findfile(@args)\n" if $dl_debug;
432 # accumulate directories but process files as they appear
433 arg: foreach(@args) {
434 # Special fast case: full filepath requires no search
436 if (m%[:>/\]]% && -f $_) {
437 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
438 last arg unless wantarray;
445 last arg unless wantarray;
451 last arg unless wantarray;
456 # Deal with directories first:
457 # Using a -L prefix is the preferred option (faster and more robust)
458 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
461 # Otherwise we try to try to spot directories by a heuristic
462 # (this is a more complicated issue than it first appears)
463 if (m/:/ && -d $_) { push(@dirs, $_); next; }
464 # Only files should get this far...
465 my(@names, $name); # what filenames to look for
468 foreach $dir (@dirs, @dl_library_path) {
470 $dir =~ s/^([^:]+)$/:$1/;
472 foreach $name (@names) {
473 my($file) = "$dir:$name";
474 print STDERR " checking in $dir for $name\n" if $dl_debug;
477 next arg; # no need to look any further
484 # Otherwise we try to try to spot directories by a heuristic
485 # (this is a more complicated issue than it first appears)
486 if (m:/: && -d $_) { push(@dirs, $_); next; }
489 # VMS: we may be using native VMS directory syntax instead of
490 # Unix emulation, so check this as well
491 if (/[:>\]]/ && -d $_) { push(@dirs, $_); next; }
494 # Only files should get this far...
495 my(@names, $name); # what filenames to look for
496 if (m:-l: ) { # convert -lname to appropriate library name
498 push(@names,"lib$_.$dl_so");
499 push(@names,"lib$_.a");
500 } else { # Umm, a bare name. Try various alternatives:
501 # these should be ordered with the most likely first
502 push(@names,"$_.$dl_dlext") unless m/\.$dl_dlext$/o;
503 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
504 push(@names,"lib$_.$dl_so") unless m:/:;
505 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
511 if ($0 =~ /^([a-z]):/i) {
513 @dirs = map { "$drive:$_" } @dirs;
514 @dl_library_path = map { "$drive:$_" } @dl_library_path;
517 foreach $dir (@dirs, @dl_library_path) {
520 chop($dir = VMS::Filespec::unixpath($dir));
522 foreach $name (@names) {
523 my($file) = "$dir$dirsep$name";
524 print STDERR " checking in $dir for $name\n" if $dl_debug;
525 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
526 #$file = _check_file($file);
529 next arg; # no need to look any further
536 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
538 print STDERR "dl_findfile found: @found\n";
540 return $found[0] unless wantarray;
547 # Optional function invoked if DynaLoader.pm sets $do_expand.
548 # Most systems do not require or use this function.
549 # Some systems may implement it in the dl_*.xs file in which case
550 # this autoload version will not be called but is harmless.
552 # This function is designed to deal with systems which treat some
553 # 'filenames' in a special way. For example VMS 'Logical Names'
554 # (something like unix environment variables - but different).
555 # This function should recognise such names and expand them into
557 # Must return undef if $spec is invalid or file does not exist.
559 my $file = $spec; # default output to input
562 # dl_expandspec should be defined in dl_vms.xs
564 Carp::croak("dl_expandspec: should be defined in XS file!\n");
566 return undef unless -f $file;
568 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
572 sub dl_find_symbol_anywhere
576 foreach $libref (@dl_librefs) {
577 my $symref = dl_find_symbol($libref,$sym);
578 return $symref if $symref;
585 DynaLoader - Dynamically load C libraries into Perl code
591 @ISA = qw(... DynaLoader ...);
592 bootstrap YourPackage;
594 # optional method for 'global' loading
595 sub dl_load_flags { 0x01 }
600 This document defines a standard generic interface to the dynamic
601 linking mechanisms available on many platforms. Its primary purpose is
602 to implement automatic dynamic loading of Perl modules.
604 This document serves as both a specification for anyone wishing to
605 implement the DynaLoader for a new platform and as a guide for
606 anyone wishing to use the DynaLoader directly in an application.
608 The DynaLoader is designed to be a very simple high-level
609 interface that is sufficiently general to cover the requirements
610 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
612 It is also hoped that the interface will cover the needs of OS/2, NT
613 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
615 It must be stressed that the DynaLoader, by itself, is practically
616 useless for accessing non-Perl libraries because it provides almost no
617 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
618 library function or supplying arguments. A C::DynaLib module
619 is available from CPAN sites which performs that function for some
620 common system types. And since the year 2000, there's also Inline::C,
621 a module that allows you to write Perl subroutines in C. Also available
622 from your local CPAN site.
