类成员函数地址

Question

Edit How is this in any way related to the supposed post? They are both completely different errors, you guys should really stop trying to farm rep

So I've been searching around google and stackoverflow but I couldn't find one solution that would help my case. I have a D3D9Device pointer and I want the EndScene address of that device, how would I approach so?

DWORD aEndScene = *(DWORD*)(&d3ddev->EndScene);

won't work with the following error

'&': illegal operation on bound member function expression

I think that's wrong because I'm actually trying to get the address of the d3ddev class

Answer 1

Member function pointers are not per object, they are per type. In your example, you could have multiple instances of a IDirect3DDevice9 , all of which would have the same pointer value for their EndScene member function (assuming they aren't different concrete types - but this isn't likely).

The specific error you are getting is because you are attempting to get the address of a pointer-to-member function from an object, which isn't valid (eg. see '&' illegal operation on bound member function expression error ).

It is possible to get the value of a member function using the type, instead of an object pointer. However, it's extremely ugly:

// Value is stored in 'end_scene':
HRESULT (IDirect3DDevice9::* end_scene)() = &IDirect3DDevice9::EndScene;
// Call the function, with the value of 'end_scene'.
(*d3ddev.*(end_scene))();
// Print the address of the pointer-to-member function:
printf("%p\n", end_scene);

I wouldn't suggest doing this here, because most functions in IDirect3DDevice9 don't have the same prototype. In fact, only BeginScene has the same prototype as EndScene , and it's hard to imagine a situation in which the call could be one or the other, since they need to be called in a specific order. You could make the case about using this for the functions that get/set vertex/pixel shader constants, as they have the same prototypes, but, it's just as easy to store some other external state to determine which function to call, and much more straightforward.