GitLab

https://gitlab.redox-os.org/redox-os/mio/blob/master/src/sys/windows/selector.rs#L493

Struct Overlapped implements Sync trait so as to be shared across threads by reference. It contains a UnsafeCell, and its method as_mut_ptr will return a mutable ptr to the inner data.

This may cause a crash if one thread writes the data while another is accessing it, all by immutable reference of the struct and will bypass compiler checking. It is rather unsafe but we marked it as safe!!!

I searched for a ref-counting version of this struct, which is much safer.

https://github.com/tokio-rs/mio/blob/master/src/sys/windows/selector.rs#L81

My suggestion is to replace the current Overlapped with this version.