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Revision 1.2 by root, Thu Jan 11 23:08:03 2007 UTC vs.
Revision 1.8 by root, Sat Jul 19 01:38:57 2008 UTC

1NAME 1NAME
2 Devel::FindRef - where is that reference to my scalar hiding? 2 Devel::FindRef - where is that reference to my variable hiding?
3 3
4SYNOPSIS 4SYNOPSIS
5 use Devel::FindRef; 5 use Devel::FindRef;
6 6
7DESCRIPTION 7DESCRIPTION
8 Tracking down reference problems (e.g. you expect some object to be 8 Tracking down reference problems (e.g. you expect some object to be
9 destroyed, but there are still references to it that keep it alive). can 9 destroyed, but there are still references to it that keep it alive) can
10 be very hard, although perl keeps track of all values. 10 be very hard. Fortunately, perl keeps track of all its values, so
11 tracking references "backwards" is usually possible.
11 12
12 The "track" function can hlep track down some of those refernces back to 13 The "track" function can help track down some of those references back
13 the variables containing them. 14 to the variables containing them.
14 15
15 For example, for this fragment: 16 For example, for this fragment:
16 17
17 package Test; 18 package Test;
18 19
19 our $var = "hi\n"; 20 our $var = "hi\n";
20 my $x = \$var; 21 my $x = \$var;
21 our %hash = (ukukey => \$var); 22 our %hash = (ukukey => \$var);
22 our $hash2 = {ukukey2 => \$var}; 23 our $hash2 = {ukukey2 => \$var};
23 24
24 sub testsub { 25 sub testsub {
25 my $local = $hash2; 26 my $local = $hash2;
26 print Devel::FindRef::track \$var; 27 print Devel::FindRef::track \$var;
27 } 28 }
28 29
29 testsub; 30 testsub;
30 31
31 The output is as follows (or similar to htis, in case I forget to update 32 The output is as follows (or similar to this, in case I forget to update
32 the manpage afetr some changes): 33 the manpage after some changes):
33 34
34 SCALAR(0x676fa0) is 35 SCALAR(0x814ece8) is
36 +- in the global $Test::var.
35 referenced by REF(0x676fb0), which is 37 +- referenced by REF(0x814f9e4), which is
36 in the lexical '$x' in CODE(0x676370), which is 38 | in the lexical '$x' in CODE(0x814ed78), which is
37 not found anywhere I looked :( 39 | the containing scope for CODE(0x820c4b0), which is
40 | in the global &Test::testsub.
38 referenced by REF(0x676360), which is 41 +- referenced by REF(0x814ed6c), which is
39 in the member 'ukukey' of HASH(0x756660), which is 42 | in the member 'ukukey' of HASH(0x81da20c), which is
40 in the global %Test::hash. 43 | in the global %Test::hash.
41 in the global $Test::var.
42 referenced by REF(0x6760e0), which is 44 +- referenced by REF(0x814ec28), which is
45 | not found anywhere I looked :(
46 +- referenced by REF(0x814eb44), which is
43 in the member 'ukukey2' of HASH(0x676f30), which is 47 in the member 'ukukey2' of HASH(0x814f99c), which is
44 referenced by REF(0x77bcf0), which is 48 +- referenced by REF(0x820c450), which is
45 in the lexical '$local' in CODE(0x77bcb0), which is 49 | in the lexical '$local' in CODE(0x820c4b0), which was seen before.
46 in the global &Test::testsub.
47 referenced by REF(0x77bc80), which is 50 +- referenced by REF(0x820c204), which is
48 in the global $Test::hash2. 51 in the global $Test::hash2.
49 52
50 It is a bit convoluted to read, but basically it says that the value 53 It is a bit convoluted to read, but basically it says that the value
51 stored in $var can be found: 54 stored in $var can be found:
52 55
… …
58 - in the hash element "ukukey2", in the hash in the my variable $local 61 - in the hash element "ukukey2", in the hash in the my variable $local
59 in the sub "Test::testsub" and also in the hash referenced by 62 in the sub "Test::testsub" and also in the hash referenced by
60 $Test::hash2. 63 $Test::hash2.
61 64
62EXPORTS 65EXPORTS
63 None. 66 None.
64 67
65FUNCTIONS 68FUNCTIONS
66 $string = Devel::FindRef::track $ref[, $depth] 69 $string = Devel::FindRef::track $ref[, $depth]
67 Track the perl value pointed to by $ref up to a depth of $depth 70 Track the perl value pointed to by $ref up to a depth of $depth and
68 and return a descriptive string. $ref can point at any perl 71 return a descriptive string. $ref can point at any perl value, be it
69 value, be it anonymous sub, hash, array, scalar etc. 72 anonymous sub, hash, array, scalar etc.
70 73
71 This is the function you most often use. 74 This is the function you most often use.
72 75
73 @references = Devel::FindRef::find $ref 76 @references = Devel::FindRef::find $ref
74 Return arrayrefs that contain [$message, $ref] pairs. The 77 Return arrayrefs that contain [$message, $ref] pairs. The message
75 message describes what kind of reference was found and the $ref 78 describes what kind of reference was found and the $ref is the
76 is the reference itself, which cna be omitted if "find" decided 79 reference itself, which can be omitted if "find" decided to end the
77 to end the search. 80 search. The returned references are all weak references.
78 81
79 The "track" function uses this to find references to the value 82 The "track" function uses this to find references to the value you
80 you are interested in and recurses on the returned references. 83 are interested in and recurses on the returned references.
81 84
82 $ref = Devel::FindRef::ref2ptr $ptr 85 $ref = Devel::FindRef::ptr2ref $integer
83 Sometimes you know (from debugging output) the address of a perl 86 Sometimes you know (from debugging output) the address of a perl
84 scalar you are interested in. This function can be used to turn 87 scalar you are interested in (e.g. "HASH(0x176ff70)"). This function
85 the address into a reference to that scalar. It is quite safe to 88 can be used to turn the address into a reference to that scalar. It
86 call on valid addresses, but extremely dangerous to call on 89 is quite safe to call on valid addresses, but extremely dangerous to
87 invalid ones. 90 call on invalid ones.
91
92 # we know that HASH(0x176ff70) exists, so turn it into a hashref:
93 my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
94
95 $ref = Devel::FindRef::ref2ptr $reference
96 The opposite of "ptr2ref", above: returns the internal address of
97 the value pointed to by the passed reference. *No checks whatsoever
98 will be done*, so don't use this.
99
100ENVIRONMENT VARIABLES
101 You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an
102 integer to override the default depth in "track". If a call explicitly
103 specified a depth it is not overridden.
88 104
89AUTHOR 105AUTHOR
90 Marc Lehmann <pcg@goof.com>. 106 Marc Lehmann <pcg@goof.com>.
91 107
92BUGS 108BUGS
93 Only code values, arrays, hashes, scalars and magic are being looked 109 Only code values, arrays, hashes, scalars and magic are being looked at.
94 at. 110
111 This is a quick hack only.
95 112
96COPYRIGHT AND LICENSE 113COPYRIGHT AND LICENSE
97 Copyright (C) 2007 by Marc Lehmann. 114 Copyright (C) 2007 by Marc Lehmann.
98 115
99 This library is free software; you can redistribute it and/or modify 116 This library is free software; you can redistribute it and/or modify it
100 it under the same terms as Perl itself, either Perl version 5.8.8 117 under the same terms as Perl itself, either Perl version 5.8.8 or, at
101 or, at your option, any later version of Perl 5 you may have 118 your option, any later version of Perl 5 you may have available.
102 available.
103 119

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