Is there any way to return a reference to a variable created in a function?

Question

I want to write a program that will write a file in 2 steps. It is likely that the file may not exist before the program is run. The filename is fixed.

The problem i

Answer 1

References are pointers. Once functions are executed, they are popped off the execution stack and resources are de-allocated.

For the following example, x is dropped at the end of the block. After that point, the reference &x will be pointing to some garbage data. Basically it is a dangling pointer. The Rust compiler does not permit such a thing since it is not safe.

fn run() -> &u32 {
    let x: u32 = 42;

    return &x;
} // x is dropped here

fn main() {
    let x = run();
}