| 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; |
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6 | |
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7 | print Devel::FindRef::track \$some_variable; |
| 6 | |
8 | |
| 7 | DESCRIPTION |
9 | DESCRIPTION |
| 8 | Tracking down reference problems (e.g. you expect some object to be |
10 | 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 |
11 | destroyed, but there are still references to it that keep it alive) can |
| 10 | be very hard. Fortunately, perl keeps track of all its values, so |
12 | be very hard. Fortunately, perl keeps track of all its values, so |
| … | |
… | |
| 14 | to the variables containing them. |
16 | to the variables containing them. |
| 15 | |
17 | |
| 16 | For example, for this fragment: |
18 | For example, for this fragment: |
| 17 | |
19 | |
| 18 | package Test; |
20 | package Test; |
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21 | |
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22 | use Devel::FindRef; |
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23 | use Scalar::Util; |
| 19 | |
24 | |
| 20 | our $var = "hi\n"; |
25 | our $var = "hi\n"; |
| 21 | my $x = \$var; |
26 | my $global_my = \$var; |
| 22 | our %hash = (ukukey => \$var); |
27 | our %global_hash = (ukukey => \$var); |
| 23 | our $hash2 = {ukukey2 => \$var}; |
28 | our $global_hashref = { ukukey2 => \$var }; |
| 24 | |
29 | |
| 25 | sub testsub { |
30 | sub testsub { |
| 26 | my $local = $hash2; |
31 | my $testsub_local = $global_hashref; |
| 27 | print Devel::FindRef::track \$var; |
32 | print Devel::FindRef::track \$var; |
| 28 | } |
33 | } |
| 29 | |
34 | |
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35 | |
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36 | my $closure = sub { |
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37 | my $closure_var = \$_[0]; |
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38 | Scalar::Util::weaken (my $weak_ref = \$var); |
| 30 | testsub; |
39 | testsub; |
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40 | }; |
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41 | |
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42 | $closure->($var); |
| 31 | |
43 | |
| 32 | The output is as follows (or similar to this, in case I forget to update |
44 | The output is as follows (or similar to this, in case I forget to update |
| 33 | the manpage after some changes): |
45 | the manpage after some changes): |
| 34 | |
46 | |
| 35 | SCALAR(0x7bd2d0) is |
47 | SCALAR(0x7cc888) [refcount 6] is |
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48 | +- referenced by REF(0x8abcc8) [refcount 1], which is |
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49 | | in the lexical '$closure_var' in CODE(0x8abc50) [refcount 4], which is |
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50 | | +- the closure created at tst:18. |
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51 | | +- referenced by REF(0x7d3c58) [refcount 1], which is |
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52 | | | in the lexical '$closure' in CODE(0x7ae530) [refcount 2], which is |
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53 | | | +- the containing scope for CODE(0x8ab430) [refcount 3], which is |
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54 | | | | in the global &Test::testsub. |
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55 | | | +- the main body of the program. |
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56 | | +- in the lexical '&' in CODE(0x7ae530) [refcount 2], which was seen before. |
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57 | +- referenced by REF(0x7cc7c8) [refcount 1], which is |
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58 | | in the lexical '$global_my' in CODE(0x7ae530) [refcount 2], which was seen before. |
| 36 | in the global $Test::var. |
59 | +- in the global $Test::var. |
| 37 | referenced by REF(0x7bd240), which is |
60 | +- referenced by REF(0x7cc558) [refcount 1], which is |
| 38 | in the member 'ukukey2' of HASH(0x7bd228), which is |
61 | | in the member 'ukukey2' of HASH(0x7ae140) [refcount 2], which is |
| 39 | referenced by REF(0x81dae8), which is |
62 | | +- referenced by REF(0x8abad0) [refcount 1], which is |
| 40 | in the lexical '$local' in CODE(0x81da88), which is |
63 | | | in the lexical '$testsub_local' in CODE(0x8ab430) [refcount 3], which was seen before. |
| 41 | in the global &Test::testsub. |
64 | | +- referenced by REF(0x8ab4f0) [refcount 1], which is |
| 42 | referenced by REF(0x81da40), which is |
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| 43 | in the global $Test::hash2. |
65 | | in the global $Test::global_hashref. |
| 44 | referenced by REF(0x79f3f8), which is |
66 | +- referenced by REF(0x7ae518) [refcount 1], which is |
| 45 | in the lexical '$x' in CODE(0x79f518), which is |
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| 46 | the containing scope for CODE(0x81da88), which is |
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| 47 | in the global &Test::testsub. |
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| 48 | referenced by REF(0x79f2f0), which is |
