c++ - 请澄清 const 限定符传播

Question

假设我们有如下一段代码:

class Base {
  public:
    int a = 5;
};

class Derived : public Base {
  public:
    Base *parent_ = new Base;
    Base* parent() const { return parent_; }
};

void f(const Derived *derived) {
    Base *p = derived->parent();
    p->a = 10; // <- is this correct?
}

我个人认为这里有一个问题:

In function f we take a pointer to const object of class Derived. This makes each member of it also const thus parent_ becomes const Base *. If it is const we should not have an ability to modify the object on which the pointer points.

我哪里错了？

Answer 1

This makes each member of it also const thus parent_ becomes const Base *.

不，指针本身会变成const，而不是它指向的对象。所以 parent_ 变成了 Base * const，而不是 const Base *，你的代码是有效的。