원시 포인터 역참조(따라가기)

포인터를 만드는 것은 안전합니다. 하지만 역참조(따라가기)할 경우 unsafe가 필요합니다:

fn main() {
    let mut s = String::from("조심하세요!");

    let r1 = &mut s as *mut String;
    let r2 = r1 as *const String;

    // Safe because r1 and r2 were obtained from references and so are
    // guaranteed to be non-null and properly aligned, the objects underlying
    // the references from which they were obtained are live throughout the
    // whole unsafe block, and they are not accessed either through the
    // references or concurrently through any other pointers.
    unsafe {
        println!("r1은 {}입니다.", *r1);
        *r1 = String::from("이런");
        println!("r2는 {}입니다.", *r2);
    }

    // 안전하지 않음. 이렇게 하지 마세요.
    /*
    let r3: &String = unsafe { &*r1 };
    drop(s);
    println!("r3 is: {}", *r3);
    */
}