Thanks, I just noticed a small mistake in my example (I don't trigger the UB because I access b[0] containing 0x80 without shifting, however I meant to do it th

Thanks, I just noticed a small mistake in my example (I don't trigger the UB because I access b[0] containing 0x80 without shifting, however I meant to do it the other way around). Still, adding an explicit cast to the left operand seems to be enough to avoid this, e.g.: uint32_t x = ((uint32_t)b[0]) << 24; In summary, I think my point that using unsigned char would be appropriate in this case still stands.