Review of Program Memory

Programs allocate memory in two ways:

• Stack: Continuous area of memory for local variables.

  • Values have fixed sizes known at compile time.
  • Extremely fast: just move a stack pointer.
  • Easy to manage: follows function calls.
  • Great memory locality.

• Heap: Storage of values outside of function calls.

  • Values have dynamic sizes determined at runtime.
  • Slower than the stack: some book-keeping needed.
  • No guarantee of memory locality.

Example

Creating a String puts fixed-sized metadata on the stack and dynamically sized data, the actual string, on the heap:

fn main() {
    let s1 = String::from("Hello");
}