Devel-FindRef/FindRef.pm

package Devel::FindRef;

use strict;

use XSLoader;
use Scalar::Util;

BEGIN {
   our $VERSION = '1.2';
   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(0x7bd2d0) is
      in the global $Test::var.
      referenced by REF(0x7bd240), which is
         in the member 'ukukey2' of HASH(0x7bd228), which is
            referenced by REF(0x81dae8), which is
               in the lexical '$local' in CODE(0x81da88), which is
                  in the global &Test::testsub.
            referenced by REF(0x81da40), which is
               in the global $Test::hash2.
      referenced by REF(0x79f3f8), which is
         in the lexical '$x' in CODE(0x79f518), which is
            the containing scope for CODE(0x81da88), which is
               in the global &Test::testsub.
      referenced by REF(0x79f2f0), which is
         not found anywhere I looked :(
      referenced by REF(0x79f140), which is
         in the member 'ukukey' of HASH(0x81d698), which is
            in the global %Test::hash.

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:	1.10
Committed:	Sat Apr 26 03:15:28 2008 UTC (16 years ago) by root
Branch:	MAIN
CVS Tags:	rel-1_2
Changes since 1.9:	+16 -14 lines
Log Message:	1.2
#	Content
1	package Devel::FindRef;
2
3	use strict;
4
5	use XSLoader;
6	use Scalar::Util;
7
8	BEGIN {
9	our $VERSION = '1.2';
10	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	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
28	The C<track> function can help track down some of those references back to
29	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	The output is as follows (or similar to this, in case I forget to update
48	the manpage after some changes):
49
50	SCALAR(0x7bd2d0) is
51	in the global $Test::var.
52	referenced by REF(0x7bd240), which is
53	in the member 'ukukey2' of HASH(0x7bd228), which is
54	referenced by REF(0x81dae8), which is
55	in the lexical '$local' in CODE(0x81da88), which is
56	in the global &Test::testsub.
57	referenced by REF(0x81da40), which is
58	in the global $Test::hash2.
59	referenced by REF(0x79f3f8), which is
60	in the lexical '$x' in CODE(0x79f518), which is
61	the containing scope for CODE(0x81da88), which is
62	in the global &Test::testsub.
63	referenced by REF(0x79f2f0), which is
64	not found anywhere I looked :(
65	referenced by REF(0x79f140), which is
66	in the member 'ukukey' of HASH(0x81d698), which is
67	in the global %Test::hash.
68
69	It is a bit convoluted to read, but basically it says that the value
70	stored in C<$var> can be found:
71
72	=over 4
73
74	=item - in some variable C<$x> whose origin is not known (I frankly have no
75	idea why, hints accepted).
76
77	=item - in the hash element with key C<ukukey> in the hash stored in C<%Test::hash>.
78
79	=item - in the global variable named C<$Test::var>.
80
81	=item - in the hash element C<ukukey2>, in the hash in the my variable
82	C<$local> in the sub C<Test::testsub> and also in the hash referenced by
83	C<$Test::hash2>.
84
85	=back
86
87	=head1 EXPORTS
88
89	None.
90
91	=head1 FUNCTIONS
92
93	=over 4
94
95	=item $string = Devel::FindRef::track $ref[, $depth]
96
97	Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and
98	return a descriptive string. C<$ref> can point at any perl value, be it
99	anonymous sub, hash, array, scalar etc.
100
101	This is the function you most often use.
102
103	=cut
104
105	sub find($);
106
107	sub track {
108	my ($ref, $depth) = @_;
109	@_ = ();
110
111	my $buf = "";
112
113	Scalar::Util::weaken $ref;
114
115	my $track; $track = sub {
116	my ($refref, $depth, $indent) = @_;
117
118	if ($depth) {
119	my (@about) = find $$refref;
120	if (@about) {
121	for my $about (@about) {
122	$buf .= (" ") x $indent;
123	$buf .= $about->[0];
124	if (@$about > 1) {
125	$buf .= " $about->[1], which is\n";
126	$track->(\$about->[1], $depth - 1, $indent + 1);
127	} else {
128	$buf .= ".\n";
129	}
130	}
131	} else {
132	$buf .= (" ") x $indent;
133	$buf .= "not found anywhere I looked :(\n";
134	}
135	} else {
136	$buf .= (" ") x $indent;
137	$buf .= "not referenced within the search depth.\n";
138	}
139	};
140
141	$buf .= "$ref is\n";
142	$track->(\$ref, $depth \|\| 10, 1);
143	$buf
144	}
145
146	=item @references = Devel::FindRef::find $ref
147
148	Return arrayrefs that contain [$message, $ref] pairs. The message
149	describes what kind of reference was found and the C<$ref> is the
150	reference itself, which can be omitted if C<find> decided to end the
151	search. The returned references are all weak references.
152
153	The C<track> function uses this to find references to the value you are
154	interested in and recurses on the returned references.
155
156	=cut
157
158	sub find($) {
159	my ($about, $excl) = &find_;
160	my %excl = map +($_ => undef), @$excl;
161	grep !exists $excl{$_->[1] + 0}, @$about
162	}
163
164	=item $ref = Devel::FindRef::ptr2ref $integer
165
166	Sometimes you know (from debugging output) the address of a perl scalar
167	you are interested in (e.g. C<HASH(0x176ff70)>). This function can be used
168	to turn the address into a reference to that scalar. It is quite safe to
169	call on valid addresses, but extremely dangerous to call on invalid ones.
170
171	# we know that HASH(0x176ff70) exists, so turn it into a hashref:
172	my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
173
174	=back
175
176	=head1 AUTHOR
177
178	Marc Lehmann <pcg@goof.com>.
179
180	=head1 BUGS
181
182	Only code values, arrays, hashes, scalars and magic are being looked at.
183
184	This is a quick hack only.
185
186	=head1 COPYRIGHT AND LICENSE
187
188	Copyright (C) 2007 by Marc Lehmann.
189
190	This library is free software; you can redistribute it and/or modify
191	it under the same terms as Perl itself, either Perl version 5.8.8 or,
192	at your option, any later version of Perl 5 you may have available.
193
194	=cut
195
196	1
197