circular reference counted pointer is never freed

[giselher]

Hi I tried to check if circular reference counted pointer are somehow freed in rust, because it is sometimes possible to accidentally create such constructs. Sadly it doesn't seem to be the case.

Here is the code I used to test this (rust playpen): http://is.gd/I40LCd

#![feature(unsafe_destructor)]

use std::rc::Rc;
use std::cell::RefCell;

struct Object {
    sub: RefCell<Option<Rc<Object>>>
}

#[unsafe_destructor]
impl Drop for Object {
    fn drop(&mut self) {
        println!("Dropped");
    }
}

fn main() {

    let obj = Rc::new(Object { sub: RefCell::new(None) });

    (*obj.sub.borrow_mut()) = Some(obj.clone());

    println!("Hello, world!")
}

I am sorry if this is a duplicate or if I did test it wrong. I don't have access to valgrind right now.

[jfager]

You need Weak. The Rc docs explain it a bit.

[giselher]

Thank you that was exactly what I was looking for.

[thestinger]

The ability to create reference cycles in safe code isn't considered a bug anymore. It used to be statically prevented with bounds, but the requirements were very strict and requiring unsafe to avoid the bounds was misusing unsafe.