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 use vars qw($VERSION @ISA) ;
25 sub import { } # override import inherited from AutoLoader
27 # enable debug/trace messages from DynaLoader perl code
28 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
31 # Flags to alter dl_load_file behaviour. Assigned bits:
32 # 0x01 make symbols available for linking later dl_load_file's.
33 # (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
35 # This is called as a class method $module->dl_load_flags. The
36 # definition here will be inherited and result on "default" loading
37 # behaviour unless a sub-class of DynaLoader defines its own version.
40 sub dl_load_flags { 0x00 }
45 = @Config::Config{'dlext', 'dlsrc'};
47 # Some systems need special handling to expand file specifications
48 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
49 # See dl_expandspec() for more details. Should be harmless but
50 # inefficient to define on systems that don't need it.
51 $do_expand = $Is_VMS = $^O eq 'VMS';
53 @dl_require_symbols = (); # names of symbols we need
54 @dl_resolve_using = (); # names of files to link with
55 @dl_library_path = (); # path to look for files
56 @dl_librefs = (); # things we have loaded
57 @dl_modules = (); # Modules we have loaded
59 # This is a fix to support DLD's unfortunate desire to relink -lc
60 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
62 # Initialise @dl_library_path with the 'standard' library path
63 # for this platform as determined by Configure
64 push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
66 # Add to @dl_library_path any extra directories we can gather from
67 # environment variables. So far LD_LIBRARY_PATH is the only known
68 # variable used for this purpose. Others may be added later.
69 push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
70 if $ENV{LD_LIBRARY_PATH};
73 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
74 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
78 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
79 print STDERR "DynaLoader not linked into this perl\n"
80 unless defined(&boot_DynaLoader);
86 # The bootstrap function cannot be autoloaded (without complications)
87 # so we define it here:
90 # use local vars to enable $module.bs script to edit values
92 local($module) = $args[0];
95 Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module;
97 # A common error on platforms which don't support dynamic loading.
98 # Since it's fatal and potentially confusing we give a detailed message.
99 Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n".
100 " (You may need to build a new perl executable which either supports\n".
101 " dynamic loading or has the $module module statically linked into it.)\n")
102 unless defined(&dl_load_file);
104 my @modparts = split(/::/,$module);
105 my $modfname = $modparts[-1];
107 # Some systems have restrictions on files names for DLL's etc.
108 # mod2fname returns appropriate file base name (typically truncated)
109 # It may also edit @modparts if required.
110 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
112 my $modpname = join('/',@modparts);
114 print STDERR "DynaLoader::bootstrap for $module ",
115 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
118 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
119 my $dir = "$_/auto/$modpname";
120 next unless -d $dir; # skip over uninteresting directories
122 # check for common cases to avoid autoload of dl_findfile
123 last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
125 # no luck here, save dir for possible later dl_findfile search
126 push(@dirs, "-L$dir");
128 # last resort, let dl_findfile have a go in all known locations
129 $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
131 Carp::croak("Can't find loadable object for module $module in \@INC (@INC)")
134 my $bootname = "boot_$module";
135 $bootname =~ s/\W/_/g;
136 @dl_require_symbols = ($bootname);
138 # Execute optional '.bootstrap' perl script for this module.
139 # The .bs file can be used to configure @dl_resolve_using etc to
140 # match the needs of the individual module on this architecture.
142 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
143 if (-s $bs) { # only read file if it's not empty
144 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
146 warn "$bs: $@\n" if $@;
149 # Many dynamic extension loading problems will appear to come from
150 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
151 # Often these errors are actually occurring in the initialisation
152 # C code of the extension XS file. Perl reports the error as being
153 # in this perl code simply because this was the last perl code
156 my $libref = dl_load_file($file, $module->dl_load_flags) or
157 Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n");
159 push(@dl_librefs,$libref); # record loaded object
161 my @unresolved = dl_undef_symbols();
162 Carp::carp("Undefined symbols present after loading $file: @unresolved\n")
165 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
166 Carp::croak("Can't find '$bootname' symbol in $file\n");
168 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
170 push(@dl_modules, $module); # record loaded module
172 # See comment block above
177 sub _check_file { # private utility to handle dl_expandspec vs -f tests
179 return $file if (!$do_expand && -f $file); # the common case
180 return $file if ( $do_expand && ($file=dl_expandspec($file)));
185 # Let autosplit and the autoloader deal with these functions:
190 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
191 # This function does not automatically consider the architecture
192 # or the perl library auto directories.
