11 unlink "DynaLoader.pm" if -f "DynaLoader.pm";
12 open OUT, ">DynaLoader.pm" or die $!;
15 # Generated from DynaLoader.pm.PL (resolved %Config::Config values)
19 # And Gandalf said: 'Many folk like to know beforehand what is to
20 # be set on the table; but those who have laboured to prepare the
21 # feast like to keep their secret; for wonder makes the words of
24 # (Quote from Tolkien suggested by Anno Siegel.)
26 # See pod text at end of file for documentation.
27 # See also ext/DynaLoader/README in source tree for other information.
29 # Tim.Bunce@ig.co.uk, August 1994
31 $VERSION = "1.04"; # avoid typo warning
34 *AUTOLOAD = \&AutoLoader::AUTOLOAD;
36 # The following require can't be removed during maintenance
37 # releases, sadly, because of the risk of buggy code that does
38 # require Carp; Carp::croak "..."; without brackets dying
39 # if Carp hasn't been loaded in earlier compile time. :-(
40 # We'll let those bugs get found on the development track.
41 require Carp if $] < 5.00450;
44 # enable debug/trace messages from DynaLoader perl code
45 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
48 # Flags to alter dl_load_file behaviour. Assigned bits:
49 # 0x01 make symbols available for linking later dl_load_file's.
50 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
51 # (ignored under VMS; effect is built-in to image linking)
53 # This is called as a class method $module->dl_load_flags. The
54 # definition here will be inherited and result on "default" loading
55 # behaviour unless a sub-class of DynaLoader defines its own version.
58 sub dl_load_flags { 0x00 }
61 # = @Config::Config{'dlext', 'dlsrc'};
64 print OUT " (\$dl_dlext, \$dlsrc) = (",
65 to_string($Config::Config{'dlext'}), ",",
66 to_string($Config::Config{'dlsrc'}), ")\n;" ;
70 # Some systems need special handling to expand file specifications
71 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
72 # See dl_expandspec() for more details. Should be harmless but
73 # inefficient to define on systems that don't need it.
74 $do_expand = $Is_VMS = $^O eq 'VMS';
75 $Is_MacOS = $^O eq 'MacOS';
77 @dl_require_symbols = (); # names of symbols we need
78 @dl_resolve_using = (); # names of files to link with
79 @dl_library_path = (); # path to look for files
80 #@dl_librefs = (); # things we have loaded
81 #@dl_modules = (); # Modules we have loaded
83 # This is a fix to support DLD's unfortunate desire to relink -lc
84 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
86 # Initialise @dl_library_path with the 'standard' library path
87 # for this platform as determined by Configure
89 # push(@dl_library_path, split(' ', $Config::Config{'libpth'});
92 print OUT "push(\@dl_library_path, split(' ', ",
93 to_string($Config::Config{'libpth'}), "));\n";
97 # Add to @dl_library_path any extra directories we can gather
98 # from environment variables.
100 push(@dl_library_path, split(/,/, $ENV{LD_LIBRARY_PATH}))
101 if exists $ENV{LD_LIBRARY_PATH};
103 # push(@dl_library_path, split(/:/, $ENV{$Config::Config{ldlibpthname}}))
104 # if exists $Config::Config{ldlibpthname} &&
105 # $Config::Config{ldlibpthname} ne '' &&
106 # exists $ENV{$Config::Config{ldlibpthname}} ;;
107 # push(@dl_library_path, split(/:/, $ENV{$Config::Config{ldlibpthname}}))
108 # if exists $Config::Config{ldlibpthname} &&
109 # $Config::Config{ldlibpthname} ne '' &&
110 # exists $ENV{$Config::Config{ldlibpthname}} ;;
111 # E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
112 # push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
113 # if exists $ENV{LD_LIBRARY_PATH};
116 # Make a list of paths to print.
117 # HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH,
118 # but for other OSes no point pushing 'LD_LIBRARY_PATH' twice.
