channel shuts down too early during program termination

[mgmeier]

I didn't check if this has been reported yet, but there seems to be an inconsistency in the runtime system at program termination.

I slightly modified the channels example from rust's tutorial:

use std::comm::DuplexStream;
use std::comm::duplex;

fn stringifier (channel: &DuplexStream<String, uint>) {
    let mut value: uint;
    loop {
        value = channel.recv();
        channel.send(value.to_str());

        // KEEP THREAD RUNNING DURING PROGRAM TERMINATION
        // if value == 0 { break; }
    }
}

fn main () {
    let (from_child, to_child) = duplex();

    spawn(proc() {
        stringifier(&to_child);
    });

    from_child.send(22);
    assert!(from_child.recv().as_slice() == "22");

    from_child.send(23);
    from_child.send(0);

    assert!(from_child.recv().as_slice() == "23");
    assert!(from_child.recv().as_slice() == "0");
    println! ("everything ok");
}

The program output is this:

everything ok
task '<unnamed>' failed at 'receiving on a closed channel', /home/rustbuild/src/rust-buildbot/slave/dist2-linux/build/src/libsync/comm/mod.rs:806

It seems to me, that during program termination, it is safe to kill everything listening on some channel before closing it, not afterwards, thus avoiding above error. Or does the ordering of the shutdown serve some purpose I overlooked?

BTW I'm using the following build
rustc 0.11.0 (aa1163b92de7717eb7c5eba002b4012e0574a7fe 2014-06-27 12:50:16 -0700)

[alexcrichton]

Closing as working as intended. The main program does not exit until all tasks have exited, and there's no rel concept of being "shut down" until all tasks themselves have exited. It is often normal for the main task to exit and child tasks to continue working.

[mgmeier]

Ok, makes sense. Thank you!