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 = @Config::Config{'dlext', 'dlsrc'};
33 # Some systems need special handling to expand file specifications
34 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
35 # See dl_expandspec() for more details. Should be harmless but
36 # inefficient to define on systems that don't need it.
37 $do_expand = $Is_VMS = $^O eq 'VMS';
39 @dl_require_symbols = (); # names of symbols we need
40 @dl_resolve_using = (); # names of files to link with
41 @dl_library_path = (); # path to look for files
43 # This is a fix to support DLD's unfortunate desire to relink -lc
44 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
46 # Initialise @dl_library_path with the 'standard' library path
47 # for this platform as determined by Configure
48 push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
50 # Add to @dl_library_path any extra directories we can gather from
51 # environment variables. So far LD_LIBRARY_PATH is the only known
52 # variable used for this purpose. Others may be added later.
53 push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
54 if $ENV{LD_LIBRARY_PATH};
57 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
58 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
62 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
63 print STDERR "DynaLoader not linked into this perl\n"
64 unless defined(&boot_DynaLoader);
70 # The bootstrap function cannot be autoloaded (without complications)
71 # so we define it here:
74 # use local vars to enable $module.bs script to edit values
76 local($module) = $args[0];
79 Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module;
81 # A common error on platforms which don't support dynamic loading.
82 # Since it's fatal and potentially confusing we give a detailed message.
83 Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n".
84 " (You may need to build a new perl executable which either supports\n".
85 " dynamic loading or has the $module module statically linked into it.)\n")
86 unless defined(&dl_load_file);
88 my @modparts = split(/::/,$module);
89 my $modfname = $modparts[-1];
91 # Some systems have restrictions on files names for DLL's etc.
92 # mod2fname returns appropriate file base name (typically truncated)
93 # It may also edit @modparts if required.
94 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
96 my $modpname = join('/',@modparts);
98 print STDERR "DynaLoader::bootstrap for $module ",
99 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
102 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
103 my $dir = "$_/auto/$modpname";
104 next unless -d $dir; # skip over uninteresting directories
106 # check for common cases to avoid autoload of dl_findfile
107 last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
109 # no luck here, save dir for possible later dl_findfile search
110 push(@dirs, "-L$dir");
112 # last resort, let dl_findfile have a go in all known locations
113 $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
115 Carp::croak("Can't find loadable object for module $module in \@INC (@INC)")
118 my $bootname = "boot_$module";
119 $bootname =~ s/\W/_/g;
120 @dl_require_symbols = ($bootname);
122 # Execute optional '.bootstrap' perl script for this module.
123 # The .bs file can be used to configure @dl_resolve_using etc to
124 # match the needs of the individual module on this architecture.
126 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
127 if (-s $bs) { # only read file if it's not empty
128 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
130 warn "$bs: $@\n" if $@;
133 # Many dynamic extension loading problems will appear to come from
134 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
135 # Often these errors are actually occurring in the initialisation
136 # C code of the extension XS file. Perl reports the error as being
137 # in this perl code simply because this was the last perl code
140 my $libref = dl_load_file($file) or
141 Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n");
143 my @unresolved = dl_undef_symbols();
144 Carp::carp("Undefined symbols present after loading $file: @unresolved\n")
147 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
148 Carp::croak("Can't find '$bootname' symbol in $file\n");
150 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
152 # See comment block above
157 sub _check_file { # private utility to handle dl_expandspec vs -f tests
159 return $file if (!$do_expand && -f $file); # the common case
160 return $file if ( $do_expand && ($file=dl_expandspec($file)));
165 # Let autosplit and the autoloader deal with these functions:
170 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
171 # This function does not automatically consider the architecture
172 # or the perl library auto directories.
174 my (@dirs, $dir); # which directories to search
175 my (@found); # full paths to real files we have found
176 my $dl_ext= $Config::Config{'dlext'}; # suffix for perl extensions
177 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
179 print STDERR "dl_findfile(@args)\n" if $dl_debug;
181 # accumulate directories but process files as they appear
182 arg: foreach(@args) {
183 # Special fast case: full filepath requires no search
184 if ($Is_VMS && m%[:>/\]]% && -f $_) {
185 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
186 last arg unless wantarray;
189 elsif (m:/: && -f $_ && !$do_expand) {
191 last arg unless wantarray;
195 # Deal with directories first:
196 # Using a -L prefix is the preferred option (faster and more robust)
197 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
199 # Otherwise we try to try to spot directories by a heuristic
200 # (this is a more complicated issue than it first appears)
201 if (m:/: && -d $_) { push(@dirs, $_); next; }
203 # VMS: we may be using native VMS directry syntax instead of
204 # Unix emulation, so check this as well
205 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
207 # Only files should get this far...
