> Valgrind is a really nice and really good tool, but not
> useful for tracking down bugs in a (conservative) collector.
It depends on the bug. The most likely bug you'll get because of GC is either 
that it freed something that was used by a C extension, or that it tries to 
free two times the same slot. In both case, valgrind will give something 
useful. You're right, however, for other cases of GC-related bugs.

As I said, Brent will have to generate a suppression file to get something 
useful. Otherwise, the real bugs will be lost inside a lot of warnings that 
are generated because of "normal" GC operations.

Best regards.
-- 
Sylvain