Latest nightly seems to cause issue with libc::isatty

[saghm]

The behavior of libc::isatty() seems to depend on whether cargo run is used (as opposed to just running the binary in target in the latest nightly (2016-03-24). For example, with the following code:

fn main() {
    let fileno = unsafe { libc::STDIN_FILENO as i32 };
    let isatty = unsafe { libc::isatty(fileno) };
    println!("fileno: {}, isatty: {}", fileno, isatty);
}

When run with the 2016-03-23 nightly, it prints out fileno: 0, isatty: 1 (whether run with cargo run or directly from the binary). However, with the 2016-03-24 nightly, it prints out fileno: 0, isatty: 1 when run directly from the binary and fileno: 0, isatty: 0 when run with cargo run. This leads me to believe that the difference might be caused by some change in cargo in dealing with standard input. Obviously a workaround is just not to use cargo run, but I'm curious about whether the previous behavior might be worth restoring at some point in the future.

I tried to look through the recent commits to see if I could track down where the change occurred, but unfortunately had no luck. Sorry about not being able to point somewhere specific in the code!

[alexcrichton]

I believe this is a dupe of rust-lang/rust#32254 caused by rust-lang/rust#31618 and fixed in rust-lang/rust#32257, so closing in favor of rust-lang/rust#32254 but thanks for the report!