That doesn't work because possibly[2] the most important single use of uintmax_t is the printf specifier "%ju", ie a ABI boundary. Ironically, this is actually

That doesn't work because possibly[2] the most important single use of uintmax_t is the printf specifier "%ju", ie a ABI boundary. Ironically, this is actually one of the only[0] legitimate uses for standard[1] PRI* macros, since that could expand to whichever of "%llu", "%w128u", etc, was appropriate to the caller. 0: And I'm not sure "one of" is actually needed. 1: as opposed to nonstandard ones like PRIu_xlib_atom or the like 2: Depending on how you define "single", it competes with (x*(uintmax_t)y)>>UINTPTR_BIT, but that's not actually reliable since uintmax_t isn't (IIRC) guaranteed to be larger than uintptr_t.