Devel-FindRef/FindRef.pm

package Devel::FindRef;

use strict;

use XSLoader;
use Scalar::Util;

BEGIN {
   our $VERSION = '1.1';
   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>.

=back

=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 ($ref, $depth) = @_;
   @_ = ();

   my $buf = "";

   Scalar::Util::weaken $ref;

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

      if ($depth) {
         my (@about) = find $$refref;
         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";
      }
   };

   $buf .= "$ref is\n";
   $track->(\$ref, $depth || 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 can be omitted if C<find> decided to end the
search. The returned references are all weak references.

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

=item $ref = Devel::FindRef::ptr2ref $integer

Sometimes you know (from debugging output) the address of a perl scalar
you are interested in (e.g. C<HASH(0x176ff70)>). 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.

   # we know that HASH(0x176ff70) exists, so turn it into a hashref:
   my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;

=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:	1.9
Committed:	Sat Dec 29 21:04:46 2007 UTC (16 years, 4 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_1
Changes since 1.8:	+14 -13 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	root	1.9	use Scalar::Util;
7	root	1.1
8			BEGIN {
9	root	1.9	our $VERSION = '1.1';
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	root	1.6	=back
84
85	root	1.1	=head1 EXPORTS
86
87			None.
88
89			=head1 FUNCTIONS
90
91			=over 4
92
93			=item $string = Devel::FindRef::track $ref[, $depth]
94
95			Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and
96			return a descriptive string. C<$ref> can point at any perl value, be it
97			anonymous sub, hash, array, scalar etc.
98
99			This is the function you most often use.
100
101			=cut
102
103			sub find($);
104
105			sub track {
106	root	1.9	my ($ref, $depth) = @_;
107			@_ = ();
108
109	root	1.1	my $buf = "";
110	root	1.9
111			Scalar::Util::weaken $ref;
112	root	1.1
113			my $track; $track = sub {
114	root	1.9	my ($refref, $depth, $indent) = @_;
115	root	1.1
116			if ($depth) {
117	root	1.9	my (@about) = find $$refref;
118	root	1.1	if (@about) {
119			for my $about (@about) {
120			$buf .= (" ") x $indent;
121			$buf .= $about->[0];
122			if (@$about > 1) {
123			$buf .= " $about->[1], which is\n";
124	root	1.9	$track->(\$about->[1], $depth - 1, $indent + 1);
125	root	1.1	} else {
126			$buf .= ".\n";
127			}
128			}
129			} else {
130			$buf .= (" ") x $indent;
131			$buf .= "not found anywhere I looked :(\n";
132			}
133			} else {
134			$buf .= (" ") x $indent;
135			$buf .= "not referenced within the search depth.\n";
136			}
137			};
138
139	root	1.9	$buf .= "$ref is\n";
140			$track->(\$ref, $depth \|\| 10, 1);
141	root	1.1	$buf
142			}
143
144			=item @references = Devel::FindRef::find $ref
145
146			Return arrayrefs that contain [$message, $ref] pairs. The message
147			describes what kind of reference was found and the C<$ref> is the
148	root	1.9	reference itself, which can be omitted if C<find> decided to end the
149			search. The returned references are all weak references.
150	root	1.1
151			The C<track> function uses this to find references to the value you are
152			interested in and recurses on the returned references.
153
154			=cut
155
156			sub find($) {
157			my ($about, $excl) = &find_;
158	root	1.6	my %excl = map +($_ => undef), @$excl;
159			grep !exists $excl{$_->[1] + 0}, @$about
160	root	1.1	}
161
162	root	1.7	=item $ref = Devel::FindRef::ptr2ref $integer
163	root	1.1
164			Sometimes you know (from debugging output) the address of a perl scalar
165	root	1.7	you are interested in (e.g. C<HASH(0x176ff70)>). This function can be used
166			to turn the address into a reference to that scalar. It is quite safe to
167			call on valid addresses, but extremely dangerous to call on invalid ones.
168
169			# we know that HASH(0x176ff70) exists, so turn it into a hashref:
170			my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
171	root	1.1
172			=back
173
174			=head1 AUTHOR
175
176			Marc Lehmann <pcg@goof.com>.
177
178			=head1 BUGS
179
180	root	1.2	Only code values, arrays, hashes, scalars and magic are being looked at.
181	root	1.1
182	root	1.4	This is a quick hack only.
183
184	root	1.1	=head1 COPYRIGHT AND LICENSE
185
186			Copyright (C) 2007 by Marc Lehmann.
187
188			This library is free software; you can redistribute it and/or modify
189			it under the same terms as Perl itself, either Perl version 5.8.8 or,
190			at your option, any later version of Perl 5 you may have available.
191
192			=cut
193
194			1
195