Static mutables in tests

[Cerber-Ursi]

@Hyeonu

And the one AtomicBool flag would not be enough. You need at least two AtomicBool to signal the initialization process is started and finished.

And here I'd like to share my own question from a little before, where this was already discussed:

"Write-once" static Option

I'm trying to create an Option-like type which can be used in "write-once" way in static variable. The gist of what I want is here (playground): pub struct UsizeHolder(Option<usize>); impl UsizeHolder { pub fn set(&mut self, val: usize) -> Result<(), (usize, usize)> { self.0.map_or_else( || { self.0.replace(val); Ok(()) }, |old_val| Err((old_val, val)), ) } pub fn get(&self) -> Option<usize> { …