Devel-FindRef/FindRef.pm

package Devel::FindRef;

use strict;

use XSLoader;


BEGIN {
   our $VERSION = '0.2';
   XSLoader::load __PACKAGE__, $VERSION;
}

=head1 NAME

Devel::FindRef - where is that reference to my scalar hiding?

=head1 SYNOPSIS

  use Devel::FindRef;

=head1 DESCRIPTION

Tracking down reference problems (e.g. you expect some object to be
destroyed, but there are still references to it that keep it alive) can be
very hard. Fortunately, perl keeps track of all its values, so tracking
references "backwards" is usually possible.

The C<track> function can help track down some of those references back to
the variables containing them.

For example, for this fragment:

   package Test;           
                         
   our $var = "hi\n";
   my $x = \$var;      
   our %hash = (ukukey => \$var);
   our $hash2 = {ukukey2 => \$var};
                           
   sub testsub {             
      my $local = $hash2;      
      print Devel::FindRef::track \$var;
   }                             
                                   
   testsub;                        

The output is as follows (or similar to this, in case I forget to update
the manpage after some changes):

   SCALAR(0x676fa0) is
      referenced by REF(0x676fb0), which is
         in the lexical '$x' in CODE(0x676370), which is
            not found anywhere I looked :(
      referenced by REF(0x676360), which is
         in the member 'ukukey' of HASH(0x756660), which is
            in the global %Test::hash.
      in the global $Test::var.
      referenced by REF(0x6760e0), which is
         in the member 'ukukey2' of HASH(0x676f30), which is
            referenced by REF(0x77bcf0), which is
               in the lexical '$local' in CODE(0x77bcb0), which is
                  in the global &Test::testsub.
            referenced by REF(0x77bc80), which is
               in the global $Test::hash2.


It is a bit convoluted to read, but basically it says that the value
stored in C<$var> can be found:

=over 4

=item - in some variable C<$x> whose origin is not known (I frankly have no
idea why, hints accepted).

=item - in the hash element with key C<ukukey> in the hash stored in C<%Test::hash>.

=item - in the global variable named C<$Test::var>.

=item - in the hash element C<ukukey2>, in the hash in the my variable
C<$local> in the sub C<Test::testsub> and also in the hash referenced by
C<$Test::hash2>.

=head1 EXPORTS

None.

=head1 FUNCTIONS

=over 4

=item $string = Devel::FindRef::track $ref[, $depth]

Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and
return a descriptive string. C<$ref> can point at any perl value, be it
anonymous sub, hash, array, scalar etc.

This is the function you most often use.

=cut

sub find($);

sub track {
   my $buf = "";

   my $track; $track = sub {
      my (undef, $depth, $indent) = @_;

      if ($depth) {
         my (@about) = find $_[0];
         if (@about) {
            for my $about (@about) {
               $buf .= ("   ") x $indent;
               $buf .= $about->[0];
               if (@$about > 1) {
                  $buf .= " $about->[1], which is\n";
                  $track->($about->[1], $depth - 1, $indent + 1);
               } else {
                  $buf .= ".\n";
               }
            }
         } else {
            $buf .= ("   ") x $indent;
            $buf .= "not found anywhere I looked :(\n";
         }
      } else {
         $buf .= ("   ") x $indent;
         $buf .= "not referenced within the search depth.\n";
      }
   };

   $buf .= "$_[0] is\n";
   $track->($_[0], $_[1] || 10, 1);
   $buf
}

=item @references = Devel::FindRef::find $ref

Return arrayrefs that contain [$message, $ref] pairs. The message
describes what kind of reference was found and the C<$ref> is the
reference itself, which cna be omitted if C<find> decided to end the
search.

The C<track> function uses this to find references to the value you are
interested in and recurses on the returned references.

=cut

sub find($) {
   my ($about, $excl) = &find_;
   my %excl = map +($_ => 1), @$excl;
   grep !$excl{$_->[1] + 0}, @$about
}

=item $ref = Devel::FindRef::ref2ptr $ptr

Sometimes you know (from debugging output) the address of a perl scalar
you are interested in. This function can be used to turn the address into
a reference to that scalar. It is quite safe to call on valid addresses,
but extremely dangerous to call on invalid ones.

=back

=head1 AUTHOR

Marc Lehmann <pcg@goof.com>.

=head1 BUGS

Only code values, arrays, hashes, scalars and magic are being looked at.

This is a quick hack only.

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2007 by Marc Lehmann.

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.8 or,
at your option, any later version of Perl 5 you may have available.

