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 };
57 # Braces used to preserve $1 et al.
59 # Try to find the autoloaded file from the package-qualified
60 # name of the sub. e.g., if the sub needed is
61 # Getopt::Long::GetOptions(), then $INC{Getopt/Long.pm} is
62 # something like '/usr/lib/perl5/Getopt/Long.pm', and the
63 # autoload file is '/usr/lib/perl5/auto/Getopt/Long/GetOptions.al'.
65 # However, if @INC is a relative path, this might not work. If,
66 # for example, @INC = ('lib'), then $INC{Getopt/Long.pm} is
67 # 'lib/Getopt/Long.pm', and we want to require
68 # 'auto/Getopt/Long/GetOptions.al' (without the leading 'lib').
69 # In this case, we simple prepend the 'auto/' and let the
70 # C<require> take care of the searching for us.
72 my ($pkg,$func) = ($sub =~ /(.*)::([^:]+)$/);
74 if (defined($filename = $INC{"$pkg.pm"})) {
78 unless $filename =~ s#^(.*)$pkg\.pm\z#$1auto:$pkg:$func.al#s;
81 unless $filename =~ s#^(.*)$pkg\.pm\z#$1auto/$pkg/$func.al#s;
84 # if the file exists, then make sure that it is a
85 # a fully anchored path (i.e either '/usr/lib/auto/foo/bar.al',
86 # or './lib/auto/foo/bar.al'. This avoids C<require> searching
87 # (and failing) to find the 'lib/auto/foo/bar.al' because it
88 # looked for 'lib/lib/auto/foo/bar.al', given @INC = ('lib').
90 if (defined $filename and -r $filename) {
91 unless ($filename =~ m|^/|s) {
93 unless ($filename =~ m{^([a-z]:)?[\\/]}is) {
94 if ($^O ne 'NetWare') {
95 $filename = "./$filename";
97 $filename = "$filename";
102 unless ($filename =~ m{^([a-z?]:)?[\\/]}is) {
103 $filename = "./$filename";
107 # XXX todo by VMSmiths
108 $filename = "./$filename";
111 $filename = "./$filename";
119 unless (defined $filename) {
120 # let C<require> do the searching
121 $filename = "auto/$sub.al";
122 $filename =~ s#::#/#g;
130 my $callpkg = caller;
133 # Export symbols, but not by accident of inheritance.
136 if ($pkg eq 'AutoLoader') {
137 if ( @_ and $_[0] =~ /^&?AUTOLOAD$/ ) {
139 *{ $callpkg . '::AUTOLOAD' } = \&AUTOLOAD;
144 # Try to find the autosplit index file. Eg., if the call package
145 # is POSIX, then $INC{POSIX.pm} is something like
146 # '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in
147 # '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that.
149 # However, if @INC is a relative path, this might not work. If,
150 # for example, @INC = ('lib'), then
151 # $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require
152 # 'auto/POSIX/autosplit.ix' (without the leading 'lib').
155 (my $calldir = $callpkg) =~ s#::#/#g;
156 my $path = $INC{$calldir . '.pm'};
157 if (defined($path)) {
158 # Try absolute path name, but only eval it if the
159 # transformation from module path to autosplit.ix path
163 (my $malldir = $calldir) =~ tr#/#:#;
164 $replaced_okay = ($path =~ s#^(.*)$malldir\.pm\z#$1auto:$malldir:autosplit.ix#s);
166 $replaced_okay = ($path =~ s#^(.*)$calldir\.pm\z#$1auto/$calldir/autosplit.ix#);
169 eval { require $path; } if $replaced_okay;
170 # If that failed, try relative path with normal @INC searching.
