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 $!;
71 # Generated from DynaLoader_pm.PL, this file is unique for every OS
75 # And Gandalf said: 'Many folk like to know beforehand what is to
76 # be set on the table; but those who have laboured to prepare the
77 # feast like to keep their secret; for wonder makes the words of
80 # (Quote from Tolkien suggested by Anno Siegel.)
82 # See pod text at end of file for documentation.
83 # See also ext/DynaLoader/README in source tree for other information.
85 # Tim.Bunce@ig.co.uk, August 1994
93 if (!$ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
94 print OUT "use Config;\n";
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)
107 # (ignored under Android; the linker always uses RTLD_LOCAL)
109 # This is called as a class method $module->dl_load_flags. The
110 # definition here will be inherited and result on "default" loading
111 # behaviour unless a sub-class of DynaLoader defines its own version.
114 sub dl_load_flags { 0x00 }
118 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
119 print OUT "(\$dl_dlext, \$dl_so, \$dlsrc) = (",
120 to_string($Config{'dlext'}), ",",
121 to_string($Config{'so'}), ",",
122 to_string($Config{'dlsrc'}), ")\n;" ;
126 ($dl_dlext, $dl_so, $dlsrc) = @Config::Config{qw(dlext so dlsrc)};
130 print OUT expand_os_specific(<<'EOT');
133 # Some systems need special handling to expand file specifications
134 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
135 # See dl_expandspec() for more details. Should be harmless but
136 # inefficient to define on systems that don't need it.
137 $Is_VMS = $^O eq 'VMS';
139 $do_expand = <<$^O-eq-VMS>>1<<|$^O-eq-VMS>>0<</$^O-eq-VMS>>;
141 @dl_require_symbols = (); # names of symbols we need<<$^O-eq-freemint>>
142 @dl_resolve_using = (); # names of files to link with<</$^O-eq-freemint>><<$^O-eq-hpux>>
143 @dl_resolve_using = (); # names of files to link with<</$^O-eq-hpux>>
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
153 my $cfg_dl_library_path = <<'EOT';
154 push(@dl_library_path, split(' ', $Config::Config{libpth}));
157 sub dquoted_comma_list {
158 join(", ", map {'"'.quotemeta($_).'"'} @_);
161 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
162 eval $cfg_dl_library_path;
163 if (!$ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
164 my $dl_library_path = dquoted_comma_list(@dl_library_path);
166 # The below \@dl_library_path has been expanded (%Config) in Perl build time.
168 \@dl_library_path = ($dl_library_path);
175 # Initialise \@dl_library_path with the 'standard' library path
176 # for this platform as determined by Configure.
184 my $ldlibpthname_defined;
187 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS}) {
188 $ldlibpthname = to_string($Config::Config{ldlibpthname});
189 $ldlibpthname_defined = to_string(defined $Config::Config{ldlibpthname} ? 1 : 0);
190 $pthsep = to_string($Config::Config{path_sep});
193 $ldlibpthname = q($Config::Config{ldlibpthname});
194 $ldlibpthname_defined = q(defined $Config::Config{ldlibpthname});
195 $pthsep = q($Config::Config{path_sep});
198 my \$ldlibpthname = $ldlibpthname;
199 my \$ldlibpthname_defined = $ldlibpthname_defined;
200 my \$pthsep = $pthsep;
204 my $env_dl_library_path = <<'EOT';
205 if ($ldlibpthname_defined &&
206 exists $ENV{$ldlibpthname}) {
207 push(@dl_library_path, split(/$pthsep/, $ENV{$ldlibpthname}));
210 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
212 if ($ldlibpthname_defined &&
213 $ldlibpthname ne 'LD_LIBRARY_PATH' &&
214 exists $ENV{LD_LIBRARY_PATH}) {
215 push(@dl_library_path, split(/$pthsep/, $ENV{LD_LIBRARY_PATH}));
219 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
220 eval $env_dl_library_path;
224 # Add to \@dl_library_path any extra directories we can gather from environment
232 if ($ENV{PERL_BUILD_EXPAND_CONFIG_VARS} && $ENV{PERL_BUILD_EXPAND_ENV_VARS}) {
233 my $dl_library_path = dquoted_comma_list(@dl_library_path);
235 # The below \@dl_library_path has been expanded (%Config, %ENV)
236 # in Perl build time.
