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

[Robert Dewar]

Ian Lance Taylor wrote:

> I believe there is a comprehensible distinction between "compiler will
> not assume that signed overflow is undefined behaviour" and "compiler
> will cause all arithmetic to wrap around."
> 
> In any case, I have no plans to continue working on this.  I described
> my work in considerable detail as I did it and the patches have gone
> through multiple rounds of review.  I would be happy to see your
> concrete proposal.

First, I would get some real figures on performance comparing

-fstrict-overflow
-fno-strict-overflow
-fwrapv

It is really hard to estimate the value of the second dubious
(dubious because ill-defined, it seems to try to create a state
of undefined definedness) switch compared to the other two
possibilities.
> 
> Ian