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

[Robert Dewar <dewar at adacore dot com>]

Richard Kenner wrote:
> > Note the interesting places in VRP where it assumes undefined signed
> > overflow is in compare_values -- we use the undefinedness to fold
> > comparisons.
>
> Unfortunately, comparisons are the trickiest case because you have to
> be careful to avoid deleting a comparison that exists to see if overflow
> occured: this is perhaps the most common place where wrapping is assumed.

Note incidentally regarding Fortran that testing for overflow is
at least as difficult in Fortran as in C (unless new stuff has been
added to Fortran since my Fortran days, which is certainly possible).