c++ - 为什么我在使用 &this 时会出错？

Question

我知道 this 指针在调用时隐式传递给成员函数。但是，当我尝试获取 this 指针的地址时(通过 &this)，我得到了编译器错误“需要左值”。为什么是这样？

class st
{    
  int a,b;
public :
  void print()
  {      
    cout << &this; //gives lvalue required... why?

    cout << this; //will print address of object.
  }   
}

Answer 1

this 不是左值而是纯右值。来自 [class.this]:

In the body of a non-static (9.3) member function, the keyword this is a prvalue expression whose value is the address of the object for which the function is called. The type of this in a member function of a class X is X*. If the member function is declared const, the type of this is const X*, if the member function is declared volatile, the type of this is volatile X*, and if the member function is declared const volatile, the type of this is const volatile X*.

^强调我的

& 需要一个左值，因此您无法获得this 的地址。