171 if (!$replaced_okay or $@) {
172 $path ="auto/$calldir/autosplit.ix";
173 eval { require $path; };
184 my $callpkg = caller;
188 for my $exported (qw( AUTOLOAD )) {
189 my $symname = $callpkg . '::' . $exported;
190 undef *{ $symname } if \&{ $symname } == \&{ $exported };
191 *{ $symname } = \&{ $symname };
201 AutoLoader - load subroutines only on demand
206 use AutoLoader 'AUTOLOAD'; # import the default AUTOLOAD subroutine
209 use AutoLoader; # don't import AUTOLOAD, define our own
212 $AutoLoader::AUTOLOAD = "...";
213 goto &AutoLoader::AUTOLOAD;
218 The B<AutoLoader> module works with the B<AutoSplit> module and the
219 C<__END__> token to defer the loading of some subroutines until they are
220 used rather than loading them all at once.
222 To use B<AutoLoader>, the author of a module has to place the
223 definitions of subroutines to be autoloaded after an C<__END__> token.
224 (See L<perldata>.) The B<AutoSplit> module can then be run manually to
225 extract the definitions into individual files F<auto/funcname.al>.
227 B<AutoLoader> implements an AUTOLOAD subroutine. When an undefined
228 subroutine in is called in a client module of B<AutoLoader>,
229 B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a
230 file with a name related to the location of the file from which the
231 client module was read. As an example, if F<POSIX.pm> is located in
232 F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl
233 subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where
234 the C<.al> file has the same name as the subroutine, sans package. If
235 such a file exists, AUTOLOAD will read and evaluate it,
236 thus (presumably) defining the needed subroutine. AUTOLOAD will then
237 C<goto> the newly defined subroutine.
239 Once this process completes for a given function, it is defined, so
240 future calls to the subroutine will bypass the AUTOLOAD mechanism.
242 =head2 Subroutine Stubs
244 In order for object method lookup and/or prototype checking to operate
245 correctly even when methods have not yet been defined it is necessary to
246 "forward declare" each subroutine (as in C<sub NAME;>). See
247 L<perlsub/"SYNOPSIS">. Such forward declaration creates "subroutine
248 stubs", which are place holders with no code.
250 The AutoSplit and B<AutoLoader> modules automate the creation of forward
251 declarations. The AutoSplit module creates an 'index' file containing
252 forward declarations of all the AutoSplit subroutines. When the
253 AutoLoader module is 'use'd it loads these declarations into its callers
256 Because of this mechanism it is important that B<AutoLoader> is always
257 C<use>d and not C<require>d.
259 =head2 Using B<AutoLoader>'s AUTOLOAD Subroutine
261 In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must>
262 explicitly import it:
264 use AutoLoader 'AUTOLOAD';
266 =head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine
268 Some modules, mainly extensions, provide their own AUTOLOAD subroutines.
269 They typically need to check for some special cases (such as constants)
270 and then fallback to B<AutoLoader>'s AUTOLOAD for the rest.
272 Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine.
273 Instead, they should define their own AUTOLOAD subroutines along these
281 (my $constname = $sub) =~ s/.*:://;
282 my $val = constant($constname, @_ ? $_[0] : 0);
284 if ($! =~ /Invalid/ || $!{EINVAL}) {
285 $AutoLoader::AUTOLOAD = $sub;
286 goto &AutoLoader::AUTOLOAD;
289 croak "Your vendor has not defined constant $constname";
292 *$sub = sub { $val }; # same as: eval "sub $sub { $val }";
296 If any module's own AUTOLOAD subroutine has no need to fallback to the
297 AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit
298 subroutines), then that module should not use B<AutoLoader> at all.
300 =head2 Package Lexicals
302 Package lexicals declared with C<my> in the main block of a package
303 using B<AutoLoader> will not be visible to auto-loaded subroutines, due to
304 the fact that the given scope ends at the C<__END__> marker. A module
305 using such variables as package globals will not work properly under the
308 The C<vars> pragma (see L<perlmod/"vars">) may be used in such
309 situations as an alternative to explicitly qualifying all globals with
310 the package namespace. Variables pre-declared with this pragma will be
311 visible to any autoloaded routines (but will not be invisible outside
312 the package, unfortunately).
314 =head2 Not Using AutoLoader
316 You can stop using AutoLoader by simply
320 =head2 B<AutoLoader> vs. B<SelfLoader>
322 The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the
323 loading of subroutines.
