error C2440: 'type cast' : cannot convert from 'unsigned int (__thiscall IEngineVGui::* )(unsigned int)' to 'void *'

Question

So i'm trying to port my friends code that was compiled with GCC to Visual C++.

Answer 1

Your problem lies here:

(void*) &IEngineVGui::GetPanel

The type of &IEngineVGui::GetPanel is int (IEngineVGui::*) (int), which is a member function pointer.

You are trying to convert it to a "regular" pointer type, which is sadly not possible because they are handled completely differently. So MSVC is acting correctly by giving you an error. If your code compiled fine on GCC, it was most likely due to a bug and/or a non-standard extension in that particular version.