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;

  print Devel::FindRef::track \$some_variable;

=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 _f($) {
   "$_[0] [refcount " . (_refcnt $_[0]) . "]"
}

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 .= " " . (_f $about->[1]) . ", which was seen before.\n";
                  } else {
                     $buf .= " " . (_f $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 .= (_f $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 COPYRIGHT AND LICENSE

Copyright (C) 2007, 2008 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:	1.18
Committed:	Mon Dec 1 13:22:43 2008 UTC (15 years, 5 months ago) by root
Branch:	MAIN
Changes since 1.17:	+7 -3 lines
Log Message:	* empty log message *
#	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	root	1.16	print Devel::FindRef::track \$some_variable;
23
24	root	1.1	=head1 DESCRIPTION
25
26			Tracking down reference problems (e.g. you expect some object to be
27	root	1.4	destroyed, but there are still references to it that keep it alive) can be
28			very hard. Fortunately, perl keeps track of all its values, so tracking
29			references "backwards" is usually possible.
30	root	1.1
31	root	1.4	The C<track> function can help track down some of those references back to
32	root	1.1	the variables containing them.
33
34			For example, for this fragment:
35
36			package Test;
37
38			our $var = "hi\n";
39			my $x = \$var;
40			our %hash = (ukukey => \$var);
41			our $hash2 = {ukukey2 => \$var};
42
43			sub testsub {
44			my $local = $hash2;
45			print Devel::FindRef::track \$var;
46			}
47
48			testsub;
49
50	root	1.4	The output is as follows (or similar to this, in case I forget to update
51	root	1.3	the manpage after some changes):
52	root	1.1
53	root	1.13	SCALAR(0x814ece8) is
54			+- in the global $Test::var.
55			+- referenced by REF(0x814f9e4), which is
56			\| in the lexical '$x' in CODE(0x814ed78), which is
57			\| the containing scope for CODE(0x820c4b0), which is
58			\| in the global &Test::testsub.
59			+- referenced by REF(0x814ed6c), which is
60			\| in the member 'ukukey' of HASH(0x81da20c), which is
61			\| in the global %Test::hash.
62			+- referenced by REF(0x814ec28), which is
63			\| not found anywhere I looked :(
64			+- referenced by REF(0x814eb44), which is
65			in the member 'ukukey2' of HASH(0x814f99c), which is
66			+- referenced by REF(0x820c450), which is
67			\| in the lexical '$local' in CODE(0x820c4b0), which was seen before.
68			+- referenced by REF(0x820c204), which is
69	root	1.1	in the global $Test::hash2.
70
71	root	1.4	It is a bit convoluted to read, but basically it says that the value
72			stored in C<$var> can be found:
73	root	1.1
74			=over 4
75
76			=item - in some variable C<$x> whose origin is not known (I frankly have no
77			idea why, hints accepted).
78
79			=item - in the hash element with key C<ukukey> in the hash stored in C<%Test::hash>.
80
81			=item - in the global variable named C<$Test::var>.
82
83			=item - in the hash element C<ukukey2>, in the hash in the my variable
84			C<$local> in the sub C<Test::testsub> and also in the hash referenced by
85			C<$Test::hash2>.
86
87	root	1.6	=back
88
89	root	1.1	=head1 EXPORTS
90
91			None.
92
93			=head1 FUNCTIONS
94
95			=over 4
96
97			=item $string = Devel::FindRef::track $ref[, $depth]
98
99			Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and
100			return a descriptive string. C<$ref> can point at any perl value, be it
101			anonymous sub, hash, array, scalar etc.
102
103			This is the function you most often use.
104
105			=cut
106
107			sub find($);
108
109	root	1.18	sub _f($) {
110			"$_[0] [refcount " . (_refcnt $_[0]) . "]"
111			}
112
113	root	1.1	sub track {
114	root	1.9	my ($ref, $depth) = @_;
115			@_ = ();
116
117	root	1.1	my $buf = "";
118	root	1.11	my %seen;
119	root	1.9
120			Scalar::Util::weaken $ref;
121	root	1.1
122			my $track; $track = sub {
123	root	1.9	my ($refref, $depth, $indent) = @_;
124	root	1.1
125			if ($depth) {
126	root	1.9	my (@about) = find $$refref;
127	root	1.1	if (@about) {
128			for my $about (@about) {
129	root	1.12	$buf .= "$indent" . (@about > 1 ? "+- " : " ") . $about->[0];
130	root	1.1	if (@$about > 1) {
131	root	1.14	if ($seen{ref2ptr $about->[1]}++) {
132	root	1.18	$buf .= " " . (_f $about->[1]) . ", which was seen before.\n";
133	root	1.11	} else {
134	root	1.18	$buf .= " " . (_f $about->[1]) . ", which is\n";
135	root	1.12	$track->(\$about->[1], $depth - 1, $about == $about[-1] ? "$indent " : "$indent\| ");
136	root	1.11	}
137	root	1.1	} else {
138			$buf .= ".\n";
139			}
140			}
141			} else {
142	root	1.12	$buf .= "$indent not found anywhere I looked :(\n";
143	root	1.1	}
144			} else {
145	root	1.12	$buf .= "$indent not referenced within the search depth.\n";
146	root	1.1	}
147			};
148
149	root	1.18	$buf .= (_f $ref) . " is\n";
150	root	1.12	$track->(\$ref, $depth \|\| $ENV{PERL_DEVEL_FINDREF_DEPTH} \|\| 10, "");
151	root	1.1	$buf
152			}
153
154			=item @references = Devel::FindRef::find $ref
155
156			Return arrayrefs that contain [$message, $ref] pairs. The message
157			describes what kind of reference was found and the C<$ref> is the
158	root	1.9	reference itself, which can be omitted if C<find> decided to end the
159			search. The returned references are all weak references.
160	root	1.1
161			The C<track> function uses this to find references to the value you are
162			interested in and recurses on the returned references.
163
164			=cut
165
166			sub find($) {
167			my ($about, $excl) = &find_;
168	root	1.6	my %excl = map +($_ => undef), @$excl;
169	root	1.14	grep !exists $excl{ref2ptr $_->[1]}, @$about
170	root	1.1	}
171
172	root	1.7	=item $ref = Devel::FindRef::ptr2ref $integer
173	root	1.1
174			Sometimes you know (from debugging output) the address of a perl scalar
175	root	1.7	you are interested in (e.g. C<HASH(0x176ff70)>). This function can be used
176			to turn the address into a reference to that scalar. It is quite safe to
177			call on valid addresses, but extremely dangerous to call on invalid ones.
178
179			# we know that HASH(0x176ff70) exists, so turn it into a hashref:
180			my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
181	root	1.1
182	root	1.14	=item $ref = Devel::FindRef::ref2ptr $reference
183
184			The opposite of C<ptr2ref>, above: returns the internal address of the
185			value pointed to by the passed reference. I<No checks whatsoever will be
186			done>, so don't use this.
187
188	root	1.1	=back
189
190	root	1.12	=head1 ENVIRONMENT VARIABLES
191
192			You can set the environment variable C<PERL_DEVEL_FINDREF_DEPTH> to an
193			integer to override the default depth in C<track>. If a call explicitly
194			specified a depth it is not overridden.
195
196	root	1.1	=head1 AUTHOR
197
198			Marc Lehmann <pcg@goof.com>.
199
200			=head1 COPYRIGHT AND LICENSE
201
202	root	1.17	Copyright (C) 2007, 2008 by Marc Lehmann.
203	root	1.1
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