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Revision 1.11 by root, Fri May 16 07:43:53 2014 UTC

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15 The "track" function can help track down some of those references back 15 The "track" function can help track down some of those references back
16 to the variables containing them. 16 to the variables containing them.
17 17
18 For example, for this fragment: 18 For example, for this fragment:
19 19
20 package Test; 20 package Test;
21 21
22 use Devel::FindRef; 22 use Devel::FindRef;
23 use Scalar::Util; 23 use Scalar::Util;
24 24
25 our $var = "hi\n"; 25 our $var = "hi\n";
26 my $global_my = \$var; 26 my $global_my = \$var;
27 our %global_hash = (ukukey => \$var); 27 our %global_hash = (ukukey => \$var);
28 our $global_hashref = { ukukey2 => \$var }; 28 our $global_hashref = { ukukey2 => \$var };
29 29
30 sub testsub { 30 sub testsub {
31 my $testsub_local = $global_hashref; 31 my $testsub_local = $global_hashref;
32 print Devel::FindRef::track \$var; 32 print Devel::FindRef::track \$var;
33 } 33 }
34
35 34
36 my $closure = sub { 35 my $closure = sub {
37 my $closure_var = \$_[0]; 36 my $closure_var = \$_[0];
38 Scalar::Util::weaken (my $weak_ref = \$var); 37 Scalar::Util::weaken (my $weak_ref = \$var);
39 testsub; 38 testsub;
… …
44 The output is as follows (or similar to this, in case I forget to update 43 The output is as follows (or similar to this, in case I forget to update
45 the manpage after some changes): 44 the manpage after some changes):
46 45
47 SCALAR(0x7cc888) [refcount 6] is 46 SCALAR(0x7cc888) [refcount 6] is
48 +- referenced by REF(0x8abcc8) [refcount 1], which is 47 +- referenced by REF(0x8abcc8) [refcount 1], which is
49 | in the lexical '$closure_var' in CODE(0x8abc50) [refcount 4], which is 48 | the lexical '$closure_var' in CODE(0x8abc50) [refcount 4], which is
50 | +- the closure created at tst:18. 49 | +- the closure created at tst:18.
51 | +- referenced by REF(0x7d3c58) [refcount 1], which is 50 | +- referenced by REF(0x7d3c58) [refcount 1], which is
52 | | in the lexical '$closure' in CODE(0x7ae530) [refcount 2], which is 51 | | the lexical '$closure' in CODE(0x7ae530) [refcount 2], which is
53 | | +- the containing scope for CODE(0x8ab430) [refcount 3], which is 52 | | +- the containing scope for CODE(0x8ab430) [refcount 3], which is
54 | | | in the global &Test::testsub. 53 | | | the global &Test::testsub.
55 | | +- the main body of the program. 54 | | +- the main body of the program.
56 | +- in the lexical '&' in CODE(0x7ae530) [refcount 2], which was seen before. 55 | +- the lexical '&' in CODE(0x7ae530) [refcount 2], which was seen before.
57 +- referenced by REF(0x7cc7c8) [refcount 1], which is 56 +- referenced by REF(0x7cc7c8) [refcount 1], which is
58 | in the lexical '$global_my' in CODE(0x7ae530) [refcount 2], which was seen before. 57 | the lexical '$global_my' in CODE(0x7ae530) [refcount 2], which was seen before.
59 +- in the global $Test::var. 58 +- the global $Test::var.
60 +- referenced by REF(0x7cc558) [refcount 1], which is 59 +- referenced by REF(0x7cc558) [refcount 1], which is
61 | in the member 'ukukey2' of HASH(0x7ae140) [refcount 2], which is 60 | the member 'ukukey2' of HASH(0x7ae140) [refcount 2], which is
62 | +- referenced by REF(0x8abad0) [refcount 1], which is 61 | +- referenced by REF(0x8abad0) [refcount 1], which is
63 | | in the lexical '$testsub_local' in CODE(0x8ab430) [refcount 3], which was seen before. 62 | | the lexical '$testsub_local' in CODE(0x8ab430) [refcount 3], which was seen before.
64 | +- referenced by REF(0x8ab4f0) [refcount 1], which is 63 | +- referenced by REF(0x8ab4f0) [refcount 1], which is
65 | in the global $Test::global_hashref. 64 | the global $Test::global_hashref.
