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"})) {
92 $filename =~ s#^(.*)$pkg\.pm\z#$1auto:$pkg:$func.al#s;
94 $filename =~ s#^(.*)$pkg\.pm\z#$1auto/$pkg/$func.al#s;
97 # if the file exists, then make sure that it is a
98 # a fully anchored path (i.e either '/usr/lib/auto/foo/bar.al',
99 # or './lib/auto/foo/bar.al'. This avoids C<require> searching
100 # (and failing) to find the 'lib/auto/foo/bar.al' because it
101 # looked for 'lib/lib/auto/foo/bar.al', given @INC = ('lib').
104 unless ($filename =~ m|^/|s) {
106 unless ($filename =~ m{^([a-z]:)?[\\/]}is) {
107 if ($^O ne 'NetWare') {
108 $filename = "./$filename";
110 $filename = "$filename";
115 unless ($filename =~ m{^([a-z?]:)?[\\/]}is) {
116 $filename = "./$filename";
120 # XXX todo by VMSmiths
121 $filename = "./$filename";
124 $filename = "./$filename";
132 unless (defined $filename) {
133 # let C<require> do the searching
134 $filename = "auto/$sub.al";
135 $filename =~ s#::#/#g;
143 my $callpkg = caller;
146 # Export symbols, but not by accident of inheritance.
149 if ($pkg eq 'AutoLoader') {
150 if ( @_ and $_[0] =~ /^&?AUTOLOAD$/ ) {
152 *{ $callpkg . '::AUTOLOAD' } = \&AUTOLOAD;
153 *{ $callpkg . '::can' } = \&can;
158 # Try to find the autosplit index file. Eg., if the call package
159 # is POSIX, then $INC{POSIX.pm} is something like
160 # '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in
161 # '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that.
163 # However, if @INC is a relative path, this might not work. If,
164 # for example, @INC = ('lib'), then
165 # $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require
166 # 'auto/POSIX/autosplit.ix' (without the leading 'lib').
169 (my $calldir = $callpkg) =~ s#::#/#g;
170 my $path = $INC{$calldir . '.pm'};
171 if (defined($path)) {
172 # Try absolute path name.
174 (my $malldir = $calldir) =~ tr#/#:#;
175 $path =~ s#^(.*)$malldir\.pm\z#$1auto:$malldir:autosplit.ix#s;
177 $path =~ s#^(.*)$calldir\.pm\z#$1auto/$calldir/autosplit.ix#;
180 eval { require $path; };
181 # If that failed, try relative path with normal @INC searching.
183 $path ="auto/$calldir/autosplit.ix";
184 eval { require $path; };
195 my $callpkg = caller;
199 for my $exported (qw( AUTOLOAD can )) {
200 my $symname = $callpkg . '::' . $exported;
201 undef *{ $symname } if \&{ $symname } == \&{ $exported };
202 *{ $symname } = \&{ $symname };
212 AutoLoader - load subroutines only on demand
217 use AutoLoader 'AUTOLOAD'; # import the default AUTOLOAD subroutine
220 use AutoLoader; # don't import AUTOLOAD, define our own
223 $AutoLoader::AUTOLOAD = "...";
224 goto &AutoLoader::AUTOLOAD;
229 The B<AutoLoader> module works with the B<AutoSplit> module and the
230 C<__END__> token to defer the loading of some subroutines until they are
231 used rather than loading them all at once.
233 To use B<AutoLoader>, the author of a module has to place the
234 definitions of subroutines to be autoloaded after an C<__END__> token.
235 (See L<perldata>.) The B<AutoSplit> module can then be run manually to
236 extract the definitions into individual files F<auto/funcname.al>.
238 B<AutoLoader> implements an AUTOLOAD subroutine. When an undefined
239 subroutine in is called in a client module of B<AutoLoader>,
240 B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a
241 file with a name related to the location of the file from which the
242 client module was read. As an example, if F<POSIX.pm> is located in
243 F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl
244 subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where
245 the C<.al> file has the same name as the subroutine, sans package. If
246 such a file exists, AUTOLOAD will read and evaluate it,
247 thus (presumably) defining the needed subroutine. AUTOLOAD will then
248 C<goto> the newly defined subroutine.
250 Once this process completes for a given function, it is defined, so
251 future calls to the subroutine will bypass the AUTOLOAD mechanism.
