override Specifier (C++11)

In a Nutshell

Appending override to the end of a virtual function declaration lets the compiler verify that it truly overrides a base class virtual function. A signature mismatch or a non-virtual base class function will result in a compile-time error.

Header

None (language keyword-level feature)

Core API Quick Reference

Operation	Signature	Description
Function declaration	ret_type func(params) override;	Used in declarations to ensure a base class virtual function is overridden
Function definition (in-class)	ret_type func(params) override { ... }	Used for in-class definitions
Pure virtual function override	ret_type func(params) override = 0;	override appears before = 0
Combined with final	ret_type func(params) override final;	Can be combined with final in any order
Destructor override	~Derived() override;	Can be used to check the overriding of virtual destructors

Minimal Example

class Sensor {
public:
    virtual void read() = 0;
    virtual ~Sensor() = default;
};

class TemperatureSensor : public Sensor {
public:
    // Correctly overrides the base class virtual function
    void read() override {
        // Read temperature data
    }

    // Compiler error: no matching function in base class
    // void reed() override;

    ~TemperatureSensor() override = default;
};

Embedded Applicability: High

• Zero runtime overhead; performs static checking at compile time only
• Embedded code often features multi-level inheritance in the HAL (Hardware Abstraction Layer), and override effectively prevents silent errors caused by base class interface modifications
• Does not affect code size or execution speed, making it ideal for resource-constrained scenarios

Compiler Support

GCC	Clang	MSVC
4.7	3.0	2012

See Also

• cppreference: override specifier

---

Some content referenced from cppreference.com, licensed under CC-BY-SA 4.0