alt Hacker News> It's obviously, trivially broken. Stores the index before storing the value, so the other thread reads nonsense whenever the race goes against it.
Are we reading the same code? The stores are clearly after value accesses.
> Also doesn't have fences on the store
?? It uses acquire/release semantics seemingly correctly. Explicit fences are not required.
Push:
buffer_[head] = value;
head_.store(next_head, std::memory_order_release);
return true;
There's no relationship between the two written variables. Stores to the two are independent and can be reordered. The aq/rel applies to the index, not to the unrelated non-atomic buffer located near the index.