253 =head2 Subroutine Stubs
255 In order for object method lookup and/or prototype checking to operate
256 correctly even when methods have not yet been defined it is necessary to
257 "forward declare" each subroutine (as in C<sub NAME;>). See
258 L<perlsub/"SYNOPSIS">. Such forward declaration creates "subroutine
259 stubs", which are place holders with no code.
261 The AutoSplit and B<AutoLoader> modules automate the creation of forward
262 declarations. The AutoSplit module creates an 'index' file containing
263 forward declarations of all the AutoSplit subroutines. When the
264 AutoLoader module is 'use'd it loads these declarations into its callers
267 Because of this mechanism it is important that B<AutoLoader> is always
268 C<use>d and not C<require>d.
270 =head2 Using B<AutoLoader>'s AUTOLOAD Subroutine
272 In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must>
273 explicitly import it:
275 use AutoLoader 'AUTOLOAD';
277 =head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine
279 Some modules, mainly extensions, provide their own AUTOLOAD subroutines.
280 They typically need to check for some special cases (such as constants)
281 and then fallback to B<AutoLoader>'s AUTOLOAD for the rest.
283 Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine.
284 Instead, they should define their own AUTOLOAD subroutines along these
292 (my $constname = $sub) =~ s/.*:://;
293 my $val = constant($constname, @_ ? $_[0] : 0);
295 if ($! =~ /Invalid/ || $!{EINVAL}) {
296 $AutoLoader::AUTOLOAD = $sub;
297 goto &AutoLoader::AUTOLOAD;
300 croak "Your vendor has not defined constant $constname";
303 *$sub = sub { $val }; # same as: eval "sub $sub { $val }";
307 If any module's own AUTOLOAD subroutine has no need to fallback to the
308 AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit
309 subroutines), then that module should not use B<AutoLoader> at all.
311 =head2 Package Lexicals
313 Package lexicals declared with C<my> in the main block of a package
314 using B<AutoLoader> will not be visible to auto-loaded subroutines, due to
315 the fact that the given scope ends at the C<__END__> marker. A module
316 using such variables as package globals will not work properly under the
319 The C<vars> pragma (see L<perlmod/"vars">) may be used in such
320 situations as an alternative to explicitly qualifying all globals with
321 the package namespace. Variables pre-declared with this pragma will be
322 visible to any autoloaded routines (but will not be invisible outside
323 the package, unfortunately).
325 =head2 Not Using AutoLoader
327 You can stop using AutoLoader by simply
331 =head2 B<AutoLoader> vs. B<SelfLoader>
333 The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the
334 loading of subroutines.
336 B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>.
337 While this avoids the use of a hierarchy of disk files and the
338 associated open/close for each routine loaded, B<SelfLoader> suffers a
339 startup speed disadvantage in the one-time parsing of the lines after
340 C<__DATA__>, after which routines are cached. B<SelfLoader> can also
341 handle multiple packages in a file.
343 B<AutoLoader> only reads code as it is requested, and in many cases
344 should be faster, but requires a mechanism like B<AutoSplit> be used to
345 create the individual files. L<ExtUtils::MakeMaker> will invoke
346 B<AutoSplit> automatically if B<AutoLoader> is used in a module source
351 AutoLoaders prior to Perl 5.002 had a slightly different interface. Any
352 old modules which use B<AutoLoader> should be changed to the new calling
353 style. Typically this just means changing a require to a use, adding
354 the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader>
357 On systems with restrictions on file name length, the file corresponding
358 to a subroutine may have a shorter name that the routine itself. This
359 can lead to conflicting file names. The I<AutoSplit> package warns of
360 these potential conflicts when used to split a module.
362 AutoLoader may fail to find the autosplit files (or even find the wrong
363 ones) in cases where C<@INC> contains relative paths, B<and> the program
368 L<SelfLoader> - an autoloader that doesn't use external files.