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[p5sagit/Mutually-Assured-Destruction.git] / notes / strong-with-getonce.pl

diff --git a/notes/strong-with-getonce.pl b/notes/strong-with-getonce.pl
new file mode 100644 (file)
index 0000000..22280a9
--- /dev/null
+++ b/notes/strong-with-getonce.pl
@@ -0,0 +1,51 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use Devel::GlobalDestruction ();
+use Scalar::Util ();
+use Variable::Magic ();
+use Carp ();
+
+BEGIN {
+  package Foo;
+
+  my $wiz;
+  $wiz = Variable::Magic::wizard
+    data => sub { $_[1] },
+    get => sub {
+      Carp::cluck "get fired";
+      Variable::Magic::dispell ${$_[0]}, $wiz;
+    };
+
+  sub DESTROY {
+    return if Devel::GlobalDestruction::in_global_destruction();
+    warn "DESTROY\n";
+
+    my $self = shift;
+
+    if (ref $self->{other_side} && $self->{other_side}{reference}) {
+      if (
+        Scalar::Util::refaddr($self->{other_side}{reference})
+        eq Scalar::Util::refaddr($self)
+      ) {
+        warn "Enlivening";
+        $self->{other_side}{reference} = $self;
+        Variable::Magic::cast $self->{other_side}{reference}, $wiz;
+        delete $self->{other_side};
+      }
+    }
+  }
+}
+
+my $near = {};
+my $far = $near->{reference} = bless({ other_side => $near }, 'Foo');
+warn $near->{reference};
+warn $far;
+Scalar::Util::weaken($near->{reference});
+warn "Setup done\n";
+undef($far);
+warn $near->{reference};
+warn $near->{reference};
+Scalar::Util::weaken($near->{reference});
+warn $near->{reference};