One point about char is that a pointer to a character type (character types are char, unsigned char, signed char - see 6.2.5.15) may alias non-char objects in a standard-compliant fashion (see 6.3.2.3.7). But uint8_t and int8_t may not necessarily be suitable replacements, because they are defined to be integer types (see B.19 - character types are a subset of integer types), and in any event may not even exist (7.20.1.1.3).