On Mon, Jan 01, 2007 at 07:33:06AM -0500, Richard Kenner wrote: > > the seemingly prevalent attitude "but it is undefined; but it is not > > C" is the opinion of the majority of middle-end maintainers. > > Does anybody DISAGREE with that "attitude"? It isn't valid C to assume that > signed overflow wraps. I've heard nobody argue that it is. The question > is how far we go in supporting existing code that's broken in this way.
The problem is that often-unconscious assumptions that int overflow wraps are very widespread. If the compiler won't build GNU/Linux distros, then we have a serious problem no matter what the standard says. For one thing, we are hypocrites if we tell people that the fact that gcc broke their code that assumes -fwrapv is not our problem, while gcc itself assumes -fwrapv in several places! We could say that the uses in fold-const are ok while others aren't, but that would require coming up with a rule that distinguishes the cases.
