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NAME |
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Devel::FindRef - where is that reference to my variable hiding? |
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|
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SYNOPSIS |
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use Devel::FindRef; |
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|
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DESCRIPTION |
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Tracking down reference problems (e.g. you expect some object to be |
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destroyed, but there are still references to it that keep it alive) can |
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be very hard. Fortunately, perl keeps track of all its values, so |
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tracking references "backwards" is usually possible. |
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|
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The "track" function can help track down some of those references back |
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to the variables containing them. |
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|
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For example, for this fragment: |
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|
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package Test; |
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|
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our $var = "hi\n"; |
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my $x = \$var; |
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our %hash = (ukukey => \$var); |
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our $hash2 = {ukukey2 => \$var}; |
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|
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sub testsub { |
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my $local = $hash2; |
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print Devel::FindRef::track \$var; |
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} |
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|
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testsub; |
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|
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The output is as follows (or similar to this, in case I forget to update |
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the manpage after some changes): |
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|
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SCALAR(0x814ece8) is |
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+- in the global $Test::var. |
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+- referenced by REF(0x814f9e4), which is |
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| in the lexical '$x' in CODE(0x814ed78), which is |
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| the containing scope for CODE(0x820c4b0), which is |
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| in the global &Test::testsub. |
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+- referenced by REF(0x814ed6c), which is |
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| in the member 'ukukey' of HASH(0x81da20c), which is |
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| in the global %Test::hash. |
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+- referenced by REF(0x814ec28), which is |
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| not found anywhere I looked :( |
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+- referenced by REF(0x814eb44), which is |
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in the member 'ukukey2' of HASH(0x814f99c), which is |
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+- referenced by REF(0x820c450), which is |
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| in the lexical '$local' in CODE(0x820c4b0), which was seen before. |
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+- referenced by REF(0x820c204), which is |
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in the global $Test::hash2. |
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|
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It is a bit convoluted to read, but basically it says that the value |
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stored in $var can be found: |
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|
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- in some variable $x whose origin is not known (I frankly have no idea |
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why, hints accepted). |
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- in the hash element with key "ukukey" in the hash stored in |
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%Test::hash. |
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- in the global variable named $Test::var. |
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- in the hash element "ukukey2", in the hash in the my variable $local |
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in the sub "Test::testsub" and also in the hash referenced by |
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$Test::hash2. |
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|
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EXPORTS |
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None. |
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|
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FUNCTIONS |
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$string = Devel::FindRef::track $ref[, $depth] |
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Track the perl value pointed to by $ref up to a depth of $depth and |
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return a descriptive string. $ref can point at any perl value, be it |
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anonymous sub, hash, array, scalar etc. |
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|
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This is the function you most often use. |
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|
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@references = Devel::FindRef::find $ref |
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Return arrayrefs that contain [$message, $ref] pairs. The message |
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describes what kind of reference was found and the $ref is the |
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reference itself, which can be omitted if "find" decided to end the |
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search. The returned references are all weak references. |
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|
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The "track" function uses this to find references to the value you |
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are interested in and recurses on the returned references. |
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|
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$ref = Devel::FindRef::ptr2ref $integer |
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Sometimes you know (from debugging output) the address of a perl |
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scalar you are interested in (e.g. "HASH(0x176ff70)"). This function |
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can be used to turn the address into a reference to that scalar. It |
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is quite safe to call on valid addresses, but extremely dangerous to |
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call on invalid ones. |
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|
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# we know that HASH(0x176ff70) exists, so turn it into a hashref: |
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my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; |
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|
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ENVIRONMENT VARIABLES |
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You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an |
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integer to override the default depth in "track". If a call explicitly |
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specified a depth it is not overridden. |
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|
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AUTHOR |
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Marc Lehmann <pcg@goof.com>. |
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|
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BUGS |
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Only code values, arrays, hashes, scalars and magic are being looked at. |
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|
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This is a quick hack only. |
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|
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COPYRIGHT AND LICENSE |
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Copyright (C) 2007 by Marc Lehmann. |
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|
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This library is free software; you can redistribute it and/or modify it |
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under the same terms as Perl itself, either Perl version 5.8.8 or, at |
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your option, any later version of Perl 5 you may have available. |
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