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; 
}