notes/saved-by-strength.pl

   1 #!/usr/bin/env perl
   2
   3 use strict;
   4 use warnings;
   5 use Devel::GlobalDestruction ();
   6 use Scalar::Util ();
   7
   8 BEGIN {
   9   package Foo;
  10
  11   sub DESTROY {
  12     return if Devel::GlobalDestruction::in_global_destruction();
  13     warn "DESTROY\n";
  14
  15     my $self = shift;
  16
  17     if (ref $self->{other_side}) {
  18       if (
  19         Scalar::Util::refaddr($self->{other_side}{reference})
  20         eq Scalar::Util::refaddr($self)
  21       ) {
  22         warn "Enlivening";
  23         $self->{other_side}{reference} = $self;
  24         delete $self->{other_side};
  25       }
  26     }
  27   }
  28 }
  29
  30 my $near = {};
  31 my $far = $near->{reference} = bless({ other_side => $near }, 'Foo');
  32 warn $near->{reference};
  33 warn $far;
  34 Scalar::Util::weaken($near->{reference});
  35 warn "Setup done\n";
  36 undef($far);
  37 warn $near->{reference};
  38 Scalar::Util::weaken($near->{reference});
  39 warn $near->{reference};