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 *
#	Content
1	package Devel::FindRef;
2
3	use strict;
4
5	use XSLoader;
6	use Scalar::Util;
7
8	BEGIN {
9	our $VERSION = '1.1';
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 = $hash2;
42	print Devel::FindRef::track \$var;
43	}
44
45	testsub;
46
47	The output is as follows (or similar to this, in case I forget to update
48	the manpage after some changes):
49
50	SCALAR(0x676fa0) is
51	referenced by REF(0x676fb0), which is
52	in the lexical '$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 $Test::hash2.
65
66
67	It is a bit convoluted to read, but basically it says that the value
68	stored in C<$var> can be found:
69
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	=back
84
85	=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($);
104
105	sub track {
106	my ($ref, $depth) = @_;
107	@_ = ();
108
109	my $buf = "";
110
111	Scalar::Util::weaken $ref;
112
113	my $track; $track = sub {
114	my ($refref, $depth, $indent) = @_;
115
116	if ($depth) {
117	my (@about) = find $$refref;
118	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	$track->(\$about->[1], $depth - 1, $indent + 1);
125	} 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	$buf .= "$ref is\n";
140	$track->(\$ref, $depth \|\| 10, 1);
141	$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	reference itself, which can be omitted if C<find> decided to end the
149	search. The returned references are all weak references.
150
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, $excl) = &find_;
158	my %excl = map +($_ => undef), @$excl;
159	grep !exists $excl{$_->[1] + 0}, @$about
160	}
161
162	=item $ref = Devel::FindRef::ptr2ref $integer
163
164	Sometimes you know (from debugging output) the address of a perl scalar
165	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
172	=back
173
174	=head1 AUTHOR
175
176	Marc Lehmann <pcg@goof.com>.
177
178	=head1 BUGS
179
180	Only code values, arrays, hashes, scalars and magic are being looked at.
181
182	This is a quick hack only.
183
184	=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