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| 49 | not found anywhere I looked :( |
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| 50 | referenced by REF(0x79f140), which is |
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| 51 | in the member 'ukukey' of HASH(0x81d698), which is |
67 | | in the member 'ukukey' of HASH(0x7d3bb0) [refcount 1], which is |
| 52 | in the global %Test::hash. |
68 | | in the global %Test::global_hash. |
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69 | +- referenced by REF(0x7ae2f0) [refcount 1], which is |
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70 | a temporary on the stack. |
| 53 | |
71 | |
| 54 | It is a bit convoluted to read, but basically it says that the value |
72 | It is a bit convoluted to read, but basically it says that the value |
| 55 | stored in $var can be found: |
73 | stored in $var is referenced by: |
| 56 | |
74 | |
| 57 | - in some variable $x whose origin is not known (I frankly have no idea |
75 | - in the lexical $closure_var (0x8abcc8), which is inside an |
| 58 | why, hints accepted). |
76 | instantiated closure, which in turn is used quite a bit. |
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77 | - in the package-level lexical $global_my. |
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78 | - in the global package variable named $Test::var. |
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79 | - in the hash element "ukukey2", in the hash in the my variable |
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80 | $testsub_local in the sub "Test::testsub" and also in the hash |
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81 | "$referenced by Test::hash2". |
| 59 | - in the hash element with key "ukukey" in the hash stored in |
82 | - in the hash element with key "ukukey" in the hash stored in |
| 60 | %Test::hash. |
83 | %Test::hash. |
| 61 | - in the global variable named $Test::var. |
84 | - some anonymous mortalised reference on the stack (which is caused by |
| 62 | - in the hash element "ukukey2", in the hash in the my variable $local |
85 | calling "track" with the expression "\$var", which creates the |
| 63 | in the sub "Test::testsub" and also in the hash referenced by |
86 | reference). |
| 64 | $Test::hash2. |
87 | |
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88 | And all these account for six reference counts. |
| 65 | |
89 | |
| 66 | EXPORTS |
90 | EXPORTS |
| 67 | None. |
91 | None. |
| 68 | |
92 | |
| 69 | FUNCTIONS |
93 | FUNCTIONS |
| … | |
… | |
| 91 | call on invalid ones. |
115 | call on invalid ones. |
| 92 | |
116 | |
| 93 | # we know that HASH(0x176ff70) exists, so turn it into a hashref: |
117 | # we know that HASH(0x176ff70) exists, so turn it into a hashref: |
| 94 | my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; |
118 | my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; |
| 95 | |
119 | |
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120 | $ref = Devel::FindRef::ref2ptr $reference |
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121 | The opposite of "ptr2ref", above: returns the internal address of |
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122 | the value pointed to by the passed reference. *No checks whatsoever |
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123 | will be done*, so don't use this. |
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124 | |
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125 | ENVIRONMENT VARIABLES |
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126 | You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an |
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127 | integer to override the default depth in "track". If a call explicitly |
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128 | specified a depth it is not overridden. |
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129 | |
| 96 | AUTHOR |
130 | AUTHOR |
| 97 | Marc Lehmann <pcg@goof.com>. |
131 | Marc Lehmann <pcg@goof.com>. |
| 98 | |
132 | |
| 99 | BUGS |
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| 100 | Only code values, arrays, hashes, scalars and magic are being looked at. |
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| 101 | |
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| 102 | This is a quick hack only. |
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| 103 | |
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| 104 | COPYRIGHT AND LICENSE |
133 | COPYRIGHT AND LICENSE |
| 105 | Copyright (C) 2007 by Marc Lehmann. |
134 | Copyright (C) 2007, 2008 by Marc Lehmann. |
| 106 | |
135 | |
| 107 | This library is free software; you can redistribute it and/or modify it |
136 | This library is free software; you can redistribute it and/or modify it |
| 108 | under the same terms as Perl itself, either Perl version 5.8.8 or, at |
137 | under the same terms as Perl itself, either Perl version 5.8.8 or, at |
| 109 | your option, any later version of Perl 5 you may have available. |
138 | your option, any later version of Perl 5 you may have available. |
| 110 | |
139 | |