238 \@dl_library_path = ($dl_library_path);
243 if ( $Config::Config{d_libname_unique} ) {
244 printf OUT <<'EOT', length($Config::Config{dlext}) + 1;
248 my $name_max = 255; # No easy way to get this here
250 my $libname = "PL_" . join("__", @$parts);
252 return $libname if (length($libname)+$so_len) <= $name_max;
254 # It's too darned big, so we need to go strip. We use the same
255 # algorithm as xsubpp does. First, strip out doubled __
256 $libname =~ s/__/_/g;
257 return $libname if (length($libname)+$so_len) <= $name_max;
259 # Strip duplicate letters
260 1 while $libname =~ s/(.)\1/\U$1/i;
261 return $libname if (length($libname)+$so_len) <= $name_max;
263 # Still too long. Truncate.
264 $libname = substr($libname, 0, $name_max - $so_len);
270 # following long string contains $^O-specific stuff, which is factored out
271 print OUT expand_os_specific(<<'EOT');
272 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
273 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
274 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
278 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
279 print STDERR "DynaLoader not linked into this perl\n"
280 unless defined(&boot_DynaLoader);
283 1; # End of main code
286 sub croak { require Carp; Carp::croak(@_) }
288 sub bootstrap_inherit {
290 local *isa = *{"$module\::ISA"};
291 local @isa = (@isa, 'DynaLoader');
292 # Cannot goto due to delocalization. Will report errors on a wrong line?
297 # use local vars to enable $module.bs script to edit values
299 local($module) = $args[0];
304 Carp::confess("Usage: DynaLoader::bootstrap(module)");
307 # A common error on platforms which don't support dynamic loading.
308 # Since it's fatal and potentially confusing we give a detailed message.
309 croak("Can't load module $module, dynamic loading not available in this perl.\n".
310 " (You may need to build a new perl executable which either supports\n".
311 " dynamic loading or has the $module module statically linked into it.)\n")
312 unless defined(&dl_load_file);
316 # Can dynaload, but cannot dynaload Perl modules...
317 die 'Dynaloaded Perl modules are not available in this build of Perl' if $OS2::is_static;
320 my @modparts = split(/::/,$module);
321 my $modfname = $modparts[-1];
322 my $modfname_orig = $modfname; # For .bs file search
324 # Some systems have restrictions on files names for DLL's etc.
325 # mod2fname returns appropriate file base name (typically truncated)
326 # It may also edit @modparts if required.
327 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
330 # Truncate the module name to 8.3 format for NetWare
331 if ((length($modfname) > 8)) {
332 $modfname = substr($modfname, 0, 8);
336 my $modpname = join('/',@modparts);
338 print STDERR "DynaLoader::bootstrap for $module ",
339 "(auto/$modpname/$modfname.$dl_dlext)\n"
344 <<$^O-eq-VMS>>chop($_ = VMS::Filespec::unixpath($_));<</$^O-eq-VMS>>
345 $dir = "$_/auto/$modpname";
347 next unless -d $dir; # skip over uninteresting directories
349 # check for common cases to avoid autoload of dl_findfile
350 my $try = "$dir/$modfname.$dl_dlext";
351 last if $file = ($do_expand) ? dl_expandspec($try) : ((-f $try) && $try);
353 # no luck here, save dir for possible later dl_findfile search
356 # last resort, let dl_findfile have a go in all known locations
357 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
359 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
360 unless $file; # wording similar to error from 'require'
362 <<$^O-eq-VMS>>$file = uc($file) if $Config::Config{d_vms_case_sensitive_symbols};<</$^O-eq-VMS>>
363 my $bootname = "boot_$module";
364 $bootname =~ s/\W/_/g;
365 @dl_require_symbols = ($bootname);
367 # Execute optional '.bootstrap' perl script for this module.