119 my @ldlibpthname = 'LD_LIBRARY_PATH';
120 if (exists $Config::Config{ldlibpthname}
121 and length $Config::Config{ldlibpthname}
122 and $Config::Config{ldlibpthname} ne 'LD_LIBRARY_PATH') {
123 unshift @ldlibpthname, $Config::Config{ldlibpthname};
126 foreach (@ldlibpthname) {
127 print OUT " push(\@dl_library_path, split(/:/, \$ENV{", to_string($_),
128 "}))\n\tif exists \$ENV{", to_string($_), "};\n";
134 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
135 # NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
136 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
140 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
141 print STDERR "DynaLoader not linked into this perl\n"
142 unless defined(&boot_DynaLoader);
145 1; # End of main code
148 sub croak { require Carp; Carp::croak(@_) }
150 sub bootstrap_inherit {
152 local *isa = *{"$module\::ISA"};
153 local @isa = (@isa, 'DynaLoader');
154 # Cannot goto due to delocalization. Will report errors on a wrong line?
158 # The bootstrap function cannot be autoloaded (without complications)
159 # so we define it here:
162 # use local vars to enable $module.bs script to edit values
164 local($module) = $args[0];
169 Carp::confess("Usage: DynaLoader::bootstrap(module)");
172 # A common error on platforms which don't support dynamic loading.
173 # Since it's fatal and potentially confusing we give a detailed message.
174 croak("Can't load module $module, dynamic loading not available in this perl.\n".
175 " (You may need to build a new perl executable which either supports\n".
176 " dynamic loading or has the $module module statically linked into it.)\n")
177 unless defined(&dl_load_file);
179 my @modparts = split(/::/,$module);
180 my $modfname = $modparts[-1];
182 # Some systems have restrictions on files names for DLL's etc.
183 # mod2fname returns appropriate file base name (typically truncated)
184 # It may also edit @modparts if required.
185 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
187 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
189 print STDERR "DynaLoader::bootstrap for $module ",
191 ? "(:auto:$modpname:$modfname.$dl_dlext)\n" :
192 "(auto/$modpname/$modfname.$dl_dlext)\n")
196 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
200 $dir = "$_:auto:$modpname";
202 $dir = "$_/auto/$modpname";
204 next unless -d $dir; # skip over uninteresting directories
206 # check for common cases to avoid autoload of dl_findfile
207 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
208 last if $file = ($do_expand) ? dl_expandspec($try) : (-f $try && $try);
210 # no luck here, save dir for possible later dl_findfile search
213 # last resort, let dl_findfile have a go in all known locations
214 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
216 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
217 unless $file; # wording similar to error from 'require'
219 $file = uc($file) if $Is_VMS && $Config{d_vms_case_sensitive_symbols};
220 my $bootname = "boot_$module";
221 $bootname =~ s/\W/_/g;
222 @dl_require_symbols = ($bootname);
224 # Execute optional '.bootstrap' perl script for this module.
225 # The .bs file can be used to configure @dl_resolve_using etc to
226 # match the needs of the individual module on this architecture.
228 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
229 if (-s $bs) { # only read file if it's not empty
230 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
232 warn "$bs: $@\n" if $@;
235 # Many dynamic extension loading problems will appear to come from
236 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
237 # Often these errors are actually occurring in the initialisation
238 # C code of the extension XS file. Perl reports the error as being
239 # in this perl code simply because this was the last perl code
242 my $libref = dl_load_file($file, $module->dl_load_flags) or
243 croak("Can't load '$file' for module $module: ".dl_error());
245 push(@dl_librefs,$libref); # record loaded object
247 my @unresolved = dl_undef_symbols();
250 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
253 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
254 croak("Can't find '$bootname' symbol in $file\n");
256 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
258 push(@dl_modules, $module); # record loaded module
260 # See comment block above
265 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
267 # return $file if (!$do_expand && -f $file); # the common case
268 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
273 # Let autosplit and the autoloader deal with these functions:
278 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
279 # This function does not automatically consider the architecture
280 # or the perl library auto directories.
282 my (@dirs, $dir); # which directories to search
283 my (@found); # full paths to real files we have found
286 print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
287 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
288 print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
289 "; # \$Config::Config{'so'} suffix for shared libraries\n";
293 print STDERR "dl_findfile(@args)\n" if $dl_debug;
295 # accumulate directories but process files as they appear
296 arg: foreach(@args) {
297 # Special fast case: full filepath requires no search
298 if ($Is_VMS && m%[:>/\]]% && -f $_) {
299 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
300 last arg unless wantarray;
306 last arg unless wantarray;
309 elsif (m:/: && -f $_ && !$do_expand) {
311 last arg unless wantarray;
315 # Deal with directories first:
316 # Using a -L prefix is the preferred option (faster and more robust)
317 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
320 # Otherwise we try to try to spot directories by a heuristic
321 # (this is a more complicated issue than it first appears)
322 if (m/:/ && -d $_) { push(@dirs, $_); next; }
323 # Only files should get this far...
