From: Asher <asher@...>
Date: 2010-08-28T03:07:39+09:00
Subject: [ruby-core:31903] Re: Garbage Collection Question

It takes place in the Hash::Weak code in []:

class Hash::Weak < Hash
  
  def []( key )

    # get the stored ID - a FixNum, not an object reference to our weak-referenced object
    obj_id = super( key )

    # theoretically this should cause non-referenced objects to get cleaned up 
    # so long as nothing looks like a pointer or reference to it
    ObjectSpace.garbage_collect

    # now get our object from ID
    # if it had no references it should have been GC'd and we should get an 
    # rb_eRangeError "is not id value" (expected) or "is recycled object" (possible)
    obj = ObjectSpace._id2ref( obj_id )

    return obj

  end
  
  def []=( key, object )

    # FixNum have a constant ID for value, so can't be copied and can't be garbage collected
    # so object.__id__ cannot be a reference to a child of object and therefore cannot prevent
    # garbage collection on the object
    super( key, object.__id__ )

  end
  
end

Asher

On Aug 27, 2010, at 2:05 PM, Evan Phoenix wrote:

> Your examples do not include calling GC.start to force a GC, thus I wonder if this is the source of your problem. Remember that by default, the GC runs whenever it wants. So you can't depend on it to run an certain times.
> 
> - Evan