208 my(@names, $name); # what filenames to look for
209 if (m:-l: ) { # convert -lname to appropriate library name
211 push(@names,"lib$_.$dl_so");
212 push(@names,"lib$_.a");
213 } else { # Umm, a bare name. Try various alternatives:
214 # these should be ordered with the most likely first
215 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
216 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
217 push(@names,"lib$_.$dl_so") unless m:/:;
218 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
221 foreach $dir (@dirs, @dl_library_path) {
223 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
224 foreach $name (@names) {
225 my($file) = "$dir/$name";
226 print STDERR " checking in $dir for $name\n" if $dl_debug;
227 $file = _check_file($file);
230 next arg; # no need to look any further
237 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
239 print STDERR "dl_findfile found: @found\n";
241 return $found[0] unless wantarray;
248 # Optional function invoked if DynaLoader.pm sets $do_expand.
249 # Most systems do not require or use this function.
250 # Some systems may implement it in the dl_*.xs file in which case
251 # this autoload version will not be called but is harmless.
253 # This function is designed to deal with systems which treat some
254 # 'filenames' in a special way. For example VMS 'Logical Names'
255 # (something like unix environment variables - but different).
256 # This function should recognise such names and expand them into
258 # Must return undef if $spec is invalid or file does not exist.
260 my $file = $spec; # default output to input
262 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
263 Carp::croak("dl_expandspec: should be defined in XS file!\n");
265 return undef unless -f $file;
267 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
274 DynaLoader - Dynamically load C libraries into Perl code
276 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_undef_symbols(), dl_install_xsub(), bootstrap() - routines used by DynaLoader modules
282 @ISA = qw(... DynaLoader ...);
283 bootstrap YourPackage;
288 This document defines a standard generic interface to the dynamic
289 linking mechanisms available on many platforms. Its primary purpose is
290 to implement automatic dynamic loading of Perl modules.
292 This document serves as both a specification for anyone wishing to
293 implement the DynaLoader for a new platform and as a guide for
294 anyone wishing to use the DynaLoader directly in an application.
296 The DynaLoader is designed to be a very simple high-level
297 interface that is sufficiently general to cover the requirements
298 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
300 It is also hoped that the interface will cover the needs of OS/2, NT
301 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
303 It must be stressed that the DynaLoader, by itself, is practically
304 useless for accessing non-Perl libraries because it provides almost no
305 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
306 library function or supplying arguments. It is anticipated that any
307 glue that may be developed in the future will be implemented in a
308 separate dynamically loaded module.
310 DynaLoader Interface Summary
317 bootstrap($modulename) Perl
318 @filepaths = dl_findfile(@names) Perl
320 $libref = dl_load_file($filename) C
321 $symref = dl_find_symbol($libref, $symbol) C
322 @symbols = dl_undef_symbols() C
323 dl_install_xsub($name, $symref [, $filename]) C
324 $message = dl_error C
328 =item @dl_library_path
330 The standard/default list of directories in which dl_findfile() will
331 search for libraries etc. Directories are searched in order:
332 $dl_library_path[0], [1], ... etc
334 @dl_library_path is initialised to hold the list of 'normal' directories
335 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
336 ensure portability across a wide range of platforms.
338 @dl_library_path should also be initialised with any other directories
339 that can be determined from the environment at runtime (such as
340 LD_LIBRARY_PATH for SunOS).
342 After initialisation @dl_library_path can be manipulated by an
343 application using push and unshift before calling dl_findfile().
344 Unshift can be used to add directories to the front of the search order
345 either to save search time or to override libraries with the same name
346 in the 'normal' directories.
348 The load function that dl_load_file() calls may require an absolute
349 pathname. The dl_findfile() function and @dl_library_path can be
350 used to search for and return the absolute pathname for the
351 library/object that you wish to load.
353 =item @dl_resolve_using
355 A list of additional libraries or other shared objects which can be
356 used to resolve any undefined symbols that might be generated by a
357 later call to load_file().
359 This is only required on some platforms which do not handle dependent
360 libraries automatically. For example the Socket Perl extension library
361 (F<auto/Socket/Socket.so>) contains references to many socket functions
362 which need to be resolved when it's loaded. Most platforms will
363 automatically know where to find the 'dependent' library (e.g.,
364 F</usr/lib/libsocket.so>). A few platforms need to to be told the location
365 of the dependent library explicitly. Use @dl_resolve_using for this.
369 @dl_resolve_using = dl_findfile('-lsocket');
371 =item @dl_require_symbols
373 A list of one or more symbol names that are in the library/object file
374 to be dynamically loaded. This is only required on some platforms.
