C++ virtual functions revealed: analysis of dynamic linking

C Virtual functions utilize virtual function tables (vtables) and virtual pointers to provide dynamic linking and allow subclasses to override base class methods: the compiler generates a vtable that contains the virtual function address. Each object contains a virtual pointer to its vtable. When calling a virtual function, the virtual pointer is used to retrieve the address of the correct function and make the call. This allows subclasses to override virtual functions without modifying the caller code. Dynamic connection implements polymorphism and can be selected at runtime to improve code flexibility.

C virtual function revealed: dynamic connection analysis

Introduction
Virtual function is in C One of the key mechanisms of polymorphism. They allow subclasses to override methods in the base class while still maintaining code compatibility with the base class interface. Understanding how virtual functions work is critical to writing robust, scalable C code.

Virtual function table and virtual pointer
When the compiler encounters a virtual function, it generates a virtual function table (vtable), which contains the class All virtual function addresses. Each instance of a class contains a virtual pointer to its vtable.

When an object calls a virtual function, the compiler uses the virtual pointer to retrieve the address pointing to the correct function and make the call. This allows subclasses to override virtual functions without modifying the caller code.

Code Example

Consider the following sample code:

class Shape {
public:
    virtual double area() = 0; // 纯虚函数
};

class Circle : public Shape {
public:
    virtual double area() override { return PI * radius * radius; }
private:
    double radius;
};

class Square : public Shape {
public:
    virtual double area() override { return side * side; }
private:
    double side;
};

int main() {
    Shape* shapes[] = { new Circle(5), new Square(3) };
    for (auto shape : shapes) {
        cout << "Area: " << shape->area() << endl;
    }
}

Practical Case: Dynamic Connection
The above code demonstration Dynamic connection. Even though the main function only knows the Shape interface, it can still access subclass methods through virtual function calls. This allows us to choose different implementations at runtime, providing great flexibility.

In the following output, virtual function dynamic linking is functioning properly:

Area: 78.5398
Area: 9

Conclusion
Understanding virtual functions is critical to writing robust, scalable C code important. By using vtables and virtual pointers, C can provide efficient dynamic linking for polymorphism at compile time while still maintaining type safety.

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