325 B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>.
326 While this avoids the use of a hierarchy of disk files and the
327 associated open/close for each routine loaded, B<SelfLoader> suffers a
328 startup speed disadvantage in the one-time parsing of the lines after
329 C<__DATA__>, after which routines are cached. B<SelfLoader> can also
330 handle multiple packages in a file.
332 B<AutoLoader> only reads code as it is requested, and in many cases
333 should be faster, but requires a mechanism like B<AutoSplit> be used to
334 create the individual files. L<ExtUtils::MakeMaker> will invoke
335 B<AutoSplit> automatically if B<AutoLoader> is used in a module source
340 AutoLoaders prior to Perl 5.002 had a slightly different interface. Any
341 old modules which use B<AutoLoader> should be changed to the new calling
342 style. Typically this just means changing a require to a use, adding
343 the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader>
346 On systems with restrictions on file name length, the file corresponding
347 to a subroutine may have a shorter name that the routine itself. This
348 can lead to conflicting file names. The I<AutoSplit> package warns of
349 these potential conflicts when used to split a module.
351 AutoLoader may fail to find the autosplit files (or even find the wrong
352 ones) in cases where C<@INC> contains relative paths, B<and> the program
357 L<SelfLoader> - an autoloader that doesn't use external files.
361 C<AutoLoader> is maintained by the perl5-porters. Please direct
362 any questions to the canonical mailing list. Anything that
363 is applicable to the CPAN release can be sent to its maintainer,
366 Author and Maintainer: The Perl5-Porters <perl5-porters@perl.org>
368 Maintainer of the CPAN release: Steffen Mueller <smueller@cpan.org>
370 =head1 COPYRIGHT AND LICENSE
372 This package has been part of the perl core since the first release
373 of perl5. It has been released separately to CPAN so older installations
374 can benefit from bug fixes.
376 This package has the same copyright and license as the perl core:
378 Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999,
379 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
380 by Larry Wall and others
384 This program is free software; you can redistribute it and/or modify
385 it under the terms of either:
387 a) the GNU General Public License as published by the Free
388 Software Foundation; either version 1, or (at your option) any
391 b) the "Artistic License" which comes with this Kit.
393 This program is distributed in the hope that it will be useful,
394 but WITHOUT ANY WARRANTY; without even the implied warranty of
395 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either
396 the GNU General Public License or the Artistic License for more details.
398 You should have received a copy of the Artistic License with this
399 Kit, in the file named "Artistic". If not, I'll be glad to provide one.
401 You should also have received a copy of the GNU General Public License
402 along with this program in the file named "Copying". If not, write to the
403 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
404 02111-1307, USA or visit their web page on the internet at
405 http://www.gnu.org/copyleft/gpl.html.
407 For those of you that choose to use the GNU General Public License,
408 my interpretation of the GNU General Public License is that no Perl
409 script falls under the terms of the GPL unless you explicitly put
410 said script under the terms of the GPL yourself. Furthermore, any
411 object code linked with perl does not automatically fall under the
412 terms of the GPL, provided such object code only adds definitions
413 of subroutines and variables, and does not otherwise impair the
414 resulting interpreter from executing any standard Perl script. I
415 consider linking in C subroutines in this manner to be the moral
416 equivalent of defining subroutines in the Perl language itself. You
417 may sell such an object file as proprietary provided that you provide
418 or offer to provide the Perl source, as specified by the GNU General
419 Public License. (This is merely an alternate way of specifying input
420 to the program.) You may also sell a binary produced by the dumping of
421 a running Perl script that belongs to you, provided that you provide or
422 offer to provide the Perl source as specified by the GPL. (The
423 fact that a Perl interpreter and your code are in the same binary file
424 is, in this case, a form of mere aggregation.) This is my interpretation
425 of the GPL. If you still have concerns or difficulties understanding
426 my intent, feel free to contact me. Of course, the Artistic License
427 spells all this out for your protection, so you may prefer to use that.