This doesn't work, because two threads may read `oldInit = 0`, i.e. both run init.
```d
    auto oldInit = _initCount;
    atomicOp!"+="(_initCount, 1);
    if (oldInit) return 1;
```
Instead it should read like so.
```d
if (atomicOp!"+="(_initCount, 1) == 1)) return 1;
```