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Revision 1.10 by root, Fri Jun 26 14:49:33 2009 UTC

1NAME 1NAME
2 Devel::FindRef - where is that reference to my variable 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
7 print Devel::FindRef::track \$some_variable;
6 8
7DESCRIPTION 9DESCRIPTION
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;
21
22 use Devel::FindRef;
23 use Scalar::Util;
24
25 our $var = "hi\n";
26 my $global_my = \$var;
27 our %global_hash = (ukukey => \$var);
28 our $global_hashref = { ukukey2 => \$var };
19 29
20 our $var = "hi\n";
21 my $x = \$var;
22 our %hash = (ukukey => \$var);
23 our $hash2 = {ukukey2 => \$var};
24
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
35
36 my $closure = sub {
37 my $closure_var = \$_[0];
38 Scalar::Util::weaken (my $weak_ref = \$var);
30 testsub; 39 testsub;
40 };
41
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(0x814ece8) is 47 SCALAR(0x7cc888) [refcount 6] is
48 +- referenced by REF(0x8abcc8) [refcount 1], which is
49 | in the lexical '$closure_var' in CODE(0x8abc50) [refcount 4], which is
50 | +- the closure created at tst:18.
51 | +- referenced by REF(0x7d3c58) [refcount 1], which is
52 | | in the lexical '$closure' in CODE(0x7ae530) [refcount 2], which is
53 | | +- the containing scope for CODE(0x8ab430) [refcount 3], which is
54 | | | in the global &Test::testsub.
55 | | +- the main body of the program.
56 | +- in the lexical '&' in CODE(0x7ae530) [refcount 2], which was seen before.
57 +- referenced by REF(0x7cc7c8) [refcount 1], which is
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 $Test::var.
37 +- referenced by REF(0x814f9e4), which is 60 +- referenced by REF(0x7cc558) [refcount 1], which is
38 | in the lexical '$x' in CODE(0x814ed78), which is
39 | the containing scope for CODE(0x820c4b0), which is
40 | in the global &Test::testsub.
41 +- referenced by REF(0x814ed6c), which is
42 | in the member 'ukukey' of HASH(0x81da20c), which is 61 | in the member 'ukukey2' of HASH(0x7ae140) [refcount 2], which is
62 | +- referenced by REF(0x8abad0) [refcount 1], which is
63 | | in the lexical '$testsub_local' in CODE(0x8ab430) [refcount 3], which was seen before.
64 | +- referenced by REF(0x8ab4f0) [refcount 1], which is
65 | in the global $Test::global_hashref.
66 +- referenced by REF(0x7ae518) [refcount 1], which is
67 | in the member 'ukukey' of HASH(0x7d3bb0) [refcount 1], which is
43 | in the global %Test::hash. 68 | in the global %Test::global_hash.
44 +- referenced by REF(0x814ec28), which is 69 +- referenced by REF(0x7ae2f0) [refcount 1], which is
45 | not found anywhere I looked :( 70 a temporary on the stack.
46 +- referenced by REF(0x814eb44), which is
47 in the member 'ukukey2' of HASH(0x814f99c), which is
48 +- referenced by REF(0x820c450), which is
49 | in the lexical '$local' in CODE(0x820c4b0), which was seen before.
50 +- referenced by REF(0x820c204), which is
51 in the global $Test::hash2.
52 71
53 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
54 stored in $var can be found: 73 stored in $var is referenced by:
55 74
56 - in some variable $x whose origin is not known (I frankly have no idea 75 - the lexical $closure_var (0x8abcc8), which is inside an instantiated
57 why, hints accepted). 76 closure, which in turn is used quite a bit.
58 - in the hash element with key "ukukey" in the hash stored in 77 - the package-level lexical $global_my.
59 %Test::hash.
60 - in the global variable named $Test::var. 78 - the global package variable named $Test::var.
61 - in the hash element "ukukey2", in the hash in the my variable $local 79 - the hash element "ukukey2", in the hash in the my variable
62 in the sub "Test::testsub" and also in the hash referenced by 80 $testsub_local in the sub "Test::testsub" and also in the hash
63 $Test::hash2. 81 "$referenced by Test::hash2".
82 - the hash element with key "ukukey" in the hash stored in %Test::hash.
83 - some anonymous mortalised reference on the stack (which is caused by
84 calling "track" with the expression "\$var", which creates the
85 reference).
86
87 And all these account for six reference counts.
64 88
65EXPORTS 89EXPORTS
66 None. 90 None.
67 91
68FUNCTIONS 92FUNCTIONS
… …
90 call on invalid ones. 114 call on invalid ones.
91 115
92 # we know that HASH(0x176ff70) exists, so turn it into a hashref: 116 # we know that HASH(0x176ff70) exists, so turn it into a hashref:
93 my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; 117 my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
94 118
119 $ref = Devel::FindRef::ref2ptr $reference
120 The opposite of "ptr2ref", above: returns the internal address of
121 the value pointed to by the passed reference. *No checks whatsoever
122 will be done*, so don't use this.
123
95ENVIRONMENT VARIABLES 124ENVIRONMENT VARIABLES
96 You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an 125 You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an
97 integer to override the default depth in "track". If a call explicitly 126 integer to override the default depth in "track". If a call explicitly
98 specified a depth it is not overridden. 127 specified a depth it is not overridden.
99 128
100AUTHOR 129AUTHOR
101 Marc Lehmann <pcg@goof.com>. 130 Marc Lehmann <pcg@goof.com>.
102 131
103BUGS
104 Only code values, arrays, hashes, scalars and magic are being looked at.
105
106 This is a quick hack only.
107
108COPYRIGHT AND LICENSE 132COPYRIGHT AND LICENSE
109 Copyright (C) 2007 by Marc Lehmann. 133 Copyright (C) 2007, 2008 by Marc Lehmann.
110 134
111 This library is free software; you can redistribute it and/or modify it 135 This library is free software; you can redistribute it and/or modify it
112 under the same terms as Perl itself, either Perl version 5.8.8 or, at 136 under the same terms as Perl itself, either Perl version 5.8.8 or, at
113 your option, any later version of Perl 5 you may have available. 137 your option, any later version of Perl 5 you may have available.
114 138

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