Code:
#include "Item.h"
#include "ShoppingCart.h"
As I said in post #6, these haven't been posted - and no corresponding .cpp either. That's why I did the code in post#6 and asked for all of the code again in post #8. Have you tried compiling the code in post #6?

I suspect the problem is how the project for clang has been set up - but I don't use clang, only VS2015 so can't help with using clang.