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
21 $VERSION = $VERSION = "1.00" ;
23 sub import { } # override import inherited from AutoLoader
25 # enable debug/trace messages from DynaLoader perl code
26 $dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
28 ($dl_dlext, $dlsrc, $osname)
29 = @Config::Config{'dlext', 'dlsrc', 'osname'};
31 # Some systems need special handling to expand file specifications
32 # (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
33 # See dl_expandspec() for more details. Should be harmless but
34 # inefficient to define on systems that don't need it.
35 $do_expand = $Is_VMS = $osname eq 'VMS';
37 @dl_require_symbols = (); # names of symbols we need
38 @dl_resolve_using = (); # names of files to link with
39 @dl_library_path = (); # path to look for files
41 # This is a fix to support DLD's unfortunate desire to relink -lc
42 @dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
44 # Initialise @dl_library_path with the 'standard' library path
45 # for this platform as determined by Configure
46 push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
48 # Add to @dl_library_path any extra directories we can gather from
49 # environment variables. So far LD_LIBRARY_PATH is the only known
50 # variable used for this purpose. Others may be added later.
51 push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
52 if $ENV{LD_LIBRARY_PATH};
55 # No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
56 boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
60 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
61 print STDERR "DynaLoader not linked into this perl\n"
62 unless defined(&boot_DynaLoader);
68 # The bootstrap function cannot be autoloaded (without complications)
69 # so we define it here:
72 # use local vars to enable $module.bs script to edit values
74 local($module) = $args[0];
77 Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module;
79 # A common error on platforms which don't support dynamic loading.
80 # Since it's fatal and potentially confusing we give a detailed message.
81 Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n".
82 " (You may need to build a new perl executable which either supports\n".
83 " dynamic loading or has the $module module statically linked into it.)\n")
84 unless defined(&dl_load_file);
86 my @modparts = split(/::/,$module);
87 my $modfname = $modparts[-1];
89 # Some systems have restrictions on files names for DLL's etc.
90 # mod2fname returns appropriate file base name (typically truncated)
91 # It may also edit @modparts if required.
92 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
94 my $modpname = join('/',@modparts);
96 print STDERR "DynaLoader::bootstrap for $module ",
97 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
100 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
101 my $dir = "$_/auto/$modpname";
102 next unless -d $dir; # skip over uninteresting directories
104 # check for common cases to avoid autoload of dl_findfile
105 last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
107 # no luck here, save dir for possible later dl_findfile search
108 push(@dirs, "-L$dir");
110 # last resort, let dl_findfile have a go in all known locations
111 $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
113 Carp::croak("Can't find loadable object for module $module in \@INC (@INC)")
116 my $bootname = "boot_$module";
117 $bootname =~ s/\W/_/g;
118 @dl_require_symbols = ($bootname);
120 # Execute optional '.bootstrap' perl script for this module.
121 # The .bs file can be used to configure @dl_resolve_using etc to
122 # match the needs of the individual module on this architecture.
124 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
125 if (-s $bs) { # only read file if it's not empty
126 print STDERR "BS: $bs ($osname, $dlsrc)\n" if $dl_debug;
128 warn "$bs: $@\n" if $@;
131 # Many dynamic extension loading problems will appear to come from
132 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
133 # Often these errors are actually occurring in the initialisation
134 # C code of the extension XS file. Perl reports the error as being
135 # in this perl code simply because this was the last perl code
138 my $libref = dl_load_file($file) or
139 Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n");
141 my @unresolved = dl_undef_symbols();
142 Carp::carp("Undefined symbols present after loading $file: @unresolved\n")
145 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
146 Carp::croak("Can't find '$bootname' symbol in $file\n");
148 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
150 # See comment block above
155 sub _check_file { # private utility to handle dl_expandspec vs -f tests
157 return $file if (!$do_expand && -f $file); # the common case
158 return $file if ( $do_expand && ($file=dl_expandspec($file)));
163 # Let autosplit and the autoloader deal with these functions:
168 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
169 # This function does not automatically consider the architecture
170 # or the perl library auto directories.
172 my (@dirs, $dir); # which directories to search
173 my (@found); # full paths to real files we have found
174 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
176 print STDERR "dl_findfile(@args)\n" if $dl_debug;
178 # accumulate directories but process files as they appear
179 arg: foreach(@args) {
180 # Special fast case: full filepath requires no search
181 if ($Is_VMS && m%[:>/\]]% && -f $_) {
182 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
183 last arg unless wantarray;
186 elsif (m:/: && -f $_ && !$do_expand) {
188 last arg unless wantarray;
192 # Deal with directories first:
193 # Using a -L prefix is the preferred option (faster and more robust)
194 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
196 # Otherwise we try to try to spot directories by a heuristic
197 # (this is a more complicated issue than it first appears)
198 if (m:/: && -d $_) { push(@dirs, $_); next; }
200 # VMS: we may be using native VMS directry syntax instead of
201 # Unix emulation, so check this as well
202 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
204 # Only files should get this far...
