Sent in by David Abrahams:

Yes, and to add to this tangent, 6.8.2 [basic.fundamental] paragraph 1 states "Plain char, signed char, and unsigned char are three distinct types." Strangely, 6.8 [basic.types] paragraph 2 talks about how "... the underlying bytes making up the object can be copied into an array of char or unsigned char. If the content of the array of char or unsigned char is copied back into the object, the object shall subsequently hold its original value." I guess there's no requirement that this copying work properly with signed chars!