Catch thread in example

[dns2utf8]

Since this is an example, the code will be copied by many people and should be over correct.

?r @steveklabnik

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[brson]

The example looks correct as written to me. Why join it?

[durka]

This line will get a "must use Result" warning -- if the idea is to put good code in examples, it should be handled.

[steveklabnik]

I agree with @brson here: unless you're specifically doing something with the thread variable, why explicitly join it?

[dns2utf8]

I had the situation, where the inner thread outlived the outer and caused unexpeced behavior: Run on play

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

fn main() {
    let spinlock = Arc::new(AtomicUsize::new(1));

    let spinlock_clone = spinlock.clone();
    let thread = thread::spawn(move|| {
        spinlock_clone.store(0, Ordering::SeqCst);

        thread::sleep(Duration::from_secs(2));
        for i in 0..10 {
            println!("{}", i);
        }
    });

    // Wait for the other thread to release the lock
    while spinlock.load(Ordering::SeqCst) != 0 {}

    // thread.join().is_ok();
    println!("END");
}

I could also add a hint to the threading model of rust, but I could not find a reference explaining what happens in this case with the inner thread.

[durka]

Yeah, the main thread exits as soon as the inner thread releases the lock (and the program ends when the main thread exits) so the numbers are never printed. If the spinlock_clone.store line is moved until after the loop, then the numbers are indeed printed.

As for using the Result, calling is_ok and not looking at the return value will technically silence the warning but is actually no better.

[steveklabnik]

@dns2utf8 ahhh yes, I can see that. Hmmm. (and @durka's explanation is correct)

[dns2utf8]

@durka you are right about is_ok.

I am thinking about a link to std::thread#The treading model in the text section.

[dns2utf8]

Hm, I seem to have broken the build with the link. Do you have an idea?

[steveklabnik]

this line has a trailing whitespace, that's what's failing the build

[dns2utf8]

Ahh, thanks 👍

[dns2utf8]

Thanks @steveklabnik, I rebased it to current master.

[steveklabnik]

@bors: r+ rollup

[bors]

📌 Commit 22615ad has been approved by steveklabnik