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Re: [Gnash-dev] Garbage collector

From: strk
Subject: Re: [Gnash-dev] Garbage collector
Date: Fri, 15 Jun 2007 23:54:17 +0200

On Fri, Jun 15, 2007 at 03:45:45PM -0600, Eric Hughes wrote:
> At 02:18 PM 6/15/2007, strk wrote:
> >var o = new Object;
> >o.hello = function() { trace("hello"); }
> >Function.prototype.constructor = o;
> >delete o;
> >Function.prototype.constructor.helo(); // expect a trace
> Two issues: the reference outward from "constructor" and the references 
> toward "o".
> First.  The reference variable for "constructor" should be able to be hold 
> either a weak or a strong reference, and it would be initialized to a weak 
> reference.  This means that in the ordinary case where constructor 
> assignment does not occur, that the incremental RC mechanism will catch it, 
> eliminating an item for the GC to deal with.
> Second. After assignment, "constructor" (an l-value) contains a strong 
> reference to the r-value of "o".  At this point both the variables "o" and 
> "constructor" have references.  Then when the variable "o" itself goes away 
> (an l-value), "constructor" still has a strong reference.
> This was the kind of thing I mentioned earlier about possibility and 
> feasibility.  To use weak references in this way requires that r-values and 
> l-values be separate, and I'm just not familiar enough with the VM 
> implementation to know if this is already there or, if lacking, what 
> requisite effort would be resolved.

Our l-values are just strings, and r-values are as_values (possibly objects, in
which case they are ref-counted).


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