Would you like signs with those chars?

Ah, indeed; I forgot that there's a difference between conversions (which is implementation-defined) and general signed overflow, which is undefined. Thanks for pointing that out :)

I don't think it's only a matter of being "completely precise"; relying on implementation-defined behavior can be reasonable choice, relying on undefined behavior that a compiler vendor has not explicitly declare they define, to me, usually cannot. (I know Linus would disagree with me :D)

Allowing an implementation-defined signal seems a bit horrible here, though, but I think I understand where the committee was coming from...