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Revision 1.8 by root, Sat Jul 19 01:38:57 2008 UTC vs.
Revision 1.9 by root, Mon Dec 1 13:47:09 2008 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;
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
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 - in the lexical $closure_var (0x8abcc8), which is inside an
57 why, hints accepted). 76 instantiated closure, which in turn is used quite a bit.
77 - in the package-level lexical $global_my.
78 - in the global package variable named $Test::var.
79 - in the hash element "ukukey2", in the hash in the my variable
80 $testsub_local in the sub "Test::testsub" and also in the hash
81 "$referenced by Test::hash2".
58 - 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
59 %Test::hash. 83 %Test::hash.
60 - in the global variable named $Test::var. 84 - some anonymous mortalised reference on the stack (which is caused by
61 - in the hash element "ukukey2", in the hash in the my variable $local 85 calling "track" with the expression "\$var", which creates the
62 in the sub "Test::testsub" and also in the hash referenced by 86 reference).
63 $Test::hash2. 87
88 And all these account for six reference counts.
64 89
65EXPORTS 90EXPORTS
66 None. 91 None.
67 92
68FUNCTIONS 93FUNCTIONS
… …
103 specified a depth it is not overridden. 128 specified a depth it is not overridden.
104 129
105AUTHOR 130AUTHOR
106 Marc Lehmann <pcg@goof.com>. 131 Marc Lehmann <pcg@goof.com>.
107 132
108BUGS
109 Only code values, arrays, hashes, scalars and magic are being looked at.
110
111 This is a quick hack only.
112
113COPYRIGHT AND LICENSE 133COPYRIGHT AND LICENSE
114 Copyright (C) 2007 by Marc Lehmann. 134 Copyright (C) 2007, 2008 by Marc Lehmann.
115 135
116 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
117 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
118 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.
119 139

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