https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63303
--- Comment #9 from mikulas at artax dot karlin.mff.cuni.cz --- > See what I wrote, any object size bigger than half of address space really > isn't supportable, because then (char *) (P) - (char *) (Q) might not fit into > ptrdiff_t. There is no point slowing down all pointer subtractions (other > than > char/signed char/unsigned char pointers) for something that really wouldn't > work reliably anyway. But the code in comment 4 doesn't perform (char *)P - (char *)Q. It performs (short *)P - (short *)Q. And that result clearly fits into the signed ptrdiff_t type. If the code in comment 4 performed (char *)b - (char *)a, that operation would be invalid because of overflow. But it doesn't.
