const shared_ptr<T>和shared_ptr<const T>区别

shared_ptr<const T> p等同于const T * p(或者相当于T const * p), 也就是说, 指向的对象是const。
而const shared_ptr<T> p 等同于T* const p。总结如下:

shared_ptr<T> p;             ---> T * p;                                    : nothing is const
const shared_ptr<T> p;       ---> T * const p;                              : p is const
shared_ptr<const T> p;       ---> const T * p;       <=> T const * p;       : *p is const
const shared_ptr<const T> p; ---> const T * const p; <=> T const * const p; : p and *p are const.

原文出处：https://stackoverflow.com/questions/17793333/difference-between-const-shared-ptrt-and-shared-ptrconst-t