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 $^O eq 'VMS' for example)
29 sub expand_os_specific {
33 s/<<\$\^O-(eq|ne)-(\w+)>>(.*?)<<\/\$\^O-\1-\2>>/
34 my ($op, $os, $expr) = ($1,$2,$3);
35 if ($op ne 'eq' and $op ne 'ne') {die "wrong eq-ne arg in $&"};
36 if ($expr =~ m[^(.*?)<<\|\$\^O-$op-$os>>(.*?)$]s) {
38 my ($if,$el) = ($1,$2);
39 if (($op eq 'eq' and $^O eq $os) || ($op eq 'ne' and $^O ne $os)) {
48 if (($op eq 'eq' and $^O eq $os) || ($op eq 'ne' and $^O ne $os)) {
56 if (/<<(=|\$\^O-)/) {die "bad <<\$^O-eq/ne-osname>> expression.".
57 " Unclosed brackets?";
63 unlink "DynaLoader.pm" if -f "DynaLoader.pm";
64 open OUT, ">DynaLoader.pm" or die $!;
67 # Generated from DynaLoader.pm.PL
71 # And Gandalf said: 'Many folk like to know beforehand what is to
72 # be set on the table; but those who have laboured to prepare the
73 # feast like to keep their secret; for wonder makes the words of
76 # (Quote from Tolkien suggested by Anno Siegel.)
78 # See pod text at end of file for documentation.
79 # See also ext/DynaLoader/README in source tree for other information.
81 # Tim.Bunce@ig.co.uk, August 1994
83 use vars qw($VERSION *AUTOLOAD);
88 *AUTOLOAD = \&AutoLoader::AUTOLOAD;
92 # The following require can't be removed during maintenance
93 # releases, sadly, because of the risk of buggy code that does
94 # require Carp; Carp::croak "..."; without brackets dying
95 # if Carp hasn't been loaded in earlier compile time. :-(
96 # We'll let those bugs get found on the development track.
97 require Carp if $] < 5.00450;
99 # enable debug/trace messages from DynaLoader perl code
100 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
103 # Flags to alter dl_load_file behaviour. Assigned bits:
104 # 0x01 make symbols available for linking later dl_load_file's.
105 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
106 # (ignored under VMS; effect is built-in to image linking)
108 # This is called as a class method $module->dl_load_flags. The
109 # definition here will be inherited and result on "default" loading
110 # behaviour unless a sub-class of DynaLoader defines its own version.
113 sub dl_load_flags { 0x00 }
115 # ($dl_dlext, $dlsrc)
116 # = @Config::Config{'dlext', 'dlsrc'};
119 $dl_dlext = $Config::Config{'dlext'};
120 $dl_so = $Config::Config{'so'};
121 print OUT " (\$dl_dlext, \$dlsrc) = ('$dl_dlext', ",
122 to_string($Config::Config{'dlsrc'}), ")\n;";
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>>;
137 $Mac_FS = eval { require Mac::FileSpec::Unixish };
140 @dl_require_symbols = (); # names of symbols we need
141 @dl_resolve_using = (); # names of files to link with
142 @dl_library_path = (); # path to look for files
144 #XSLoader.pm may have added elements before we were required
145 #@dl_shared_objects = (); # shared objects for symbols we have
146 #@dl_librefs = (); # things we have loaded
147 #@dl_modules = (); # Modules we have loaded
149 # This is a fix to support DLD's unfortunate desire to relink -lc
150 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
154 my $cfg_dl_library_path = <<'EOT';
155 push(@dl_library_path, split(' ', $Config::Config{libpth}));
158 sub dquoted_comma_list {
159 join(", ", map {'"'.quotemeta($_).'"'} @_);
162 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
163 eval $cfg_dl_library_path;
164 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
165 my $dl_library_path = dquoted_comma_list(@dl_library_path);
167 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
169 \@dl_library_path = ($dl_library_path);
176 # Initialise \@dl_library_path with the 'standard' library path
177 # for this platform as determined by Configure.
