pointer-to-vec.rs

se std::{mem, ptr};

fn swap_ptr(p1: &mut *mut Vec<i32>, p2: &mut *mut Vec<i32>) {
    let mut p3: *mut Vec<i32> = ptr::null_mut();
    p3 = *p1;
    *p1 = *p2;
    *p2 = p3;
}

fn main() {
    let mut v1 = vec![1, 2, 3];
    let mut v2 = vec![4, 5, 6];
    println!("v1 at {:p}", &v1);
    println!("v2 at {:p}", &v2);

    let mut p1: *mut Vec<i32> = &mut v1;
    let mut p2: *mut Vec<i32> = &mut v2;
    println!("before swap");
    println!("p1={:p}", p1);
    println!("p2={:p}", p2);

    let mut p3: *mut Vec<i32> = ptr::null_mut();
    p3 = p1;
    p1 = p2;
    p2 = p3;
    println!("swap directly");
    println!("p1={:p}", p1);
    println!("p2={:p}", p2);

    swap_ptr(&mut p1, &mut p2);
    println!("swap with function");
    println!("p1={:p}", p1);
    println!("p2={:p}", p2);

    unsafe { (*p1).push(4); }
    println!("v1: {:?}", v1);
    println!("v2: {:?}", v2);
}