[ViewVC] Annotation of: cvs/Devel-FindRef/README

NAME
    Devel::FindRef - where is that reference to my scalar hiding?

SYNOPSIS
      use Devel::FindRef;

DESCRIPTION
    Tracking down reference problems (e.g. you expect some object to be
    destroyed, but there are still references to it that keep it alive) can
    be very hard. Fortunately, perl keeps track of all its values, so
    tracking references "backwards" is usually possible.

    The "track" function can help track down some of those references back
    to the variables containing them.

    For example, for this fragment:

       package Test;           
                             
   our $var = "hi\n";
       my $x = \$var;      
       our %hash = (ukukey => \$var);
       our $hash2 = {ukukey2 => \$var};
                               
   sub testsub {             
          my $local = $hash2;      
          print Devel::FindRef::track \$var;
       }                             
                                       
   testsub;

    The output is as follows (or similar to this, in case I forget to update
    the manpage after some changes):

       SCALAR(0x7bd2d0) is
          in the global $Test::var.
          referenced by REF(0x7bd240), which is
             in the member 'ukukey2' of HASH(0x7bd228), which is
                referenced by REF(0x81dae8), which is
                   in the lexical '$local' in CODE(0x81da88), which is
                      in the global &Test::testsub.
                referenced by REF(0x81da40), which is
                   in the global $Test::hash2.
          referenced by REF(0x79f3f8), which is
             in the lexical '$x' in CODE(0x79f518), which is
                the containing scope for CODE(0x81da88), which is
                   in the global &Test::testsub.
          referenced by REF(0x79f2f0), which is
             not found anywhere I looked :(
          referenced by REF(0x79f140), which is
             in the member 'ukukey' of HASH(0x81d698), which is
                in the global %Test::hash.

    It is a bit convoluted to read, but basically it says that the value
    stored in $var can be found:

    - in some variable $x whose origin is not known (I frankly have no idea
    why, hints accepted).
    - in the hash element with key "ukukey" in the hash stored in
    %Test::hash.
    - in the global variable named $Test::var.
    - in the hash element "ukukey2", in the hash in the my variable $local
    in the sub "Test::testsub" and also in the hash referenced by
    $Test::hash2.

EXPORTS
    None.

FUNCTIONS
    $string = Devel::FindRef::track $ref[, $depth]
        Track the perl value pointed to by $ref up to a depth of $depth and
        return a descriptive string. $ref can point at any perl value, be it
        anonymous sub, hash, array, scalar etc.

        This is the function you most often use.

    @references = Devel::FindRef::find $ref
        Return arrayrefs that contain [$message, $ref] pairs. The message
        describes what kind of reference was found and the $ref is the
        reference itself, which can be omitted if "find" decided to end the
        search. The returned references are all weak references.

        The "track" function uses this to find references to the value you
        are interested in and recurses on the returned references.

    $ref = Devel::FindRef::ptr2ref $integer
        Sometimes you know (from debugging output) the address of a perl
        scalar you are interested in (e.g. "HASH(0x176ff70)"). This function
        can be used to turn the address into a reference to that scalar. It
        is quite safe to call on valid addresses, but extremely dangerous to
        call on invalid ones.

           # we know that HASH(0x176ff70) exists, so turn it into a hashref:
           my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;

AUTHOR
    Marc Lehmann <pcg@goof.com>.

BUGS
    Only code values, arrays, hashes, scalars and magic are being looked at.

    This is a quick hack only.

COPYRIGHT AND LICENSE
    Copyright (C) 2007 by Marc Lehmann.

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself, either Perl version 5.8.8 or, at
    your option, any later version of Perl 5 you may have available.

