On Sat, 1 Mar 2008, Richard Kenner wrote:
> > int f(int a, int b) { return 0 * (a + b); }
> >
> > get the potentially trapping arithmetic folded away. If -ftrapv is to
> > have properly defined semantics, those must include trapping if (a + b)
> > overflows in the above code.
>
> Why? Is there any language that requires such semantics?
They are the natural interpretation of -ftrapv that's simplest to describe
in terms of the abstract machine of the C standard: any signed integer
arithmetic overflow in the abstract machine (and maybe integer division by
0, signed or unsigned) should be guaranteed to yield a trap at runtime.
http://gcc.gnu.org/ml/gcc-patches/2007-01/msg02026.html
http://gcc.gnu.org/ml/gcc/2007-09/msg00399.html
describe my understanding of these natural semantics.
--
Joseph S. Myers
[EMAIL PROTECTED]
