bindings.Future_register_callback_fn(this.ptr, callback == null ? 0 : callback.ptr);
Reference.reachabilityFence(this);
Reference.reachabilityFence(callback);
bindings.Future_register_callback_fn(this.ptr, callback == null ? 0 : callback.ptr);
Reference.reachabilityFence(this);
Reference.reachabilityFence(callback);