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Rust 1.27.1
5f2b325f6

FFI

There is a new edition of the book and this is an old link.

Sometimes, your Rust code may need to interact with code written in another language. To do this, Rust has a keyword, extern, that facilitates creating and using a Foreign Function Interface (FFI).

extern "C" {
    fn abs(input: i32) -> i32;
}

fn main() {
    unsafe {
        println!("Absolute value of -3 according to C: {}", abs(-3));
    }
}Run

Here are the relevant sections in the new and old books: