6 our($VERSION, $AUTOLOAD);
14 $is_dosish = $^O eq 'dos' || $^O eq 'os2' || $^O eq 'MSWin32' || $^O eq 'NetWare';
15 $is_epoc = $^O eq 'epoc';
16 $is_vms = $^O eq 'VMS';
17 $is_macos = $^O eq 'MacOS';
23 my $filename = AutoLoader::find_filename( $sub );
26 local $!; # Do not munge the value.
27 eval { local $SIG{__DIE__}; require $filename };
29 if (substr($sub,-9) eq '::DESTROY') {
33 } elsif ($@ =~ /^Can't locate/) {
34 # The load might just have failed because the filename was too
35 # long for some old SVR3 systems which treat long names as errors.
36 # If we can successfully truncate a long name then it's worth a go.
37 # There is a slight risk that we could pick up the wrong file here
38 # but autosplit should have warned about that when splitting.
39 if ($filename =~ s/(\w{12,})\.al$/substr($1,0,11).".al"/e){
40 eval { local $SIG{__DIE__}; require $filename };
55 my ($self, $method) = @_;
57 my $parent = $self->SUPER::can( $method );
58 return $parent if $parent;
60 my $package = ref( $self ) || $self;
61 my $filename = AutoLoader::find_filename( $package . '::' . $method );
63 return unless eval { require $filename };
66 return \&{ $package . '::' . $method };
72 # Braces used to preserve $1 et al.
74 # Try to find the autoloaded file from the package-qualified
75 # name of the sub. e.g., if the sub needed is
76 # Getopt::Long::GetOptions(), then $INC{Getopt/Long.pm} is
77 # something like '/usr/lib/perl5/Getopt/Long.pm', and the
78 # autoload file is '/usr/lib/perl5/auto/Getopt/Long/GetOptions.al'.
80 # However, if @INC is a relative path, this might not work. If,
81 # for example, @INC = ('lib'), then $INC{Getopt/Long.pm} is
82 # 'lib/Getopt/Long.pm', and we want to require
83 # 'auto/Getopt/Long/GetOptions.al' (without the leading 'lib').
84 # In this case, we simple prepend the 'auto/' and let the
85 # C<require> take care of the searching for us.
87 my ($pkg,$func) = ($sub =~ /(.*)::([^:]+)$/);
89 if (defined($filename = $INC{"$pkg.pm"})) {
93 unless $filename =~ s#^(.*)$pkg\.pm\z#$1auto:$pkg:$func.al#s;
96 unless $filename =~ s#^(.*)$pkg\.pm\z#$1auto/$pkg/$func.al#s;
99 # if the file exists, then make sure that it is a
100 # a fully anchored path (i.e either '/usr/lib/auto/foo/bar.al',
101 # or './lib/auto/foo/bar.al'. This avoids C<require> searching
102 # (and failing) to find the 'lib/auto/foo/bar.al' because it
103 # looked for 'lib/lib/auto/foo/bar.al', given @INC = ('lib').
105 if (defined $filename and -r $filename) {
106 unless ($filename =~ m|^/|s) {
108 unless ($filename =~ m{^([a-z]:)?[\\/]}is) {
109 if ($^O ne 'NetWare') {
110 $filename = "./$filename";
112 $filename = "$filename";
117 unless ($filename =~ m{^([a-z?]:)?[\\/]}is) {
118 $filename = "./$filename";
122 # XXX todo by VMSmiths
123 $filename = "./$filename";
126 $filename = "./$filename";
134 unless (defined $filename) {
135 # let C<require> do the searching
136 $filename = "auto/$sub.al";
137 $filename =~ s#::#/#g;
145 my $callpkg = caller;
148 # Export symbols, but not by accident of inheritance.
151 if ($pkg eq 'AutoLoader') {
152 if ( @_ and $_[0] =~ /^&?AUTOLOAD$/ ) {
154 *{ $callpkg . '::AUTOLOAD' } = \&AUTOLOAD;
155 *{ $callpkg . '::can' } = \&can;
160 # Try to find the autosplit index file. Eg., if the call package
161 # is POSIX, then $INC{POSIX.pm} is something like
162 # '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in
163 # '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that.
165 # However, if @INC is a relative path, this might not work. If,
166 # for example, @INC = ('lib'), then
167 # $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require
168 # 'auto/POSIX/autosplit.ix' (without the leading 'lib').