185 my $ldlibpthname_defined;
188 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
189 $ldlibpthname = to_string($Config::Config{ldlibpthname});
190 $ldlibpthname_defined = to_string(defined $Config::Config{ldlibpthname} ? 1 : 0);
191 $pthsep = to_string($Config::Config{path_sep});
194 $ldlibpthname = q($Config::Config{ldlibpthname});
195 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
196 $pthsep = q($Config::Config{path_sep});
199 my \$ldlibpthname = $ldlibpthname;
200 my \$ldlibpthname_defined = $ldlibpthname_defined;
201 my \$pthsep = $pthsep;
205 my $env_dl_library_path = <<'EOT';
206 if ($ldlibpthname_defined &&
207 exists $ENV{$ldlibpthname}) {
208 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
211 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
213 if ($ldlibpthname_defined &&
214 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
215 exists $ENV{LD_LIBRARY_PATH}) {
216 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
220 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
221 eval $env_dl_library_path;
225 # Add to \@dl_library_path any extra directories we can gather from environment
233 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
234 my $dl_library_path = dquoted_comma_list(@dl_library_path);
236 # The below \@dl_library_path has been expanded (%Config, %ENV)
237 # in Perl build time.
239 \@dl_library_path = ($dl_library_path);
245 # following long string contains $^O-specific stuff, which is factored out
246 print OUT expand_os_specific(<<'EOT');
247 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
248 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
249 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
253 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
254 print STDERR "DynaLoader not linked into this perl\n"
255 unless defined(&boot_DynaLoader);
258 1; # End of main code
261 sub croak { require Carp; Carp::croak(@_) }
263 sub bootstrap_inherit {
265 local *isa = *{"$module\::ISA"};
266 local @isa = (@isa, 'DynaLoader');
267 # Cannot goto due to delocalization. Will report errors on a wrong line?
271 # The bootstrap function cannot be autoloaded (without complications)
272 # so we define it here:
275 # use local vars to enable $module.bs script to edit values
277 local($module) = $args[0];
282 Carp::confess("Usage: DynaLoader::bootstrap(module)");
285 # A common error on platforms which don't support dynamic loading.
286 # Since it's fatal and potentially confusing we give a detailed message.
287 croak("Can't load module $module, dynamic loading not available in this perl.\n".
288 " (You may need to build a new perl executable which either supports\n".
289 " dynamic loading or has the $module module statically linked into it.)\n")
290 unless defined(&dl_load_file);
294 # Can dynaload, but cannot dynaload Perl modules...
295 die 'Dynaloaded Perl modules are not available in this build of Perl' if $OS2::is_static;
298 my @modparts = split(/::/,$module);
299 my $modfname = $modparts[-1];
301 # Some systems have restrictions on files names for DLL's etc.
302 # mod2fname returns appropriate file base name (typically truncated)
303 # It may also edit @modparts if required.
304 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
307 # Truncate the module name to 8.3 format for NetWare
308 if ((length($modfname) > 8)) {
309 $modfname = substr($modfname, 0, 8);
313 my $modpname = join(<<$^O-eq-MacOS>>':'<<|$^O-eq-MacOS>>'/'<</$^O-eq-MacOS>>,@modparts);
315 print STDERR "DynaLoader::bootstrap for $module ",
316 <<$^O-eq-MacOS>> "(:auto:$modpname:$modfname.<<=$dl_dlext>>)\n"
317 <<|$^O-eq-MacOS>>"(auto/$modpname/$modfname.<<=$dl_dlext>>)\n"<</$^O-eq-MacOS>>
321 <<$^O-eq-VMS>>chop($_ = VMS::Filespec::unixpath($_));<</$^O-eq-VMS>>
324 if ($Mac_FS && ! -d $path) {
325 $path = Mac::FileSpec::Unixish::nativize($path);
327 $path .= ":" unless /:$/;
328 my $dir = "${path}auto:$modpname";
330 my $dir = "$_/auto/$modpname";
333 next unless -d $dir; # skip over uninteresting directories
335 # check for common cases to avoid autoload of dl_findfile
336 my $try = <<$^O-eq-MacOS>> "$dir:$modfname.<<=$dl_dlext>>" <<|$^O-eq-MacOS>> "$dir/$modfname.<<=$dl_dlext>>"<</$^O-eq-MacOS>>;
337 last if $file = <<$^O-eq-VMS>>($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
338 <<|$^O-eq-VMS>>(-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, $name); # what filenames to look for
496 if (m:-l: ) { # convert -lname to appropriate library name
498 push(@names,"lib$_.<<=to_string($Config::Config{'so'})>>");
499 push(@names,"lib$_.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";
508 foreach $dir (@dirs, @dl_library_path) {
511 chop($dir = VMS::Filespec::unixpath($dir));
513 foreach $name (@names) {
514 my($file) = "$dir/$name";
515 print STDERR " checking in $dir for $name\n" if $dl_debug;
516 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
517 #$file = _check_file($file);
520 next arg; # no need to look any further
527 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
529 print STDERR "dl_findfile found: @found\n";
531 return $found[0] unless wantarray;
538 # Optional function invoked if DynaLoader.pm sets $do_expand.
