Memory leak in Rust (Create circular reference using Arc/Mutex)

memory_leak.rs

use std::sync::{Arc, Mutex};

struct Data{ data: Option<Arc<Mutex<Data>>> }

fn main() {
  for _ in 0..5000000 {
    let val = Arc::new(Mutex::new(Data{
        data: Some(Arc::new(Mutex::new(Data { data: None })))
    }));
    let mut child = Arc::new(Mutex::new(Data{ data: None }));
    let val_data = val.lock().unwrap();
    if let Some(ref child_ref) = val_data.data {
      child = child_ref.clone();
    }
    child.lock().unwrap().data = Some(val.clone());
  }
  println!("done");
  loop {}
}

Thanks for posting! In case anybody else ends up here who has a hard time parsing this (like me), here's a significantly pared down example:

use std::sync::{Arc, Mutex};

struct Data(Option<Arc<Mutex<Data>>>);

fn main() {
    for _ in 0..5000000 {
        let val = Arc::new(Mutex::new(Data(None)));
        val.lock().unwrap().0 = Some(val.clone());
    }
    println!("done");
    loop {}
}