Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."

[Joe Buck <Joe dot Buck at synopsys dot COM>]

On Sat, Dec 30, 2006 at 04:13:08PM -0800, Paul Eggert wrote:
> I am.  I just now looked and found another example.
> gcc-4.3-20061223/gcc/fold-const.c's neg_double function
> contains this line:
> 
>       *hv = - h1;
> 
> This one is a bit less obvious because it doesn't have a
> "Danger Will Robinson!" comment next to it, but h1 is a
> signed integer and it's easy to arrange for h1 to have its
> minimal value, so that "- h1" overflows.

This code would blow up if an integer overflow caused a trap.
I wonder if -ftrapv could be used to catch these kinds of
problems?

I suppose there is

      *hv = (HOST_WIDE_INT) -(unsigned HOST_WIDE_INT) h1;

to make it safe.