3 # And Gandalf said: 'Many folk like to know beforehand what is to
4 # be set on the table; but those who have laboured to prepare the
5 # feast like to keep their secret; for wonder makes the words of
8 # (Quote from Tolkien sugested by Anno Siegel.)
10 # See pod text at end of file for documentation.
11 # See also ext/DynaLoader/README in source tree for other information.
13 # Tim.Bunce@ig.co.uk, August 1994
15 $VERSION = $VERSION = "1.03"; # avoid typo warning
20 *AUTOLOAD = \&AutoLoader::AUTOLOAD;
22 # The following require can't be removed during maintenance
23 # releases, sadly, because of the risk of buggy code that does
24 # require Carp; Carp::croak "..."; without brackets dying
25 # if Carp hasn't been loaded in earlier compile time. :-(
26 # We'll let those bugs get found on the development track.
27 require Carp if $] < 5.00450;
30 # enable debug/trace messages from DynaLoader perl code
31 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
34 # Flags to alter dl_load_file behaviour. Assigned bits:
35 # 0x01 make symbols available for linking later dl_load_file's.
36 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
37 # (ignored under VMS; effect is built-in to image linking)
39 # This is called as a class method $module->dl_load_flags. The
40 # definition here will be inherited and result on "default" loading
41 # behaviour unless a sub-class of DynaLoader defines its own version.
44 sub dl_load_flags { 0x00 }
49 = @Config::Config{'dlext', 'dlsrc'};
51 # Some systems need special handling to expand file specifications
52 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
53 # See dl_expandspec() for more details. Should be harmless but
54 # inefficient to define on systems that don't need it.
55 $do_expand = $Is_VMS = $^O eq 'VMS';
57 @dl_require_symbols = (); # names of symbols we need
58 @dl_resolve_using = (); # names of files to link with
59 @dl_library_path = (); # path to look for files
60 @dl_librefs = (); # things we have loaded
61 @dl_modules = (); # Modules we have loaded
63 # This is a fix to support DLD's unfortunate desire to relink -lc
64 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
66 # Initialise @dl_library_path with the 'standard' library path
67 # for this platform as determined by Configure
68 push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
70 # Add to @dl_library_path any extra directories we can gather from
71 # environment variables. So far LD_LIBRARY_PATH is the only known
72 # variable used for this purpose. Others may be added later.
73 push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
74 if $ENV{LD_LIBRARY_PATH};
77 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
78 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
82 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
83 print STDERR "DynaLoader not linked into this perl\n"
84 unless defined(&boot_DynaLoader);
90 sub croak { require Carp; Carp::croak(@_) }
92 # The bootstrap function cannot be autoloaded (without complications)
93 # so we define it here:
96 # use local vars to enable $module.bs script to edit values
98 local($module) = $args[0];
103 Carp::confess("Usage: DynaLoader::bootstrap(module)");
106 # A common error on platforms which don't support dynamic loading.
107 # Since it's fatal and potentially confusing we give a detailed message.
108 croak("Can't load module $module, dynamic loading not available in this perl.\n".
109 " (You may need to build a new perl executable which either supports\n".
110 " dynamic loading or has the $module module statically linked into it.)\n")
111 unless defined(&dl_load_file);
113 my @modparts = split(/::/,$module);
114 my $modfname = $modparts[-1];
116 # Some systems have restrictions on files names for DLL's etc.
117 # mod2fname returns appropriate file base name (typically truncated)
118 # It may also edit @modparts if required.
119 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
121 my $modpname = join('/',@modparts);
123 print STDERR "DynaLoader::bootstrap for $module ",
124 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
127 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
128 my $dir = "$_/auto/$modpname";
129 next unless -d $dir; # skip over uninteresting directories
131 # check for common cases to avoid autoload of dl_findfile
132 my $try = "$dir/$modfname.$dl_dlext";
133 last if $file = ($do_expand) ? dl_expandspec($try) : (-f $try && $try);
135 # no luck here, save dir for possible later dl_findfile search
138 # last resort, let dl_findfile have a go in all known locations
139 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
141 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
142 unless $file; # wording similar to error from 'require'
144 my $bootname = "boot_$module";
145 $bootname =~ s/\W/_/g;
146 @dl_require_symbols = ($bootname);
148 # Execute optional '.bootstrap' perl script for this module.
149 # The .bs file can be used to configure @dl_resolve_using etc to
150 # match the needs of the individual module on this architecture.
