# V689. Destructor of 'Foo' class is not declared as virtual. A smart pointer may not destroy an object correctly.

The analyzer has detected an issue when a smart pointer may destroy an object incorrectly. This error is caused by a missing virtual destructor in the base class.

For example:

    class Base
    {
      public:
      ~Base() { }
    };
    class Derived : public Base
    {
      public:
      Derived()
      {
        data = new int[5];
      }
      ~Derived()
      {
        delete [] data;
      }
      int* data;
    };

    void GO()
    {
      std::auto_ptr<Base> smartPtr(new Derived);
    }

Notice that the object created in this code belongs to the 'Derived' class. However, the smart pointer stores a reference to the Base class. The destructor in the Base class is not virtual, and that's why an error will occur when the smart pointer tries to destroy an object it has been storing.

The fixed code of the Base class:

    class Base
    {
      public:
      virtual ~Base() { }
    };

P.S.

The V599 diagnostic message is related to this one.

References:

- Wikipedia. Virtual method table.
- Wikipedia. Virtual function.
- Wikipedia. Destructor.
- Discussion on Stack Overflow. When to use virtual destructors?
- The Old New Thing. When should your destructor be virtual?

This diagnostic is classified as:

CWE-404 CERT-OOP52-CPP