Re: racy leak sanitizer builds, was Re: [PATCH 0/9] commit-reach: -Wsign-compare follow-ups

> One of the reasons I hadn't sent anything is that I was waffling between
> two approaches:
>
>   - implement barriers everywhere and just use them. More work, but we'd
>     have the tool if we wanted to use it later, and all builds behave
>     the same.
>
>   - make a "maybe_barrier" interface that might be a noop, and let most
>     platforms compile without them. They are not needed for correct
>     operation in most cases, but only to work around a sanitizer problem.
>     And it is not even a problem that comes up frequently; it is a race
>     that we occasionally see in CI. So enabling it only for our
>     linux-leaks CI job would be enough to dull the pain.
>
>     And there is no risk of any portability or run-time issues, because
>     the code is a noop for most builds.