call to os::args() suppresses nonzero exit code & "root task failed" line

[jbclements]

The following program calls 'fail!()', but still results in an exit code of zero:

fn main () {
    os::args();
    fail!();
}

Here's what it looks like:

jclements-09740:~/clements/projects/rust-experimenting clements> rustc ./foo.rs && ./foo && echo "done" 
Running /usr/local/bin/rustc:
warning: no debug symbols in executable (-arch x86_64)
rust: task failed at 'explicit failure', ./foo.rs:3
done

Commenting out the call to "os::args()" produces the expected output:

jclements-09740:~/clements/projects/rust-experimenting clements> rustc ./foo.rs && ./foo && echo "done"
Running /usr/local/bin/rustc:
warning: no debug symbols in executable (-arch x86_64)
rust: task failed at 'explicit failure', ./foo.rs:3
rust: domain main @0x7fdd91815e10 root task failed

... note the extra line of output, and the lack of the "done" message, indicating a nonzero exit code.

[jbclements]

I've narrowed this further; it's triggered by any call to local_data_get:

fn bogus_key(_v: @uint) {}


pub fn cause_bug()  {
    unsafe {
        task::local_data::local_data_get(bogus_key);
    }
}

fn main () {
    cause_bug();
    fail!();
}

[brson]

Looks like a duplicate of #4547. We had a discussion of how to fix this somewhere, but I can't locate it now.

[brson]

Discussion is in #5054

[brson]

Closing as duplicate.