override Specifier (C++11)

In a Nutshell

Appending override to a virtual function declaration instructs the compiler to verify that the function successfully overrides a base class virtual function. Signature mismatches or attempts to override non-virtual functions will result in a compilation error.

Header

None (This is a language-level keyword feature)

Core API Quick Reference

Operation	Signature	Description
Function declaration	void foo() override;	Used in declarations to ensure overriding of a base class virtual function
Function definition (in-class)	void foo() override { }	Used when defining the function inside the class
Pure virtual function override	void foo() override = 0;	override appears before = 0
Combined with final	void foo() override final;	Can be combined with final in any order
Destructor override	~Derived() override;	Can be used to check overriding of virtual destructors

Minimal Example

struct Base {
    virtual void func() { /* ... */ }
    virtual void only_in_base() { /* ... */ }
};

struct Derived : Base {
    // Correctly overrides Base::func
    void func() override { /* ... */ }

    // Error: 'only_in_base' is not virtual in Base
    // void only_in_base() override;

    // Error: signature mismatch (const qualifier)
    // void func() const override;
};

Embedded Applicability: High

• Zero runtime overhead; performs static checks exclusively at compile time.
• Embedded code often features multi-layer Hardware Abstraction Layers (HALs); override effectively prevents silent errors caused by changes to base class interfaces.
• Does not impact code size or execution speed, making it suitable for resource-constrained environments.

Compiler Support

GCC	Clang	MSVC
4.7	3.0	2012

See Also

• cppreference: override specifier

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