| 1 |
package Devel::FindRef; |
| 2 |
|
| 3 |
no warnings; # I hate warning nazis |
| 4 |
use strict; |
| 5 |
|
| 6 |
use XSLoader; |
| 7 |
use Scalar::Util; |
| 8 |
|
| 9 |
BEGIN { |
| 10 |
our $VERSION = '1.31'; |
| 11 |
XSLoader::load __PACKAGE__, $VERSION; |
| 12 |
} |
| 13 |
|
| 14 |
=head1 NAME |
| 15 |
|
| 16 |
Devel::FindRef - where is that reference to my variable hiding? |
| 17 |
|
| 18 |
=head1 SYNOPSIS |
| 19 |
|
| 20 |
use Devel::FindRef; |
| 21 |
|
| 22 |
=head1 DESCRIPTION |
| 23 |
|
| 24 |
Tracking down reference problems (e.g. you expect some object to be |
| 25 |
destroyed, but there are still references to it that keep it alive) can be |
| 26 |
very hard. Fortunately, perl keeps track of all its values, so tracking |
| 27 |
references "backwards" is usually possible. |
| 28 |
|
| 29 |
The C<track> function can help track down some of those references back to |
| 30 |
the variables containing them. |
| 31 |
|
| 32 |
For example, for this fragment: |
| 33 |
|
| 34 |
package Test; |
| 35 |
|
| 36 |
our $var = "hi\n"; |
| 37 |
my $x = \$var; |
| 38 |
our %hash = (ukukey => \$var); |
| 39 |
our $hash2 = {ukukey2 => \$var}; |
| 40 |
|
| 41 |
sub testsub { |
| 42 |
my $local = $hash2; |
| 43 |
print Devel::FindRef::track \$var; |
| 44 |
} |
| 45 |
|
| 46 |
testsub; |
| 47 |
|
| 48 |
The output is as follows (or similar to this, in case I forget to update |
| 49 |
the manpage after some changes): |
| 50 |
|
| 51 |
SCALAR(0x814ece8) is |
| 52 |
+- in the global $Test::var. |
| 53 |
+- referenced by REF(0x814f9e4), which is |
| 54 |
| in the lexical '$x' in CODE(0x814ed78), which is |
| 55 |
| the containing scope for CODE(0x820c4b0), which is |
| 56 |
| in the global &Test::testsub. |
| 57 |
+- referenced by REF(0x814ed6c), which is |
| 58 |
| in the member 'ukukey' of HASH(0x81da20c), which is |
| 59 |
| in the global %Test::hash. |
| 60 |
+- referenced by REF(0x814ec28), which is |
| 61 |
| not found anywhere I looked :( |
| 62 |
+- referenced by REF(0x814eb44), which is |
| 63 |
in the member 'ukukey2' of HASH(0x814f99c), which is |
| 64 |
+- referenced by REF(0x820c450), which is |
| 65 |
| in the lexical '$local' in CODE(0x820c4b0), which was seen before. |
| 66 |
+- referenced by REF(0x820c204), which is |
| 67 |
in the global $Test::hash2. |
| 68 |
|
| 69 |
It is a bit convoluted to read, but basically it says that the value |
| 70 |
stored in C<$var> can be found: |
| 71 |
|
| 72 |
=over 4 |
| 73 |
|
| 74 |
=item - in some variable C<$x> whose origin is not known (I frankly have no |
| 75 |
idea why, hints accepted). |
| 76 |
|
| 77 |
=item - in the hash element with key C<ukukey> in the hash stored in C<%Test::hash>. |
| 78 |
|
| 79 |
=item - in the global variable named C<$Test::var>. |
| 80 |
|
| 81 |
=item - in the hash element C<ukukey2>, in the hash in the my variable |
| 82 |
C<$local> in the sub C<Test::testsub> and also in the hash referenced by |
| 83 |
C<$Test::hash2>. |
| 84 |
|
| 85 |
=back |
| 86 |
|
| 87 |
=head1 EXPORTS |
| 88 |
|
| 89 |
None. |
| 90 |
|
| 91 |
=head1 FUNCTIONS |
| 92 |
|
| 93 |
=over 4 |
| 94 |
|
| 95 |
=item $string = Devel::FindRef::track $ref[, $depth] |
| 96 |
|
| 97 |
Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and |
| 98 |
return a descriptive string. C<$ref> can point at any perl value, be it |
| 99 |
anonymous sub, hash, array, scalar etc. |
| 100 |
|
| 101 |
This is the function you most often use. |
| 102 |
|
| 103 |
=cut |
| 104 |
|
| 105 |
sub find($); |
| 106 |
|
| 107 |
sub track { |
| 108 |
my ($ref, $depth) = @_; |
| 109 |
@_ = (); |
| 110 |
|
| 111 |
my $buf = ""; |
| 112 |
my %seen; |
