I'm building an HTTP server using Hyper, and I'm wondering if there are any concerns about using Box::leak for a shared state.

In Hyper's examples, an Arc is used to pass a shared state to the service_fn (see here).

However, since I can guarantee that the shared state will last for the entire application, I think passing around a static reference to the state would be possible (and more efficient).

I don't want to use a static variable because I want to be able to create multiple independent states for testing purposes.

This would be my adapted hyper example:

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let addr: SocketAddr = ([127, 0, 0, 1], 4000).into();

    // Using Box::leak instead of Arc.
    let counter: &'static AtomicUsize = Box::leak(Box::new(AtomicUsize::new(0)));
    // let counter = Arc::new(AtomicUsize::new(0));

    let listener = TcpListener::bind(addr).await?;
    println!("Listening on http://{}", addr);
    loop {
        let (stream, _) = listener.accept().await?;
        let io = TokioIo::new(stream);

        let service = service_fn(move |_req| {
            let count = counter.fetch_add(1, Ordering::AcqRel);
            async move {
                Ok::<_, Error>(Response::new(Full::new(Bytes::from(format!(
                    "Request #{}",
                    count
                )))))
            }
        });

        if let Err(err) = http1::Builder::new().serve_connection(io, service).await {
            println!("Error serving connection: {:?}", err);
        }
    }
}

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