Question

安全转换指针类型，但目标读写操作仍须 unsafe 担保。

• 不同类型指针间转换。
• 指针转换为整数。
• 整数转换为指针。
• 数组引用转换为指针。
• 函数指针转换为其他指针。
• 函数指针转换为整数。

fn main() {
  let x = 100;
  let p: *const i32 = &x;

  let p2 = p as *const i16;      // ptr   -> ptr
  let addr = p as usize;       // ptr   -> usize
  let p3 = addr as *const i32;     // usize -> ptr

  println!("{:p}, {:x}", p2, addr);
  assert_eq!(p, p3);
}

fn main() {
  let d = [10, 11, 12, 13, 14];

  let p1 = &d as *const i32;     // &array   -> ptr
  let p2 = &d[2] as *const i32;  // &element -> ptr

  unsafe {
    assert_eq!(10, *p1);
    assert_eq!(12, *p2);
  }
}

fn test() {
  println!("hello, world!");
}

fn main() {
  let p = test as *const usize;   // fn -> void_ptr
  let x = test as usize;      // fn -> usize

  println!("{:p}, {:x}", p, x);
}