Passing this to void *

[Tim Hsu]

On Wednesday, 22 November 2017 at 15:17:33 UTC, Adam D. Ruppe 
wrote:
> On Wednesday, 22 November 2017 at 15:07:54 UTC, Stefan Koch 
> wrote:
>> &this will do.
>
> Even if it were an lvalue, that would be the address of a 
> local. You should basically NEVER do that with D classes.
>
> Just `cast(void*) this` if you must pass it to such a function.

I am afraid what will happen when casting this reference to void *

glfwSetWindowUserPointer gives us a chance to provide a pointer 
to userdata. so that in callback function, we can retrieve the 
data and don't have to declare global variable.

class App {
public this() {

    m_window = glfwCreateWindow();
    glfwSetWindowUserPointer(m_window, cast(void *)(&this));
}
}

How do I use this function in Dlang?

sorry for my bad english.