194 my (@dirs, $dir); # which directories to search
195 my (@found); # full paths to real files we have found
196 my $dl_ext= $Config::Config{'dlext'}; # suffix for perl extensions
197 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
199 print STDERR "dl_findfile(@args)\n" if $dl_debug;
201 # accumulate directories but process files as they appear
202 arg: foreach(@args) {
203 # Special fast case: full filepath requires no search
204 if ($Is_VMS && m%[:>/\]]% && -f $_) {
205 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
206 last arg unless wantarray;
209 elsif (m:/: && -f $_ && !$do_expand) {
211 last arg unless wantarray;
215 # Deal with directories first:
216 # Using a -L prefix is the preferred option (faster and more robust)
217 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
219 # Otherwise we try to try to spot directories by a heuristic
220 # (this is a more complicated issue than it first appears)
221 if (m:/: && -d $_) { push(@dirs, $_); next; }
223 # VMS: we may be using native VMS directry syntax instead of
224 # Unix emulation, so check this as well
225 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
227 # Only files should get this far...
228 my(@names, $name); # what filenames to look for
229 if (m:-l: ) { # convert -lname to appropriate library name
231 push(@names,"lib$_.$dl_so");
232 push(@names,"lib$_.a");
233 } else { # Umm, a bare name. Try various alternatives:
234 # these should be ordered with the most likely first
235 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
236 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
237 push(@names,"lib$_.$dl_so") unless m:/:;
238 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
241 foreach $dir (@dirs, @dl_library_path) {
243 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
244 foreach $name (@names) {
245 my($file) = "$dir/$name";
246 print STDERR " checking in $dir for $name\n" if $dl_debug;
247 $file = _check_file($file);
250 next arg; # no need to look any further
257 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
259 print STDERR "dl_findfile found: @found\n";
261 return $found[0] unless wantarray;
268 # Optional function invoked if DynaLoader.pm sets $do_expand.
269 # Most systems do not require or use this function.
270 # Some systems may implement it in the dl_*.xs file in which case
271 # this autoload version will not be called but is harmless.
273 # This function is designed to deal with systems which treat some
274 # 'filenames' in a special way. For example VMS 'Logical Names'
275 # (something like unix environment variables - but different).
276 # This function should recognise such names and expand them into
278 # Must return undef if $spec is invalid or file does not exist.
280 my $file = $spec; # default output to input
282 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
283 Carp::croak("dl_expandspec: should be defined in XS file!\n");
285 return undef unless -f $file;
287 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
291 sub dl_find_symbol_anywhere
295 foreach $libref (@dl_librefs) {
296 my $symref = dl_find_symbol($libref,$sym);
297 return $symref if $symref;
304 DynaLoader - Dynamically load C libraries into Perl code
306 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
312 @ISA = qw(... DynaLoader ...);
313 bootstrap YourPackage;
315 # optional method for 'global' loading
316 sub dl_load_flags { 0x01 }
321 This document defines a standard generic interface to the dynamic
322 linking mechanisms available on many platforms. Its primary purpose is
323 to implement automatic dynamic loading of Perl modules.
325 This document serves as both a specification for anyone wishing to
326 implement the DynaLoader for a new platform and as a guide for
327 anyone wishing to use the DynaLoader directly in an application.
329 The DynaLoader is designed to be a very simple high-level
330 interface that is sufficiently general to cover the requirements
331 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
333 It is also hoped that the interface will cover the needs of OS/2, NT
334 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
336 It must be stressed that the DynaLoader, by itself, is practically
337 useless for accessing non-Perl libraries because it provides almost no
338 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
339 library function or supplying arguments. It is anticipated that any
340 glue that may be developed in the future will be implemented in a
341 separate dynamically loaded module.
