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1 | NAME |
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2 | Devel::FindRef - where is that reference to my variable hiding? |
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3 | |
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4 | SYNOPSIS |
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5 | use Devel::FindRef; |
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6 | |
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7 | DESCRIPTION |
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8 | Tracking down reference problems (e.g. you expect some object to be |
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9 | destroyed, but there are still references to it that keep it alive) can |
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10 | be very hard. Fortunately, perl keeps track of all its values, so |
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11 | tracking references "backwards" is usually possible. |
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12 | |
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13 | The "track" function can help track down some of those references back |
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14 | to the variables containing them. |
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15 | |
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16 | For example, for this fragment: |
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17 | |
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18 | package Test; |
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19 | |
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20 | our $var = "hi\n"; |
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21 | my $x = \$var; |
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22 | our %hash = (ukukey => \$var); |
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23 | our $hash2 = {ukukey2 => \$var}; |
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24 | |
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25 | sub testsub { |
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26 | my $local = $hash2; |
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27 | print Devel::FindRef::track \$var; |
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28 | } |
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29 | |
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30 | testsub; |
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31 | |
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32 | The output is as follows (or similar to this, in case I forget to update |
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33 | the manpage after some changes): |
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34 | |
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35 | SCALAR(0x814ece8) is |
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36 | +- in the global $Test::var. |
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37 | +- referenced by REF(0x814f9e4), which is |
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38 | | in the lexical '$x' in CODE(0x814ed78), which is |
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39 | | the containing scope for CODE(0x820c4b0), which is |
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40 | | in the global &Test::testsub. |
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41 | +- referenced by REF(0x814ed6c), which is |
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42 | | in the member 'ukukey' of HASH(0x81da20c), which is |
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43 | | in the global %Test::hash. |
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44 | +- referenced by REF(0x814ec28), which is |
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45 | | not found anywhere I looked :( |
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46 | +- referenced by REF(0x814eb44), which is |
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47 | in the member 'ukukey2' of HASH(0x814f99c), which is |
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48 | +- referenced by REF(0x820c450), which is |
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49 | | in the lexical '$local' in CODE(0x820c4b0), which was seen before. |
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50 | +- referenced by REF(0x820c204), which is |
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51 | in the global $Test::hash2. |
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52 | |
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53 | It is a bit convoluted to read, but basically it says that the value |
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54 | stored in $var can be found: |
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55 | |
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56 | - in some variable $x whose origin is not known (I frankly have no idea |
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57 | why, hints accepted). |
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58 | - in the hash element with key "ukukey" in the hash stored in |
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59 | %Test::hash. |
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60 | - in the global variable named $Test::var. |
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61 | - in the hash element "ukukey2", in the hash in the my variable $local |
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62 | in the sub "Test::testsub" and also in the hash referenced by |
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63 | $Test::hash2. |
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64 | |
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65 | EXPORTS |
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66 | None. |
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67 | |
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68 | FUNCTIONS |
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69 | $string = Devel::FindRef::track $ref[, $depth] |
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70 | Track the perl value pointed to by $ref up to a depth of $depth and |
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71 | return a descriptive string. $ref can point at any perl value, be it |
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72 | anonymous sub, hash, array, scalar etc. |
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73 | |
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74 | This is the function you most often use. |
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75 | |
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76 | @references = Devel::FindRef::find $ref |
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77 | Return arrayrefs that contain [$message, $ref] pairs. The message |
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78 | describes what kind of reference was found and the $ref is the |
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79 | reference itself, which can be omitted if "find" decided to end the |
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80 | search. The returned references are all weak references. |
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81 | |
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82 | The "track" function uses this to find references to the value you |
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83 | are interested in and recurses on the returned references. |
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84 | |
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85 | $ref = Devel::FindRef::ptr2ref $integer |
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86 | Sometimes you know (from debugging output) the address of a perl |
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87 | scalar you are interested in (e.g. "HASH(0x176ff70)"). This function |
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88 | can be used to turn the address into a reference to that scalar. It |
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89 | is quite safe to call on valid addresses, but extremely dangerous to |
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90 | call on invalid ones. |
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91 | |
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92 | # we know that HASH(0x176ff70) exists, so turn it into a hashref: |
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93 | my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; |
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94 | |
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95 | ENVIRONMENT VARIABLES |
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96 | You can set the environment variable "PERL_DEVEL_FINDREF_DEPTH" to an |
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97 | integer to override the default depth in "track". If a call explicitly |
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98 | specified a depth it is not overridden. |
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99 | |
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100 | AUTHOR |
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101 | Marc Lehmann <pcg@goof.com>. |
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102 | |
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103 | BUGS |
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104 | Only code values, arrays, hashes, scalars and magic are being looked at. |
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105 | |
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106 | This is a quick hack only. |
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107 | |
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108 | COPYRIGHT AND LICENSE |
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109 | Copyright (C) 2007 by Marc Lehmann. |
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110 | |
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111 | This library is free software; you can redistribute it and/or modify it |
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112 | under the same terms as Perl itself, either Perl version 5.8.8 or, at |
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113 | your option, any later version of Perl 5 you may have available. |
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114 | |