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(Previous discussion continued)
Re: Comparing Pika-syle and JNI-style Per Bothner (15 Jan 2004 01:26 UTC)

Re: Comparing Pika-syle and JNI-style Per Bothner 15 Jan 2004 01:26 UTC

bear wrote:

> You were referring, then, to correctness issues, where the C compiler
> makes some optimization (probably an optimization involving pointer
> arithmetic or pointer bit-operations) and as a result the conservative
> collector erroneously frees live data that the program is using it to
> refer to?

Yes.

> I'd think that schemes might be particularly vulnerable to this since
> a lot of implementations use "flag bits" in their pointers to identify
> representations, types, etc.

This qualifies as "mangling" pointers.  Obviously you'd better not
used mangled pointers in conjunction with a GC that doesn't
know about pointer mangling.  You could modify a GC to handle mangled
pointers, but a conservative GC is unlikely to work well.  It might
if it's just 2-3 low-order bits that are used for typecodes.
--
	--Per Bothner
xxxxxx@bothner.com   http://per.bothner.com/