My biggest annoyance with the design of this extension is that it must be applied explicitly to every instance of the given type. In C++, you get RAII destruct

My biggest annoyance with the design of this extension is that it must be applied explicitly to every instance of the given type. In C++, you get RAII destructor tied to the type, not the instance. With this GNU C extension, you must remember to use it, which IMO is error prone.