624 DynaLoader Interface Summary
634 bootstrap($modulename) Perl
635 @filepaths = dl_findfile(@names) Perl
636 $flags = $modulename->dl_load_flags Perl
637 $symref = dl_find_symbol_anywhere($symbol) Perl
639 $libref = dl_load_file($filename, $flags) C
640 $status = dl_unload_file($libref) C
641 $symref = dl_find_symbol($libref, $symbol) C
642 @symbols = dl_undef_symbols() C
643 dl_install_xsub($name, $symref [, $filename]) C
644 $message = dl_error C
648 =item @dl_library_path
650 The standard/default list of directories in which dl_findfile() will
651 search for libraries etc. Directories are searched in order:
652 $dl_library_path[0], [1], ... etc
654 @dl_library_path is initialised to hold the list of 'normal' directories
655 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
656 ensure portability across a wide range of platforms.
658 @dl_library_path should also be initialised with any other directories
659 that can be determined from the environment at runtime (such as
660 LD_LIBRARY_PATH for SunOS).
662 After initialisation @dl_library_path can be manipulated by an
663 application using push and unshift before calling dl_findfile().
664 Unshift can be used to add directories to the front of the search order
665 either to save search time or to override libraries with the same name
666 in the 'normal' directories.
668 The load function that dl_load_file() calls may require an absolute
669 pathname. The dl_findfile() function and @dl_library_path can be
670 used to search for and return the absolute pathname for the
671 library/object that you wish to load.
673 =item @dl_resolve_using
675 A list of additional libraries or other shared objects which can be
676 used to resolve any undefined symbols that might be generated by a
677 later call to load_file().
679 This is only required on some platforms which do not handle dependent
680 libraries automatically. For example the Socket Perl extension
681 library (F<auto/Socket/Socket.so>) contains references to many socket
682 functions which need to be resolved when it's loaded. Most platforms
683 will automatically know where to find the 'dependent' library (e.g.,
684 F</usr/lib/libsocket.so>). A few platforms need to be told the
685 location of the dependent library explicitly. Use @dl_resolve_using
690 @dl_resolve_using = dl_findfile('-lsocket');
692 =item @dl_require_symbols
694 A list of one or more symbol names that are in the library/object file
695 to be dynamically loaded. This is only required on some platforms.
699 An array of the handles returned by successful calls to dl_load_file(),
700 made by bootstrap, in the order in which they were loaded.
701 Can be used with dl_find_symbol() to look for a symbol in any of
706 An array of module (package) names that have been bootstrap'ed.
708 =item @dl_shared_objects
710 An array of file names for the shared objects that were loaded.
716 $message = dl_error();
718 Error message text from the last failed DynaLoader function. Note
719 that, similar to errno in unix, a successful function call does not
722 Implementations should detect the error as soon as it occurs in any of
723 the other functions and save the corresponding message for later
724 retrieval. This will avoid problems on some platforms (such as SunOS)
725 where the error message is very temporary (e.g., dlerror()).
729 Internal debugging messages are enabled when $dl_debug is set true.
730 Currently setting $dl_debug only affects the Perl side of the
731 DynaLoader. These messages should help an application developer to
732 resolve any DynaLoader usage problems.
734 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
736 For the DynaLoader developer/porter there is a similar debugging
737 variable added to the C code (see dlutils.c) and enabled if Perl was
738 built with the B<-DDEBUGGING> flag. This can also be set via the
739 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
746 @filepaths = dl_findfile(@names)
748 Determine the full paths (including file suffix) of one or more
749 loadable files given their generic names and optionally one or more
750 directories. Searches directories in @dl_library_path by default and
751 returns an empty list if no files were found.
753 Names can be specified in a variety of platform independent forms. Any
754 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
755 an appropriate suffix for the platform.
757 If a name does not already have a suitable prefix and/or suffix then
758 the corresponding file will be searched for by trying combinations of
759 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
762 If any directories are included in @names they are searched before
763 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
764 names are treated as filenames to be searched for.
766 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
770 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
773 =item dl_expandspec()
777 $filepath = dl_expandspec($spec)
779 Some unusual systems, such as VMS, require special filename handling in
780 order to deal with symbolic names for files (i.e., VMS's Logical Names).
782 To support these systems a dl_expandspec() function can be implemented
783 either in the F<dl_*.xs> file or code can be added to the autoloadable
784 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
791 $libref = dl_load_file($filename, $flags)
793 Dynamically load $filename, which must be the path to a shared object
794 or library. An opaque 'library reference' is returned as a handle for
795 the loaded object. Returns undef on error.
797 The $flags argument to alters dl_load_file behaviour.
800 0x01 make symbols available for linking later dl_load_file's.
801 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
802 (ignored under VMS; this is a normal part of image linking)
804 (On systems that provide a handle for the loaded object such as SunOS
805 and HPUX, $libref will be that handle. On other systems $libref will
806 typically be $filename or a pointer to a buffer containing $filename.
807 The application should not examine or alter $libref in any way.)
809 This is the function that does the real work. It should use the
810 current values of @dl_require_symbols and @dl_resolve_using if required.
