Devel-FindRef/FindRef.pm

package Devel::FindRef;

no warnings; # I hate warning nazis
use strict;

use XSLoader;
use Scalar::Util;

BEGIN {
   our $VERSION = '1.31';
   XSLoader::load __PACKAGE__, $VERSION;
}

=head1 NAME

Devel::FindRef - where is that reference to my variable 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(0x814ece8) is
   +- in the global $Test::var.
   +- referenced by REF(0x814f9e4), which is
   |     in the lexical '$x' in CODE(0x814ed78), which is
   |        the containing scope for CODE(0x820c4b0), which is
   |           in the global &Test::testsub.
   +- referenced by REF(0x814ed6c), which is
   |     in the member 'ukukey' of HASH(0x81da20c), which is
   |        in the global %Test::hash.
   +- referenced by REF(0x814ec28), which is
   |     not found anywhere I looked :(
   +- referenced by REF(0x814eb44), which is
         in the member 'ukukey2' of HASH(0x814f99c), which is
         +- referenced by REF(0x820c450), which is
         |     in the lexical '$local' in CODE(0x820c4b0), which was seen before.
         +- referenced by REF(0x820c204), 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 = "";
   my %seen;

   Scalar::Util::weaken $ref;

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

      if ($depth) {
         my (@about) = find $$refref;
         if (@about) {
            for my $about (@about) {
               $buf .= "$indent" . (@about > 1 ? "+- " : "   ") . $about->[0];
               if (@$about > 1) {
                  if ($seen{ref2ptr $about->[1]}++) {
                     $buf .= " $about->[1], which was seen before.\n";
                  } else {
                     $buf .= " $about->[1], which is\n";
                     $track->(\$about->[1], $depth - 1, $about == $about[-1] ? "$indent   " : "$indent|  ");
                  }
               } else {
                  $buf .= ".\n";
               }
            }
         } else {
            $buf .= "$indent   not found anywhere I looked :(\n";
         }
      } else {
         $buf .= "$indent   not referenced within the search depth.\n";
      }
   };

   $buf .= "$ref is\n";
   $track->(\$ref, $depth || $ENV{PERL_DEVEL_FINDREF_DEPTH} || 10, "");
   $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{ref2ptr $_->[1]}, @$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;

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

The opposite of C<ptr2ref>, above: returns the internal address of the
value pointed to by the passed reference. I<No checks whatsoever will be
done>, so don't use this.

=back

=head1 ENVIRONMENT VARIABLES

You can set the environment variable C<PERL_DEVEL_FINDREF_DEPTH> to an
integer to override the default depth in C<track>. If a call explicitly
specified a depth it is not overridden.

