virtual_inline.cpp

/**
 * @file virtual_inline.cpp
 * @brief 通常类成员函数都会被编译器考虑是否进行内联。
 * 但通过基类指针或者引用调用的虚函数必定不能被内联。
 * 当然，实体对象调用虚函数或者静态调用时可以被内联，虚析构函数的静态调用也一定会被内联展开。
 * @author 光城
 * @version v1
 * @date 2019-07-24
 */

#include <iostream>
using namespace std;
class Base {
public:
  virtual void who() { cout << "I am Base\n"; }
};
class Derived : public Base {
public:
  void who() { cout << "I am Derived\n"; }
};

int main() {
  // note here virtual function who() is called through
  // object of the class (it will be resolved at compile
  // time) so it can be inlined.
  Base b;
  b.who();

  // Here virtual function is called through pointer,
  // so it cannot be inlined
  Base *ptr = new Derived();
  ptr->who();

  return 0;
}