| 113 |
|
| 114 |
Scalar::Util::weaken $ref; |
| 115 |
|
| 116 |
my $track; $track = sub { |
| 117 |
my ($refref, $depth, $indent) = @_; |
| 118 |
|
| 119 |
if ($depth) { |
| 120 |
my (@about) = find $$refref; |
| 121 |
if (@about) { |
| 122 |
for my $about (@about) { |
| 123 |
$buf .= "$indent" . (@about > 1 ? "+- " : " ") . $about->[0]; |
| 124 |
if (@$about > 1) { |
| 125 |
if ($seen{ref2ptr $about->[1]}++) { |
| 126 |
$buf .= " $about->[1], which was seen before.\n"; |
| 127 |
} else { |
| 128 |
$buf .= " $about->[1], which is\n"; |
| 129 |
$track->(\$about->[1], $depth - 1, $about == $about[-1] ? "$indent " : "$indent| "); |
| 130 |
} |
| 131 |
} else { |
| 132 |
$buf .= ".\n"; |
| 133 |
} |
| 134 |
} |
| 135 |
} else { |
| 136 |
$buf .= "$indent not found anywhere I looked :(\n"; |
| 137 |
} |
| 138 |
} else { |
| 139 |
$buf .= "$indent not referenced within the search depth.\n"; |
| 140 |
} |
| 141 |
}; |
| 142 |
|
| 143 |
$buf .= "$ref is\n"; |
| 144 |
$track->(\$ref, $depth || $ENV{PERL_DEVEL_FINDREF_DEPTH} || 10, ""); |
| 145 |
$buf |
| 146 |
} |
| 147 |
|
| 148 |
=item @references = Devel::FindRef::find $ref |
| 149 |
|
| 150 |
Return arrayrefs that contain [$message, $ref] pairs. The message |
| 151 |
describes what kind of reference was found and the C<$ref> is the |
| 152 |
reference itself, which can be omitted if C<find> decided to end the |
| 153 |
search. The returned references are all weak references. |
| 154 |
|
| 155 |
The C<track> function uses this to find references to the value you are |
| 156 |
interested in and recurses on the returned references. |
| 157 |
|
| 158 |
=cut |
| 159 |
|
| 160 |
sub find($) { |
| 161 |
my ($about, $excl) = &find_; |
| 162 |
my %excl = map +($_ => undef), @$excl; |
| 163 |
grep !exists $excl{ref2ptr $_->[1]}, @$about |
| 164 |
} |
| 165 |
|
| 166 |
=item $ref = Devel::FindRef::ptr2ref $integer |
| 167 |
|
| 168 |
Sometimes you know (from debugging output) the address of a perl scalar |
| 169 |
you are interested in (e.g. C<HASH(0x176ff70)>). This function can be used |
| 170 |
to turn the address into a reference to that scalar. It is quite safe to |
| 171 |
call on valid addresses, but extremely dangerous to call on invalid ones. |
| 172 |
|
| 173 |
# we know that HASH(0x176ff70) exists, so turn it into a hashref: |
| 174 |
my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; |
| 175 |
|
| 176 |
=item $ref = Devel::FindRef::ref2ptr $reference |
| 177 |
|
| 178 |
The opposite of C<ptr2ref>, above: returns the internal address of the |
| 179 |
value pointed to by the passed reference. I<No checks whatsoever will be |
| 180 |
done>, so don't use this. |
| 181 |
|
| 182 |
=back |
| 183 |
|
| 184 |
=head1 ENVIRONMENT VARIABLES |
| 185 |
|
| 186 |
You can set the environment variable C<PERL_DEVEL_FINDREF_DEPTH> to an |
| 187 |
integer to override the default depth in C<track>. If a call explicitly |
| 188 |
specified a depth it is not overridden. |
| 189 |
|
| 190 |
=head1 AUTHOR |
| 191 |
|
| 192 |
Marc Lehmann <pcg@goof.com>. |
| 193 |
|
| 194 |
=head1 BUGS |
| 195 |
|
| 196 |
Only code values, arrays, hashes, scalars and magic are being looked at. |
| 197 |
|
| 198 |
This is a quick hack only. |
| 199 |
|
| 200 |
=head1 COPYRIGHT AND LICENSE |
| 201 |
|
| 202 |
Copyright (C) 2007 by Marc Lehmann. |
| 203 |
|
| 204 |
This library is free software; you can redistribute it and/or modify |
| 205 |
it under the same terms as Perl itself, either Perl version 5.8.8 or, |
| 206 |
at your option, any later version of Perl 5 you may have available. |
| 207 |
|
| 208 |
=cut |
| 209 |
|
| 210 |
1 |
| 211 |
|
