Visual studio adding capital A to function name in error message - c++

Question

I've tried making a minimal testcase to reproduce it, but haven't been able to.
Adding a screenshot to show the error
this is the call to the SetClass function
m_luaState["MyClass"].SetClass<MyClass, I32>("AddTo", &MyClass::Add);
This is the MyClass:
class MyClass
{
public:
MyClass(I32 i) : m_i(i), m_j(2*i)
{
}
I32 m_j;
void Add(I32 iv)
{
std::cout << iv + m_i + m_j;
}
private:
I32 m_i;
};

Answer 1

Your RegisterClass(...) method name is being replaced by a Windows #define RegisterClass. Since you are compiling as ANSI, you are picking up the ANSI alias for RegisterClass which is RegisterClassA (it would be RegisterClassW if you were compiling Unicode).
You could either rename your RegisterClass(...) method if that's a viable option, exclude the conflicting Windows header (probably not an option), or conditionally #undef RegisterClass at the top of your header which declares your RegisterClass(...) method, something like:
#ifdef RegisterClass
#undef RegisterClass
#endif
Some additional reference about the conflicting symbol: RegisterClass function

Answer 2

This problem is actually quite interesting, and is nothing you have done wrong. It's because the RegisterClass Windows function and how Windows handle Unicode when programming.
Windows have two variants for almost all its function, if you see the table at the bottom of the linked MSDN reference you will see them mentioned as RegisterClassW and RegisterClassA. The W function is used for Unicode builds, where all strings and characters are of type wchar_t. The A variant is the "ANSI" variant, using normal char characters.
The problem here is that Windows uses macros to decide which of the funcitons to use, basically it does this
#ifdef UNICODE
# define RegisterClass RegisterClassW
#else
# define RegisterClass RegisterClassA
#endif
This is problematic because the preprocessor will replace your call to the RegisterClass member function with the RegisterClassA symbol, leading to your error.
The simple solution is to #undef the RegisterClass macro directly after including <windows.h> (or in some other suitable place). Another is to rename RegisterClass to something which doesn't clash with the Windows function.