C++ keep getting error LNK2019: unresolved external symbol [duplicate]

Question

I tried to google this but always come back with different issues. I am getting 3 unresolved externals when I try to compile this program:

1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall DynIntStack<char>::~DynIntStack<char>(void)" (??1?$DynIntStack@D@@QAE@XZ) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol "public: void __thiscall DynIntStack<char>::pop(char &)" (?pop@?$DynIntStack@D@@QAEXAAD@Z) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol "public: void __thiscall DynIntStack<char>::push(char)" (?push@?$DynIntStack@D@@QAEXD@Z) referenced in function _main

DynIntStack.h

/****************************************************************************
DynIntStack class.

Chad Peppers

This class creates a object for stacking nodes

In addition, there should be member functions to perform the following 
operations:
- Push to the stack
- Pop to the stack
- Function to check if empty

****************************************************************************/
// Specification file for the DynIntStack class
#ifndef DYNINTSTACK_H
#define DYNINTSTACK_H

template <class T>
class DynIntStack
{
private:
   // Structure for stack nodes
   struct StackNode
   {
      T value;        // Value in the node
      StackNode *next;  // Pointer to the next node
   };

   StackNode *top;      // Pointer to the stack top

public:
   // Constructor
   DynIntStack()
      {  top = NULL; }

   // Destructor
   ~DynIntStack();

   // Stack operations
   void push(T);
   void pop(T &);
   bool isEmpty();
}; 
#endif

DynIntStack.cpp

/****************************************************************************
DynIntStack class.

Chad Peppers

This class creates a object for stacking nodes

In addition, there should be member functions to perform the following 
operations:
- Push to the stack
- Pop to the stack
- Function to check if empty

****************************************************************************/

#include <iostream>
#include "DynIntStack.h"
using namespace std;

/*************************************************************************
Basic class constructor.

Input Parameters:  Information to build the  stack

Return Type:  void

*************************************************************************/

template<class T>
DynIntStack<T>::~DynIntStack()
{
   StackNode *nodePtr, *nextNode;

   // Position nodePtr at the top of the stack.
   nodePtr = top;

   // Traverse the list deleting each node.
   while (nodePtr != NULL)
   {
      nextNode = nodePtr->next;
      delete nodePtr;
      nodePtr = nextNode;
   }
}

/*************************************************************************
Function to push an item in the stack

Input Parameters:  T

Return Type:  void

*************************************************************************/

template<class T>
void DynIntStack<T>::push(T num)
{
   StackNode *newNode; // Pointer to a new node

   // Allocate a new node and store num there.
   newNode = new StackNode;
   newNode->value = num;

   // If there are no nodes in the list
   // make newNode the first node.
   if (isEmpty())
   {
      top = newNode;
      newNode->next = NULL;
   }
   else  // Otherwise, insert NewNode before top.
   {
      newNode->next = top;
      top = newNode;
   }
}

/*************************************************************************
Function to pop an item in the stack

Input Parameters:  T

Return Type:  void

*************************************************************************/
template<class T>
void DynIntStack<T>::pop(T &num)
{
   StackNode *temp; // Temporary pointer

   // First make sure the stack isn't empty.
   if (isEmpty())
   {
      cout << "The stack is empty.\n";
   }
   else  // pop value off top of stack
   {
      num = top->value;
      temp = top->next;
      delete top;
      top = temp;
   }
}

/*************************************************************************
Basic class deconstructor.

Input Parameters:  None

Return Type:  void

*************************************************************************/
template<class T>
bool DynIntStack<T>::isEmpty()
{
   bool status;

   if (!top)
      status = true;
   else
      status = false;

   return status;
}

main.cpp

#include <iostream>
#include "DynIntStack.h"
using namespace std;

int main(){

    int value = 0;
    char value2;
    //DynIntStack<int> stack;
    DynIntStack<char> stack1;

    cout << "Pushing 1\n";
    stack1.push('T');
    stack1.pop(value2);
    cout << value2;

    system("pause");
    return 0;
}

Answer 1

You need to put all the template implementations that you have in your .cpp file in the header file, or in a file included by the header. And don't try to compile the implementation file. Some systems attempt to compile files with a .cpp suffix. The compiler needs to see the code in order to instantiate templates.

Answer 2

at the bottom of DynIntStack.h, put

#include <DynIntStack.cpp>

what's happening is the compiler doesn't see the template implementation code so cannot emit anything for it.