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 $dl_debug;
30 ($dl_dlext, $dlsrc, $osname)
31 = @Config::Config{'dlext', 'dlsrc', 'osname'};
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 = $osname 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: $bs ($osname, $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_so = $Config::Config{'so'}; # suffix for shared libraries
178 print STDERR "dl_findfile(@args)\n" if $dl_debug;
180 # accumulate directories but process files as they appear
181 arg: foreach(@args) {
182 # Special fast case: full filepath requires no search
183 if ($Is_VMS && m%[:>/\]]% && -f $_) {
184 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
185 last arg unless wantarray;
188 elsif (m:/: && -f $_ && !$do_expand) {
190 last arg unless wantarray;
194 # Deal with directories first:
195 # Using a -L prefix is the preferred option (faster and more robust)
196 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
198 # Otherwise we try to try to spot directories by a heuristic
199 # (this is a more complicated issue than it first appears)
200 if (m:/: && -d $_) { push(@dirs, $_); next; }
202 # VMS: we may be using native VMS directry syntax instead of
203 # Unix emulation, so check this as well
204 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
206 # Only files should get this far...
207 my(@names, $name); # what filenames to look for
208 if (m:-l: ) { # convert -lname to appropriate library name
210 push(@names,"lib$_.$dl_so");
211 push(@names,"lib$_.a");
212 } else { # Umm, a bare name. Try various alternatives:
213 # these should be ordered with the most likely first
214 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
215 push(@names,"lib$_.$dl_so") unless m:/:;
216 push(@names,"$_.o") unless m/\.(o|$dl_so)$/o;
217 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
220 foreach $dir (@dirs, @dl_library_path) {
222 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
223 foreach $name (@names) {
224 my($file) = "$dir/$name";
225 print STDERR " checking in $dir for $name\n" if $dl_debug;
226 $file = _check_file($file);
229 next arg; # no need to look any further
236 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
238 print STDERR "dl_findfile found: @found\n";
240 return $found[0] unless wantarray;
247 # Optional function invoked if DynaLoader.pm sets $do_expand.
248 # Most systems do not require or use this function.
249 # Some systems may implement it in the dl_*.xs file in which case
250 # this autoload version will not be called but is harmless.
252 # This function is designed to deal with systems which treat some
253 # 'filenames' in a special way. For example VMS 'Logical Names'
254 # (something like unix environment variables - but different).
255 # This function should recognise such names and expand them into
257 # Must return undef if $spec is invalid or file does not exist.
259 my $file = $spec; # default output to input
261 if ($osname eq 'VMS') { # dl_expandspec should be defined in dl_vms.xs
262 Carp::croak("dl_expandspec: should be defined in XS file!\n");
264 return undef unless -f $file;
266 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
273 DynaLoader - Dynamically load C libraries into Perl code
275 dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_undef_symbols(), dl_install_xsub(), boostrap() - routines used by DynaLoader modules
281 @ISA = qw(... DynaLoader ...);
282 bootstrap YourPackage;
287 This document defines a standard generic interface to the dynamic
288 linking mechanisms available on many platforms. Its primary purpose is
289 to implement automatic dynamic loading of Perl modules.
291 This document serves as both a specification for anyone wishing to
292 implement the DynaLoader for a new platform and as a guide for
293 anyone wishing to use the DynaLoader directly in an application.
295 The DynaLoader is designed to be a very simple high-level
296 interface that is sufficiently general to cover the requirements
297 of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
299 It is also hoped that the interface will cover the needs of OS/2, NT
300 etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
302 It must be stressed that the DynaLoader, by itself, is practically
303 useless for accessing non-Perl libraries because it provides almost no
304 Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
305 library function or supplying arguments. It is anticipated that any
306 glue that may be developed in the future will be implemented in a
307 separate dynamically loaded module.
309 DynaLoader Interface Summary
316 bootstrap($modulename) Perl
317 @filepaths = dl_findfile(@names) Perl
319 $libref = dl_load_file($filename) C
320 $symref = dl_find_symbol($libref, $symbol) C
321 @symbols = dl_undef_symbols() C
322 dl_install_xsub($name, $symref [, $filename]) C
323 $message = dl_error C
327 =item @dl_library_path
329 The standard/default list of directories in which dl_findfile() will
330 search for libraries etc. Directories are searched in order:
331 $dl_library_path[0], [1], ... etc
333 @dl_library_path is initialised to hold the list of 'normal' directories
334 (F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
335 ensure portability across a wide range of platforms.
337 @dl_library_path should also be initialised with any other directories
338 that can be determined from the environment at runtime (such as
339 LD_LIBRARY_PATH for SunOS).
341 After initialisation @dl_library_path can be manipulated by an
342 application using push and unshift before calling dl_findfile().
343 Unshift can be used to add directories to the front of the search order
344 either to save search time or to override libraries with the same name
345 in the 'normal' directories.
347 The load function that dl_load_file() calls may require an absolute
348 pathname. The dl_findfile() function and @dl_library_path can be
349 used to search for and return the absolute pathname for the
350 library/object that you wish to load.
352 =item @dl_resolve_using
354 A list of additional libraries or other shared objects which can be
355 used to resolve any undefined symbols that might be generated by a
356 later call to load_file().
358 This is only required on some platforms which do not handle dependent
359 libraries automatically. For example the Socket Perl extension library
360 (F<auto/Socket/Socket.so>) contains references to many socket functions
361 which need to be resolved when it's loaded. Most platforms will
362 automatically know where to find the 'dependent' library (e.g.,
363 F</usr/lib/libsocket.so>). A few platforms need to to be told the location
364 of the dependent library explicitly. Use @dl_resolve_using for this.
