As far as I know, C99 makes no requirements about the byte width of int8_t, only about its bit width. The relevant bits are in section 7.18.1.1 . There are few

As far as I know, C99 makes no requirements about the byte width of int8_t, only about its bit width. The relevant bits are in section 7.18.1.1 . There are few architectures and runtimes where this is relevant anymore, and the answer is really best given on a case-by-case basis. I think it's technically possible to make the two pointer-compatible on architectures with wider bytes. Last time I used one it was Analog Devices' SHARC, and I think they were pointer-compatible, but that was a long time ago, so take it with a grain of salt.