I find this decision frustrating. They made it clear by making it trap in debug that this is a "bug" but denied the optimization benefits of calling it undefined behaviour on release.

I'm assuming the rationalization is "wrapping is better than undefined behaviour" but I have not seen any evidence that the average program is actually more likely to behave correctly in the face of wrapping.

The combinations that make the most sense to me are:

1. debug: trap, release: trap. Bad performance, correct.

2. debug: wrap, release: wrap. Good performance

3. debug: trap, release: undefined. Great performance.

I guess my point is make up your mind. Is "overflow" allowed and wrapping or a bug?