539 # Most systems do not require or use this function.
540 # Some systems may implement it in the dl_*.xs file in which case
541 # this autoload version will not be called but is harmless.
543 # This function is designed to deal with systems which treat some
544 # 'filenames' in a special way. For example VMS 'Logical Names'
545 # (something like unix environment variables - but different).
546 # This function should recognise such names and expand them into
548 # Must return undef if $spec is invalid or file does not exist.
550 my $file = $spec; # default output to input
553 # dl_expandspec should be defined in dl_vms.xs
555 Carp::croak("dl_expandspec: should be defined in XS file!\n");
557 return undef unless -f $file;
559 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
563 sub dl_find_symbol_anywhere
567 foreach $libref (@dl_librefs) {
568 my $symref = dl_find_symbol($libref,$sym);
569 return $symref if $symref;
576 DynaLoader - Dynamically load C libraries into Perl code
582 @ISA = qw(... DynaLoader ...);
583 bootstrap YourPackage;
585 # optional method for 'global' loading
586 sub dl_load_flags { 0x01 }
591 This document defines a standard generic interface to the dynamic
592 linking mechanisms available on many platforms. Its primary purpose is
593 to implement automatic dynamic loading of Perl modules.
595 This document serves as both a specification for anyone wishing to
596 implement the DynaLoader for a new platform and as a guide for
597 anyone wishing to use the DynaLoader directly in an application.
599 The DynaLoader is designed to be a very simple high-level
600 interface that is sufficiently general to cover the requirements
601 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
603 It is also hoped that the interface will cover the needs of OS/2, NT
604 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
606 It must be stressed that the DynaLoader, by itself, is practically
607 useless for accessing non-Perl libraries because it provides almost no
608 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
609 library function or supplying arguments. A C::DynaLib module
610 is available from CPAN sites which performs that function for some
611 common system types. And since the year 2000, there's also Inline::C,
612 a module that allows you to write Perl subroutines in C. Also available
613 from your local CPAN site.
615 DynaLoader Interface Summary
625 bootstrap($modulename) Perl
626 @filepaths = dl_findfile(@names) Perl
627 $flags = $modulename->dl_load_flags Perl
628 $symref = dl_find_symbol_anywhere($symbol) Perl
630 $libref = dl_load_file($filename, $flags) C
631 $status = dl_unload_file($libref) C
632 $symref = dl_find_symbol($libref, $symbol) C
633 @symbols = dl_undef_symbols() C
634 dl_install_xsub($name, $symref [, $filename]) C
635 $message = dl_error C
639 =item @dl_library_path
641 The standard/default list of directories in which dl_findfile() will
642 search for libraries etc. Directories are searched in order:
643 $dl_library_path[0], [1], ... etc
645 @dl_library_path is initialised to hold the list of 'normal' directories
646 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
647 ensure portability across a wide range of platforms.
649 @dl_library_path should also be initialised with any other directories
650 that can be determined from the environment at runtime (such as
651 LD_LIBRARY_PATH for SunOS).
653 After initialisation @dl_library_path can be manipulated by an
654 application using push and unshift before calling dl_findfile().
655 Unshift can be used to add directories to the front of the search order
656 either to save search time or to override libraries with the same name
657 in the 'normal' directories.
659 The load function that dl_load_file() calls may require an absolute
660 pathname. The dl_findfile() function and @dl_library_path can be
661 used to search for and return the absolute pathname for the
662 library/object that you wish to load.
