The Rust stdlib is already using synchronization on the versions of these functions that are exposed from the Rust stdlib. That's why those functions were allowed to be marked as safe in the first place.

The problem is that people are calling C code from Rust (which already requires an unsafe annotation), and then that C code is doing silly thread-unsafe shenanigans for regrettable historical reasons.

It's beyond Rust's power to fix without cooperation from the underlying C code, which happens to be provided by the OS, which is just being compliant with Posix. Rust can only do so much when the platform itself is hell-bent on sabotaging you.