Question

I’m using Eclipse and MinGW. I’ve got undefined reference to error to all that I write in h files, that I do include in cpp-file where main located. I create an empty project, and the same thing again (

main.cpp

#include <iostream>
#include "Stack.h"

using namespace std;

int main(){
    Stack<int> stack(10);
    cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!
    return 0;
}

stack.h

#ifndef STACK_H_
#define STACK_H_

template <class T>
class Stack{
private:
    struct StackEl;
    StackEl *top;
public:
    Stack();
    Stack(T el);
    ~Stack();
    void Push(const T& el);
    T Pop();
};

#endif /* STACK_H_ */

and stack.cpp inplements everything from stack.h
If I include not h-file, but cpp – all works. Help please!

I’ve got following errors

D:/Workspacee/Stack2/Debug/../src/Stack2.cpp:16: undefined reference to `Stack<int>::Stack(int)'
D:/Workspacee/Stack2/Debug/../src/Stack2.cpp:18: undefined reference to `Stack<int>::~Stack()'
D:/Workspacee/Stack2/Debug/../src/Stack2.cpp:18: undefined reference to `Stack<int>::~Stack()'

Answer 1

My bad, that is becouse templates! When you use template, all code, including realization of functions, must be in header-file, or you have to write prototypes for every type you are going to use you template-functions with. I’ve forgot about that working with templates is not the same as with usual function 🙁