Variable locations in memory during copy and move operations in Rust

copy-vs-move.rs

//! Demonstrates memory layout using copy and move semantics in Rust.
//!
//! # Examples
//!
//! The memory locations that you see by running this program will almost certainly be different
//! than what is found in the examples below. The important thing to pay attention to is the memory
//! location of the variable `x`.
//!
//! ```console
//! $ cargo run --release -- --copy
//!    Compiling move-vs-copy v0.1.0 (/home/kmdouglass/src/rust/move-vs-copy)
//!     Finished release [optimized] target(s) in 0.00s
//!      Running `target/release/move-vs-copy --copy`
//! Memory address of x: 0x7ffee579d544
//! Memory address of y: 0x7ffee579d548
//! Memory address of x: 0x7ffee579d544
//! Memory address of x: 0x7ffee579d544
//!
//! $ cargo run --release -- --move
//!     Finished release [optimized] target(s) in 0.31s
//!      Running `target/release/move-vs-copy --move`
//! Memory address of x: 0x7ffded2aa3d0
//! Memory address of y: 0x7ffded2aa3f0
//! Memory address of x: 0x7ffded2aa3d0
//! ```
use std::env;
use std::process::exit;

fn copy_semantics() {
    let mut x = 42;
    println!("Memory address of x: {:p}", &x);

    // Move occurs here
    let y = x;
    println!("Memory address of y: {:p}", &y);

    // Printing the memory address of x is not an error because its value was copied.
    println!("Memory address of x: {:p}", &x);

    // Assign new integer to x
    x = 0;
    println!("Memory address of x: {:p}", &x);
}

fn move_semantics() {
    let mut x = String::from("foo");
    println!("Memory address of x: {:p}", &x);

    // Move occurs here
    let y = x;
    println!("Memory address of y: {:p}", &y);

    // Printing the memory address of x is an error because its value was moved.
    // println!("Memory address of x: {:p}", &x)

    // Assign new string to x
    x = String::from("bar");
    println!("Memory address of x: {:p}", &x);
}

fn print_help() {
    println!("Possible options: --copy, --move");
}

fn main() {
    let args: Vec<String> = env::args().collect();
    match args[1].as_ref() {
        "--copy" => copy_semantics(),
        "--move" => move_semantics(),
        "--help" => {
            print_help();
            exit(0);
        }
        _ => {
            print_help();
            exit(1);
        }
    }
}

This gist is referred to in the blog post: https://kmdouglass.github.io/posts/variable-locations-in-rust-during-copy-and-move/

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