Similarities and differences between C++ inline functions and virtual functions

Inline functions embed the function body into the call point, which improves performance and code volume, but has lower readability; virtual functions call functions overridden by subclasses through polymorphism, improving flexibility, but have higher runtime overhead. .

The similarities and differences between C inline functions and virtual functions

Inline functions

Inline functions are compiled The compiler embeds the function body into the call site when it is called, rather than the function that performs the function call process.

Advantages:

• Improve performance: avoid calling overhead.
• Reduce code size: The function body will not appear repeatedly in multiple call points.

Disadvantages:

• Increased compilation time: the function body needs to be compiled for each call point.
• Reduced code readability: function bodies are scattered throughout the code base.

Syntax:

inline int sum(int a, int b) {
  return a + b;
}

Virtual function

Virtual function is a function that achieves polymorphism through the inheritance mechanism . When a virtual function on a parent class object is called, the actual function called is determined by the object's dynamic type.

Advantages:

• Realize polymorphism: subclasses can override the virtual functions of the parent class.
• Improve the scalability and flexibility of the code.

Disadvantages:

• Runtime overhead: Virtual function table maintenance and indirect calls need to be maintained.
• Increased code complexity: virtual and override keywords are required.

Grammar:

class Base {
 public:
  virtual void print() {
    std::cout << "Base" << std::endl;
  }
};

class Derived : public Base {
 public:
  virtual void print() override {
    std::cout << "Derived" << std::endl;
  }
};

Comparison of similarities and differences:

Features	Inline function	Virtual function
Calling mechanism	Function body embedding	Indirect call
Performance	Higher	Lower
Code size	Smaller	Bigger
Readability	Lower	Higher
Polymorphism	Not supported	Supported

##Actual case:

You can use inline functions to implement simple mathematical operations, such as summation:

inline int sum(int a, int b) {
  return a + b;
}

int main() {
  std::cout << sum(1, 2) << std::endl;  // 输出：3
}

You can use virtual functions to implement the graphics drawing interface:

class Shape {
 public:
  virtual void draw() = 0;
};

class Circle : public Shape {
 public:
  virtual void draw() override {
    std::cout << "Drawing a circle" << std::endl;
  }
};

int main() {
  Shape* shape = new Circle();
  shape->draw(); // 输出：Drawing a circle
}

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