If you really insist on not having a distinction between "u8"/"i8" and "unsigned char"/"signed char", and you've gone to the trouble of refusing to accept CHAR_BIT!=8, I'm pretty sure it'd be safer to typedef unsigned char u8 and typedef signed char i8. uint8_t/int8_t are not necessarily character types (see 6.2.5.20 and 7.22.1.1) and there are ramifications (see, e.g., 6.2.6.1, 6.3.2.3, 6.5.1).