152 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
153 if (-s $bs) { # only read file if it's not empty
154 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
156 warn "$bs: $@\n" if $@;
159 # Many dynamic extension loading problems will appear to come from
160 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
161 # Often these errors are actually occurring in the initialisation
162 # C code of the extension XS file. Perl reports the error as being
163 # in this perl code simply because this was the last perl code
166 my $libref = dl_load_file($file, $module->dl_load_flags) or
167 croak("Can't load '$file' for module $module: ".dl_error()."\n");
169 push(@dl_librefs,$libref); # record loaded object
171 my @unresolved = dl_undef_symbols();
174 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
177 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
178 croak("Can't find '$bootname' symbol in $file\n");
180 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
182 push(@dl_modules, $module); # record loaded module
184 # See comment block above
189 #sub _check_file { # private utility to handle dl_expandspec vs -f tests
191 # return $file if (!$do_expand && -f $file); # the common case
192 # return $file if ( $do_expand && ($file=dl_expandspec($file)));
197 # Let autosplit and the autoloader deal with these functions:
202 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
203 # This function does not automatically consider the architecture
204 # or the perl library auto directories.
206 my (@dirs, $dir); # which directories to search
207 my (@found); # full paths to real files we have found
208 my $dl_ext= $Config::Config{'dlext'}; # suffix for perl extensions
209 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
211 print STDERR "dl_findfile(@args)\n" if $dl_debug;
213 # accumulate directories but process files as they appear
214 arg: foreach(@args) {
215 # Special fast case: full filepath requires no search
216 if ($Is_VMS && m%[:>/\]]% && -f $_) {
217 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
218 last arg unless wantarray;
221 elsif (m:/: && -f $_ && !$do_expand) {
223 last arg unless wantarray;
227 # Deal with directories first:
228 # Using a -L prefix is the preferred option (faster and more robust)
229 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
231 # Otherwise we try to try to spot directories by a heuristic
232 # (this is a more complicated issue than it first appears)
233 if (m:/: && -d $_) { push(@dirs, $_); next; }
235 # VMS: we may be using native VMS directry syntax instead of
236 # Unix emulation, so check this as well
237 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
239 # Only files should get this far...
240 my(@names, $name); # what filenames to look for
241 if (m:-l: ) { # convert -lname to appropriate library name
243 push(@names,"lib$_.$dl_so");
244 push(@names,"lib$_.a");
245 } else { # Umm, a bare name. Try various alternatives:
246 # these should be ordered with the most likely first
247 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
248 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
249 push(@names,"lib$_.$dl_so") unless m:/:;
250 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
253 foreach $dir (@dirs, @dl_library_path) {
255 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
256 foreach $name (@names) {
257 my($file) = "$dir/$name";
258 print STDERR " checking in $dir for $name\n" if $dl_debug;
259 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
260 #$file = _check_file($file);
263 next arg; # no need to look any further
270 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
272 print STDERR "dl_findfile found: @found\n";
274 return $found[0] unless wantarray;
281 # Optional function invoked if DynaLoader.pm sets $do_expand.
282 # Most systems do not require or use this function.
283 # Some systems may implement it in the dl_*.xs file in which case
284 # this autoload version will not be called but is harmless.
286 # This function is designed to deal with systems which treat some
287 # 'filenames' in a special way. For example VMS 'Logical Names'
288 # (something like unix environment variables - but different).
289 # This function should recognise such names and expand them into
291 # Must return undef if $spec is invalid or file does not exist.
293 my $file = $spec; # default output to input
295 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
297 Carp::croak("dl_expandspec: should be defined in XS file!\n");
299 return undef unless -f $file;
301 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
305 sub dl_find_symbol_anywhere
309 foreach $libref (@dl_librefs) {
310 my $symref = dl_find_symbol($libref,$sym);
311 return $symref if $symref;
318 DynaLoader - Dynamically load C libraries into Perl code
320 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
326 @ISA = qw(... DynaLoader ...);
327 bootstrap YourPackage;
329 # optional method for 'global' loading
330 sub dl_load_flags { 0x01 }
335 This document defines a standard generic interface to the dynamic
336 linking mechanisms available on many platforms. Its primary purpose is
337 to implement automatic dynamic loading of Perl modules.
339 This document serves as both a specification for anyone wishing to
340 implement the DynaLoader for a new platform and as a guide for
341 anyone wishing to use the DynaLoader directly in an application.
