Rust Networking test code which triggers an odd linker error relating to `rt::sched::__extensions__`.

tcptest.rs

// Cribbed from Rust libstd test code
// Causes a linker error on OS X

use std::cell::Cell;
use std::task::Task;
use std::rt::io::net::tcp;
use std::rt::io::net::ip;
use std::rt::local::Local;
use std::rt::io::{Reader, Writer, Listener};

/// Creates a new scheduler in a new thread and runs a task in it,
/// then waits for the scheduler to exit. Failure of the task
/// will abort the process.
fn run_in_newsched_task(f: ~fn()) {
    use std::rt::sched::*;
    use std::rt::task::Task;
    use std::unstable::run_in_bare_thread;
    use std::rt::uv::uvio::UvEventLoop;

    let f = Cell::new(f);

    do run_in_bare_thread {
        let mut sched = ~UvEventLoop::new_scheduler();
        let task = ~Coroutine::with_task(&mut sched.stack_pool,
                                         ~Task::without_unwinding(),
                                         f.take());
        sched.enqueue_task(task);
        sched.run();
    }
}

/// Create a new task and run it right now. Aborts on failure
fn spawntask_immediately(f: ~fn()) {
    use std::rt::sched::*;
    use std::rt::task::Task;

    let mut sched = Local::take::<Scheduler>();
    let task = ~Coroutine::with_task(&mut sched.stack_pool,
                                     ~Task::without_unwinding(),
                                     f);
    do sched.switch_running_tasks_and_then(task) |task| {
        let task = Cell::new(task);
        do Local::borrow::<Scheduler> |sched| {
            sched.enqueue_task(task.take());
        }
    }
}

fn main() {
    do run_in_newsched_task {
        let addr = ip::Ipv4(127, 0, 0, 1, 5080);

        do spawntask_immediately {
            let mut listener = tcp::TcpListener::bind(addr);
            let mut stream = listener.accept();
            let mut buf = [0];
            stream.read(buf);
            assert!(buf[0] == 99);
        }

        do spawntask_immediately {
            let mut stream = tcp::TcpStream::connect(addr);
            stream.write([99]);
        }
    }
}