# V762. Consider inspecting virtual function arguments. See NN argument of function 'Foo' in derived class and base class.

This diagnostic detects errors related to overriding of virtual functions and is generated in two situations.

Situation 1. A base class includes a virtual function with a parameter of some type. There is also a derived class with the same function, but its corresponding parameter is of another type. The types involved can be integer, enumerations, or pointers or references to the base and derived classes.

The diagnostic helps detect errors that occur during extensive refactoring, when you change the function type in one of the classes but forget to change it in the other.

Consider the following example:

    struct Q            { virtual int x(short) { return 1; } };
    struct W : public Q {         int x(int)   { return 2; } };

This code should actually look like this:

    struct Q            { virtual int x(short) { return 1; } };
    struct W : public Q {         int x(short) { return 2; } };

If there are two functions 'x' with arguments 'int' and 'short' in the base class, the analyzer will not generate the V762 warning.

Situation 2. The diagnostic is triggered when an argument has been added to or removed from a function in the base class, while the number of arguments in the function declaration in one of the derived classes is left unchanged.

Consider the following example:

    struct Q            { virtual int x(int, int=3) { return 1; } };
    struct W : public Q {         int x(int)   { return 2; } };

Fixed code:

    struct Q            { virtual int x(int, int=3) { return 1; } };
    struct W : public Q {         int x(int, int) { return 2; } };

Here is an example of how errors in this scenario can occur. There is a hierarchy of classes. At some point, an argument is added to a function of the base or a derived class, which results in declaring a new function that is not related to the function of the base class in any way.

Such declaration looks strange and might be a sign of an error. Perhaps the programmer forgot to fix one of the classes or did not take into account that the function was virtual. However, the analyzer cannot understand if this code is correct based on the function's logic. If this behavior is intended and is not an error, use one of the false-positive suppression mechanisms to suppress the warning.

Consider the following example:

    struct CA
    {
        virtual void Do(int Arg);
    };
    struct CB : CA
    {
        virtual void Do(int Arg1, double Arg2);
    };

To avoid errors like that when using the C++11 standard and better, use the 'override' keyword, which will help avoid signature mismatch at the compilation stage.

This diagnostic is classified as:

CWE-670

You can look at examples of errors detected by the V762 diagnostic.