[tialaramex]

That's actually an entirely reasonable question, Rust's memory model is scarcely as well nailed down as the Java Memory Model (which is a GC model that does promise memory safety under concurrency and is worth reading about if you'd like to see how much thought is needed).

https://jcp.org/aboutJava/communityprocess/final/jsr133/inde...

(section 17.4 of the full specification)

However in a sense Rust is cheating. Java has to do a lot of work because they can't stop you writing a data race in Java, so they want that to be safe anyway if it happens. (Safe) Rust just won't emit the data race in the first place.

A data race requires (as mentioned below in the thread about Python concurrency) that there's mutation concurrently with access to the same memory. In Java that's a bad idea, but it does happen, usually by mistake. In (Safe) Rust mutation requires that nobody else has a shared (immutable) reference to the object, so the data race can't occur because if we can mutate something by definition nobody else has a reference to it - programs with this mistake won't compile.

[moosedev]

Thank you!