How to check if a thread has finished in Rust?

Question

When I spawn a thread in Rust, I get a JoinHandle, which is good for... joining (a blocking operation), and not much else. How can I check if a ch

Answer 1

It's possible, friends. Use refcounters which Rust will drop on end or panic. 100% safe. Example:

use std::time::Duration;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::thread;

fn main() {
    // Play with this flag
    let fatal_flag = true;
    let do_stop = true;

    let working = Arc::new(AtomicBool::new(true));
    let control = Arc::downgrade(&working);

    thread::spawn(move || {
        while (*working).load(Ordering::Relaxed) {
            if fatal_flag {
                panic!("Oh, my God!");
            } else {
                thread::sleep(Duration::from_millis(20));
                println!("I'm alive!");
            }
        }
    });

    thread::sleep(Duration::from_millis(50));

    // To stop thread
    if do_stop {
        match control.upgrade() {
            Some(working) => (*working).store(false, Ordering::Relaxed),
            None => println!("Sorry, but thread died already."),
        }
    }

    thread::sleep(Duration::from_millis(50));

    // To check it's alive / died
    match control.upgrade() {
        Some(_) => println!("Thread alive!"),
        None => println!("Thread ends!"),
    }
}

Gist: https://gist.github.com/DenisKolodin/edea80f2f5becb86f718c330219178e2

At playground: https://play.rust-lang.org/?gist=9a0cf161ba0bbffe3824b9db4308e1fb&version=stable&backtrace=0

UPD: I've created thread-control crate which implements this approach: https://github.com/DenisKolodin/thread-control