I have tried the following hierarchy and it doesn't link. The call to c->Execute() is not seen since it seems to be masked by the Execute in Derived and it doesn't find an adequate type to use. I would have thought that if there was a problem, it would have to show at compilation. I have tried with GCC 4.8 online and with the borland compiler on Windows. The error message is similar in both cases. Something in the order of:
/tmp/ccrT5mNy.o:(.rodata._ZTV7DerivedI5TypeCE[_ZTV7DerivedI5TypeCE]+0x10): undefined reference to `Derived<TypeC>::Execute()'
collect2: error: ld returned 1 exit status
I would be very grateful for any pointers.
#include <iostream>
class BaseType
{
public:
BaseType() {}
virtual void Execute() { std::cout << "BaseType execute..." << std::endl; };
protected:
};
struct TypeA;
struct TypeB;
struct TypeC;
class Derived2 : public BaseType
{
public:
Derived2() : BaseType() {}
virtual void Execute() { std::cout << "Derived execute2" << std::endl; }
protected:
};
template <typename T>
class Derived : public BaseType
{
public:
Derived() : BaseType() {}
virtual void Execute();
protected:
};
template <typename T>
class GrandChild : public Derived<T>
{
public:
GrandChild() : Derived<T>() {}
void Execute();
};
template<>
void Derived<TypeA>::Execute() { std::cout << "Derived execute... TypeA" << std::endl; }
template<>
void Derived<TypeB>::Execute() { std::cout << "Derived execute... TypeB" << std::endl; }
template<>
void GrandChild<TypeC>::Execute() { std::cout << "Derived execute... TypeC" << std::endl; }
int main()
{
BaseType* a = new Derived<TypeA>();
BaseType* b = new Derived<TypeB>();
BaseType* c = new GrandChild<TypeC>();
BaseType* d2 = new Derived2();
a->Execute();
b->Execute();
c->Execute();
d2->Execute();
delete a;
delete b;
delete c;
delete d2;
}
