> a memory barrier, which is most of the cost of an un-contended futex-style lock already Yes, but it's not a lock. > unconditionally doing the init work at p

> a memory barrier, which is most of the cost of an un-contended futex-style lock already Yes, but it's not a lock. > unconditionally doing the init work at process start time when you know there's not multiple threads That's the most obvious fix, yes. I was thinking (but I've not checked yet) that when `my_environ` is not set up yet then `getenv()` can use `_environ` directly.