"undefined reference" to Virtual Base class destructor
abstract-class, c++, undefined-reference
Solution
You've declared the destructor, but not defined it. Change the declaration to:
virtual ~Force() {}
to define it to do nothing.
You also want to make all the functions in the abstract interface pure virtual, otherwise they will need to be defined too:
virtual VECTOR eval(VECTOR x, double t) = 0;
Problem
Possible Duplicate: What is an undefined reference/unresolved external symbol error and how do I fix it? I have some experience with Java, and am now doing a C++ course. I wanted to try writing an interface, but I have run into some trouble with destructors which I have not been able to resolve, even with the help on the Internet... Here's my code: ``` class Force { public: virtual ~Force(); virtual VECTOR eval(VECTOR x, double t); }; class InvSquare : public Force { public: InvSquare(double A) { c = A; } ~InvSquare(){}; VECTOR eval(VECTOR x, double t) { // omitted stuff } private: double c; }; ``` I have tried to declare a virtual destructor for the base class, and a non-virtual one for the derived class, but I get an error saying "undefined reference to `Force::~Force()'". What does it mean, and how can I fix it? Forgive me if this is a silly question! Thank you very much for your help, noctilux