Revision:	1.6
Committed:	Sat Apr 26 03:15:28 2008 UTC (16 years ago) by root
Branch:	MAIN
CVS Tags:	rel-1_2
Changes since 1.5:	+21 -18 lines
Log Message:	1.2
#	User	Rev	Content
1	root	1.2	NAME
2			Devel::FindRef - where is that reference to my scalar hiding?
3
4			SYNOPSIS
5			use Devel::FindRef;
6
7			DESCRIPTION
8			Tracking down reference problems (e.g. you expect some object to be
9	root	1.3	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
11			tracking references "backwards" is usually possible.
12	root	1.2
13	root	1.3	The "track" function can help track down some of those references back
14			to the variables containing them.
15	root	1.2
16			For example, for this fragment:
17
18			package Test;
19	root	1.6
20			our $var = "hi\n";
21	root	1.2	my $x = \$var;
22			our %hash = (ukukey => \$var);
23			our $hash2 = {ukukey2 => \$var};
24	root	1.6
25			sub testsub {
26	root	1.2	my $local = $hash2;
27			print Devel::FindRef::track \$var;
28			}
29	root	1.6
30			testsub;
31	root	1.2
32	root	1.3	The output is as follows (or similar to this, in case I forget to update
33			the manpage after some changes):
34	root	1.2
35	root	1.6	SCALAR(0x7bd2d0) is
36	root	1.2	in the global $Test::var.
37	root	1.6	referenced by REF(0x7bd240), which is
38			in the member 'ukukey2' of HASH(0x7bd228), which is
39			referenced by REF(0x81dae8), which is
40			in the lexical '$local' in CODE(0x81da88), which is
41	root	1.2	in the global &Test::testsub.
42	root	1.6	referenced by REF(0x81da40), which is
43	root	1.2	in the global $Test::hash2.
44	root	1.6	referenced by REF(0x79f3f8), which is
45			in the lexical '$x' in CODE(0x79f518), which is
46			the containing scope for CODE(0x81da88), which is
47			in the global &Test::testsub.
48			referenced by REF(0x79f2f0), which is
49			not found anywhere I looked :(
50			referenced by REF(0x79f140), which is
51			in the member 'ukukey' of HASH(0x81d698), which is
52			in the global %Test::hash.
53	root	1.2
54			It is a bit convoluted to read, but basically it says that the value
55			stored in $var can be found:
56
57			- in some variable $x whose origin is not known (I frankly have no idea
58			why, hints accepted).
59			- in the hash element with key "ukukey" in the hash stored in
60			%Test::hash.
61			- in the global variable named $Test::var.
62			- in the hash element "ukukey2", in the hash in the my variable $local
63			in the sub "Test::testsub" and also in the hash referenced by
64			$Test::hash2.
65
66			EXPORTS
67	root	1.4	None.
68	root	1.2
69			FUNCTIONS
70	root	1.4	$string = Devel::FindRef::track $ref[, $depth]
71			Track the perl value pointed to by $ref up to a depth of $depth and
72			return a descriptive string. $ref can point at any perl value, be it
73			anonymous sub, hash, array, scalar etc.
74
75			This is the function you most often use.
76
77			@references = Devel::FindRef::find $ref
78			Return arrayrefs that contain [$message, $ref] pairs. The message
79			describes what kind of reference was found and the $ref is the
80	root	1.5	reference itself, which can be omitted if "find" decided to end the
81			search. The returned references are all weak references.
82	root	1.4
83			The "track" function uses this to find references to the value you
84			are interested in and recurses on the returned references.
85
86			$ref = Devel::FindRef::ptr2ref $integer
87			Sometimes you know (from debugging output) the address of a perl
88			scalar you are interested in (e.g. "HASH(0x176ff70)"). This function
89			can be used to turn the address into a reference to that scalar. It
90			is quite safe to call on valid addresses, but extremely dangerous to
91			call on invalid ones.
92
93			# we know that HASH(0x176ff70) exists, so turn it into a hashref:
94			my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70;
95	root	1.2
96			AUTHOR
97	root	1.4	Marc Lehmann <pcg@goof.com>.
98	root	1.2
99			BUGS
100	root	1.4	Only code values, arrays, hashes, scalars and magic are being looked at.
101	root	1.2
102	root	1.4	This is a quick hack only.
103	root	1.3
104	root	1.2	COPYRIGHT AND LICENSE
105	root	1.4	Copyright (C) 2007 by Marc Lehmann.
106	root	1.2
107	root	1.4	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
109			your option, any later version of Perl 5 you may have available.
110	root	1.2