ab wants to call ba::hello(). ab should be the one dynamically loaded here, but it shouldn't matter I think.

ab : src : main.rs

mod ba {
    #[link(name="ba")]
    extern "Rust" {
        #[link_name = "_ZN2ba5hello17hb8c57573de8c5a19E"]
        pub fn hello();
    }
}

fn main() {
    unsafe { ba::hello() }
}

ba : src : lib.rs

pub extern fn hello() {
    println!("hello");
}