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
22 sub import { } # override import inherited from AutoLoader
24 # enable debug/trace messages from DynaLoader perl code
25 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
27 ($dl_dlext, $dlsrc, $osname)
28 = @Config::Config{'dlext', 'dlsrc', 'osname'};
30 # Some systems need special handling to expand file specifications
31 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
32 # See dl_expandspec() for more details. Should be harmless but
33 # inefficient to define on systems that don't need it.
34 $do_expand = $Is_VMS = $osname eq 'VMS';
36 @dl_require_symbols = (); # names of symbols we need
37 @dl_resolve_using = (); # names of files to link with
38 @dl_library_path = (); # path to look for files
40 # This is a fix to support DLD's unfortunate desire to relink -lc
41 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
43 # Initialise @dl_library_path with the 'standard' library path
44 # for this platform as determined by Configure
45 push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
47 # Add to @dl_library_path any extra directories we can gather from
48 # environment variables. So far LD_LIBRARY_PATH is the only known
49 # variable used for this purpose. Others may be added later.
50 push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
51 if $ENV{LD_LIBRARY_PATH};
54 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
55 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
59 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
60 print STDERR "DynaLoader not linked into this perl\n"
61 unless defined(&boot_DynaLoader);
67 # The bootstrap function cannot be autoloaded (without complications)
68 # so we define it here:
71 # use local vars to enable $module.bs script to edit values
73 local($module) = $args[0];
76 Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module;
78 # A common error on platforms which don't support dynamic loading.
79 # Since it's fatal and potentially confusing we give a detailed message.
80 Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n".
81 " (You may need to build a new perl executable which either supports\n".
82 " dynamic loading or has the $module module statically linked into it.)\n")
83 unless defined(&dl_load_file);
85 my @modparts = split(/::/,$module);
86 my $modfname = $modparts[-1];
88 # Some systems have restrictions on files names for DLL's etc.
89 # mod2fname returns appropriate file base name (typically truncated)
90 # It may also edit @modparts if required.
91 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
93 my $modpname = join('/',@modparts);
95 print STDERR "DynaLoader::bootstrap for $module ",
96 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
99 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
100 my $dir = "$_/auto/$modpname";
101 next unless -d $dir; # skip over uninteresting directories
103 # check for common cases to avoid autoload of dl_findfile
104 last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
106 # no luck here, save dir for possible later dl_findfile search
107 push(@dirs, "-L$dir");
109 # last resort, let dl_findfile have a go in all known locations
110 $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
112 Carp::croak("Can't find loadable object for module $module in \@INC (@INC)")
115 my $bootname = "boot_$module";
116 $bootname =~ s/\W/_/g;
117 @dl_require_symbols = ($bootname);
119 # Execute optional '.bootstrap' perl script for this module.
120 # The .bs file can be used to configure @dl_resolve_using etc to
121 # match the needs of the individual module on this architecture.
123 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
124 if (-s $bs) { # only read file if it's not empty
125 print STDERR "BS: $bs ($osname, $dlsrc)\n" if $dl_debug;
127 warn "$bs: $@\n" if $@;
130 # Many dynamic extension loading problems will appear to come from
131 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
132 # Often these errors are actually occurring in the initialisation
133 # C code of the extension XS file. Perl reports the error as being
134 # in this perl code simply because this was the last perl code
137 my $libref = dl_load_file($file) or
138 Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n");
140 my @unresolved = dl_undef_symbols();
141 Carp::carp("Undefined symbols present after loading $file: @unresolved\n")
144 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
145 Carp::croak("Can't find '$bootname' symbol in $file\n");
147 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
149 # See comment block above
154 sub _check_file { # private utility to handle dl_expandspec vs -f tests
156 return $file if (!$do_expand && -f $file); # the common case
157 return $file if ( $do_expand && ($file=dl_expandspec($file)));
162 # Let autosplit and the autoloader deal with these functions:
167 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
168 # This function does not automatically consider the architecture
169 # or the perl library auto directories.
171 my (@dirs, $dir); # which directories to search
172 my (@found); # full paths to real files we have found
173 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
175 print STDERR "dl_findfile(@args)\n" if $dl_debug;
177 # accumulate directories but process files as they appear
178 arg: foreach(@args) {
179 # Special fast case: full filepath requires no search
180 if ($Is_VMS && m%[:>/\]]% && -f $_) {
181 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
182 last arg unless wantarray;
185 elsif (m:/: && -f $_ && !$do_expand) {
187 last arg unless wantarray;
191 # Deal with directories first:
192 # Using a -L prefix is the preferred option (faster and more robust)
193 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
195 # Otherwise we try to try to spot directories by a heuristic
196 # (this is a more complicated issue than it first appears)
197 if (m:/: && -d $_) { push(@dirs, $_); next; }
199 # VMS: we may be using native VMS directry syntax instead of
200 # Unix emulation, so check this as well
201 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
203 # Only files should get this far...
