Hi Mike, > How about GET_MODE_SIZE (STACK_SAVEAREA_MODE (SAVE_NONLOCAL)) / GET_MODE_SIZE (Pmode) + 2 + /* slop for mips, see builtin_setjmp_setup */ 1 - 1. This retains the slop for mips, and fixes ports like ia64 and s390 (see STACK_SAVEAREA_MODE on those ports, it is larger one might expect)? OK - revised patch attached. I have added a comment before the computation to explain each of the numbers, and adjusted the comments in the other files to match the new size of the jump buffer. What do you think of this version ? Cheers Nick