368 # The .bs file can be used to configure @dl_resolve_using etc to
369 # match the needs of the individual module on this architecture.
370 # N.B. The .bs file does not following the naming convention used
372 my $bs = "$dir/$modfname_orig";
373 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
374 if (-s $bs) { # only read file if it's not empty
375 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
377 warn "$bs: $@\n" if $@;
383 if ($boot_symbol_ref = dl_find_symbol(0, $bootname, 1)) {
384 goto boot; #extension library has already been loaded, e.g. darwin
388 # Many dynamic extension loading problems will appear to come from
389 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
390 # Often these errors are actually occurring in the initialisation
391 # C code of the extension XS file. Perl reports the error as being
392 # in this perl code simply because this was the last perl code
395 my $flags = $module->dl_load_flags;
397 # See the note above regarding the linker.
400 my $libref = dl_load_file($file, $flags) or
401 croak("Can't load '$file' for module $module: ".dl_error());
403 push(@dl_librefs,$libref); # record loaded object
405 my @unresolved = dl_undef_symbols();
408 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
411 $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
412 croak("Can't find '$bootname' symbol in $file\n");
414 push(@dl_modules, $module); # record loaded module
417 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
419 # See comment block above
421 push(@dl_shared_objects, $file); # record files loaded
427 # This function does not automatically consider the architecture
428 # or the perl library auto directories.
430 my (@dirs, $dir); # which directories to search
431 my (@found); # full paths to real files we have found
432 #my $dl_ext= <<=to_string($Config::Config{'dlext'})>>; # $Config::Config{'dlext'} suffix for perl extensions
433 #my $dl_so = <<=to_string($Config::Config{'so'})>>; # $Config::Config{'so'} suffix for shared libraries
435 print STDERR "dl_findfile(@args)\n" if $dl_debug;
437 # accumulate directories but process files as they appear
438 arg: foreach(@args) {
439 # Special fast case: full filepath requires no search
441 if (m%[:>/\]]% && -f $_) {
442 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
443 last arg unless wantarray;
450 last arg unless wantarray;
455 # Deal with directories first:
456 # Using a -L prefix is the preferred option (faster and more robust)
457 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
459 # Otherwise we try to try to spot directories by a heuristic
460 # (this is a more complicated issue than it first appears)
461 if (m:/: && -d $_) { push(@dirs, $_); next; }
464 # VMS: we may be using native VMS directory syntax instead of
465 # Unix emulation, so check this as well
466 if (/[:>\]]/ && -d $_) { push(@dirs, $_); next; }
469 # Only files should get this far...
470 my(@names, $name); # what filenames to look for
471 if (m:-l: ) { # convert -lname to appropriate library name
473 push(@names,"lib$_.$dl_so");
474 push(@names,"lib$_.a");
475 } else { # Umm, a bare name. Try various alternatives:
476 # these should be ordered with the most likely first
477 push(@names,"$_.$dl_dlext") unless m/\.$dl_dlext$/o;
478 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
480 push(@names,"cyg$_.$dl_so") unless m:/:;
482 push(@names,"lib$_.$dl_so") unless m:/:;
488 if ($0 =~ /^([a-z]):/i) {
490 @dirs = map { "$drive:$_" } @dirs;
491 @dl_library_path = map { "$drive:$_" } @dl_library_path;
494 foreach $dir (@dirs, @dl_library_path) {
497 chop($dir = VMS::Filespec::unixpath($dir));
499 foreach $name (@names) {
500 my($file) = "$dir$dirsep$name";
501 print STDERR " checking in $dir for $name\n" if $dl_debug;
502 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
503 #$file = _check_file($file);
506 next arg; # no need to look any further
513 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
515 print STDERR "dl_findfile found: @found\n";
517 return $found[0] unless wantarray;
523 # dl_expandspec should be defined in dl_vms.xs
527 # Optional function invoked if DynaLoader.pm sets $do_expand.