324 my(@names, $name); # what filenames to look for
327 foreach $dir (@dirs, @dl_library_path) {
329 $dir =~ s/^([^:]+)$/:$1/;
331 foreach $name (@names) {
332 my($file) = "$dir:$name";
333 print STDERR " checking in $dir for $name\n" if $dl_debug;
336 next arg; # no need to look any further
343 # Otherwise we try to try to spot directories by a heuristic
344 # (this is a more complicated issue than it first appears)
345 if (m:/: && -d $_) { push(@dirs, $_); next; }
347 # VMS: we may be using native VMS directry syntax instead of
348 # Unix emulation, so check this as well
349 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
351 # Only files should get this far...
352 my(@names, $name); # what filenames to look for
353 if (m:-l: ) { # convert -lname to appropriate library name
355 push(@names,"lib$_.$dl_so");
356 push(@names,"lib$_.a");
357 } else { # Umm, a bare name. Try various alternatives:
358 # these should be ordered with the most likely first
359 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
360 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
361 push(@names,"lib$_.$dl_so") unless m:/:;
362 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
365 foreach $dir (@dirs, @dl_library_path) {
367 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
368 foreach $name (@names) {
369 my($file) = "$dir/$name";
370 print STDERR " checking in $dir for $name\n" if $dl_debug;
371 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
372 #$file = _check_file($file);
375 next arg; # no need to look any further
382 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
384 print STDERR "dl_findfile found: @found\n";
386 return $found[0] unless wantarray;
393 # Optional function invoked if DynaLoader.pm sets $do_expand.
394 # Most systems do not require or use this function.
395 # Some systems may implement it in the dl_*.xs file in which case
396 # this autoload version will not be called but is harmless.
398 # This function is designed to deal with systems which treat some
399 # 'filenames' in a special way. For example VMS 'Logical Names'
400 # (something like unix environment variables - but different).
401 # This function should recognise such names and expand them into
403 # Must return undef if $spec is invalid or file does not exist.
405 my $file = $spec; # default output to input
407 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
409 Carp::croak("dl_expandspec: should be defined in XS file!\n");
411 return undef unless -f $file;
413 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
417 sub dl_find_symbol_anywhere
421 foreach $libref (@dl_librefs) {
422 my $symref = dl_find_symbol($libref,$sym);
423 return $symref if $symref;
430 DynaLoader - Dynamically load C libraries into Perl code
432 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_unload_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
438 @ISA = qw(... DynaLoader ...);
439 bootstrap YourPackage;
441 # optional method for 'global' loading
442 sub dl_load_flags { 0x01 }
447 This document defines a standard generic interface to the dynamic
448 linking mechanisms available on many platforms. Its primary purpose is
449 to implement automatic dynamic loading of Perl modules.
451 This document serves as both a specification for anyone wishing to
452 implement the DynaLoader for a new platform and as a guide for
453 anyone wishing to use the DynaLoader directly in an application.
455 The DynaLoader is designed to be a very simple high-level
456 interface that is sufficiently general to cover the requirements
457 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
459 It is also hoped that the interface will cover the needs of OS/2, NT
460 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
462 It must be stressed that the DynaLoader, by itself, is practically
463 useless for accessing non-Perl libraries because it provides almost no
464 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
465 library function or supplying arguments. A C::DynaLib module
466 is available from CPAN sites which performs that function for some
469 DynaLoader Interface Summary
478 bootstrap($modulename) Perl
479 @filepaths = dl_findfile(@names) Perl
480 $flags = $modulename->dl_load_flags Perl
481 $symref = dl_find_symbol_anywhere($symbol) Perl
483 $libref = dl_load_file($filename, $flags) C
484 $status = dl_unload_file($libref) C
485 $symref = dl_find_symbol($libref, $symbol) C
486 @symbols = dl_undef_symbols() C
487 dl_install_xsub($name, $symref [, $filename]) C
488 $message = dl_error C
492 =item @dl_library_path
494 The standard/default list of directories in which dl_findfile() will
495 search for libraries etc. Directories are searched in order:
496 $dl_library_path[0], [1], ... etc
498 @dl_library_path is initialised to hold the list of 'normal' directories
499 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
500 ensure portability across a wide range of platforms.