812 SunOS: dlopen($filename)
813 HP-UX: shl_load($filename)
814 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
815 NeXT: rld_load($filename, @dl_resolve_using)
816 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
818 (The dlopen() function is also used by Solaris and some versions of
819 Linux, and is a common choice when providing a "wrapper" on other
820 mechanisms as is done in the OS/2 port.)
822 =item dl_unload_file()
826 $status = dl_unload_file($libref)
828 Dynamically unload $libref, which must be an opaque 'library reference' as
829 returned from dl_load_file. Returns one on success and zero on failure.
831 This function is optional and may not necessarily be provided on all platforms.
832 If it is defined, it is called automatically when the interpreter exits for
833 every shared object or library loaded by DynaLoader::bootstrap. All such
834 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
835 loads the libraries. The files are unloaded in last-in, first-out order.
837 This unloading is usually necessary when embedding a shared-object perl (e.g.
838 one configured with -Duseshrplib) within a larger application, and the perl
839 interpreter is created and destroyed several times within the lifetime of the
840 application. In this case it is possible that the system dynamic linker will
841 unload and then subsequently reload the shared libperl without relocating any
842 references to it from any files DynaLoaded by the previous incarnation of the
843 interpreter. As a result, any shared objects opened by DynaLoader may point to
844 a now invalid 'ghost' of the libperl shared object, causing apparently random
845 memory corruption and crashes. This behaviour is most commonly seen when using
846 Apache and mod_perl built with the APXS mechanism.
848 SunOS: dlclose($libref)
854 (The dlclose() function is also used by Solaris and some versions of
855 Linux, and is a common choice when providing a "wrapper" on other
856 mechanisms as is done in the OS/2 port.)
858 =item dl_load_flags()
862 $flags = dl_load_flags $modulename;
864 Designed to be a method call, and to be overridden by a derived class
865 (i.e. a class which has DynaLoader in its @ISA). The definition in
866 DynaLoader itself returns 0, which produces standard behavior from
869 =item dl_find_symbol()
873 $symref = dl_find_symbol($libref, $symbol)
875 Return the address of the symbol $symbol or C<undef> if not found. If the
876 target system has separate functions to search for symbols of different
877 types then dl_find_symbol() should search for function symbols first and
880 The exact manner in which the address is returned in $symref is not
881 currently defined. The only initial requirement is that $symref can
882 be passed to, and understood by, dl_install_xsub().
884 SunOS: dlsym($libref, $symbol)
885 HP-UX: shl_findsym($libref, $symbol)
886 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
887 NeXT: rld_lookup("_$symbol")
888 VMS: lib$find_image_symbol($libref,$symbol)
891 =item dl_find_symbol_anywhere()
895 $symref = dl_find_symbol_anywhere($symbol)
897 Applies dl_find_symbol() to the members of @dl_librefs and returns
898 the first match found.
900 =item dl_undef_symbols()
904 @symbols = dl_undef_symbols()
906 Return a list of symbol names which remain undefined after load_file().
907 Returns C<()> if not known. Don't worry if your platform does not provide
908 a mechanism for this. Most do not need it and hence do not provide it,
909 they just return an empty list.
912 =item dl_install_xsub()
916 dl_install_xsub($perl_name, $symref [, $filename])
918 Create a new Perl external subroutine named $perl_name using $symref as
919 a pointer to the function which implements the routine. This is simply
920 a direct call to newXSUB(). Returns a reference to the installed
923 The $filename parameter is used by Perl to identify the source file for
924 the function if required by die(), caller() or the debugger. If
925 $filename is not defined then "DynaLoader" will be used.
934 This is the normal entry point for automatic dynamic loading in Perl.
936 It performs the following actions:
942 locates an auto/$module directory by searching @INC
946 uses dl_findfile() to determine the filename to load
950 sets @dl_require_symbols to C<("boot_$module")>
954 executes an F<auto/$module/$module.bs> file if it exists
955 (typically used to add to @dl_resolve_using any files which
956 are required to load the module on the current platform)
960 calls dl_load_flags() to determine how to load the file.
964 calls dl_load_file() to load the file
968 calls dl_undef_symbols() and warns if any symbols are undefined
972 calls dl_find_symbol() for "boot_$module"
976 calls dl_install_xsub() to install it as "${module}::bootstrap"
980 calls &{"${module}::bootstrap"} to bootstrap the module (actually
981 it uses the function reference returned by dl_install_xsub for speed)
990 Tim Bunce, 11 August 1994.
992 This interface is based on the work and comments of (in no particular
993 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
994 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
996 Larry Wall designed the elegant inherited bootstrap mechanism and
997 implemented the first Perl 5 dynamic loader using it.
999 Solaris global loading added by Nick Ing-Simmons with design/coding
1000 assistance from Tim Bunce, January 1996.
1005 close OUT or die $!;