Devel-FindRef/FindRef.pm

package Devel::FindRef;

use strict;

use XSLoader;

BEGIN {
   our $VERSION = '1.0';
   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 $buf = "";
   my %ignore;

   my $track; $track = sub {
      my ($target, $depth, $indent) = @_;
      @_ = ();
      local $ignore{$target+0} = undef;

      if ($depth) {
         my (@about) = grep !exists $ignore{$_->[1]}, find $target;
         if (@about) {
            local @ignore{map $_->[1]+0, @about} = ();
            for my $about (@about) {
               local $ignore{$about+0} = undef;
               $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, $excl) = &find_;
   my %excl = map +($_ => 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:	1.8
Committed:	Wed Nov 28 12:20:33 2007 UTC (16 years, 5 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_0
Changes since 1.7:	+1 -2 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			BEGIN {
8	root	1.8	our $VERSION = '1.0';
9	root	1.1	XSLoader::load __PACKAGE__, $VERSION;
10			}
11
12			=head1 NAME
13
14			Devel::FindRef - where is that reference to my scalar hiding?
15
16			=head1 SYNOPSIS
17
18			use Devel::FindRef;
19
20			=head1 DESCRIPTION
21
22			Tracking down reference problems (e.g. you expect some object to be
23	root	1.4	destroyed, but there are still references to it that keep it alive) can be
24			very hard. Fortunately, perl keeps track of all its values, so tracking
25			references "backwards" is usually possible.
26	root	1.1
27	root	1.4	The C<track> function can help track down some of those references back to
28	root	1.1	the variables containing them.
29
30			For example, for this fragment:
31
32			package Test;
33
34			our $var = "hi\n";
35			my $x = \$var;
36			our %hash = (ukukey => \$var);
37			our $hash2 = {ukukey2 => \$var};
38
39			sub testsub {
40			my $local = $hash2;
41			print Devel::FindRef::track \$var;
42			}
43
44			testsub;
45
46	root	1.4	The output is as follows (or similar to this, in case I forget to update
47	root	1.3	the manpage after some changes):
48	root	1.1
49			SCALAR(0x676fa0) is
50			referenced by REF(0x676fb0), which is
51			in the lexical '$x' in CODE(0x676370), which is
52			not found anywhere I looked :(
53			referenced by REF(0x676360), which is
54			in the member 'ukukey' of HASH(0x756660), which is
55			in the global %Test::hash.
56			in the global $Test::var.
57			referenced by REF(0x6760e0), which is
58			in the member 'ukukey2' of HASH(0x676f30), which is
59			referenced by REF(0x77bcf0), which is
60			in the lexical '$local' in CODE(0x77bcb0), which is
61			in the global &Test::testsub.
62			referenced by REF(0x77bc80), which is
63			in the global $Test::hash2.
64
65
66	root	1.4	It is a bit convoluted to read, but basically it says that the value
67			stored in C<$var> can be found:
68	root	1.1
69			=over 4
70
71			=item - in some variable C<$x> whose origin is not known (I frankly have no
72			idea why, hints accepted).
73
74			=item - in the hash element with key C<ukukey> in the hash stored in C<%Test::hash>.
75
76			=item - in the global variable named C<$Test::var>.
77
78			=item - in the hash element C<ukukey2>, in the hash in the my variable
79			C<$local> in the sub C<Test::testsub> and also in the hash referenced by
80			C<$Test::hash2>.
81
82	root	1.6	=back
83
84	root	1.1	=head1 EXPORTS
85
86			None.
87
88			=head1 FUNCTIONS
89
90			=over 4
91
92			=item $string = Devel::FindRef::track $ref[, $depth]
93
94			Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and
95			return a descriptive string. C<$ref> can point at any perl value, be it
96			anonymous sub, hash, array, scalar etc.
97
98			This is the function you most often use.
99
100			=cut
101
102			sub find($);
103
104			sub track {
105			my $buf = "";
106	root	1.6	my %ignore;
107	root	1.1
108			my $track; $track = sub {
109	root	1.6	my ($target, $depth, $indent) = @_;
110			@_ = ();
111			local $ignore{$target+0} = undef;
112	root	1.1
113			if ($depth) {
114	root	1.6	my (@about) = grep !exists $ignore{$_->[1]}, find $target;
115	root	1.1	if (@about) {
116	root	1.6	local @ignore{map $_->[1]+0, @about} = ();
117	root	1.1	for my $about (@about) {
118	root	1.6	local $ignore{$about+0} = undef;
119	root	1.1	$buf .= (" ") x $indent;
120			$buf .= $about->[0];
121			if (@$about > 1) {
122			$buf .= " $about->[1], which is\n";
123			$track->($about->[1], $depth - 1, $indent + 1);
124			} else {
125			$buf .= ".\n";
126			}
127			}
128			} else {
129			$buf .= (" ") x $indent;
130			$buf .= "not found anywhere I looked :(\n";
131			}
132			} else {
133			$buf .= (" ") x $indent;
134			$buf .= "not referenced within the search depth.\n";
135			}
136			};
137
138			$buf .= "$_[0] is\n";
139			$track->($_[0], $_[1] \|\| 10, 1);
140			$buf
141			}
142
143			=item @references = Devel::FindRef::find $ref
144
145			Return arrayrefs that contain [$message, $ref] pairs. The message
146			describes what kind of reference was found and the C<$ref> is the
147			reference itself, which cna be omitted if C<find> decided to end the
148			search.
149
150			The C<track> function uses this to find references to the value you are
151			interested in and recurses on the returned references.
152
153			=cut
154
155			sub find($) {
156			my ($about, $excl) = &find_;
157	root	1.6	my %excl = map +($_ => undef), @$excl;
158			grep !exists $excl{$_->[1] + 0}, @$about
159	root	1.1	}
160
161	root	1.7	=item $ref = Devel::FindRef::ptr2ref $integer
162	root	1.1
163			Sometimes you know (from debugging output) the address of a perl scalar
164	root	1.7	you are interested in (e.g. C<HASH(0x176ff70)>). This function can be used
165			to turn the address into a reference to that scalar. It is quite safe to
166			call on valid addresses, but extremely dangerous to call on invalid ones.
167
168			# we know that HASH(0x176ff70) exists, so turn it into a hashref:
169			my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
170	root	1.1
171			=back
172
173			=head1 AUTHOR
174
175			Marc Lehmann <pcg@goof.com>.
176
177			=head1 BUGS
178
179	root	1.2	Only code values, arrays, hashes, scalars and magic are being looked at.
180	root	1.1
181	root	1.4	This is a quick hack only.
182
183	root	1.1	=head1 COPYRIGHT AND LICENSE
184
185			Copyright (C) 2007 by Marc Lehmann.
186
187			This library is free software; you can redistribute it and/or modify
188			it under the same terms as Perl itself, either Perl version 5.8.8 or,
189			at your option, any later version of Perl 5 you may have available.
190
191			=cut
192
193			1
194