Null Pointer Error when working with Mutex

[kiwistrongis]

Hi there :). I had a little issue when working with a mutex. The following code results in a null pointer error:

//standard library imports
use std::rt::thread::Thread;
use std::sync::{ Arc, Mutex};

fn main(){
    //make mutex
    let done = Arc::new( Mutex::new( false));

    //spawn producer
    println!("starting producer");
    let mut prod_done = done.clone();
    let producer = Thread::start(
        proc(){ *( prod_done.lock()) = true;});

    //spawn consumer
    println!("starting consumer");
    let consumer = Thread::start(
        proc(){
            while ! *( done.lock()) {}
        });

    //finish up
    println!("joining threads");
    producer.join();
    consumer.join();
    println!("threads joined");
}

Thanks to some help from people on reddit, I managed to get around it with AtomicBool, but this error still stands.

[sfackler]

Thread::start is a low level interface to raw threads. It specifically doesn't do the initialization required to start up the runtime. The spawn function should be used instead:

spawn(proc() {
    while !*done.lock()) {}
})

[kiwistrongis]

And if I need to join the thread later? use try?

[sfackler]

You could use http://doc.rust-lang.org/std/task/fn.try_future.html

[kiwistrongis]

Aren't futures for returning a value? I mean technically it's returning (), but still...
Do you know why spawn doesn't just return a reference to the spawned thread? Also is this still a bug, or what?

My adjustment to use try_future:

//standard library imports
use std::rt::thread::Thread;
use std::sync::{ Arc, Mutex};

fn main(){
    //make mutex
    let done = Arc::new( Mutex::new( false));

    //spawn producer
    println!("starting producer");
    let mut prod_done = done.clone();
    let producer = std::task::try_future(
        proc(){ *( prod_done.lock()) = true;});

    //spawn consumer
    println!("starting consumer");
    let consumer = std::task::try_future(
        proc(){
            while ! *( done.lock()) {}});

    //finish up
    println!("joining threads");
    producer.unwrap();
    consumer.unwrap();
    println!("threads joined");
}

[sfackler]

The future returned by try_future wraps a Result that indicates if the task completed successfully or failed.

[kiwistrongis]

I'll take that as "this isn't the bug you're looking for".