> From: Joe Buck <[EMAIL PROTECTED]> >> On Fri, Jun 03, 2005 at 11:43:32AM -0400, Andrew Pinski wrote: >> Everyone's who writes C/C++ should know that overflow of signed is undefined. > > In practice, however, this issue is commonly ignored, because people code > in a hurry, then test the behavior of the executable code, and if on all > platforms tested there are overflows, but the overflows wrap and as a > result the expected thing happens, the problem will not be noticed. > > I'm sure there are plenty of production codes that assume signed integer > overflow wraps, or at least make the weaker assumption that in > > a = b + c + d; > > where all variables are integers, if one of the intermediate terms > can't be represented in an integer, we still get the correct result > if the final result is representable in an integer.
Agreed: - which why it should be assumed to wrap, especially given that most/all current target, and likely most/all future targets do wrap (not trap) signed overflows. (so would expect the compiler to ideally reflect reality when analyzing code for optimization, not assume that "undefined" means "ignore reality")?
