Returning a reference to the stack

202307251510
Status: #idea
Tags: Rust

Returning a reference to the stack

fn return_a_string() -> &String {
	let s = String::from("Hello world");
	&s
}

Move ownership outside the function

fn return_a_string() -> String {
	let s = String::from("Hello world");
	s
}

Notice that this returns a String object, but the owner will be the one who calls the function.

Return a static string literal

fn return_a_string() -> &'static str {
	"Hello world"
}

This is possible because the function always returns the same string.
Note that the returned string should remain unchanged throughout the program

Defer borrow-checking to runtime by using garbage collection

For example, we can use a [reference-counted pointer](Rc, the Reference Counted Smart Pointer)

use std::rc::Rc;
fn return_a_string() -> Rc<String> {
	let s = Rc::newfrom("Hello world");
	Rc::clone(&s)
}

In short, Rc::clone only clones the pointer to s. At runtime, the Rc checks when the last Rc pointing to the data has been dropped. Only then does it deallocates the data.

Caller provides a slot for returning the string

Create a dummy argument, into which the answer is written
Similar to how file descriptors are returned in C

fn return_a_string(output: &mut String) {
	output.replace_range(.., "Hello world");
}

References