Question

I’m fairly noobish at C++, but very comfortable with pointers, dereferencing, etc. I’m having a problem with my overload of the << operator for a class, in that it compiles fine but crashes when run. It feels like an infinite loop, but I’m not certain. Here’s the code, and any help is appreciated.

#include <string>
#include <iostream>

using namespace std;

class Person
{

private:

 string _name;
 Person* _manager;

public:

 Person(string name, Person *manager);
 Person(string name);

 friend ostream &operator<<(ostream &stream, Person &p);

};


Person::Person(string name, Person *manager)
{
 _name = name;
 _manager = manager;
}

Person::Person(string name)
{
 _name = name;
}

ostream &operator<<(ostream &stream, Person &p)
{
 Person* mgr = p._manager;

 stream << p._name << std::endl;
 stream << mgr->_name << std::endl;
 return stream;
}


int main()
{
 Person *pEmployee = new Person("John Doe Employee");
 Person *pManager = new Person("John Doe Manager", pEmployee);

 cout << *pEmployee;
 cout << *pManager;

 return 0;
}

Answer 1

In your constructor with just a single argument, you need to set _manager to NULL/0. Test for this in your operator<< and don’t output mgr->name if it is NULL/0. As it stands, you are dereferencing an uninitialised pointer.

Person::Person(string name)
{
    _name = name;
    _manager = 0;
}

ostream &operator<<(ostream &stream, Person &p)
{
    Person* mgr = p._manager;

    stream << p._name << std::endl;
    if (mgr)
        stream << mgr->_name << std::endl;
    return stream;
}

There are a number of other things you could do better, such as using const references on arguments and using the constructor initialiser list, but they wont be the cause of your problem. You should also address ownership issues with the manager object you pass in to the constructor to ensure it does not get double-deleted.