204 my(@names, $name); # what filenames to look for
205 if (m:-l: ) { # convert -lname to appropriate library name
207 push(@names,"lib$_.$dl_so");
208 push(@names,"lib$_.a");
209 } else { # Umm, a bare name. Try various alternatives:
210 # these should be ordered with the most likely first
211 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
212 push(@names,"lib$_.$dl_so") unless m:/:;
213 push(@names,"$_.o") unless m/\.(o|$dl_so)$/o;
214 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
217 foreach $dir (@dirs, @dl_library_path) {
219 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
220 foreach $name (@names) {
221 my($file) = "$dir/$name";
222 print STDERR " checking in $dir for $name\n" if $dl_debug;
223 $file = _check_file($file);
226 next arg; # no need to look any further
233 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
235 print STDERR "dl_findfile found: @found\n";
237 return $found[0] unless wantarray;
244 # Optional function invoked if DynaLoader.pm sets $do_expand.
245 # Most systems do not require or use this function.
246 # Some systems may implement it in the dl_*.xs file in which case
247 # this autoload version will not be called but is harmless.
249 # This function is designed to deal with systems which treat some
250 # 'filenames' in a special way. For example VMS 'Logical Names'
251 # (something like unix environment variables - but different).
252 # This function should recognise such names and expand them into
254 # Must return undef if $spec is invalid or file does not exist.
256 my $file = $spec; # default output to input
258 if ($osname eq 'VMS') { # dl_expandspec should be defined in dl_vms.xs
259 Carp::croak("dl_expandspec: should be defined in XS file!\n");
261 return undef unless -f $file;
263 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
270 DynaLoader - Dynamically load C libraries into Perl code
272 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_undef_symbols(), dl_install_xsub(), boostrap() - routines used by DynaLoader modules
278 @ISA = qw(... DynaLoader ...);
279 bootstrap YourPackage;
284 This document defines a standard generic interface to the dynamic
285 linking mechanisms available on many platforms. Its primary purpose is
286 to implement automatic dynamic loading of Perl modules.
288 This document serves as both a specification for anyone wishing to
289 implement the DynaLoader for a new platform and as a guide for
290 anyone wishing to use the DynaLoader directly in an application.
292 The DynaLoader is designed to be a very simple high-level
293 interface that is sufficiently general to cover the requirements
294 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
296 It is also hoped that the interface will cover the needs of OS/2, NT
297 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
299 It must be stressed that the DynaLoader, by itself, is practically
300 useless for accessing non-Perl libraries because it provides almost no
301 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
302 library function or supplying arguments. It is anticipated that any
303 glue that may be developed in the future will be implemented in a
304 separate dynamically loaded module.
306 DynaLoader Interface Summary
313 bootstrap($modulename) Perl
314 @filepaths = dl_findfile(@names) Perl
316 $libref = dl_load_file($filename) C
317 $symref = dl_find_symbol($libref, $symbol) C
318 @symbols = dl_undef_symbols() C
319 dl_install_xsub($name, $symref [, $filename]) C
320 $message = dl_error C
324 =item @dl_library_path
326 The standard/default list of directories in which dl_findfile() will
327 search for libraries etc. Directories are searched in order:
328 $dl_library_path[0], [1], ... etc
330 @dl_library_path is initialised to hold the list of 'normal' directories
331 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
332 ensure portability across a wide range of platforms.
334 @dl_library_path should also be initialised with any other directories
335 that can be determined from the environment at runtime (such as
336 LD_LIBRARY_PATH for SunOS).
338 After initialisation @dl_library_path can be manipulated by an
339 application using push and unshift before calling dl_findfile().
340 Unshift can be used to add directories to the front of the search order
341 either to save search time or to override libraries with the same name
342 in the 'normal' directories.
344 The load function that dl_load_file() calls may require an absolute
345 pathname. The dl_findfile() function and @dl_library_path can be
346 used to search for and return the absolute pathname for the
347 library/object that you wish to load.
349 =item @dl_resolve_using
351 A list of additional libraries or other shared objects which can be
352 used to resolve any undefined symbols that might be generated by a
353 later call to load_file().
355 This is only required on some platforms which do not handle dependent
356 libraries automatically. For example the Socket Perl extension library
357 (F<auto/Socket/Socket.so>) contains references to many socket functions
358 which need to be resolved when it's loaded. Most platforms will
359 automatically know where to find the 'dependent' library (e.g.,
360 F</usr/lib/libsocket.so>). A few platforms need to to be told the location
361 of the dependent library explicitly. Use @dl_resolve_using for this.
365 @dl_resolve_using = dl_findfile('-lsocket');
367 =item @dl_require_symbols
369 A list of one or more symbol names that are in the library/object file
370 to be dynamically loaded. This is only required on some platforms.
