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Program Repair Shop

19

Garbage collection

• Another serious error:

• Observers aren't garbage-collected properly

• The module must use weak references to garbage-collect them at all

• But then they are collected prematurely:

        my $alarm = Alarm->new();
        $alarm->add_observer(Guard->new);
        $alarm->notify_observers("I like pie!");

        Failed to send observation from 'Alarm=HASH(0x8113f74)' to '':
        Can't call method "update" on an undefined value at
        lib/Class/Observable.pm line 95.

• What happened here?

• The Guard object was garbage-collected

• The reference to it that was stored in %O became undef

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