| 1 | NAME |
1 | NAME |
| 2 | Devel::FindRef - where is that reference to my scalar hiding? |
2 | Devel::FindRef - where is that reference to my variable hiding? |
| 3 | |
3 | |
| 4 | SYNOPSIS |
4 | SYNOPSIS |
| 5 | use Devel::FindRef; |
5 | use Devel::FindRef; |
| 6 | |
6 | |
| 7 | DESCRIPTION |
7 | DESCRIPTION |
| 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 |
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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 |
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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 |
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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 $Test::var. |
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|
| 42 | referenced by REF(0x6760e0), which is |
44 | +- referenced by REF(0x814ec28), which is |
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45 | | not found anywhere I looked :( |
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46 | +- referenced by REF(0x814eb44), which is |
| 43 | in the member 'ukukey2' of HASH(0x676f30), which is |
47 | in the member 'ukukey2' of HASH(0x814f99c), which is |
| 44 | referenced by REF(0x77bcf0), which is |
48 | +- referenced by REF(0x820c450), which is |
| 45 | in the lexical '$local' in CODE(0x77bcb0), which is |
49 | | in the lexical '$local' in CODE(0x820c4b0), which was seen before. |
| 46 | in the global &Test::testsub. |
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| 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 | |
| 62 | EXPORTS |
65 | EXPORTS |
| 63 | None. |
66 | None. |
| 64 | |
67 | |
| 65 | FUNCTIONS |
68 | FUNCTIONS |
| 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. |
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91 | |
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92 | # we know that HASH(0x176ff70) exists, so turn it into a hashref: |
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93 | my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; |
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94 | |
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95 | ENVIRONMENT VARIABLES |
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96 | You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an |
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97 | integer to override the default depth in "track". If a call explicitly |
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98 | specified a depth it is not overridden. |
| 88 | |
99 | |
| 89 | AUTHOR |
100 | AUTHOR |
| 90 | Marc Lehmann <pcg@goof.com>. |
101 | Marc Lehmann <pcg@goof.com>. |
| 91 | |
102 | |
| 92 | BUGS |
103 | BUGS |
| 93 | Only code values, arrays, hashes, scalars and magic are being looked |
104 | Only code values, arrays, hashes, scalars and magic are being looked at. |
| 94 | at. |
105 | |
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106 | This is a quick hack only. |
| 95 | |
107 | |
| 96 | COPYRIGHT AND LICENSE |
108 | COPYRIGHT AND LICENSE |
| 97 | Copyright (C) 2007 by Marc Lehmann. |
109 | Copyright (C) 2007 by Marc Lehmann. |
| 98 | |
110 | |
| 99 | This library is free software; you can redistribute it and/or modify |
111 | 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 |
112 | 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 |
113 | your option, any later version of Perl 5 you may have available. |
| 102 | available. |
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| 103 | |
114 | |
