通过const对象调用函数只能调用const函数或者是static函数

class Base{
public:
    static void statmem() {
    std::cout << "in statmem of base\n" << std::endl;
  }
};
class Derived final :public Base{
public:
    void statmem() const {
    std::cout << "in statmem of Derived\n" << std::endl;
  }
};
void Derived::f(const Derived& deprived_obj){
  Base::statmem();
  Derived::statmem();
  deprived_obj.statmem();
  statmem();
}

今日在使用deprived_obj调用函数时编译没有什么问题，当去掉关键字static以后：

class Base{
public:
    void statmem() {
    std::cout << "in statmem of base\n" << std::endl;
  }
};
class Derived final :public Base{
public:
   void statmem() {
    std::cout << "in statmem of Derived\n" << std::endl;
  }
};
void Derived::f(const Derived& deprived_obj){
  Base::statmem();
  Derived::statmem();
  deprived_obj.statmem();
  statmem();
}

编译器报错：

error: passing 'const Derived' as 'this' argument discards qualifiers [-fpermissive]

deprived_obj.statmem();

 in call to 'void Derived::statmem()'

百度以后发现，const 的对象调用静态函数没有什么问题，但是调用非const函数就会有问题了。添加了const申明以后，编译通过。

class Base{
public:
    void statmem() const{
    std::cout << "in statmem of base\n" << std::endl;
  }
};
class Derived final :public Base{
public:
   void statmem() const {
    std::cout << "in statmem of Derived\n" << std::endl;
  }
};
void Derived::f(const Derived& deprived_obj){
  Base::statmem();
  Derived::statmem();
  deprived_obj.statmem();
  statmem();
}