Overriding environment on Mac OS X works strangely

[catamorphism]

Working on rustpkg, I noticed that run::Process::new, and then calling finish_with_output, works strangely if you provide a Some value for the env field of the process options struct. My hypothesis at first was that on OS X, this was effectively extending the environment instead of overwriting the entire environment. However, I think there might be something more that's wrong. Code:

use std::{io, run, str};

fn main() {
    let mut outp = run::Process::new("/bin/echo", [~"monkeybutts"],
            run::ProcessOptions {
            env: Some(&[(~"QUUX", ~"blat")]),
            dir: None,
            in_fd: None,
            out_fd: None,
            err_fd: None
        });
    let rs = outp.finish_with_output();
    io::println(fmt!("output: %s", str::from_bytes(rs.output)));

The resulting executable sometimes prints out "output: monkeybutts" but sometimes prints out just "output:". So the process I'm spawning doesn't use the environment at all, but adding an environment variable still makes it non-deterministically print the wrong result. This doesn't happen if I change the env field to None.

I'm investigating more, just wanted to write this down.

[catamorphism]

After more exploration, I think the problem has to do with the Option<&[(~str, ~str)]> that's a field in the ProcessOptions struct. If I change it to a Option<~[(~str, ~str)]>, I don't see the non-deterministic behavior. I'll try to make a test case that just involves the option-of-a-vector-slice and not process spawning, and then close this.

[catamorphism]

Isolated the bug; will open a new issue.

[catamorphism]

See #8498