Empty arguments to processes aren't handled correctly on windows

[alexcrichton]

For example, this program prints "1\n3" on unix, and "1\n2" on windows:

use std::io::{process, Command};
use std::os;

fn main() {
    let len = os::args().len();
    println!("{}", len);

    if len == 1 {
        Command::new(os::self_exe_name().unwrap())
                .arg("foo").arg("")
                .stdout(process::InheritFd(1))
                .spawn().unwrap();
    }
}

[alexcrichton]

The appears to be different on windows for both libgreen and libnative.

[aturon]

I believe this happens because the arguments end up being quoted for Windows. Simplest fix would be to drop empty arguments. Thoughts?

[aturon]

(Alternatively, we could quote empty arguments on Unix.)

[alexcrichton]

I would expect the empty arguments to be passed through as significant argument position. I ran into this in cargo because Command::new("rustdoc").arg("--test-args").arg("") passed on unix but on windows it would try to consume the next argument for the test args.

It looks like to fix this we just need to alter this condition to see if the argument is 0-length, and if so we quote it. Libuv already does something similar.

I'm investigating a fix for libgreen, it looks like it should be working...