380 $message = dl_error();
382 Error message text from the last failed DynaLoader function. Note
383 that, similar to errno in unix, a successful function call does not
386 Implementations should detect the error as soon as it occurs in any of
387 the other functions and save the corresponding message for later
388 retrieval. This will avoid problems on some platforms (such as SunOS)
389 where the error message is very temporary (e.g., dlerror()).
393 Internal debugging messages are enabled when $dl_debug is set true.
394 Currently setting $dl_debug only affects the Perl side of the
395 DynaLoader. These messages should help an application developer to
396 resolve any DynaLoader usage problems.
398 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
400 For the DynaLoader developer/porter there is a similar debugging
401 variable added to the C code (see dlutils.c) and enabled if Perl was
402 built with the B<-DDEBUGGING> flag. This can also be set via the
403 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
410 @filepaths = dl_findfile(@names)
412 Determine the full paths (including file suffix) of one or more
413 loadable files given their generic names and optionally one or more
414 directories. Searches directories in @dl_library_path by default and
415 returns an empty list if no files were found.
417 Names can be specified in a variety of platform independent forms. Any
418 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
419 an appropriate suffix for the platform.
421 If a name does not already have a suitable prefix and/or suffix then
422 the corresponding file will be searched for by trying combinations of
423 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
426 If any directories are included in @names they are searched before
427 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
428 names are treated as filenames to be searched for.
430 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
434 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
437 =item dl_expandspec()
441 $filepath = dl_expandspec($spec)
443 Some unusual systems, such as VMS, require special filename handling in
444 order to deal with symbolic names for files (i.e., VMS's Logical Names).
446 To support these systems a dl_expandspec() function can be implemented
447 either in the F<dl_*.xs> file or code can be added to the autoloadable
448 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
455 $libref = dl_load_file($filename)
457 Dynamically load $filename, which must be the path to a shared object
458 or library. An opaque 'library reference' is returned as a handle for
459 the loaded object. Returns undef on error.
461 (On systems that provide a handle for the loaded object such as SunOS
462 and HPUX, $libref will be that handle. On other systems $libref will
463 typically be $filename or a pointer to a buffer containing $filename.
464 The application should not examine or alter $libref in any way.)
466 This is function that does the real work. It should use the current
467 values of @dl_require_symbols and @dl_resolve_using if required.
469 SunOS: dlopen($filename)
470 HP-UX: shl_load($filename)
471 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
472 NeXT: rld_load($filename, @dl_resolve_using)
473 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
476 =item dl_find_symbol()
480 $symref = dl_find_symbol($libref, $symbol)
482 Return the address of the symbol $symbol or C<undef> if not found. If the
483 target system has separate functions to search for symbols of different
484 types then dl_find_symbol() should search for function symbols first and
487 The exact manner in which the address is returned in $symref is not
488 currently defined. The only initial requirement is that $symref can
489 be passed to, and understood by, dl_install_xsub().
491 SunOS: dlsym($libref, $symbol)
492 HP-UX: shl_findsym($libref, $symbol)
493 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
494 NeXT: rld_lookup("_$symbol")
495 VMS: lib$find_image_symbol($libref,$symbol)
498 =item dl_undef_symbols()
502 @symbols = dl_undef_symbols()
504 Return a list of symbol names which remain undefined after load_file().
505 Returns C<()> if not known. Don't worry if your platform does not provide
506 a mechanism for this. Most do not need it and hence do not provide it,
507 they just return an empty list.
510 =item dl_install_xsub()
514 dl_install_xsub($perl_name, $symref [, $filename])
516 Create a new Perl external subroutine named $perl_name using $symref as
517 a pointer to the function which implements the routine. This is simply
518 a direct call to newXSUB(). Returns a reference to the installed
521 The $filename parameter is used by Perl to identify the source file for
522 the function if required by die(), caller() or the debugger. If
523 $filename is not defined then "DynaLoader" will be used.
532 This is the normal entry point for automatic dynamic loading in Perl.
534 It performs the following actions:
540 locates an auto/$module directory by searching @INC
544 uses dl_findfile() to determine the filename to load
548 sets @dl_require_symbols to C<("boot_$module")>
552 executes an F<auto/$module/$module.bs> file if it exists
553 (typically used to add to @dl_resolve_using any files which
554 are required to load the module on the current platform)
558 calls dl_load_file() to load the file
562 calls dl_undef_symbols() and warns if any symbols are undefined
566 calls dl_find_symbol() for "boot_$module"
570 calls dl_install_xsub() to install it as "${module}::bootstrap"
574 calls &{"${module}::bootstrap"} to bootstrap the module (actually
575 it uses the function reference returned by dl_install_xsub for speed)
584 Tim Bunce, 11 August 1994.
586 This interface is based on the work and comments of (in no particular
587 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
588 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
590 Larry Wall designed the elegant inherited bootstrap mechanism and
591 implemented the first Perl 5 dynamic loader using it.