528 # Most systems do not require or use this function.
529 # Some systems may implement it in the dl_*.xs file in which case
530 # this Perl version should be excluded at build time.
532 # This function is designed to deal with systems which treat some
533 # 'filenames' in a special way. For example VMS 'Logical Names'
534 # (something like unix environment variables - but different).
535 # This function should recognise such names and expand them into
537 # Must return undef if $spec is invalid or file does not exist.
539 my $file = $spec; # default output to input
541 return undef unless -f $file;
542 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
547 sub dl_find_symbol_anywhere
551 foreach $libref (@dl_librefs) {
552 my $symref = dl_find_symbol($libref,$sym,1);
553 return $symref if $symref;
562 DynaLoader - Dynamically load C libraries into Perl code
568 @ISA = qw(... DynaLoader ...);
569 bootstrap YourPackage;
571 # optional method for 'global' loading
572 sub dl_load_flags { 0x01 }
577 This document defines a standard generic interface to the dynamic
578 linking mechanisms available on many platforms. Its primary purpose is
579 to implement automatic dynamic loading of Perl modules.
581 This document serves as both a specification for anyone wishing to
582 implement the DynaLoader for a new platform and as a guide for
583 anyone wishing to use the DynaLoader directly in an application.
585 The DynaLoader is designed to be a very simple high-level
586 interface that is sufficiently general to cover the requirements
587 of SunOS, HP-UX, Linux, VMS and other platforms.
589 It is also hoped that the interface will cover the needs of OS/2, NT
590 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
592 It must be stressed that the DynaLoader, by itself, is practically
593 useless for accessing non-Perl libraries because it provides almost no
594 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
595 library function or supplying arguments. A C::DynaLib module
596 is available from CPAN sites which performs that function for some
597 common system types. And since the year 2000, there's also Inline::C,
598 a module that allows you to write Perl subroutines in C. Also available
599 from your local CPAN site.
601 DynaLoader Interface Summary
612 bootstrap($modulename) Perl
613 @filepaths = dl_findfile(@names) Perl
614 $flags = $modulename->dl_load_flags Perl
615 $symref = dl_find_symbol_anywhere($symbol) Perl
617 $libref = dl_load_file($filename, $flags) C
618 $status = dl_unload_file($libref) C
619 $symref = dl_find_symbol($libref, $symbol) C
620 @symbols = dl_undef_symbols() C
621 dl_install_xsub($name, $symref [, $filename]) C
622 $message = dl_error C
626 =item @dl_library_path
628 The standard/default list of directories in which dl_findfile() will
629 search for libraries etc. Directories are searched in order:
630 $dl_library_path[0], [1], ... etc
632 @dl_library_path is initialised to hold the list of 'normal' directories
633 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
634 ensure portability across a wide range of platforms.
636 @dl_library_path should also be initialised with any other directories
637 that can be determined from the environment at runtime (such as
638 LD_LIBRARY_PATH for SunOS).
640 After initialisation @dl_library_path can be manipulated by an
641 application using push and unshift before calling dl_findfile().
642 Unshift can be used to add directories to the front of the search order
643 either to save search time or to override libraries with the same name
644 in the 'normal' directories.
646 The load function that dl_load_file() calls may require an absolute
647 pathname. The dl_findfile() function and @dl_library_path can be
648 used to search for and return the absolute pathname for the
649 library/object that you wish to load.
651 =item @dl_resolve_using
653 A list of additional libraries or other shared objects which can be
654 used to resolve any undefined symbols that might be generated by a
655 later call to load_file().
657 This is only required on some platforms which do not handle dependent
658 libraries automatically. For example the Socket Perl extension
659 library (F<auto/Socket/Socket.so>) contains references to many socket
660 functions which need to be resolved when it's loaded. Most platforms
661 will automatically know where to find the 'dependent' library (e.g.,
662 F</usr/lib/libsocket.so>). A few platforms need to be told the
663 location of the dependent library explicitly. Use @dl_resolve_using
668 @dl_resolve_using = dl_findfile('-lsocket');
670 =item @dl_require_symbols
672 A list of one or more symbol names that are in the library/object file
673 to be dynamically loaded. This is only required on some platforms.
