i don't know if this changes your analysis, but don't forget that whether or not char is signed or unsigned by default is platform-dependent. e.g. on ARM platforms (the ones i've developed on, anyway), char is unsigned by default, whereas it's signed on most platforms. Also don't forget that numeric overflow/underflow for *signed* types technically has undefined behavior (though it's likely to work identically/predictably on all recent platforms, it's not guaranteed to).