343 The DynaLoader is designed to be a very simple high-level
344 interface that is sufficiently general to cover the requirements
345 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
347 It is also hoped that the interface will cover the needs of OS/2, NT
348 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
350 It must be stressed that the DynaLoader, by itself, is practically
351 useless for accessing non-Perl libraries because it provides almost no
352 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
353 library function or supplying arguments. A ExtUtils::DynaLib module
354 is available from CPAN sites which performs that function for some
357 DynaLoader Interface Summary
366 bootstrap($modulename) Perl
367 @filepaths = dl_findfile(@names) Perl
368 $flags = $modulename->dl_load_flags Perl
369 $symref = dl_find_symbol_anywhere($symbol) Perl
371 $libref = dl_load_file($filename, $flags) C
372 $symref = dl_find_symbol($libref, $symbol) C
373 @symbols = dl_undef_symbols() C
374 dl_install_xsub($name, $symref [, $filename]) C
375 $message = dl_error C
379 =item @dl_library_path
381 The standard/default list of directories in which dl_findfile() will
382 search for libraries etc. Directories are searched in order:
383 $dl_library_path[0], [1], ... etc
385 @dl_library_path is initialised to hold the list of 'normal' directories
386 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
387 ensure portability across a wide range of platforms.
389 @dl_library_path should also be initialised with any other directories
390 that can be determined from the environment at runtime (such as
391 LD_LIBRARY_PATH for SunOS).
393 After initialisation @dl_library_path can be manipulated by an
394 application using push and unshift before calling dl_findfile().
395 Unshift can be used to add directories to the front of the search order
396 either to save search time or to override libraries with the same name
397 in the 'normal' directories.
399 The load function that dl_load_file() calls may require an absolute
400 pathname. The dl_findfile() function and @dl_library_path can be
401 used to search for and return the absolute pathname for the
402 library/object that you wish to load.
404 =item @dl_resolve_using
406 A list of additional libraries or other shared objects which can be
407 used to resolve any undefined symbols that might be generated by a
408 later call to load_file().
410 This is only required on some platforms which do not handle dependent
411 libraries automatically. For example the Socket Perl extension
412 library (F<auto/Socket/Socket.so>) contains references to many socket
413 functions which need to be resolved when it's loaded. Most platforms
414 will automatically know where to find the 'dependent' library (e.g.,
415 F</usr/lib/libsocket.so>). A few platforms need to be told the
416 location of the dependent library explicitly. Use @dl_resolve_using
421 @dl_resolve_using = dl_findfile('-lsocket');
423 =item @dl_require_symbols
425 A list of one or more symbol names that are in the library/object file
426 to be dynamically loaded. This is only required on some platforms.
430 An array of the handles returned by successful calls to dl_load_file(),
431 made by bootstrap, in the order in which they were loaded.
432 Can be used with dl_find_symbol() to look for a symbol in any of
437 An array of module (package) names that have been bootstrap'ed.
443 $message = dl_error();
445 Error message text from the last failed DynaLoader function. Note
446 that, similar to errno in unix, a successful function call does not
449 Implementations should detect the error as soon as it occurs in any of
450 the other functions and save the corresponding message for later
451 retrieval. This will avoid problems on some platforms (such as SunOS)
452 where the error message is very temporary (e.g., dlerror()).
456 Internal debugging messages are enabled when $dl_debug is set true.
457 Currently setting $dl_debug only affects the Perl side of the
458 DynaLoader. These messages should help an application developer to
459 resolve any DynaLoader usage problems.
461 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
463 For the DynaLoader developer/porter there is a similar debugging
464 variable added to the C code (see dlutils.c) and enabled if Perl was
465 built with the B<-DDEBUGGING> flag. This can also be set via the
466 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
473 @filepaths = dl_findfile(@names)
475 Determine the full paths (including file suffix) of one or more
476 loadable files given their generic names and optionally one or more
477 directories. Searches directories in @dl_library_path by default and
478 returns an empty list if no files were found.
480 Names can be specified in a variety of platform independent forms. Any
481 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
482 an appropriate suffix for the platform.
484 If a name does not already have a suitable prefix and/or suffix then
485 the corresponding file will be searched for by trying combinations of
486 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
489 If any directories are included in @names they are searched before
490 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
491 names are treated as filenames to be searched for.
493 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
497 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
500 =item dl_expandspec()
504 $filepath = dl_expandspec($spec)
506 Some unusual systems, such as VMS, require special filename handling in
507 order to deal with symbolic names for files (i.e., VMS's Logical Names).
