C++ Logo


Advanced search

Re: [SG14] SG14 Sept 8 (Games) zoom call

From: John McFarlane <john_at_[hidden]>
Date: Mon, 25 Oct 2021 10:59:45 +0100
On Sun, 24 Oct 2021 at 03:45, Matt Bentley via SG14 <sg14_at_[hidden]>

> * "Opt-in UB on Unsigned Overflow" = more info on this and how it could
> present performance gains would be good.

Technically, unsigned overflow is not a thing
<https://eel.is/c++draft/basic.fundamental#2>. I read "Opt-in UB on
Unsigned Overflow" to mean "Opt-in overflow on unsigned integers".

Overflow is an unambiguous bug in C++ which affords signed integers some
opportunities for optimisation that are lacking in unsigned integers. Some
helpful examples can be found in this article
and in the second half of this talk
<https://www.youtube.com/watch?v=yG1OZ69H_-o> by Chandler Carruth.

Note that lack of UB also makes it harder to test for bugs in code that
uses unsigned integers.


Received on 2021-10-25 04:59:59