Class loading from a DLL is one thing, persisting the state and reloading that state on-top is another. In Java, you can use the class loader to load new instances of a class, but it's up to you to transfer state before giving that class over to your program again. In C# it's a similar story with System.Runtime.CompilerServices. The trivial bits are the fact that you can use reflection to do this rather easily in both Java and C#. In C++ isn't not as simple. The struct/data signature may change, you need a temporary storage vessel (old object?) to copy to the new class object. While it's still "digital plumbing", it's not that easy to do and then hot-reload the whole stack.