677 An array of the handles returned by successful calls to dl_load_file(),
678 made by bootstrap, in the order in which they were loaded.
679 Can be used with dl_find_symbol() to look for a symbol in any of
684 An array of module (package) names that have been bootstrap'ed.
686 =item @dl_shared_objects
688 An array of file names for the shared objects that were loaded.
694 $message = dl_error();
696 Error message text from the last failed DynaLoader function. Note
697 that, similar to errno in unix, a successful function call does not
700 Implementations should detect the error as soon as it occurs in any of
701 the other functions and save the corresponding message for later
702 retrieval. This will avoid problems on some platforms (such as SunOS)
703 where the error message is very temporary (e.g., dlerror()).
707 Internal debugging messages are enabled when $dl_debug is set true.
708 Currently setting $dl_debug only affects the Perl side of the
709 DynaLoader. These messages should help an application developer to
710 resolve any DynaLoader usage problems.
712 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
714 For the DynaLoader developer/porter there is a similar debugging
715 variable added to the C code (see dlutils.c) and enabled if Perl was
716 built with the B<-DDEBUGGING> flag. This can also be set via the
717 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
722 When specified (localised) in a module's F<.pm> file, indicates the extension
723 which the module's loadable object will have. For example:
725 local $DynaLoader::dl_dlext = 'unusual_ext';
727 would indicate that the module's loadable object has an extension of
728 C<unusual_ext> instead of the more usual C<$Config{dlext}>. NOTE: This also
729 requires that the module's F<Makefile.PL> specify (in C<WriteMakefile()>):
731 DLEXT => 'unusual_ext',
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 dl_expandspec()
775 function in F<DynaLoader.pm>. See F<DynaLoader_pm.PL> for more information.
781 $libref = dl_load_file($filename, $flags)
783 Dynamically load $filename, which must be the path to a shared object
784 or library. An opaque 'library reference' is returned as a handle for
785 the loaded object. Returns undef on error.
787 The $flags argument to alters dl_load_file behaviour.
790 0x01 make symbols available for linking later dl_load_file's.
791 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
792 (ignored under VMS; this is a normal part of image linking)
794 (On systems that provide a handle for the loaded object such as SunOS
795 and HPUX, $libref will be that handle. On other systems $libref will
796 typically be $filename or a pointer to a buffer containing $filename.
797 The application should not examine or alter $libref in any way.)
799 This is the function that does the real work. It should use the
800 current values of @dl_require_symbols and @dl_resolve_using if required.
802 SunOS: dlopen($filename)
803 HP-UX: shl_load($filename)
804 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
805 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
807 (The dlopen() function is also used by Solaris and some versions of
808 Linux, and is a common choice when providing a "wrapper" on other
809 mechanisms as is done in the OS/2 port.)
811 =item dl_unload_file()
815 $status = dl_unload_file($libref)
817 Dynamically unload $libref, which must be an opaque 'library reference' as
818 returned from dl_load_file. Returns one on success and zero on failure.
819 This function is optional and may not necessarily be provided on all platforms.
821 If it is defined and perl is compiled with the C macro C<DL_UNLOAD_ALL_AT_EXIT>
822 defined, then it is called automatically when the interpreter exits for
823 every shared object or library loaded by DynaLoader::bootstrap. All such
824 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
825 loads the libraries. The files are unloaded in last-in, first-out order.