664 =item @dl_resolve_using
666 A list of additional libraries or other shared objects which can be
667 used to resolve any undefined symbols that might be generated by a
668 later call to load_file().
670 This is only required on some platforms which do not handle dependent
671 libraries automatically. For example the Socket Perl extension
672 library (F<auto/Socket/Socket.so>) contains references to many socket
673 functions which need to be resolved when it's loaded. Most platforms
674 will automatically know where to find the 'dependent' library (e.g.,
675 F</usr/lib/libsocket.so>). A few platforms need to be told the
676 location of the dependent library explicitly. Use @dl_resolve_using
681 @dl_resolve_using = dl_findfile('-lsocket');
683 =item @dl_require_symbols
685 A list of one or more symbol names that are in the library/object file
686 to be dynamically loaded. This is only required on some platforms.
690 An array of the handles returned by successful calls to dl_load_file(),
691 made by bootstrap, in the order in which they were loaded.
692 Can be used with dl_find_symbol() to look for a symbol in any of
697 An array of module (package) names that have been bootstrap'ed.
699 =item @dl_shared_objects
701 An array of file names for the shared objects that were loaded.
707 $message = dl_error();
709 Error message text from the last failed DynaLoader function. Note
710 that, similar to errno in unix, a successful function call does not
713 Implementations should detect the error as soon as it occurs in any of
714 the other functions and save the corresponding message for later
715 retrieval. This will avoid problems on some platforms (such as SunOS)
716 where the error message is very temporary (e.g., dlerror()).
720 Internal debugging messages are enabled when $dl_debug is set true.
721 Currently setting $dl_debug only affects the Perl side of the
722 DynaLoader. These messages should help an application developer to
723 resolve any DynaLoader usage problems.
725 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
727 For the DynaLoader developer/porter there is a similar debugging
728 variable added to the C code (see dlutils.c) and enabled if Perl was
729 built with the B<-DDEBUGGING> flag. This can also be set via the
730 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
737 @filepaths = dl_findfile(@names)
739 Determine the full paths (including file suffix) of one or more
740 loadable files given their generic names and optionally one or more
741 directories. Searches directories in @dl_library_path by default and
742 returns an empty list if no files were found.
744 Names can be specified in a variety of platform independent forms. Any
745 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
746 an appropriate suffix for the platform.
748 If a name does not already have a suitable prefix and/or suffix then
749 the corresponding file will be searched for by trying combinations of
750 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
753 If any directories are included in @names they are searched before
754 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
755 names are treated as filenames to be searched for.
757 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
761 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
764 =item dl_expandspec()
768 $filepath = dl_expandspec($spec)
770 Some unusual systems, such as VMS, require special filename handling in
771 order to deal with symbolic names for files (i.e., VMS's Logical Names).
773 To support these systems a dl_expandspec() function can be implemented
774 either in the F<dl_*.xs> file or code can be added to the autoloadable
775 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
782 $libref = dl_load_file($filename, $flags)
784 Dynamically load $filename, which must be the path to a shared object
785 or library. An opaque 'library reference' is returned as a handle for
786 the loaded object. Returns undef on error.
788 The $flags argument to alters dl_load_file behaviour.
791 0x01 make symbols available for linking later dl_load_file's.
792 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
793 (ignored under VMS; this is a normal part of image linking)
795 (On systems that provide a handle for the loaded object such as SunOS
796 and HPUX, $libref will be that handle. On other systems $libref will
797 typically be $filename or a pointer to a buffer containing $filename.
798 The application should not examine or alter $libref in any way.)
800 This is the function that does the real work. It should use the
801 current values of @dl_require_symbols and @dl_resolve_using if required.
803 SunOS: dlopen($filename)
804 HP-UX: shl_load($filename)
805 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
806 NeXT: rld_load($filename, @dl_resolve_using)
807 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
809 (The dlopen() function is also used by Solaris and some versions of
810 Linux, and is a common choice when providing a "wrapper" on other
811 mechanisms as is done in the OS/2 port.)
813 =item dl_unload_file()
817 $status = dl_unload_file($libref)
819 Dynamically unload $libref, which must be an opaque 'library reference' as
820 returned from dl_load_file. Returns one on success and zero on failure.
