On Mon, 3 Jun 2019 at 11:41, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > > On Mon, 3 Jun 2019 at 10:49, esoteric escape <manips88@xxxxxxxxx> wrote: > > > > Thanks! I see, yes speaking of C++17. Just to make sure I grasped it I'll say how I get it: > > > > 1. In the std::string's case, we care about bits regardless of the value of the chars inside std::string, so because mapping is precise that makes it well-defined. > > 2. In case of char, the underlying bit representation changes > > On most implementations, no. The underlying bit representation is the > same. 0xC8 as an unsigned char is 11001000 and as a char is also > 11001000. What is implementation-defined is the value of 11001000 as a > char. For signed char with GCC that value is (char)-56. For an > unsigned char it's (char)200. One a one's complement system Sorry, that last sentence was garbled. I meant to say that on a one's complement system that also has signed char the bit pattern of (char)0xC8 might be different (maybe ... I don't speak one's complement so I don't know if that's true), but that's not relevant to GCC which always uses two's complement.