509 To support these systems a dl_expandspec() function can be implemented
510 either in the F<dl_*.xs> file or code can be added to the autoloadable
511 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
518 $libref = dl_load_file($filename, $flags)
520 Dynamically load $filename, which must be the path to a shared object
521 or library. An opaque 'library reference' is returned as a handle for
522 the loaded object. Returns undef on error.
524 The $flags argument to alters dl_load_file behaviour.
527 0x01 make symbols available for linking later dl_load_file's.
528 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
529 (ignored under VMS; this is a normal part of image linking)
531 (On systems that provide a handle for the loaded object such as SunOS
532 and HPUX, $libref will be that handle. On other systems $libref will
533 typically be $filename or a pointer to a buffer containing $filename.
534 The application should not examine or alter $libref in any way.)
536 This is the function that does the real work. It should use the
537 current values of @dl_require_symbols and @dl_resolve_using if required.
539 SunOS: dlopen($filename)
540 HP-UX: shl_load($filename)
541 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
542 NeXT: rld_load($filename, @dl_resolve_using)
543 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
545 (The dlopen() function is also used by Solaris and some versions of
546 Linux, and is a common choice when providing a "wrapper" on other
547 mechanisms as is done in the OS/2 port.)
553 $flags = dl_loadflags $modulename;
555 Designed to be a method call, and to be overridden by a derived class
556 (i.e. a class which has DynaLoader in its @ISA). The definition in
557 DynaLoader itself returns 0, which produces standard behavior from
560 =item dl_find_symbol()
564 $symref = dl_find_symbol($libref, $symbol)
566 Return the address of the symbol $symbol or C<undef> if not found. If the
567 target system has separate functions to search for symbols of different
568 types then dl_find_symbol() should search for function symbols first and
571 The exact manner in which the address is returned in $symref is not
572 currently defined. The only initial requirement is that $symref can
573 be passed to, and understood by, dl_install_xsub().
575 SunOS: dlsym($libref, $symbol)
576 HP-UX: shl_findsym($libref, $symbol)
577 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
578 NeXT: rld_lookup("_$symbol")
579 VMS: lib$find_image_symbol($libref,$symbol)
582 =item dl_find_symbol_anywhere()
586 $symref = dl_find_symbol_anywhere($symbol)
588 Applies dl_find_symbol() to the members of @dl_librefs and returns
589 the first match found.
591 =item dl_undef_symbols()
595 @symbols = dl_undef_symbols()
597 Return a list of symbol names which remain undefined after load_file().
598 Returns C<()> if not known. Don't worry if your platform does not provide
599 a mechanism for this. Most do not need it and hence do not provide it,
600 they just return an empty list.
603 =item dl_install_xsub()
607 dl_install_xsub($perl_name, $symref [, $filename])
609 Create a new Perl external subroutine named $perl_name using $symref as
610 a pointer to the function which implements the routine. This is simply
611 a direct call to newXSUB(). Returns a reference to the installed
614 The $filename parameter is used by Perl to identify the source file for
615 the function if required by die(), caller() or the debugger. If
616 $filename is not defined then "DynaLoader" will be used.
625 This is the normal entry point for automatic dynamic loading in Perl.
627 It performs the following actions:
633 locates an auto/$module directory by searching @INC
637 uses dl_findfile() to determine the filename to load
641 sets @dl_require_symbols to C<("boot_$module")>
645 executes an F<auto/$module/$module.bs> file if it exists
646 (typically used to add to @dl_resolve_using any files which
647 are required to load the module on the current platform)
651 calls dl_load_flags() to determine how to load the file.
655 calls dl_load_file() to load the file
659 calls dl_undef_symbols() and warns if any symbols are undefined
663 calls dl_find_symbol() for "boot_$module"
667 calls dl_install_xsub() to install it as "${module}::bootstrap"
671 calls &{"${module}::bootstrap"} to bootstrap the module (actually
672 it uses the function reference returned by dl_install_xsub for speed)
681 Tim Bunce, 11 August 1994.
683 This interface is based on the work and comments of (in no particular
684 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
685 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
687 Larry Wall designed the elegant inherited bootstrap mechanism and
688 implemented the first Perl 5 dynamic loader using it.
690 Solaris global loading added by Nick Ing-Simmons with design/coding
691 assistance from Tim Bunce, January 1996.