c++ - shared_ptr 奇怪的行为

Question

这是我做的第一个问题。我搜索了很多但找不到答案。我正在学习在 c++14 上使用智能指针，编译器是 g++5.4。我想知道为什么当 shared_ptr 的重新分配应该销毁该对象时变量“t”仍然打印一个值。正如在第二个示例中所做的那样。提前致谢!

shared_ptr<string> p = make_shared<string>("test1");
    string& t = *p.get();
    cout<<t<<endl;
    p = make_shared<string>("test2");
    cout<<t<<endl;
    cout<<"Second Example\n";
    string *p1 = new string("test1");
    string& t1 = *p1;
    cout<<t1<<endl;
    delete p1;
    cout<<t1<<endl;

Answer 1

I want to know why is the variable "t" still prints a value when the reassignment of the shared_ptr should destroy that object.

因为访问被销毁对象的行为是未定义的。可能的行为包括，但都不能保证:

 - working
 - not working
 - random output
 - non-random output
 - the expected output
 - unexpected output
 - no output
 - any output
 - crashing at random
 - crashing always
 - not crashing at all
 - corruption of data
 - different behaviour, when executed on another system
 -                    , when compiled with another compiler
 -                    , on tuesday
 -                    , only when you are not looking
 - same behaviour in any or all of the above cases
 - anything else within the power of the computer (hopefully limited by the OS)