rustc version: rustc 0.8-pre (05f1bbb 2013-08-25 12:26:16 -0700)

Code:

extern "C"
{
    fn a();
}

trait A
{
    #[fixed_stack_segment]
    fn foo()
    {
        unsafe
        {
            a();
        }
    }
}

fn main()
{
}

Error:

test.rs:13:3: 13:4 error: invoking non-Rust fn in fn without #[fixed_stack_segment] [-D cstack (default)]
test.rs:13                      a();
                                ^
error: aborting due to previous error

Note that I'm not sure the attribute is being applied correctly, in which case the lint is correctly identifying the issue and the bug is elsewhere... I don't know how to verify this though.