New IO stdout is not flushed at program exit

[shepmaster]

I know that the new IO is being worked on, but I could see this being a sneaky thing that gets lost.

#![feature(io)]
use std::io::Write;
fn main() {
    write!(&mut std::io::stdout(), "Hello world").unwrap();
}

This code prints nothing. If we use stderr instead, there is output.

rustc 1.0.0-nightly (270a677d4 2015-03-07) (built 2015-03-07)

[alexcrichton]

Unfortunately this is a duplicate of #20012. The buffers would all be properly flushed if we actually ran the at_exit callbacks. I'll try to prioritize fixing that this coming week!