make with aix5.1 compiler vac5 (xlc) was failing in checks until I added if (n == 0) n = 1; before calling malloc. The technical reference for AIX 5L 5.1 says: If the malloc or valloc subroutine is called with a size of 0, the subroutine returns a null pointer The better way to fix this would probably be to allow a NULL being returned if malloc(0) was called. gnupg-1.0.7/util/memory.c Winona