Handwritten FFI

We can declare external functions by hand:

# // Copyright 2022 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
unsafe extern "C" {
    safe fn abs(x: i32) -> i32;
}

fn main() {
    let x = -42;
    let abs_x = abs(x);
    println!("{x}, {abs_x}");
}

We already saw this in the Safe FFI Wrapper exercise.

This assumes full knowledge of the target platform. Not recommended for production.

• This is just a motivating example. For a real library, you want to use bindgen as shown on the next slide.