343 DynaLoader Interface Summary
352 bootstrap($modulename) Perl
353 @filepaths = dl_findfile(@names) Perl
354 $flags = $modulename->dl_load_flags Perl
355 $symref = dl_find_symbol_anywhere($symbol) Perl
357 $libref = dl_load_file($filename, $flags) C
358 $symref = dl_find_symbol($libref, $symbol) C
359 @symbols = dl_undef_symbols() C
360 dl_install_xsub($name, $symref [, $filename]) C
361 $message = dl_error C
365 =item @dl_library_path
367 The standard/default list of directories in which dl_findfile() will
368 search for libraries etc. Directories are searched in order:
369 $dl_library_path[0], [1], ... etc
371 @dl_library_path is initialised to hold the list of 'normal' directories
372 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
373 ensure portability across a wide range of platforms.
375 @dl_library_path should also be initialised with any other directories
376 that can be determined from the environment at runtime (such as
377 LD_LIBRARY_PATH for SunOS).
379 After initialisation @dl_library_path can be manipulated by an
380 application using push and unshift before calling dl_findfile().
381 Unshift can be used to add directories to the front of the search order
382 either to save search time or to override libraries with the same name
383 in the 'normal' directories.
385 The load function that dl_load_file() calls may require an absolute
386 pathname. The dl_findfile() function and @dl_library_path can be
387 used to search for and return the absolute pathname for the
388 library/object that you wish to load.
390 =item @dl_resolve_using
392 A list of additional libraries or other shared objects which can be
393 used to resolve any undefined symbols that might be generated by a
394 later call to load_file().
396 This is only required on some platforms which do not handle dependent
397 libraries automatically. For example the Socket Perl extension library
398 (F<auto/Socket/Socket.so>) contains references to many socket functions
399 which need to be resolved when it's loaded. Most platforms will
400 automatically know where to find the 'dependent' library (e.g.,
401 F</usr/lib/libsocket.so>). A few platforms need to to be told the location
402 of the dependent library explicitly. Use @dl_resolve_using for this.
406 @dl_resolve_using = dl_findfile('-lsocket');
408 =item @dl_require_symbols
410 A list of one or more symbol names that are in the library/object file
411 to be dynamically loaded. This is only required on some platforms.
415 An array of the handles returned by successful calls to dl_load_file(),
416 made by bootstrap, in the order in which they were loaded.
417 Can be used with dl_find_symbol() to look for a symbol in any of
422 An array of module (package) names that have been bootstrap'ed.
428 $message = dl_error();
430 Error message text from the last failed DynaLoader function. Note
431 that, similar to errno in unix, a successful function call does not
434 Implementations should detect the error as soon as it occurs in any of
435 the other functions and save the corresponding message for later
436 retrieval. This will avoid problems on some platforms (such as SunOS)
437 where the error message is very temporary (e.g., dlerror()).
441 Internal debugging messages are enabled when $dl_debug is set true.
442 Currently setting $dl_debug only affects the Perl side of the
443 DynaLoader. These messages should help an application developer to
444 resolve any DynaLoader usage problems.
446 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
448 For the DynaLoader developer/porter there is a similar debugging
449 variable added to the C code (see dlutils.c) and enabled if Perl was
450 built with the B<-DDEBUGGING> flag. This can also be set via the
451 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
458 @filepaths = dl_findfile(@names)
460 Determine the full paths (including file suffix) of one or more
461 loadable files given their generic names and optionally one or more
462 directories. Searches directories in @dl_library_path by default and
463 returns an empty list if no files were found.
465 Names can be specified in a variety of platform independent forms. Any
466 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
467 an appropriate suffix for the platform.
469 If a name does not already have a suitable prefix and/or suffix then
470 the corresponding file will be searched for by trying combinations of
471 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
474 If any directories are included in @names they are searched before
475 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
476 names are treated as filenames to be searched for.
478 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
482 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
485 =item dl_expandspec()
489 $filepath = dl_expandspec($spec)
491 Some unusual systems, such as VMS, require special filename handling in
492 order to deal with symbolic names for files (i.e., VMS's Logical Names).
494 To support these systems a dl_expandspec() function can be implemented
495 either in the F<dl_*.xs> file or code can be added to the autoloadable
496 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
503 $libref = dl_load_file($filename, $flags)
505 Dynamically load $filename, which must be the path to a shared object
506 or library. An opaque 'library reference' is returned as a handle for
507 the loaded object. Returns undef on error.
509 The $flags argument to alters dl_load_file behaviour.
512 0x01 make symbols available for linking later dl_load_file's.
513 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
515 (On systems that provide a handle for the loaded object such as SunOS
516 and HPUX, $libref will be that handle. On other systems $libref will
517 typically be $filename or a pointer to a buffer containing $filename.
518 The application should not examine or alter $libref in any way.)
520 This is the function that does the real work. It should use the
521 current values of @dl_require_symbols and @dl_resolve_using if required.
523 SunOS: dlopen($filename)
524 HP-UX: shl_load($filename)
525 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
526 NeXT: rld_load($filename, @dl_resolve_using)
527 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
529 (The dlopen() function is also used by Solaris and some versions of
530 Linux, and is a common choice when providing a "wrapper" on other
531 mechanisms as is done in the OS/2 port.)
537 $flags = dl_loadflags $modulename;
539 Designed to be a method call, and to be overridden by a derived class
540 (i.e. a class which has DynaLoader in its @ISA). The definition in
541 DynaLoader itself returns 0, which produces standard behavior from
544 =item dl_find_symbol()
548 $symref = dl_find_symbol($libref, $symbol)
550 Return the address of the symbol $symbol or C<undef> if not found. If the
551 target system has separate functions to search for symbols of different
552 types then dl_find_symbol() should search for function symbols first and
555 The exact manner in which the address is returned in $symref is not
556 currently defined. The only initial requirement is that $symref can
557 be passed to, and understood by, dl_install_xsub().
559 SunOS: dlsym($libref, $symbol)
560 HP-UX: shl_findsym($libref, $symbol)
561 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
562 NeXT: rld_lookup("_$symbol")
563 VMS: lib$find_image_symbol($libref,$symbol)
566 =item dl_find_symbol_anywhere()
570 $symref = dl_find_symbol_anywhere($symbol)
572 Applies dl_find_symbol() to the members of @dl_librefs and returns
573 the first match found.
575 =item dl_undef_symbols()
579 @symbols = dl_undef_symbols()
581 Return a list of symbol names which remain undefined after load_file().
582 Returns C<()> if not known. Don't worry if your platform does not provide
583 a mechanism for this. Most do not need it and hence do not provide it,
584 they just return an empty list.
587 =item dl_install_xsub()
591 dl_install_xsub($perl_name, $symref [, $filename])
593 Create a new Perl external subroutine named $perl_name using $symref as
594 a pointer to the function which implements the routine. This is simply
595 a direct call to newXSUB(). Returns a reference to the installed
598 The $filename parameter is used by Perl to identify the source file for
599 the function if required by die(), caller() or the debugger. If
600 $filename is not defined then "DynaLoader" will be used.
609 This is the normal entry point for automatic dynamic loading in Perl.
611 It performs the following actions:
617 locates an auto/$module directory by searching @INC
621 uses dl_findfile() to determine the filename to load
625 sets @dl_require_symbols to C<("boot_$module")>
629 executes an F<auto/$module/$module.bs> file if it exists
630 (typically used to add to @dl_resolve_using any files which
631 are required to load the module on the current platform)
635 calls dl_load_flags() to determine how to load the file.
639 calls dl_load_file() to load the file
643 calls dl_undef_symbols() and warns if any symbols are undefined
647 calls dl_find_symbol() for "boot_$module"
651 calls dl_install_xsub() to install it as "${module}::bootstrap"
655 calls &{"${module}::bootstrap"} to bootstrap the module (actually
656 it uses the function reference returned by dl_install_xsub for speed)
665 Tim Bunce, 11 August 1994.
667 This interface is based on the work and comments of (in no particular
668 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
669 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
671 Larry Wall designed the elegant inherited bootstrap mechanism and
672 implemented the first Perl 5 dynamic loader using it.
674 Solaris global loading added by Nick Ing-Simmons with design/coding
675 assistance from Tim Bunce, January 1996.