Weird result for modulus operation

[Paolo Bonzini]

Ang Way Chuang wrote:
> Ang Way Chuang wrote:
>> Andrew Pinski wrote:
>>> On Tue, Apr 29, 2008 at 9:08 PM, Ang Way Chuang <wcang@nav6.org> wrote:
>>>>  Thanks for the speedy reply. But why this code:
>>>>
>>>>         int a = 17, b = 16;
>>>>         a = a++ % 16;
>>>>
>>>>  results in a = 2 then? I think I need to know what is sequence 
>>>> point. I'll
>>>> google that.
>>>
>>> As I mentioned, the code is undefined so it could be any value.
>>
>> Is there any flag in gcc that can provide warning to code that relies 
>> on undefined behaviours?
> 
> Found it. -Wsequence-point which is enabled by -Wall. But gcc didn't 
> fart out any warning with -Wall or -Wsequence-point flag :(

You found a bug, it does point out the problem with the second example here.

Paolo