GCC Undefined Behavior Sanitizer

[via Digitalmars-d]

On Saturday, 18 October 2014 at 08:22:25 UTC, monarch_dodra wrote:
> On Friday, 17 October 2014 at 13:44:24 UTC, ketmar via 
> Digitalmars-d wrote:
>> On Fri, 17 Oct 2014 09:46:48 +0000
>> via Digitalmars-d <digitalmars-d at puremagic.com> wrote:
>>> In D (and C++) you would get:
>>> 
>>> if (x < ((x+1)&0xffffffff)){…}
>> perfect. nice and straightforward way to do overflow checks.

It wasn't an overflow check as ketmar suggested… It was a check 
that should stay true, always for this instantiation. So the 
wrong code is bypassed on overflow, possibly missing a 
termination. The code would have been correct with an 
optimization that set it to true or with a higher resolution 
register.

> Besides, the code uses x + 1, so the code is already in 
> undefined state. It's just as wrong as the "horrible code with 
> UB" we wère trying to avoid in the first place.
>
> So much for convincing me that it's a good idea...

Not sure if you are saying that modulo-arithmetic as a default is 
a bad or good idea?

In D and (C++ for uint) it is modulo-arithmetic so it is defined 
as a circular type with at discontinuity which makes reasoning 
about integers harder.