# `override` specifier (since C++11)

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Specifies that a virtual function overrides another virtual function.

### Syntax

The identifier `override`, if used, appears immediately after the declarator in the syntax of a member function declaration or a member function definition inside a class definition.

declarator virt-specifier-seq﻿(optional) pure-specifier﻿(optional) | (1) |
declarator virt-specifier-seq﻿(optional) function-body | (2) |

1) In a member function declaration, `override` may appear in virt-specifier-seq immediately after the declarator, and before the pure-specifier, if used.
2) In a member function definition inside a class definition, `override` may appear in virt-specifier-seq immediately after the declarator and just before function-body.

In both cases, virt-specifier-seq, if used, is either `override` or `final`, or `final override` or `override final`.

### Explanation

In a member function declaration or definition, `override` specifier ensures that the function is virtual and is overriding a virtual function from a base class. The program is ill-formed (a compile-time error is generated) if this is not true.

override is an identifier with a special meaning when used after member function declarators: it's not a reserved keyword otherwise.

### Example

Run this code

    #include <iostream>

    struct A
    {
        virtual void foo();
        void bar();
        virtual ~A();
    };

    // member functions definitions of struct A:
    void A::foo() { std::cout << "A::foo();\n"; }
    A::~A() { std::cout << "A::~A();\n"; }

    struct B : A
    {
    //  void foo() const override; // Error: B::foo does not override A::foo
                                   // (signature mismatch)
        void foo() override; // OK: B::foo overrides A::foo
    //  void bar() override; // Error: A::bar is not virtual
        ~B() override; // OK: `override` can also be applied to virtual
                       // special member functions, e.g. destructors
        void override(); // OK, member function name, not a reserved keyword
    };

    // member functions definitions of struct B:
    void B::foo() { std::cout << "B::foo();\n"; }
    B::~B() { std::cout << "B::~B();\n"; }
    void B::override() { std::cout << "B::override();\n"; }

    int main()
    {
        B b;
        b.foo();
        b.override(); // OK, invokes the member function `override()`
        int override{42}; // OK, defines an integer variable
        std::cout << "override: " << override << '\n';
    }

Output:

    B::foo();
    B::override();
    override: 42
    B::~B();
    A::~A();

### See also

`final` specifier(C++11) | declares that a method cannot be overridden

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