205 my(@names, $name); # what filenames to look for
206 if (m:-l: ) { # convert -lname to appropriate library name
208 push(@names,"lib$_.$dl_so");
209 push(@names,"lib$_.a");
210 } else { # Umm, a bare name. Try various alternatives:
211 # these should be ordered with the most likely first
212 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
213 push(@names,"lib$_.$dl_so") unless m:/:;
214 push(@names,"$_.o") unless m/\.(o|$dl_so)$/o;
215 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
218 foreach $dir (@dirs, @dl_library_path) {
220 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
221 foreach $name (@names) {
222 my($file) = "$dir/$name";
223 print STDERR " checking in $dir for $name\n" if $dl_debug;
224 $file = _check_file($file);
227 next arg; # no need to look any further
234 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
236 print STDERR "dl_findfile found: @found\n";
238 return $found[0] unless wantarray;
245 # Optional function invoked if DynaLoader.pm sets $do_expand.
246 # Most systems do not require or use this function.
247 # Some systems may implement it in the dl_*.xs file in which case
248 # this autoload version will not be called but is harmless.
250 # This function is designed to deal with systems which treat some
251 # 'filenames' in a special way. For example VMS 'Logical Names'
252 # (something like unix environment variables - but different).
253 # This function should recognise such names and expand them into
255 # Must return undef if $spec is invalid or file does not exist.
257 my $file = $spec; # default output to input
259 if ($osname eq 'VMS') { # dl_expandspec should be defined in dl_vms.xs
260 Carp::croak("dl_expandspec: should be defined in XS file!\n");
262 return undef unless -f $file;
264 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
271 DynaLoader - Dynamically load C libraries into Perl code
273 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_undef_symbols(), dl_install_xsub(), boostrap() - routines used by DynaLoader modules
279 @ISA = qw(... DynaLoader ...);
280 bootstrap YourPackage;
285 This document defines a standard generic interface to the dynamic
286 linking mechanisms available on many platforms. Its primary purpose is
287 to implement automatic dynamic loading of Perl modules.
289 This document serves as both a specification for anyone wishing to
290 implement the DynaLoader for a new platform and as a guide for
291 anyone wishing to use the DynaLoader directly in an application.
293 The DynaLoader is designed to be a very simple high-level
294 interface that is sufficiently general to cover the requirements
295 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
297 It is also hoped that the interface will cover the needs of OS/2, NT
298 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
300 It must be stressed that the DynaLoader, by itself, is practically
301 useless for accessing non-Perl libraries because it provides almost no
302 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
303 library function or supplying arguments. It is anticipated that any
304 glue that may be developed in the future will be implemented in a
305 separate dynamically loaded module.
307 DynaLoader Interface Summary
314 bootstrap($modulename) Perl
315 @filepaths = dl_findfile(@names) Perl
317 $libref = dl_load_file($filename) C
318 $symref = dl_find_symbol($libref, $symbol) C
319 @symbols = dl_undef_symbols() C
320 dl_install_xsub($name, $symref [, $filename]) C
321 $message = dl_error C
325 =item @dl_library_path
327 The standard/default list of directories in which dl_findfile() will
328 search for libraries etc. Directories are searched in order:
329 $dl_library_path[0], [1], ... etc
331 @dl_library_path is initialised to hold the list of 'normal' directories
332 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
333 ensure portability across a wide range of platforms.
335 @dl_library_path should also be initialised with any other directories
336 that can be determined from the environment at runtime (such as
337 LD_LIBRARY_PATH for SunOS).
339 After initialisation @dl_library_path can be manipulated by an
340 application using push and unshift before calling dl_findfile().
341 Unshift can be used to add directories to the front of the search order
342 either to save search time or to override libraries with the same name
343 in the 'normal' directories.
345 The load function that dl_load_file() calls may require an absolute
346 pathname. The dl_findfile() function and @dl_library_path can be
347 used to search for and return the absolute pathname for the
348 library/object that you wish to load.
350 =item @dl_resolve_using
352 A list of additional libraries or other shared objects which can be
353 used to resolve any undefined symbols that might be generated by a
354 later call to load_file().
356 This is only required on some platforms which do not handle dependent
357 libraries automatically. For example the Socket Perl extension library
358 (F<auto/Socket/Socket.so>) contains references to many socket functions
359 which need to be resolved when it's loaded. Most platforms will
360 automatically know where to find the 'dependent' library (e.g.,
361 F</usr/lib/libsocket.so>). A few platforms need to to be told the location
362 of the dependent library explicitly. Use @dl_resolve_using for this.
366 @dl_resolve_using = dl_findfile('-lsocket');
368 =item @dl_require_symbols
370 A list of one or more symbol names that are in the library/object file
371 to be dynamically loaded. This is only required on some platforms.
