After weeks of wrestling with Apple's buggy version of gdb, registerized compilation on MacOS X finally works! I've tested it on GHC itself and on my own (H)OpenGL program, VOP, and it seems to work now. I'm attaching my patches. I've had trouble compiling the newest version from CVS. Instead, I've stayed behind by one week (13th of March, to be exact). Bootstrapping from the old ghc 5.00.2 binary version seems to work only up to around 4th of March (Binary IO doesn't work properly with GHC 5.00.2/MacOS X). If I find enough webspace, I'll upload a binary version, too, to save other people the work of recompiling GHC twice in a row. Profiling doesn't work, I just get some segfaults. Is there anything specific that needs to be done to get profiling to work, or should I just go on another long bug-hunt? So, Mac users, please try it out and tell me if it works for your programs, too! Cheers, Wolfgang P.S. to Simon Marlow: You were right, those segfaults _are_ fun! Who would have thought that the PowerPC has so many registers that a clobbered callee-save only shows up _seconds_ later?