c++ - auto_ptr 和原始指针之间的 const 区别？

Question

我意识到当你做 const auto_ptr<X> ptr = variable ，您仍然可以修改 auto_ptr 指向的变量的内容。对于原始指针 const X * ptr = variable , const 阻止你修改它。

那么在 auto_ptr 前面加上 const 的目的到底是什么？

Answer 1

这个声明:

auto_ptr<X> ptr = variable;
// non-const auto_ptr object pointing to a non-const X object
// Can change the contents of the X object being pointed at.
// Can change where the auto_ptr itself points at.

等同于:

X* ptr = variable;
// non-const pointer to a non-const X object
// Can change the contents of the X object being pointed at.
// Can change where the pointer itself points at.

这个声明:

const auto_ptr<X> ptr = variable;
// const auto_ptr object pointing to a non-const X object
// Can change the contents of the X object being pointed at.
// Can't change where the auto_ptr itself points at.

等同于:

X* const ptr = variable;
// const pointer to a non-const X object
// Can change the contents of the X object being pointed at.
// Can't change where the pointer itself points at.

这个声明:

auto_ptr<const X> ptr = variable;
// non-const auto_ptr object pointing to a const X object
// Can't change the contents of the X object being pointed at.
// Can change where the auto_ptr itself points at.

等同于:

const X * ptr = variable;
// non-const pointer to a const X object
// Can't change the contents of the X object being pointed at.
// Can change where the pointer itself points at.

这个声明:

const auto_ptr<const X> ptr = variable;
// const auto_ptr object pointing to a const X object
// Can't change the contents of the X object being pointed at.
// Can't change where the auto_ptr itself points at.

等同于:

const X* const ptr = variable;
// const pointer to a const X object
// Can't change the contents of the X object being pointed at.
// Can't change where the pointer itself points at.