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From Anthony Green <gr...@redhat.com>
Subject Re: GC Compatibility (was: Re: State of the World)
Date Mon, 09 May 2005 20:35:58 GMT
On Mon, 2005-05-09 at 13:08 -0700, Steven Augart wrote:
> I'd like to take off on a tangent here.  At one point I had the naive
> idea that I could make Jikes RVM able to play nicely with GCJ.  What
> really quashed the idea was the issue of garbage collection -- GCC is not
> designed to pass type information down to the lower levels of the
> compiler, so GCJ doesn't build a "gc map", which you need in order to be
> use any GC other than a Boehm-style conservative non-copying collector. 
> In other words, GCJ is restricted to using a garbage collection that
> looks for any bit patterns in the data that might be pointers, and it has
> to assume that all of them are pointers.  If I am mis-stating the
> problem, I would appreciate someone publicly correcting me. 

You are correct.  Although I'll point out that this kind of support was
once hacked into GCC by Rick Hudson and others for their experimental
GCC-based compiler for Modula-3 (Rick is now at Intel and was (is?)
involved in ORP).  Perhaps this could be done again.


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