66 +- referenced by REF(0x7ae518) [refcount 1], which is 65 +- referenced by REF(0x7ae518) [refcount 1], which is
67 | in the member 'ukukey' of HASH(0x7d3bb0) [refcount 1], which is 66 | the member 'ukukey' of HASH(0x7d3bb0) [refcount 1], which is
68 | in the global %Test::global_hash. 67 | the global %Test::global_hash.
69 +- referenced by REF(0x7ae2f0) [refcount 1], which is 68 +- referenced by REF(0x7ae2f0) [refcount 1], which is
70 a temporary on the stack. 69 a temporary on the stack.
71 70
72 It is a bit convoluted to read, but basically it says that the value 71 It is a bit convoluted to read, but basically it says that the value
73 stored in $var is referenced by: 72 stored in $var is referenced by:
… …
93 $string = Devel::FindRef::track $ref[, $depth] 92 $string = Devel::FindRef::track $ref[, $depth]
94 Track the perl value pointed to by $ref up to a depth of $depth and 93 Track the perl value pointed to by $ref up to a depth of $depth and
95 return a descriptive string. $ref can point at any perl value, be it 94 return a descriptive string. $ref can point at any perl value, be it
96 anonymous sub, hash, array, scalar etc. 95 anonymous sub, hash, array, scalar etc.
97 96
98 This is the function you most often use. 97 This is the function you most likely want to use when tracking down
98 references.
99 99
100 @references = Devel::FindRef::find $ref 100 @references = Devel::FindRef::find $ref
101 Return arrayrefs that contain [$message, $ref] pairs. The message 101 Return arrayrefs that contain [$message, $ref] pairs. The message
102 describes what kind of reference was found and the $ref is the 102 describes what kind of reference was found and the $ref is the
103 reference itself, which can be omitted if "find" decided to end the 103 reference itself, which can be omitted if "find" decided to end the
… …
106 The "track" function uses this to find references to the value you 106 The "track" function uses this to find references to the value you
107 are interested in and recurses on the returned references. 107 are interested in and recurses on the returned references.
108 108
109 $ref = Devel::FindRef::ptr2ref $integer 109 $ref = Devel::FindRef::ptr2ref $integer
110 Sometimes you know (from debugging output) the address of a perl 110 Sometimes you know (from debugging output) the address of a perl
111 scalar you are interested in (e.g. "HASH(0x176ff70)"). This function 111 value you are interested in (e.g. "HASH(0x176ff70)"). This function
112 can be used to turn the address into a reference to that scalar. It 112 can be used to turn the address into a reference to that value. It
113 is quite safe to call on valid addresses, but extremely dangerous to 113 is quite safe to call on valid addresses, but extremely dangerous to
114 call on invalid ones. 114 call on invalid ones. *No checks whatsoever will be done*, so don't
115 use this unless you really know the value is the address of a valid
116 perl value.
115 117
116 # we know that HASH(0x176ff70) exists, so turn it into a hashref: 118 # we know that HASH(0x176ff70) exists, so turn it into a hashref:
117 my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; 119 my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
118 120
119 $ref = Devel::FindRef::ref2ptr $reference 121 $ptr = Devel::FindRef::ref2ptr $reference
120 The opposite of "ptr2ref", above: returns the internal address of 122 The opposite of "ptr2ref", above: returns the internal address of
121 the value pointed to by the passed reference. *No checks whatsoever 123 the value pointed to by the passed reference. This function is safe
122 will be done*, so don't use this. 124 to call on anything, and returns the same value taht a normal
125 reference would if used in a numeric context.
123 126
124ENVIRONMENT VARIABLES 127ENVIRONMENT VARIABLES
125 You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an 128 You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an
126 integer to override the default depth in "track". If a call explicitly 129 integer to override the default depth in "track". If a call explicitly
127 specified a depth it is not overridden. 130 specifies a depth, it is not overridden.
128 131
129AUTHOR 132AUTHOR
130 Marc Lehmann <pcg@goof.com>. 133 Marc Lehmann <pcg@goof.com>.
131 134
132COPYRIGHT AND LICENSE 135COPYRIGHT AND LICENSE
133 Copyright (C) 2007, 2008 by Marc Lehmann. 136 Copyright (C) 2007, 2008, 2009, 2013 by Marc Lehmann.
134 137
135 This library is free software; you can redistribute it and/or modify it 138 This library is free software; you can redistribute it and/or modify it
136 under the same terms as Perl itself, either Perl version 5.8.8 or, at 139 under the same terms as Perl itself, either Perl version 5.8.8 or, at
137 your option, any later version of Perl 5 you may have available. 140 your option, any later version of Perl 5 you may have available.
138 141

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