Hacker News Reader

Indeed, if you re-interpret the article's usage of the phrase "optimizer bug", then the advice becomes useful: if changing the optimization level fixes your broken code, you have an undefined-behavior bug.

View on HN

Either that, or a race condition.

I'm not sure that's necessarily the case. See my comment above about sequential consistency.

Aren't those undefined behavior bugs?

Imagine two threads that safely lock a resource, increment it, copy the value, and then unlock it. This is entirely defined, but also a race condition.

Race conditions are a lot like unsanitized input. They don't cause problems by themselves, but if you make incorrect assumptions it's easy to write incorrect code.

It's data races specifically that are undefined behaviour.

Reply on news.ycombinator.com