Rust 1.63 Released, Adding Scoped Threads

This week the Rust team announced the release of Rust 1.63. One noteable update? Adding scoped threads to the standard library:Rust code could launch new threads with std::thread::spawn since 1.0, but this function bounds its closure with 'static. Roughly, this means that threads currently must have ownership of any arguments passed into their closure; you can't pass borrowed data into a thread. In cases where the threads are expected to exit by the end of the function (by being join()'d), this isn't strictly necessary and can require workarounds like placing the data in an Arc. Now, with 1.63.0, the standard library is adding scoped threads, which allow spawning a thread borrowing from the local stack frame. The std::thread::scope API provides the necessary guarantee that any spawned threads will have exited prior to itself returning, which allows for safely borrowing data. The official Rust RFC book says "The main drawback is that scoped threads make the standard library a little bit bigger," but calls it "a very common and useful utility...great for learning, testing, and exploratory programming. "Every person learning Rust will at some point encounter interaction of borrowing and threads. There's a very important lesson to be taught that threads can in fact borrow local variables, but the standard library [didn't] reflect this." And otherwise, "Implementing scoped threads is very tricky to get right so it's good to have a reliable solution provided by the standard library."

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