Memory Rule: Single Owner

Ownership is Rust's most unique feature. It enables complete memory safety without requiring a garbage collector.

The Three Laws of Ownership

1. Each value in Rust has an owner (a variable).
2. There can only be one owner at a time.
3. When the owner goes out of scope, the value is automatically cleaned up (dropped).

Ownership Move Semantics

When you assign a heap-allocated resource (such as a String or Vec) to another variable, or pass it by value to a function, ownership is moved. The original variable is invalidated:

struct Profile {
    id: u32,
}

let profile = Profile { id: 1 };

// register_engine takes ownership of profile
register_engine(profile);

// ERROR: profile can no longer be accessed here!
// println!("{}", profile.id);

Why?

Single ownership guarantees that there is exactly one variable responsible for freeing memory. This prevents double-free vulnerabilities and dangling pointers at zero runtime cost.