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Message-ID: <486244B6.3090003@gmail.com>
Date: Wed, 25 Jun 2008 14:14:30 +0100
From: Tim Ellison <t.p.ellison@gmail.com>
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To: dev@harmony.apache.org
Subject: Re: java.lang.ref.ReferenceQueue.enqueue allocates array during GC
References: <48623E95.2010500@gmail.com>
In-Reply-To: <48623E95.2010500@gmail.com>
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Ian Rogers wrote:
> I'm having a problem with java.lang.ref.ReferenceQueue.enqueue in that 
> it queues references onto an array during GC, and that this array may 
> need to be grown during the GC. Generating new objects during GC is 
> something of a gray area, in the VM I'm working with it is not allowed. 
> An alternative is to have a field in Reference that allows references to 
> be linked together. Should this approach be adopted for all of Harmony 
> or just within our VM?

This is the approach taken by Harmony's DRLVM too.  DRLVM doesn't use 
the implementation of ReferenceQueue in the classlib code [1], it has 
it's own implementation in the kernel classes [2].

This is (another) case where the contract between VM implementor and the 
class library code would need to be changed if we were to adopt the 
'linked list' implementation of the queue.

[1] 
http://svn.apache.org/viewvc/harmony/enhanced/classlib/trunk/modules/luni/src/main/java/java/lang/ref/ReferenceQueue.java?view=markup
[2] 
http://svn.apache.org/viewvc/harmony/enhanced/drlvm/trunk/vm/vmcore/src/kernel_classes/javasrc/java/lang/ref/ReferenceQueue.java?view=markup

Regards,
Tim