502 @dl_library_path should also be initialised with any other directories
503 that can be determined from the environment at runtime (such as
504 LD_LIBRARY_PATH for SunOS).
506 After initialisation @dl_library_path can be manipulated by an
507 application using push and unshift before calling dl_findfile().
508 Unshift can be used to add directories to the front of the search order
509 either to save search time or to override libraries with the same name
510 in the 'normal' directories.
512 The load function that dl_load_file() calls may require an absolute
513 pathname. The dl_findfile() function and @dl_library_path can be
514 used to search for and return the absolute pathname for the
515 library/object that you wish to load.
517 =item @dl_resolve_using
519 A list of additional libraries or other shared objects which can be
520 used to resolve any undefined symbols that might be generated by a
521 later call to load_file().
523 This is only required on some platforms which do not handle dependent
524 libraries automatically. For example the Socket Perl extension
525 library (F<auto/Socket/Socket.so>) contains references to many socket
526 functions which need to be resolved when it's loaded. Most platforms
527 will automatically know where to find the 'dependent' library (e.g.,
528 F</usr/lib/libsocket.so>). A few platforms need to be told the
529 location of the dependent library explicitly. Use @dl_resolve_using
534 @dl_resolve_using = dl_findfile('-lsocket');
536 =item @dl_require_symbols
538 A list of one or more symbol names that are in the library/object file
539 to be dynamically loaded. This is only required on some platforms.
543 An array of the handles returned by successful calls to dl_load_file(),
544 made by bootstrap, in the order in which they were loaded.
545 Can be used with dl_find_symbol() to look for a symbol in any of
550 An array of module (package) names that have been bootstrap'ed.
556 $message = dl_error();
558 Error message text from the last failed DynaLoader function. Note
559 that, similar to errno in unix, a successful function call does not
562 Implementations should detect the error as soon as it occurs in any of
563 the other functions and save the corresponding message for later
564 retrieval. This will avoid problems on some platforms (such as SunOS)
565 where the error message is very temporary (e.g., dlerror()).
569 Internal debugging messages are enabled when $dl_debug is set true.
570 Currently setting $dl_debug only affects the Perl side of the
571 DynaLoader. These messages should help an application developer to
572 resolve any DynaLoader usage problems.
574 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
576 For the DynaLoader developer/porter there is a similar debugging
577 variable added to the C code (see dlutils.c) and enabled if Perl was
578 built with the B<-DDEBUGGING> flag. This can also be set via the
579 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
586 @filepaths = dl_findfile(@names)
588 Determine the full paths (including file suffix) of one or more
589 loadable files given their generic names and optionally one or more
590 directories. Searches directories in @dl_library_path by default and
591 returns an empty list if no files were found.
593 Names can be specified in a variety of platform independent forms. Any
594 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
595 an appropriate suffix for the platform.
597 If a name does not already have a suitable prefix and/or suffix then
598 the corresponding file will be searched for by trying combinations of
599 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
602 If any directories are included in @names they are searched before
603 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
604 names are treated as filenames to be searched for.
606 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
610 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
613 =item dl_expandspec()
617 $filepath = dl_expandspec($spec)
619 Some unusual systems, such as VMS, require special filename handling in
620 order to deal with symbolic names for files (i.e., VMS's Logical Names).
622 To support these systems a dl_expandspec() function can be implemented
623 either in the F<dl_*.xs> file or code can be added to the autoloadable
624 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
631 $libref = dl_load_file($filename, $flags)
633 Dynamically load $filename, which must be the path to a shared object
634 or library. An opaque 'library reference' is returned as a handle for
635 the loaded object. Returns undef on error.
637 The $flags argument to alters dl_load_file behaviour.
640 0x01 make symbols available for linking later dl_load_file's.
641 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
642 (ignored under VMS; this is a normal part of image linking)
644 (On systems that provide a handle for the loaded object such as SunOS
645 and HPUX, $libref will be that handle. On other systems $libref will
646 typically be $filename or a pointer to a buffer containing $filename.
647 The application should not examine or alter $libref in any way.)
649 This is the function that does the real work. It should use the
650 current values of @dl_require_symbols and @dl_resolve_using if required.
652 SunOS: dlopen($filename)
653 HP-UX: shl_load($filename)
654 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
655 NeXT: rld_load($filename, @dl_resolve_using)
656 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
658 (The dlopen() function is also used by Solaris and some versions of
659 Linux, and is a common choice when providing a "wrapper" on other
660 mechanisms as is done in the OS/2 port.)
