PassByVal、PassByRef 和 PassByConstRef 的比较 std::shared_ptr (什么

#include <iostream>
#include <string>
#include <memory>
std::shared_ptr<std::string> ptrStr(new std::string("One"));
// increases the reference count to std::string("One") by one after entering the function
// decreases the reference count to std::string("One") by one before exiting the function
void PassByValue(std::shared_ptr<std::string> msg)
{
    msg->clear();                              // clears the string pointed by ptrStr
    msg.reset(new std::string("hello world")); // doesn't change the value of ptrStr
                                               // because it only changes a local copy of ptrStr
                                               // which will be destroyed when the function is returned.
                                               // Note the msg, the local copy of ptrStr, points to the same
                                               // resource where ptrStr points to.
}
// doesn't affect the reference count
void PassByReference(std::shared_ptr<std::string> &msg)
{
    msg->clear();                              // clears the string pointed by ptrStr
    msg.reset(new std::string("hello world")); // does change the value of ptrStr
}
// doesn't affect the reference count
void PassByConstReference(const std::shared_ptr<std::string>& msg)
{
    msg->clear();                              // clears the string pointed by ptrStr
    msg.reset(new std::string("hello world")); // compilation errors
}
int main(int argc, char* argv[])
{
    // Each time only one of the following three lines is executed
    //PassByValue(ptrStr);
    //PassByReference(ptrStr);
    //PassByConstReference(ptrStr)
    std::cout << *ptrStr << std::endl;
    return 0;
}

注意：我不是在争论哪种传递机制是好是坏。我只想了解std::shared_ptr传递机制不同的后果，只想关注传递std::shared_ptr作为函数参数。

问题1>如果我错了，请帮助阅读评论并纠正我

问题2>是不是真的，不管选择哪种机制，总能改变std::shared_ptr所指的资源？

问题 3> std::shared_ptr 是否与其他函数参数相似，并且在 PassByValue、PassByReference 和 PassByConstReference 方面具有类似的行为。

谢谢