#[no_mangle] is unsafe

a.rs

extern crate b;
extern crate c;

fn main() {
    println!("{} {}", b::identity(), c::identity());
}

b.rs

#![crate_type="lib"]

#[no_mangle]
pub fn identity() -> &'static str {
    "b"
}

c.rs

#![crate_type="lib"]

#[no_mangle]
pub fn identity() -> &'static str {
    "c"
}

shell.txt

geofft@titan:/tmp/libparty$ rustc b.rs
geofft@titan:/tmp/libparty$ rustc c.rs
geofft@titan:/tmp/libparty$ rustc a.rs -L .
geofft@titan:/tmp/libparty$ ./a
b b