376 $message = dl_error();
378 Error message text from the last failed DynaLoader function. Note
379 that, similar to errno in unix, a successful function call does not
382 Implementations should detect the error as soon as it occurs in any of
383 the other functions and save the corresponding message for later
384 retrieval. This will avoid problems on some platforms (such as SunOS)
385 where the error message is very temporary (e.g., dlerror()).
389 Internal debugging messages are enabled when $dl_debug is set true.
390 Currently setting $dl_debug only affects the Perl side of the
391 DynaLoader. These messages should help an application developer to
392 resolve any DynaLoader usage problems.
394 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
396 For the DynaLoader developer/porter there is a similar debugging
397 variable added to the C code (see dlutils.c) and enabled if Perl was
398 built with the B<-DDEBUGGING> flag. This can also be set via the
399 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
406 @filepaths = dl_findfile(@names)
408 Determine the full paths (including file suffix) of one or more
409 loadable files given their generic names and optionally one or more
410 directories. Searches directories in @dl_library_path by default and
411 returns an empty list if no files were found.
413 Names can be specified in a variety of platform independent forms. Any
414 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
415 an appropriate suffix for the platform.
417 If a name does not already have a suitable prefix and/or suffix then
418 the corresponding file will be searched for by trying combinations of
419 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
422 If any directories are included in @names they are searched before
423 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
424 names are treated as filenames to be searched for.
426 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
430 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
433 =item dl_expandspec()
437 $filepath = dl_expandspec($spec)
439 Some unusual systems, such as VMS, require special filename handling in
440 order to deal with symbolic names for files (i.e., VMS's Logical Names).
442 To support these systems a dl_expandspec() function can be implemented
443 either in the F<dl_*.xs> file or code can be added to the autoloadable
444 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
451 $libref = dl_load_file($filename)
453 Dynamically load $filename, which must be the path to a shared object
454 or library. An opaque 'library reference' is returned as a handle for
455 the loaded object. Returns undef on error.
457 (On systems that provide a handle for the loaded object such as SunOS
458 and HPUX, $libref will be that handle. On other systems $libref will
459 typically be $filename or a pointer to a buffer containing $filename.
460 The application should not examine or alter $libref in any way.)
462 This is function that does the real work. It should use the current
463 values of @dl_require_symbols and @dl_resolve_using if required.
465 SunOS: dlopen($filename)
466 HP-UX: shl_load($filename)
467 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
468 NeXT: rld_load($filename, @dl_resolve_using)
469 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
472 =item dl_find_symbol()
476 $symref = dl_find_symbol($libref, $symbol)
478 Return the address of the symbol $symbol or C<undef> if not found. If the
479 target system has separate functions to search for symbols of different
480 types then dl_find_symbol() should search for function symbols first and
483 The exact manner in which the address is returned in $symref is not
484 currently defined. The only initial requirement is that $symref can
485 be passed to, and understood by, dl_install_xsub().
487 SunOS: dlsym($libref, $symbol)
488 HP-UX: shl_findsym($libref, $symbol)
489 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
490 NeXT: rld_lookup("_$symbol")
491 VMS: lib$find_image_symbol($libref,$symbol)
494 =item dl_undef_symbols()
498 @symbols = dl_undef_symbols()
500 Return a list of symbol names which remain undefined after load_file().
501 Returns C<()> if not known. Don't worry if your platform does not provide
502 a mechanism for this. Most do not need it and hence do not provide it,
503 they just return an empty list.
506 =item dl_install_xsub()
510 dl_install_xsub($perl_name, $symref [, $filename])
512 Create a new Perl external subroutine named $perl_name using $symref as
513 a pointer to the function which implements the routine. This is simply
514 a direct call to newXSUB(). Returns a reference to the installed
517 The $filename parameter is used by Perl to identify the source file for
518 the function if required by die(), caller() or the debugger. If
519 $filename is not defined then "DynaLoader" will be used.
528 This is the normal entry point for automatic dynamic loading in Perl.
530 It performs the following actions:
536 locates an auto/$module directory by searching @INC
540 uses dl_findfile() to determine the filename to load
544 sets @dl_require_symbols to C<("boot_$module")>
548 executes an F<auto/$module/$module.bs> file if it exists
549 (typically used to add to @dl_resolve_using any files which
550 are required to load the module on the current platform)
554 calls dl_load_file() to load the file
558 calls dl_undef_symbols() and warns if any symbols are undefined
562 calls dl_find_symbol() for "boot_$module"
566 calls dl_install_xsub() to install it as "${module}::bootstrap"
570 calls &{"${module}::bootstrap"} to bootstrap the module (actually
571 it uses the function reference returned by dl_install_xsub for speed)
580 Tim Bunce, 11 August 1994.
582 This interface is based on the work and comments of (in no particular
583 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
584 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
586 Larry Wall designed the elegant inherited bootstrap mechanism and
587 implemented the first Perl 5 dynamic loader using it.