=cut

1

Revision:	1.5
Committed:	Wed Feb 7 21:34:02 2007 UTC (17 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	rel-0_2
Changes since 1.4:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	package Devel::FindRef;
2
3			use strict;
4
5			use XSLoader;
6
7
8			BEGIN {
9	root	1.5	our $VERSION = '0.2';
10	root	1.1	XSLoader::load __PACKAGE__, $VERSION;
11			}
12
13			=head1 NAME
14
15			Devel::FindRef - where is that reference to my scalar hiding?
16
17			=head1 SYNOPSIS
18
19			use Devel::FindRef;
20
21			=head1 DESCRIPTION
22
23			Tracking down reference problems (e.g. you expect some object to be
24	root	1.4	destroyed, but there are still references to it that keep it alive) can be
25			very hard. Fortunately, perl keeps track of all its values, so tracking
26			references "backwards" is usually possible.
27	root	1.1
28	root	1.4	The C<track> function can help track down some of those references back to
29	root	1.1	the variables containing them.
30
31			For example, for this fragment:
32
33			package Test;
34
35			our $var = "hi\n";
36			my $x = \$var;
37			our %hash = (ukukey => \$var);
38			our $hash2 = {ukukey2 => \$var};
39
40			sub testsub {
41			my $local = $hash2;
42			print Devel::FindRef::track \$var;
43			}
44
45			testsub;
46
47	root	1.4	The output is as follows (or similar to this, in case I forget to update
48	root	1.3	the manpage after some changes):
49	root	1.1
50			SCALAR(0x676fa0) is
51			referenced by REF(0x676fb0), which is
52			in the lexical '$x' in CODE(0x676370), which is
53			not found anywhere I looked :(
54			referenced by REF(0x676360), which is
55			in the member 'ukukey' of HASH(0x756660), which is
56			in the global %Test::hash.
57			in the global $Test::var.
58			referenced by REF(0x6760e0), which is
59			in the member 'ukukey2' of HASH(0x676f30), which is
60			referenced by REF(0x77bcf0), which is
61			in the lexical '$local' in CODE(0x77bcb0), which is
62			in the global &Test::testsub.
63			referenced by REF(0x77bc80), which is
64			in the global $Test::hash2.
65
66
67	root	1.4	It is a bit convoluted to read, but basically it says that the value
68			stored in C<$var> can be found:
69	root	1.1
70			=over 4
71
72			=item - in some variable C<$x> whose origin is not known (I frankly have no
73			idea why, hints accepted).
74
75			=item - in the hash element with key C<ukukey> in the hash stored in C<%Test::hash>.
76
77			=item - in the global variable named C<$Test::var>.
78
79			=item - in the hash element C<ukukey2>, in the hash in the my variable
80			C<$local> in the sub C<Test::testsub> and also in the hash referenced by
81			C<$Test::hash2>.
82
83			=head1 EXPORTS
84
85			None.
86
87			=head1 FUNCTIONS
88
89			=over 4
90
91			=item $string = Devel::FindRef::track $ref[, $depth]
92
93			Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and
94			return a descriptive string. C<$ref> can point at any perl value, be it
95			anonymous sub, hash, array, scalar etc.
96
97			This is the function you most often use.
98
99			=cut
100
101			sub find($);
102
103			sub track {
104			my $buf = "";
105
106			my $track; $track = sub {
107			my (undef, $depth, $indent) = @_;
108
109			if ($depth) {
110			my (@about) = find $_[0];
111			if (@about) {
112			for my $about (@about) {
113			$buf .= (" ") x $indent;
114			$buf .= $about->[0];
115			if (@$about > 1) {
116			$buf .= " $about->[1], which is\n";
117			$track->($about->[1], $depth - 1, $indent + 1);
118			} else {
119			$buf .= ".\n";
120			}
121			}
122			} else {
123			$buf .= (" ") x $indent;
124			$buf .= "not found anywhere I looked :(\n";
125			}
126			} else {
127			$buf .= (" ") x $indent;
128			$buf .= "not referenced within the search depth.\n";
129			}
130			};
131
132			$buf .= "$_[0] is\n";
133			$track->($_[0], $_[1] \|\| 10, 1);
134			$buf
135			}
136
137			=item @references = Devel::FindRef::find $ref
138
139			Return arrayrefs that contain [$message, $ref] pairs. The message
140			describes what kind of reference was found and the C<$ref> is the
141			reference itself, which cna be omitted if C<find> decided to end the
142			search.
143
144			The C<track> function uses this to find references to the value you are
145			interested in and recurses on the returned references.
146
147			=cut
148
149			sub find($) {
150			my ($about, $excl) = &find_;
151			my %excl = map +($_ => 1), @$excl;
152			grep !$excl{$_->[1] + 0}, @$about
153			}
154
155			=item $ref = Devel::FindRef::ref2ptr $ptr
156
157			Sometimes you know (from debugging output) the address of a perl scalar
158			you are interested in. This function can be used to turn the address into
159			a reference to that scalar. It is quite safe to call on valid addresses,
160			but extremely dangerous to call on invalid ones.
161
162			=back
163
164			=head1 AUTHOR
165
166			Marc Lehmann <pcg@goof.com>.
167
168			=head1 BUGS
169
170	root	1.2	Only code values, arrays, hashes, scalars and magic are being looked at.
171	root	1.1
172	root	1.4	This is a quick hack only.
173
174	root	1.1	=head1 COPYRIGHT AND LICENSE
175
176			Copyright (C) 2007 by Marc Lehmann.
177
178			This library is free software; you can redistribute it and/or modify
179			it under the same terms as Perl itself, either Perl version 5.8.8 or,
180			at your option, any later version of Perl 5 you may have available.
181
182			=cut
183
184			1
185