garbage collector

Someone here was building Hugs on powerpc-apple-darwin6.6, and getting INTERNAL ERROR: importEntity. The import entity in question had been garbage collected. Recompiling module.c without optimization avoids the problem, so my guess is that the optimizer's use of registers is confusing the garbage collector. I'm starting to think that marking the C stack isn't working very well, and wondering if this is why optimization is turned off for some of the other files.