171 (my $calldir = $callpkg) =~ s#::#/#g;
172 my $path = $INC{$calldir . '.pm'};
173 if (defined($path)) {
174 # Try absolute path name.
176 (my $malldir = $calldir) =~ tr#/#:#;
177 $path =~ s#^(.*)$malldir\.pm\z#$1auto:$malldir:autosplit.ix#s;
179 $path =~ s#^(.*)$calldir\.pm\z#$1auto/$calldir/autosplit.ix#;
182 eval { require $path; };
183 # If that failed, try relative path with normal @INC searching.
185 $path ="auto/$calldir/autosplit.ix";
186 eval { require $path; };
197 my $callpkg = caller;
201 for my $exported (qw( AUTOLOAD can )) {
202 my $symname = $callpkg . '::' . $exported;
203 undef *{ $symname } if \&{ $symname } == \&{ $exported };
204 *{ $symname } = \&{ $symname };
214 AutoLoader - load subroutines only on demand
219 use AutoLoader 'AUTOLOAD'; # import the default AUTOLOAD subroutine
222 use AutoLoader; # don't import AUTOLOAD, define our own
225 $AutoLoader::AUTOLOAD = "...";
226 goto &AutoLoader::AUTOLOAD;
231 The B<AutoLoader> module works with the B<AutoSplit> module and the
232 C<__END__> token to defer the loading of some subroutines until they are
233 used rather than loading them all at once.
235 To use B<AutoLoader>, the author of a module has to place the
236 definitions of subroutines to be autoloaded after an C<__END__> token.
237 (See L<perldata>.) The B<AutoSplit> module can then be run manually to
238 extract the definitions into individual files F<auto/funcname.al>.
240 B<AutoLoader> implements an AUTOLOAD subroutine. When an undefined
241 subroutine in is called in a client module of B<AutoLoader>,
242 B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a
243 file with a name related to the location of the file from which the
244 client module was read. As an example, if F<POSIX.pm> is located in
245 F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl
246 subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where
247 the C<.al> file has the same name as the subroutine, sans package. If
248 such a file exists, AUTOLOAD will read and evaluate it,
249 thus (presumably) defining the needed subroutine. AUTOLOAD will then
250 C<goto> the newly defined subroutine.
252 Once this process completes for a given function, it is defined, so
253 future calls to the subroutine will bypass the AUTOLOAD mechanism.
255 =head2 Subroutine Stubs
257 In order for object method lookup and/or prototype checking to operate
258 correctly even when methods have not yet been defined it is necessary to
259 "forward declare" each subroutine (as in C<sub NAME;>). See
260 L<perlsub/"SYNOPSIS">. Such forward declaration creates "subroutine
261 stubs", which are place holders with no code.
263 The AutoSplit and B<AutoLoader> modules automate the creation of forward
264 declarations. The AutoSplit module creates an 'index' file containing
265 forward declarations of all the AutoSplit subroutines. When the
266 AutoLoader module is 'use'd it loads these declarations into its callers
269 Because of this mechanism it is important that B<AutoLoader> is always
270 C<use>d and not C<require>d.
272 =head2 Using B<AutoLoader>'s AUTOLOAD Subroutine
274 In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must>
275 explicitly import it:
277 use AutoLoader 'AUTOLOAD';
279 =head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine
281 Some modules, mainly extensions, provide their own AUTOLOAD subroutines.
282 They typically need to check for some special cases (such as constants)
283 and then fallback to B<AutoLoader>'s AUTOLOAD for the rest.
285 Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine.
286 Instead, they should define their own AUTOLOAD subroutines along these
294 (my $constname = $sub) =~ s/.*:://;
295 my $val = constant($constname, @_ ? $_[0] : 0);
297 if ($! =~ /Invalid/ || $!{EINVAL}) {
298 $AutoLoader::AUTOLOAD = $sub;
299 goto &AutoLoader::AUTOLOAD;
302 croak "Your vendor has not defined constant $constname";
305 *$sub = sub { $val }; # same as: eval "sub $sub { $val }";
309 If any module's own AUTOLOAD subroutine has no need to fallback to the
310 AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit
311 subroutines), then that module should not use B<AutoLoader> at all.
313 =head2 Package Lexicals
315 Package lexicals declared with C<my> in the main block of a package
316 using B<AutoLoader> will not be visible to auto-loaded subroutines, due to
317 the fact that the given scope ends at the C<__END__> marker. A module
318 using such variables as package globals will not work properly under the
321 The C<vars> pragma (see L<perlmod/"vars">) may be used in such
322 situations as an alternative to explicitly qualifying all globals with
323 the package namespace. Variables pre-declared with this pragma will be
324 visible to any autoloaded routines (but will not be invisible outside
325 the package, unfortunately).