368 @dl_resolve_using = dl_findfile('-lsocket');
370 =item @dl_require_symbols
372 A list of one or more symbol names that are in the library/object file
373 to be dynamically loaded. This is only required on some platforms.
379 $message = dl_error();
381 Error message text from the last failed DynaLoader function. Note
382 that, similar to errno in unix, a successful function call does not
385 Implementations should detect the error as soon as it occurs in any of
386 the other functions and save the corresponding message for later
387 retrieval. This will avoid problems on some platforms (such as SunOS)
388 where the error message is very temporary (e.g., dlerror()).
392 Internal debugging messages are enabled when $dl_debug is set true.
393 Currently setting $dl_debug only affects the Perl side of the
394 DynaLoader. These messages should help an application developer to
395 resolve any DynaLoader usage problems.
397 $dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
399 For the DynaLoader developer/porter there is a similar debugging
400 variable added to the C code (see dlutils.c) and enabled if Perl was
401 built with the B<-DDEBUGGING> flag. This can also be set via the
402 PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
409 @filepaths = dl_findfile(@names)
411 Determine the full paths (including file suffix) of one or more
412 loadable files given their generic names and optionally one or more
413 directories. Searches directories in @dl_library_path by default and
414 returns an empty list if no files were found.
416 Names can be specified in a variety of platform independent forms. Any
417 names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
418 an appropriate suffix for the platform.
420 If a name does not already have a suitable prefix and/or suffix then
421 the corresponding file will be searched for by trying combinations of
422 prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
425 If any directories are included in @names they are searched before
426 @dl_library_path. Directories may be specified as B<-Ldir>. Any other
427 names are treated as filenames to be searched for.
429 Using arguments of the form C<-Ldir> and C<-lname> is recommended.
433 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
436 =item dl_expandspec()
440 $filepath = dl_expandspec($spec)
442 Some unusual systems, such as VMS, require special filename handling in
443 order to deal with symbolic names for files (i.e., VMS's Logical Names).
445 To support these systems a dl_expandspec() function can be implemented
446 either in the F<dl_*.xs> file or code can be added to the autoloadable
447 dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
454 $libref = dl_load_file($filename)
456 Dynamically load $filename, which must be the path to a shared object
457 or library. An opaque 'library reference' is returned as a handle for
458 the loaded object. Returns undef on error.
460 (On systems that provide a handle for the loaded object such as SunOS
461 and HPUX, $libref will be that handle. On other systems $libref will
462 typically be $filename or a pointer to a buffer containing $filename.
463 The application should not examine or alter $libref in any way.)
465 This is function that does the real work. It should use the current
466 values of @dl_require_symbols and @dl_resolve_using if required.
468 SunOS: dlopen($filename)
469 HP-UX: shl_load($filename)
470 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
471 NeXT: rld_load($filename, @dl_resolve_using)
472 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
475 =item dl_find_symbol()
479 $symref = dl_find_symbol($libref, $symbol)
481 Return the address of the symbol $symbol or C<undef> if not found. If the
482 target system has separate functions to search for symbols of different
483 types then dl_find_symbol() should search for function symbols first and
486 The exact manner in which the address is returned in $symref is not
487 currently defined. The only initial requirement is that $symref can
488 be passed to, and understood by, dl_install_xsub().
490 SunOS: dlsym($libref, $symbol)
491 HP-UX: shl_findsym($libref, $symbol)
492 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
493 NeXT: rld_lookup("_$symbol")
494 VMS: lib$find_image_symbol($libref,$symbol)
497 =item dl_undef_symbols()
501 @symbols = dl_undef_symbols()
503 Return a list of symbol names which remain undefined after load_file().
504 Returns C<()> if not known. Don't worry if your platform does not provide
505 a mechanism for this. Most do not need it and hence do not provide it,
506 they just return an empty list.
509 =item dl_install_xsub()
513 dl_install_xsub($perl_name, $symref [, $filename])
515 Create a new Perl external subroutine named $perl_name using $symref as
516 a pointer to the function which implements the routine. This is simply
517 a direct call to newXSUB(). Returns a reference to the installed
520 The $filename parameter is used by Perl to identify the source file for
521 the function if required by die(), caller() or the debugger. If
522 $filename is not defined then "DynaLoader" will be used.
531 This is the normal entry point for automatic dynamic loading in Perl.
533 It performs the following actions:
539 locates an auto/$module directory by searching @INC
543 uses dl_findfile() to determine the filename to load
547 sets @dl_require_symbols to C<("boot_$module")>
551 executes an F<auto/$module/$module.bs> file if it exists
552 (typically used to add to @dl_resolve_using any files which
553 are required to load the module on the current platform)
557 calls dl_load_file() to load the file
561 calls dl_undef_symbols() and warns if any symbols are undefined
565 calls dl_find_symbol() for "boot_$module"
569 calls dl_install_xsub() to install it as "${module}::bootstrap"
573 calls &{"${module}::bootstrap"} to bootstrap the module (actually
574 it uses the function reference returned by dl_install_xsub for speed)
583 Tim Bunce, 11 August 1994.
585 This interface is based on the work and comments of (in no particular
586 order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
587 Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
589 Larry Wall designed the elegant inherited bootstrap mechanism and
590 implemented the first Perl 5 dynamic loader using it.