pub fn insertion_sort(n: i32, p: &mut [i32]) {
        for i in 1..n as usize {
            let tmp = p[i];
            let mut j = i;
            while j > 0 && p[j - 1] > tmp {
                p[j] = p[j - 1];
                j -= 1;
            }
            p[j] = tmp;
        }
    }

    fn main() {
        let mut arr1: [i32; 3] = [1, 3, 2];
        insertion_sort(3, &mut arr1);
        // …
    }

(funnily enough, passing in the "original" code without the `unsafe extern "C"` part makes it produce the exact same output as the above)