327 =head2 Not Using AutoLoader
329 You can stop using AutoLoader by simply
333 =head2 B<AutoLoader> vs. B<SelfLoader>
335 The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the
336 loading of subroutines.
338 B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>.
339 While this avoids the use of a hierarchy of disk files and the
340 associated open/close for each routine loaded, B<SelfLoader> suffers a
341 startup speed disadvantage in the one-time parsing of the lines after
342 C<__DATA__>, after which routines are cached. B<SelfLoader> can also
343 handle multiple packages in a file.
345 B<AutoLoader> only reads code as it is requested, and in many cases
346 should be faster, but requires a mechanism like B<AutoSplit> be used to
347 create the individual files. L<ExtUtils::MakeMaker> will invoke
348 B<AutoSplit> automatically if B<AutoLoader> is used in a module source
353 AutoLoaders prior to Perl 5.002 had a slightly different interface. Any
354 old modules which use B<AutoLoader> should be changed to the new calling
355 style. Typically this just means changing a require to a use, adding
356 the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader>
359 On systems with restrictions on file name length, the file corresponding
360 to a subroutine may have a shorter name that the routine itself. This
361 can lead to conflicting file names. The I<AutoSplit> package warns of
362 these potential conflicts when used to split a module.
364 AutoLoader may fail to find the autosplit files (or even find the wrong
365 ones) in cases where C<@INC> contains relative paths, B<and> the program
370 L<SelfLoader> - an autoloader that doesn't use external files.
374 C<AutoLoader> is maintained by the perl5-porters. Please direct
375 any questions to the canonical mailing list. Anything that
376 is applicable to the CPAN release can be sent to its maintainer,
379 Author and Maintainer: The Perl5-Porters <perl5-porters@perl.org>
381 Maintainer of the CPAN release: Steffen Mueller <smueller@cpan.org>
383 =head1 COPYRIGHT AND LICENSE
385 This package has been part of the perl core since the first release
386 of perl5. It has been released separately to CPAN so older installations
387 can benefit from bug fixes.
389 This package has the same copyright and license as the perl core:
391 Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999,
392 2000, 2001, 2002, 2003, 2004, 2005, 2006 by Larry Wall and others
396 This program is free software; you can redistribute it and/or modify
397 it under the terms of either:
399 a) the GNU General Public License as published by the Free
400 Software Foundation; either version 1, or (at your option) any
403 b) the "Artistic License" which comes with this Kit.
405 This program is distributed in the hope that it will be useful,
406 but WITHOUT ANY WARRANTY; without even the implied warranty of
407 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either
408 the GNU General Public License or the Artistic License for more details.
410 You should have received a copy of the Artistic License with this
411 Kit, in the file named "Artistic". If not, I'll be glad to provide one.
413 You should also have received a copy of the GNU General Public License
414 along with this program in the file named "Copying". If not, write to the
415 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
416 02111-1307, USA or visit their web page on the internet at
417 http://www.gnu.org/copyleft/gpl.html.
419 For those of you that choose to use the GNU General Public License,
420 my interpretation of the GNU General Public License is that no Perl
421 script falls under the terms of the GPL unless you explicitly put
422 said script under the terms of the GPL yourself. Furthermore, any
423 object code linked with perl does not automatically fall under the
424 terms of the GPL, provided such object code only adds definitions
425 of subroutines and variables, and does not otherwise impair the
426 resulting interpreter from executing any standard Perl script. I
427 consider linking in C subroutines in this manner to be the moral
428 equivalent of defining subroutines in the Perl language itself. You
429 may sell such an object file as proprietary provided that you provide
430 or offer to provide the Perl source, as specified by the GNU General
431 Public License. (This is merely an alternate way of specifying input
432 to the program.) You may also sell a binary produced by the dumping of
433 a running Perl script that belongs to you, provided that you provide or
434 offer to provide the Perl source as specified by the GPL. (The
435 fact that a Perl interpreter and your code are in the same binary file
436 is, in this case, a form of mere aggregation.) This is my interpretation
437 of the GPL. If you still have concerns or difficulties understanding
438 my intent, feel free to contact me. Of course, the Artistic License
439 spells all this out for your protection, so you may prefer to use that.