=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:	1.15
Committed:	Sat Jul 19 01:38:57 2008 UTC (15 years, 10 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_31
Changes since 1.14:	+2 -1 lines
Log Message:	lots of fixes by paul evans
#	User	Rev	Content
1	root	1.1	package Devel::FindRef;
2
3	root	1.15	no warnings; # I hate warning nazis
4	root	1.1	use strict;
5
6			use XSLoader;
7	root	1.9	use Scalar::Util;
8	root	1.1
9			BEGIN {
10	root	1.15	our $VERSION = '1.31';
11	root	1.1	XSLoader::load __PACKAGE__, $VERSION;
12			}
13
14			=head1 NAME
15
16	root	1.13	Devel::FindRef - where is that reference to my variable hiding?
17	root	1.1
18			=head1 SYNOPSIS
19
20			use Devel::FindRef;
21
22			=head1 DESCRIPTION
23
24			Tracking down reference problems (e.g. you expect some object to be
25	root	1.4	destroyed, but there are still references to it that keep it alive) can be
26			very hard. Fortunately, perl keeps track of all its values, so tracking
27			references "backwards" is usually possible.
28	root	1.1
29	root	1.4	The C<track> function can help track down some of those references back to
30	root	1.1	the variables containing them.
31
32			For example, for this fragment:
33
34			package Test;
35
36			our $var = "hi\n";
37			my $x = \$var;
38			our %hash = (ukukey => \$var);
39			our $hash2 = {ukukey2 => \$var};
40
41			sub testsub {
42			my $local = $hash2;
43			print Devel::FindRef::track \$var;
44			}
45
46			testsub;
47
48	root	1.4	The output is as follows (or similar to this, in case I forget to update
49	root	1.3	the manpage after some changes):
50	root	1.1
51	root	1.13	SCALAR(0x814ece8) is
52			+- in the global $Test::var.
53			+- referenced by REF(0x814f9e4), which is
54			\| in the lexical '$x' in CODE(0x814ed78), which is
55			\| the containing scope for CODE(0x820c4b0), which is
56			\| in the global &Test::testsub.
57			+- referenced by REF(0x814ed6c), which is
58			\| in the member 'ukukey' of HASH(0x81da20c), which is
59			\| in the global %Test::hash.
60			+- referenced by REF(0x814ec28), which is
61			\| not found anywhere I looked :(
62			+- referenced by REF(0x814eb44), which is
63			in the member 'ukukey2' of HASH(0x814f99c), which is
64			+- referenced by REF(0x820c450), which is
65			\| in the lexical '$local' in CODE(0x820c4b0), which was seen before.
66			+- referenced by REF(0x820c204), which is
67	root	1.1	in the global $Test::hash2.
68
69	root	1.4	It is a bit convoluted to read, but basically it says that the value
70			stored in C<$var> can be found:
71	root	1.1
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	root	1.6	=back
86
87	root	1.1	=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($);
106
107			sub track {
108	root	1.9	my ($ref, $depth) = @_;
109			@_ = ();
110
111	root	1.1	my $buf = "";
112	root	1.11	my %seen;
113	root	1.9
114			Scalar::Util::weaken $ref;
115	root	1.1
116			my $track; $track = sub {
117	root	1.9	my ($refref, $depth, $indent) = @_;
118	root	1.1
119			if ($depth) {
120	root	1.9	my (@about) = find $$refref;
121	root	1.1	if (@about) {
122			for my $about (@about) {
123	root	1.12	$buf .= "$indent" . (@about > 1 ? "+- " : " ") . $about->[0];
124	root	1.1	if (@$about > 1) {
125	root	1.14	if ($seen{ref2ptr $about->[1]}++) {
126	root	1.11	$buf .= " $about->[1], which was seen before.\n";
127			} else {
128			$buf .= " $about->[1], which is\n";
129	root	1.12	$track->(\$about->[1], $depth - 1, $about == $about[-1] ? "$indent " : "$indent\| ");
130	root	1.11	}
131	root	1.1	} else {
132			$buf .= ".\n";
133			}
134			}
135			} else {
136	root	1.12	$buf .= "$indent not found anywhere I looked :(\n";
137	root	1.1	}
138			} else {
139	root	1.12	$buf .= "$indent not referenced within the search depth.\n";
140	root	1.1	}
141			};
142
143	root	1.9	$buf .= "$ref is\n";
144	root	1.12	$track->(\$ref, $depth \|\| $ENV{PERL_DEVEL_FINDREF_DEPTH} \|\| 10, "");
145	root	1.1	$buf
146			}
147
148			=item @references = Devel::FindRef::find $ref
149
150			Return arrayrefs that contain [$message, $ref] pairs. The message
151			describes what kind of reference was found and the C<$ref> is the
152	root	1.9	reference itself, which can be omitted if C<find> decided to end the
153			search. The returned references are all weak references.
154	root	1.1
155			The C<track> function uses this to find references to the value you are
156			interested in and recurses on the returned references.
157
158			=cut
159
160			sub find($) {
161			my ($about, $excl) = &find_;
162	root	1.6	my %excl = map +($_ => undef), @$excl;
163	root	1.14	grep !exists $excl{ref2ptr $_->[1]}, @$about
164	root	1.1	}
165
166	root	1.7	=item $ref = Devel::FindRef::ptr2ref $integer
167	root	1.1
168			Sometimes you know (from debugging output) the address of a perl scalar
169	root	1.7	you are interested in (e.g. C<HASH(0x176ff70)>). This function can be used
170			to turn the address into a reference to that scalar. It is quite safe to
171			call on valid addresses, but extremely dangerous to call on invalid ones.
172
173			# we know that HASH(0x176ff70) exists, so turn it into a hashref:
174			my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
175	root	1.1
176	root	1.14	=item $ref = Devel::FindRef::ref2ptr $reference
177
178			The opposite of C<ptr2ref>, above: returns the internal address of the
179			value pointed to by the passed reference. I<No checks whatsoever will be
180			done>, so don't use this.
181
182	root	1.1	=back
183
184	root	1.12	=head1 ENVIRONMENT VARIABLES
185
186			You can set the environment variable C<PERL_DEVEL_FINDREF_DEPTH> to an
187			integer to override the default depth in C<track>. If a call explicitly
188			specified a depth it is not overridden.
189
190	root	1.1	=head1 AUTHOR
191
192			Marc Lehmann <pcg@goof.com>.
193
194			=head1 BUGS
195
196	root	1.2	Only code values, arrays, hashes, scalars and magic are being looked at.
197	root	1.1
198	root	1.4	This is a quick hack only.
199
200	root	1.1	=head1 COPYRIGHT AND LICENSE
201
202			Copyright (C) 2007 by Marc Lehmann.
203
204			This library is free software; you can redistribute it and/or modify
205			it under the same terms as Perl itself, either Perl version 5.8.8 or,
206			at your option, any later version of Perl 5 you may have available.
207
208			=cut
209
210			1
211