Linked list while loop not terminating at NULL

[moonman239]

I have a linked list with three Persons: "Tom", "Dick", and "Harry". Each Person is stored in a PersonNode with a pointer to another PersonNode.

As you can see, the organization goes like this:
Tom->Dick->Harry.

By default, the "nextNode" pointer is set to NULL in a constructor. I coded my program to output the names of Tom, Dick, and Harry. When I run the code, it prints Harry's name, and then the "while" loop continues. Thus, Visual Studio complains about an access violation immediately thereafter.

  Person *tom = new Person();
	PersonNode *tomNode = new PersonNode(tom);
	tom->name = "Tom";
	Person *dick = new Person();
	PersonNode *dickNode = new PersonNode(dick);
	dick->name = "Dick";
	tomNode->nextNode = dickNode;
	Person *harry = new Person();
	PersonNode *harryNode = new PersonNode(harry);
	dickNode->nextNode = harryNode;
	harry->name = "Harry";
	// Print person names from list.
	PersonNode *currentNode = tomNode;
	cout << "Person names: " << endl;
	bool notNull = true;
	while (notNull)
	{
		Person *currentPerson = currentNode->__person;
		cout << currentPerson->name << endl;
		currentNode = currentNode->nextNode;
		notNull = (currentNode != NULL);
	}

[Zhuge]

Did you try using a debugger to inspect the values as the program runs? Something is probably not set up the way you think it is and a debugger can help you find out what.

[moonman239]

@Zhuge: Yeah, currentNode becomes 0xcdcdcd after Harry.

[Zhuge]

Did you check to see how it gets set to that? 0xCDCDCD looks like Visual Studio's uninitialized pointer value. Are you sure the constructor is working like it should?

[snoh]

Hey this is your tutor from the labs, I tracked down your post.
Make sure to initialize the harryNode nextNode to NULL before entering your loop.

harryNode->nextNode = NULL;


This will clear up your error!

[moonman239]

@snoh: My PersonNode constructor's supposed to be handling that. Each nextNode is null by default.

[moonman239]

I talked to an old professor of mine about NULL. Basically, nullptr should be used in place of NULL.

[snoh]

Good to know, I had deleted your project so I couldn't reference your code after you commented.

[Zhuge]

Could you show your constructor? Because if it is ending up as 0xCDCDCD it is not nullptr, so something clearly did not work.

[AlexanderThomas1983]

I will try to solve it today. If it won't work I will give it to my friend :)