Unable to print when using libgreen

[mrmonday]

When running the following code, printing to stdout, and other I/O fails to work.

extern crate green;
extern crate rustuv;

use self::green::{SchedPool, PoolConfig, GreenTaskBuilder};
use std::task::{TaskBuilder};

fn main() {
    let mut pool = SchedPool::new(PoolConfig::new());
    {
        let tb = TaskBuilder::new().green(&mut pool);

        let res = tb.try_future(proc() {
            println!("test")
        });
        let _ = res.unwrap();
    }
    pool.shutdown();
}

The code is based on: http://doc.rust-lang.org/green/index.html#using-a-scheduler-pool

Resulting error:

task '<unnamed>' failed at 'called `Result::unwrap()` on an `Err` value: invalid argument', /home/robert/rust/src/libcore/result.rs:545

I was told to CC @alexcrichton.

[alexcrichton]

The documentation isn't super helpful on this one sadly, but if you look at PoolConfig's event_loop_factory field, you'll see:

A factory function used to create new event loops. If this is not specified then the default event loop factory is used.

The default factory is the green::basic loop, which does not have an I/O implementation. In short, if you want I/O, you should use rustuv::event_loop as the event loop.

[mrmonday]

Ah, thank you - I didn't spot this.