The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
template<typename T>
class VirtualClass {
public:
virtual ~VirtualClass() {}
virtual T vmem(); // Likely ERROR if instantiated without definition
};
int main()
{
VirtualClass<int> inst;
}