override specifier (since C++11)

 

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Technical Specifications

 

C++ language

 

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virtual member functions

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override(C++11)

final(C++11)

 

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

struct A
{
    virtual void foo();
    void bar();
};
 
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
};
 
int main() {}

Possible output:

main.cpp:9:10: error: 'void B::foo() const' marked 'override', but does not override
    9 |     void foo() const override; // Error: B::foo does not override A::foo
      |          ^~~
main.cpp:12:10: error: 'void B::bar()' marked 'override', but does not override
   12 |     void bar() override; // Error: A::bar is not virtual
      |          ^~~

See also

final specifier(C++11)

declares that a method cannot be overridden