Question

Is there any issue with partially overriding a set of virtual functions defined by a base class?

My compiler provides the following warning:

overloaded virtual function "MyBaseClass::setValue" is only partially overridden in class "MyDerivedClass".

The classes look like this:

class MyBaseClass
{
public:
    virtual void setValue(int);
    virtual void setValue(SpecialType*);
}

class MyDerivedClass : public MyBaseClass
{
public:
    virtual void setValue(int);
}

The easy way to get rid of this warning is to use different names for the base functions, but I wanted to know if there was any compelling reason to fix this specific warning. I do not believe this violates the C++ standard. My guess is that it’s to warn a programmer that they may have forgotten to implement the behavior for all possible input types. In our case, it is intentional to exclude some of the specific types.

Would you discourage suppressing this warning altogether?

Answer 1

The override for setValue(int) hides setValue(SpecialType*) of the base class (see the C++ FAQ Lite), so if you try to call setValue(new SpecialType()) you will get an error.

You can avoid this by adding a using directive to the derived class that “imports” the overloads from the base class:

class MyDerivedClass : public MyBaseClass
{
public:
    using MyBaseClass::setValue;
    virtual void setValue(int);
};