Copy, Clone & Drop

Copy vs Clone

• Copy: implicit bitwise copy (cheap, stack-ish types)
• Clone: explicit .clone() — may allocate

#[derive(Copy, Clone, Debug)]
struct TickSize {
    cents: i32,
}

You can only derive Copy if all fields are Copy — so a struct with String cannot be Copy.

Drop

When a value goes out of scope, Rust runs its destructor. For String, that frees the heap buffer. You rarely implement Drop yourself at first — but knowing it runs at } explains why dangling pointers can’t exist in safe Rust.

Example

fn main() {
    {
        let s = String::from("temp");
        println!("{s}");
    } // s dropped here
    println!("after scope");
}

temp
after scope

Exercise

Define a Copy quote-tick struct and pass it around freely.