827 This unloading is usually necessary when embedding a shared-object perl (e.g.
828 one configured with -Duseshrplib) within a larger application, and the perl
829 interpreter is created and destroyed several times within the lifetime of the
830 application. In this case it is possible that the system dynamic linker will
831 unload and then subsequently reload the shared libperl without relocating any
832 references to it from any files DynaLoaded by the previous incarnation of the
833 interpreter. As a result, any shared objects opened by DynaLoader may point to
834 a now invalid 'ghost' of the libperl shared object, causing apparently random
835 memory corruption and crashes. This behaviour is most commonly seen when using
836 Apache and mod_perl built with the APXS mechanism.
838 SunOS: dlclose($libref)
843 (The dlclose() function is also used by Solaris and some versions of
844 Linux, and is a common choice when providing a "wrapper" on other
845 mechanisms as is done in the OS/2 port.)
847 =item dl_load_flags()
851 $flags = dl_load_flags $modulename;
853 Designed to be a method call, and to be overridden by a derived class
854 (i.e. a class which has DynaLoader in its @ISA). The definition in
855 DynaLoader itself returns 0, which produces standard behavior from
858 =item dl_find_symbol()
862 $symref = dl_find_symbol($libref, $symbol)
864 Return the address of the symbol $symbol or C<undef> if not found. If the
865 target system has separate functions to search for symbols of different
866 types then dl_find_symbol() should search for function symbols first and
869 The exact manner in which the address is returned in $symref is not
870 currently defined. The only initial requirement is that $symref can
871 be passed to, and understood by, dl_install_xsub().
873 SunOS: dlsym($libref, $symbol)
874 HP-UX: shl_findsym($libref, $symbol)
875 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
876 VMS: lib$find_image_symbol($libref,$symbol)
879 =item dl_find_symbol_anywhere()
883 $symref = dl_find_symbol_anywhere($symbol)
885 Applies dl_find_symbol() to the members of @dl_librefs and returns
886 the first match found.
888 =item dl_undef_symbols()
892 @symbols = dl_undef_symbols()
894 Return a list of symbol names which remain undefined after load_file().
895 Returns C<()> if not known. Don't worry if your platform does not provide
896 a mechanism for this. Most do not need it and hence do not provide it,
897 they just return an empty list.
900 =item dl_install_xsub()
904 dl_install_xsub($perl_name, $symref [, $filename])
906 Create a new Perl external subroutine named $perl_name using $symref as
907 a pointer to the function which implements the routine. This is simply
908 a direct call to newXS()/newXS_flags(). Returns a reference to the installed
911 The $filename parameter is used by Perl to identify the source file for
912 the function if required by die(), caller() or the debugger. If
913 $filename is not defined then "DynaLoader" will be used.
920 bootstrap($module [...])
922 This is the normal entry point for automatic dynamic loading in Perl.
924 It performs the following actions:
930 locates an auto/$module directory by searching @INC
934 uses dl_findfile() to determine the filename to load
938 sets @dl_require_symbols to C<("boot_$module")>
942 executes an F<auto/$module/$module.bs> file if it exists
943 (typically used to add to @dl_resolve_using any files which
944 are required to load the module on the current platform)
948 calls dl_load_flags() to determine how to load the file.
952 calls dl_load_file() to load the file
956 calls dl_undef_symbols() and warns if any symbols are undefined
960 calls dl_find_symbol() for "boot_$module"
964 calls dl_install_xsub() to install it as "${module}::bootstrap"
968 calls &{"${module}::bootstrap"} to bootstrap the module (actually
969 it uses the function reference returned by dl_install_xsub for speed)
973 All arguments to bootstrap() are passed to the module's bootstrap function.
974 The default code generated by F<xsubpp> expects $module [, $version]
975 If the optional $version argument is not given, it defaults to
976 C<$XS_VERSION // $VERSION> in the module's symbol table. The default code
977 compares the Perl-space version with the version of the compiled XS code,
978 and croaks with an error if they do not match.
985 Tim Bunce, 11 August 1994.
987 This interface is based on the work and comments of (in no particular
988 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
989 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
991 Larry Wall designed the elegant inherited bootstrap mechanism and
992 implemented the first Perl 5 dynamic loader using it.
994 Solaris global loading added by Nick Ing-Simmons with design/coding
995 assistance from Tim Bunce, January 1996.
1000 close OUT or die $!;