inheritance from a template base class

[ericM]

Hello,

I am writing the skeleton for an algorithm following the Strategy pattern presented in a plethora of c++ books, although my compiler does not like the way I am doing things.

If I compile the following code:

#include <iostream>
using namespace std;

template<typename T> 
class base{
protected:
	T _foo;
	T _bar;
protected:
	virtual void foo() = 0;
	virtual void bar() = 0;
public:
	void iteration(){
	foo();
	bar();
	};
};

class derived : public base<double>
{
public:
	derived(double foo, double bar){ 
	_foo=foo,
	_bar=bar;
}
	~derived();
protected:
	void foo() override {
		_foo++;
		cout << "calling overridden foo()" << endl;
	}
		void bar() override {
		_bar*=0.5;
		cout << "calling overridden bar()" << endl;
	}
};

int main (){
	derived *myClass = new derived(11,13);
	myClass->iteration();
	delete myClass;
	return 0;
}

I get as result:

Undefined symbols for architecture x86_64:
  "__ZN7derivedD1Ev", referenced from:
      _main in icpcMBZo0b.o
ld: symbol(s) not found for architecture x86_64

which is unexpected as all works if I specify the type T in the base class.

[lastchance]

Do you actually define a destructor for the derived class anywhere?

[ericM]

Non I dont, and that solves my issue.