description: "Microsoft C++ Code Analysis warning C26434 for the C++ Core Guidelines case C.128."

ms.date: 08/21/2020

When you introduce a function that has the same name as a non-virtual function in a base class, you may get unexpected behavior. It's like introducing a variable name which conflicts with a name from an outer scope. For example, you may have intended to override a base class function. If the signatures of the functions don't match, the override you intended may turn into an overload instead. In general, name hiding is dangerous and error-prone.

In the Core Guidelines checks:

- Only non-overriding functions in the current class are checked.

This example demonstrates how a derived class can hide non-virtual functions, and how virtual functions allow both overloads and overrides:

struct Base

{

virtual ~Base() = default;

virtual void is_virtual() noexcept {}

void not_virtual() noexcept {}

};

struct Derived : Base

{

void is_virtual() noexcept override {} // Okay, override existing function

virtual void is_virtual(int i) noexcept {} // Add a virtual overload for function

void not_virtual() noexcept {} // C26434, hides a non-virtual function

virtual void not_virtual(int i) noexcept {} // C26434, and parameters ignored

};