On Monday, 7 May 2012 at 08:06:01 UTC, Don Clugston wrote:
I think the reason that C makes no guarantees, was because of ones-complement machines
Maybe but that's not the full reason, as Mehrdad says the compiler can use the fact that overflow are undefined to optimise the code generated.
In my opinion, there are only two valid options for the integer operation's overflow by default: either the compiler should make sure that the overflow is noticed (Ada: exception, adding 'Not-a-Number' values would work too) or C's signed undefined behaviour. Modulo operation (except where really useful) are bad: slower than the 'undefined' semantic, yet it still produce obviously incorrect behaviour such as negative absolute value..