377 $message = dl_error();
379 Error message text from the last failed DynaLoader function. Note
380 that, similar to errno in unix, a successful function call does not
383 Implementations should detect the error as soon as it occurs in any of
384 the other functions and save the corresponding message for later
385 retrieval. This will avoid problems on some platforms (such as SunOS)
386 where the error message is very temporary (e.g., dlerror()).
390 Internal debugging messages are enabled when $dl_debug is set true.
391 Currently setting $dl_debug only affects the Perl side of the
392 DynaLoader. These messages should help an application developer to
393 resolve any DynaLoader usage problems.
395 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
397 For the DynaLoader developer/porter there is a similar debugging
398 variable added to the C code (see dlutils.c) and enabled if Perl was
399 built with the B<-DDEBUGGING> flag. This can also be set via the
400 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
407 @filepaths = dl_findfile(@names)
409 Determine the full paths (including file suffix) of one or more
410 loadable files given their generic names and optionally one or more
411 directories. Searches directories in @dl_library_path by default and
412 returns an empty list if no files were found.
414 Names can be specified in a variety of platform independent forms. Any
415 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
416 an appropriate suffix for the platform.
418 If a name does not already have a suitable prefix and/or suffix then
419 the corresponding file will be searched for by trying combinations of
420 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
423 If any directories are included in @names they are searched before
424 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
425 names are treated as filenames to be searched for.
427 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
431 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
434 =item dl_expandspec()
438 $filepath = dl_expandspec($spec)
440 Some unusual systems, such as VMS, require special filename handling in
441 order to deal with symbolic names for files (i.e., VMS's Logical Names).
443 To support these systems a dl_expandspec() function can be implemented
444 either in the F<dl_*.xs> file or code can be added to the autoloadable
445 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
452 $libref = dl_load_file($filename)
454 Dynamically load $filename, which must be the path to a shared object
455 or library. An opaque 'library reference' is returned as a handle for
456 the loaded object. Returns undef on error.
458 (On systems that provide a handle for the loaded object such as SunOS
459 and HPUX, $libref will be that handle. On other systems $libref will
460 typically be $filename or a pointer to a buffer containing $filename.
461 The application should not examine or alter $libref in any way.)
463 This is function that does the real work. It should use the current
464 values of @dl_require_symbols and @dl_resolve_using if required.
466 SunOS: dlopen($filename)
467 HP-UX: shl_load($filename)
468 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
469 NeXT: rld_load($filename, @dl_resolve_using)
470 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
473 =item dl_find_symbol()
477 $symref = dl_find_symbol($libref, $symbol)
479 Return the address of the symbol $symbol or C<undef> if not found. If the
480 target system has separate functions to search for symbols of different
481 types then dl_find_symbol() should search for function symbols first and
484 The exact manner in which the address is returned in $symref is not
485 currently defined. The only initial requirement is that $symref can
486 be passed to, and understood by, dl_install_xsub().
488 SunOS: dlsym($libref, $symbol)
489 HP-UX: shl_findsym($libref, $symbol)
490 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
491 NeXT: rld_lookup("_$symbol")
492 VMS: lib$find_image_symbol($libref,$symbol)
495 =item dl_undef_symbols()
499 @symbols = dl_undef_symbols()
501 Return a list of symbol names which remain undefined after load_file().
502 Returns C<()> if not known. Don't worry if your platform does not provide
503 a mechanism for this. Most do not need it and hence do not provide it,
504 they just return an empty list.
507 =item dl_install_xsub()
511 dl_install_xsub($perl_name, $symref [, $filename])
513 Create a new Perl external subroutine named $perl_name using $symref as
514 a pointer to the function which implements the routine. This is simply
515 a direct call to newXSUB(). Returns a reference to the installed
518 The $filename parameter is used by Perl to identify the source file for
519 the function if required by die(), caller() or the debugger. If
520 $filename is not defined then "DynaLoader" will be used.
529 This is the normal entry point for automatic dynamic loading in Perl.
531 It performs the following actions:
537 locates an auto/$module directory by searching @INC
541 uses dl_findfile() to determine the filename to load
545 sets @dl_require_symbols to C<("boot_$module")>
549 executes an F<auto/$module/$module.bs> file if it exists
550 (typically used to add to @dl_resolve_using any files which
551 are required to load the module on the current platform)
555 calls dl_load_file() to load the file
559 calls dl_undef_symbols() and warns if any symbols are undefined
563 calls dl_find_symbol() for "boot_$module"
567 calls dl_install_xsub() to install it as "${module}::bootstrap"
571 calls &{"${module}::bootstrap"} to bootstrap the module (actually
572 it uses the function reference returned by dl_install_xsub for speed)
581 Tim Bunce, 11 August 1994.
583 This interface is based on the work and comments of (in no particular
584 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
585 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
587 Larry Wall designed the elegant inherited bootstrap mechanism and
588 implemented the first Perl 5 dynamic loader using it.