Rule Definition
A missing virtual keyword in front of a destructor "overriding" a virtual destructor will hide the polymorphic nature of the destructor from developers using the class. They may not know that at execution time other destructors in the inheritance tree will be executed. A missing virtual keyword may also be an indication that the author of the destructor ignored the fact that it needed to be virtual and thus was not aware that the destructor requires specific attention and specific coding.

Remediation
Add the virtual keyword in the destructor declaration, checks that the destructor is implemented as expected and matches the class hierarchy design requirements, and documents the destructor for future extension of the class hierarchy and modification of the method. Alternatively, if the derived class destructor is empty, remove it.

Violation Code Sample

class Vehicle 
{
public:
    Vehicle();
    virtual ~Vehicle();
    void start();
    void stop();
    virtual void run();
protected:
    Engine* theEngine;
};

class Car : public Vehicle
{
public:
    Car();
    ~Car();           // VIOLATION
protected:
    int numberOfWheels;
};

Fixed Code Sample

class Car : public Vehicle
{
public:
    Car();
    virtual ~Car();           // FIXED
protected:
    int numberOfWheels;
};