Re: 20040309-1.c vs overflow being undefined

[Andrew Pinski <pinskia at physics dot uc dot edu>]

> 
> Andrew Pinski <pinskia@physics.uc.edu> writes:
> 
> > If we look at this testcase, we have a function like:
> > int foo(unsigned short x)
> > {
> >   unsigned short y;
> >   y = x > 32767 ? x - 32768 : 0;
> >   return y;
> > }
> >
> >
> > x is promoted to a signed int by the front-end as the type
> > of 32768 is signed.  So when we pass 65535 to foo (like in the testcase),
> > we get some large negative number for (signed int)x
> 
> That shouldn't happen. Promoting from unsigned short to int shouldn't
> sign extend. If you see it happening, then that's a bug.

Actually I am not seeing that but instead I am seeing the subtraction done in
short and not in int (which is far as I can tell and remember reading the
promotion rules in C doing).

-- Pinski