Walt> Thanks Tom. My math shows the kernel sizes as Walt> Redzone 128 Walt> math frame/xstate 840 Walt> rt_sigframe 456 Walt> That's a total of 1424 bytes, so maybe GDB is saving less than it should? It seems to me that there's no need to save the red zone. However, I don't really know. All I can suggest is trying to write a test case and/or debug it to see. Tom