On Tue, Jul 26, 2011 at 1:49 AM, Ian Lance Taylor <iant@xxxxxxxxxx> wrote:
> Jeffrey Walton <noloader@xxxxxxxxx> writes:
>
>> A simplified example (I know you gave a previous work around) assuming
>> 32 bit ints:
>>
>> // liboverflow, compiled with -fwrapv
>> int my_abs(int x, int* r)
>> {
>> int y = abs(x);
>> if (y < 0)
>> return 0;
>>
>> *r = y;
>> return 1;
>> }
>>
>> // myprogram, compiled with -O2 and linked against liboverflow
>> int x = 0x80000000, r = 0;
>> if(my_abs(x, &r))
>> printf(...)
>>
>> Will the resulting program enjoy O2 and/or produce incorrect results?
>
> If you are asking whether this program has signed overflow problems, the
> answer is no. Compiling liboverflow with -fwrapv does not affect
> myprogram. Similarly, compiling myprogram without -fwrapv does not
> affect liboverflow.
As always, thank you very much.
Jeff
