Re: Question on -fwrapv and -fwrapv-pointer

[Richard Biener via Gcc-patches]

> Am 15.09.2023 um 17:25 schrieb Qing Zhao <qing.z...@oracle.com>:
> 
> 
> 
>> On Sep 15, 2023, at 8:41 AM, Arsen Arsenović <ar...@aarsen.me> wrote:
>> 
>> 
>> Qing Zhao <qing.z...@oracle.com> writes:
>> 
>>> Even though unsigned integer overflow is well defined, it might be
>>> unintentional, shall we warn user about this?
>> 
>> This would be better addressed by providing operators or functions that
>> do overflow checking in the language, so that they can be explicitly
>> used where overflow is unexpected.
> 
> Yes, that will be very helpful to prevent unexpected overflow in the program 
> in general.
> However, this will mainly benefit new codes.
> 
> For the existing C codes, especially large applications, we still need to 
> identify all the places 
> Where the overflow is unexpected, and fix them. 
> 
> One good example is linux kernel. 
> 
>> One could easily imagine a scenario
>> where overflow is not expected in some region of code but is in the
>> larger application.
> 
> Yes, that’s exactly the same situation Linux kernel faces now, the unexpected 
> Overflow and 
> expected wrap-around are mixed together inside one module. 
> It’s hard to detect the unexpected overflow under such situation based on the 
> current GCC. 

But that’s hardly GCCs fault nor can GCC fix that in any way.  Only the 
programmer can distinguish both cases.

Richard 

> Thanks.
> 
> Qing
>> -- 
>> Arsen Arsenović
>