822 This function is optional and may not necessarily be provided on all platforms.
823 If it is defined, it is called automatically when the interpreter exits for
824 every shared object or library loaded by DynaLoader::bootstrap. All such
825 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
826 loads the libraries. The files are unloaded in last-in, first-out order.
828 This unloading is usually necessary when embedding a shared-object perl (e.g.
829 one configured with -Duseshrplib) within a larger application, and the perl
830 interpreter is created and destroyed several times within the lifetime of the
831 application. In this case it is possible that the system dynamic linker will
832 unload and then subsequently reload the shared libperl without relocating any
833 references to it from any files DynaLoaded by the previous incarnation of the
834 interpreter. As a result, any shared objects opened by DynaLoader may point to
835 a now invalid 'ghost' of the libperl shared object, causing apparently random
836 memory corruption and crashes. This behaviour is most commonly seen when using
837 Apache and mod_perl built with the APXS mechanism.
839 SunOS: dlclose($libref)
845 (The dlclose() function is also used by Solaris and some versions of
846 Linux, and is a common choice when providing a "wrapper" on other
847 mechanisms as is done in the OS/2 port.)
849 =item dl_load_flags()
853 $flags = dl_load_flags $modulename;
855 Designed to be a method call, and to be overridden by a derived class
856 (i.e. a class which has DynaLoader in its @ISA). The definition in
857 DynaLoader itself returns 0, which produces standard behavior from
860 =item dl_find_symbol()
864 $symref = dl_find_symbol($libref, $symbol)
866 Return the address of the symbol $symbol or C<undef> if not found. If the
867 target system has separate functions to search for symbols of different
868 types then dl_find_symbol() should search for function symbols first and
871 The exact manner in which the address is returned in $symref is not
872 currently defined. The only initial requirement is that $symref can
873 be passed to, and understood by, dl_install_xsub().
875 SunOS: dlsym($libref, $symbol)
876 HP-UX: shl_findsym($libref, $symbol)
877 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
878 NeXT: rld_lookup("_$symbol")
879 VMS: lib$find_image_symbol($libref,$symbol)
882 =item dl_find_symbol_anywhere()
886 $symref = dl_find_symbol_anywhere($symbol)
888 Applies dl_find_symbol() to the members of @dl_librefs and returns
889 the first match found.
891 =item dl_undef_symbols()
895 @symbols = dl_undef_symbols()
897 Return a list of symbol names which remain undefined after load_file().
898 Returns C<()> if not known. Don't worry if your platform does not provide
899 a mechanism for this. Most do not need it and hence do not provide it,
900 they just return an empty list.
903 =item dl_install_xsub()
907 dl_install_xsub($perl_name, $symref [, $filename])
909 Create a new Perl external subroutine named $perl_name using $symref as
910 a pointer to the function which implements the routine. This is simply
911 a direct call to newXSUB(). Returns a reference to the installed
914 The $filename parameter is used by Perl to identify the source file for
915 the function if required by die(), caller() or the debugger. If
916 $filename is not defined then "DynaLoader" will be used.
925 This is the normal entry point for automatic dynamic loading in Perl.
927 It performs the following actions:
933 locates an auto/$module directory by searching @INC
937 uses dl_findfile() to determine the filename to load
941 sets @dl_require_symbols to C<("boot_$module")>
945 executes an F<auto/$module/$module.bs> file if it exists
946 (typically used to add to @dl_resolve_using any files which
947 are required to load the module on the current platform)
951 calls dl_load_flags() to determine how to load the file.
955 calls dl_load_file() to load the file
959 calls dl_undef_symbols() and warns if any symbols are undefined
963 calls dl_find_symbol() for "boot_$module"
967 calls dl_install_xsub() to install it as "${module}::bootstrap"
971 calls &{"${module}::bootstrap"} to bootstrap the module (actually
972 it uses the function reference returned by dl_install_xsub for speed)
981 Tim Bunce, 11 August 1994.
983 This interface is based on the work and comments of (in no particular
984 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
985 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
987 Larry Wall designed the elegant inherited bootstrap mechanism and
988 implemented the first Perl 5 dynamic loader using it.
990 Solaris global loading added by Nick Ing-Simmons with design/coding
991 assistance from Tim Bunce, January 1996.