Mac OS X data corruption bug
Wednesday, May 9, 2007
Another day, another bug in the infrastructure underlying Factor.
I submitted this one to Apple. This test
case demonstrates the problem;
if you’re doing memcpy() when there is a probability that an interval
timer set by setitimer() might be fired, then you’re screwed. This
problem is reproducible on PowerMac G5’s, but not PowerMac G4’s or Intel
Macs. So it might be that the signal handling code is not
saving/restoring the G5’s AltiVec registers correctly (memcpy() uses
AltiVec).
How did I come across this bug? I’m working on a (statistical sampling) profiler. It can profile both interpreted and compiled code. Except on Mac OS X/PPC, it kills Factor with a GC assertion…
I love Mac OS X, I really do. But I wish the basic stuff like signal handlers, threads, and so on, was implemented properly.