662 =item dl_unload_file()
666 $status = dl_unload_file($libref)
668 Dynamically unload $libref, which must be an opaque 'library reference' as
669 returned from dl_load_file. Returns one on success and zero on failure.
671 This function is optional and may not necessarily be provided on all platforms.
672 If it is defined, it is called automatically when the interpreter exits for
673 every shared object or library loaded by DynaLoader::bootstrap. All such
674 library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
675 loads the libraries. The files are unloaded in last-in, first-out order.
677 This unloading is usually necessary when embedding a shared-object perl (e.g.
678 one configured with -Duseshrplib) within a larger application, and the perl
679 interpreter is created and destroyed several times within the lifetime of the
680 application. In this case it is possible that the system dynamic linker will
681 unload and then subsequently reload the shared libperl without relocating any
682 references to it from any files DynaLoaded by the previous incarnation of the
683 interpreter. As a result, any shared objects opened by DynaLoader may point to
684 a now invalid 'ghost' of the libperl shared object, causing apparently random
685 memory corruption and crashes. This behaviour is most commonly seen when using
686 Apache and mod_perl built with the APXS mechanism.
688 SunOS: dlclose($libref)
694 (The dlclose() function is also used by Solaris and some versions of
695 Linux, and is a common choice when providing a "wrapper" on other
696 mechanisms as is done in the OS/2 port.)
702 $flags = dl_loadflags $modulename;
704 Designed to be a method call, and to be overridden by a derived class
705 (i.e. a class which has DynaLoader in its @ISA). The definition in
706 DynaLoader itself returns 0, which produces standard behavior from
709 =item dl_find_symbol()
713 $symref = dl_find_symbol($libref, $symbol)
715 Return the address of the symbol $symbol or C<undef> if not found. If the
716 target system has separate functions to search for symbols of different
717 types then dl_find_symbol() should search for function symbols first and
720 The exact manner in which the address is returned in $symref is not
721 currently defined. The only initial requirement is that $symref can
722 be passed to, and understood by, dl_install_xsub().
724 SunOS: dlsym($libref, $symbol)
725 HP-UX: shl_findsym($libref, $symbol)
726 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
727 NeXT: rld_lookup("_$symbol")
728 VMS: lib$find_image_symbol($libref,$symbol)
731 =item dl_find_symbol_anywhere()
735 $symref = dl_find_symbol_anywhere($symbol)
737 Applies dl_find_symbol() to the members of @dl_librefs and returns
738 the first match found.
740 =item dl_undef_symbols()
744 @symbols = dl_undef_symbols()
746 Return a list of symbol names which remain undefined after load_file().
747 Returns C<()> if not known. Don't worry if your platform does not provide
748 a mechanism for this. Most do not need it and hence do not provide it,
749 they just return an empty list.
752 =item dl_install_xsub()
756 dl_install_xsub($perl_name, $symref [, $filename])
758 Create a new Perl external subroutine named $perl_name using $symref as
759 a pointer to the function which implements the routine. This is simply
760 a direct call to newXSUB(). Returns a reference to the installed
763 The $filename parameter is used by Perl to identify the source file for
764 the function if required by die(), caller() or the debugger. If
765 $filename is not defined then "DynaLoader" will be used.
774 This is the normal entry point for automatic dynamic loading in Perl.
776 It performs the following actions:
782 locates an auto/$module directory by searching @INC
786 uses dl_findfile() to determine the filename to load
790 sets @dl_require_symbols to C<("boot_$module")>
794 executes an F<auto/$module/$module.bs> file if it exists
795 (typically used to add to @dl_resolve_using any files which
796 are required to load the module on the current platform)
800 calls dl_load_flags() to determine how to load the file.
804 calls dl_load_file() to load the file
808 calls dl_undef_symbols() and warns if any symbols are undefined
812 calls dl_find_symbol() for "boot_$module"
816 calls dl_install_xsub() to install it as "${module}::bootstrap"
820 calls &{"${module}::bootstrap"} to bootstrap the module (actually
821 it uses the function reference returned by dl_install_xsub for speed)
830 Tim Bunce, 11 August 1994.
832 This interface is based on the work and comments of (in no particular
833 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
834 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
836 Larry Wall designed the elegant inherited bootstrap mechanism and
837 implemented the first Perl 5 dynamic loader using it.
839 Solaris global loading added by Nick Ing-Simmons with design/coding
840 assistance from Tim Bunce, January 1996.