use std::sync::atomic::{AtomicPtr,Ordering};
use std::sync::{Arc};

struct Thing<T> {
    data: Arc<AtomicPtr<Option<T>>>,
}

impl<T> Thing<T> {
    fn new () -> Thing<T> {
        Thing {data: Arc::new(AtomicPtr::new(&mut None))}
    }
    fn clone (&self) -> Thing<T> {
        Thing {data: self.data.clone()}
    }
}

fn main () {
    let ap: Thing<int> = Thing::new();
    let ap2 = ap.clone();
    //let ap3 = ap.clone(); //uncommenting produces: ap2: Some(16777217)
    ap.data.store(&mut Some(1),Ordering::Relaxed);

    spawn(proc() {
        let r = unsafe{*ap2.data.load(Ordering::Relaxed)};
        println!("ap2: {}",r); // produces "ap2: None" unless we uncomment others
    });


    // finally, with uncommenting all below each threads expectantly print out:
    //ap3: Some(1)
    //ap2: Some(1)

   // let r = unsafe{*ap3.data.load(Ordering::Relaxed)};
   // println!("ap3: {}",r);
}