Except that __attribute__((__mode__(__QI__))) makes that effectively equivalent to "unsigned char". From https://groups.google.com/g/comp.lang.c/c/sE6I4sgGyPs

Except that __attribute__((__mode__(__QI__))) makes that effectively equivalent to "unsigned char". From https://groups.google.com/g/comp.lang.c/c/sE6I4sgGyPs https://groups.google.com/g/comp.lang.c/c/sE6I4sgGyPs > A few tests on generated code, however, suggest that gcc treats these exactly as signed char and unsigned char, both in how the react to _Generic and in how the compiler handles them for alias analysis. So, that means that there are currently zero existing compilers that treat uint8_t differently from unsigned char.