template<class T>
struct remove_member_pointer {
  typedef T type;
};

template<class Parent, class T> 
struct remove_member_pointer<T Parent::*> {
  typedef T type;
};

template<class T>
struct baseof_member_pointer {
  typedef T type;
};

template<class Parent, class T>
struct baseof_member_pointer<T Parent::*> {
  typedef Parent type;
};

template<class Owner, class DataType, DataType Owner::*Member, unsigned _pos, unsigned _size>
struct _PtrByteAccess {
  // ...
};

// Without C++17 need this
#define PtrByteAccess(MemberPtr, pos, size) \
  _PtrByteAccess<baseof_member_pointer<decltype(MemberPtr)>::type, \
            remove_member_pointer<decltype(MemberPtr)>::type, \
            MemberPtr, pos, size>