Thread: LNK2019 and LNK1120 Errors?

Hello,
I have downloaded source code from the textbook website and have run into these linker errors:

T3Q21_List_Back error LNK2019: unresolved external symbol "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class orderedLinkedListType<int> const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@ std@@AAV01@ABV?$orderedLinkedListType@H@@@Z) referenced in function _main

T3Q21_List_Back fatal error LNK1120: 1 unresolved externals

I have been able to narrow the source of the problem to the ostream operator overloading function because when I remark out the cout statements that output the class object the program compiles fine. But, I don't know what is wrong with the code because every program in this chapter has the same problem. The overload function is below and the main function is below that. I am running VS2003 as my IDE. Any insight to my problem would help me a bunch.

Code:

//Overloading the stream insertion operator
template<class Type>
ostream& operator<<(ostream& osObject, const linkedListType<Type>& list)
{
	nodeType<Type> *current; //pointer to traverse the list
	current = list.first;                //set current so that it points to 
                                                            //the first node
	while(current != NULL)         //while more data to print
	{
	   osObject << current->info << " ";
	   current = current->link;
	}

	return osObject;
}

Code:

//Program to test various operations on an ordered linked list
#include <iostream> 
#include "orderedLinkedList.h"
using namespace std;
int main()
{
     orderedLinkedListType<int> list1, list2;              //Line 1
     int num;                                                              //Line 2
     cout<<"Line 3: Enter integers ending with -999"
           <<endl;                                                         //Line 3
     cin>>num;                                                          //Line 4
     while(num != -999)                                             //Line 5
     {
		list1.insertNode(num);             //Line 6
		cin>>num;                               //Line 7
     }
     cout<<endl;                                                        //Line 8
     cout<<"Line 9: List 1: "<<list1<<endl;               //Line 9
     list2 = list1; //test the assignment operator; Line 10
     cout<<"Line 11: List 2: "<<list2<<endl;             //Line 11
     cout<<"Line 12: Enter the number to be "
            <<"deleted: ";			//Line 12
     cin>>num;                                                          //Line 13
     cout<<endl;                                                        //Line 14
     list2.deleteNode(num);                                       //Line 15
     cout<<"Line 16: After deleting the node, "
           <<"List 2: "<<endl<<list2
           <<endl;                                                         //Line 16
     return 0;					
}

I don't see an #include statement in your main .cpp that's including the header where your operator<<() is defined.

Also, you need to include <ostream> in the header with your operator<<() as well as your linked list header.

The operator << is declared as a friend and the definition is written in the linked list header file. The ordered link list class is derived from linked list and contains the include statement for linked list. The .cpp file is just the test file for these two linked list classes. That is all there is to the project. two header files and the cpp test file.

I still can't figure out what is wrong with the operator << overload function that keeps it from compiling.

Code:

using namespace std;

This is unrelated to your problem, but you should NEVER have a using statement in a header file. When you start writing larger programs, it could bite you in the ass with namespace conflicts...

The code is incorrect.

Here's a (handy) explanation and solution.

https://forums.microsoft.com/MSDN/Sh...60571&SiteID=1

gg