Possible Duplicate: Why can templates only be implemented in the header file?
I got the following error while compiling in g++ 4.5.5 on Linux while allegedly my code works fine on Windows.
A.o: In function `A::NewObj(int)':
A.cpp:(.text+0x39): undefined reference to `List<A>::Add(A*)'
collect2: ld returned 1 exit status
make: *** [program] Error 1
I have no idea what is wrong with my code. I'm not sure if I declared object list_A correctly.
The files:
A.h
#ifndef A_H
#define A_H
class A
{
public:
int key;
A() { key=0; }
A(int i) { key = i; }
void NewObj(int i);
};
#endif
A.cpp
#include "A.h"
#include "List.h"
static List<A> *list_A = new List<A>();
void A::NewObj(int i)
{
A *nobject = new A(i);
list_A->Add( nobject );
}
List.h
#ifndef LIST_H
#define LIST_H
template<typename Objct>
class Node
{
public:
Objct* datapiece;
Node *next, *previous;
Node() { next = previous = 0; }
Node ( Objct *object, Node *n = 0, Node *p = 0)
{
datapiece = object;
next = n; previous = p;
}
};
template<typename Objct>
class List
{
public:
List() { head = tail = 0; }
void Add( Objct* );
protected:
Node<Objct> *head, *tail;
};
#endif
List.cpp
#include "List.h"
#include <iostream>
template<typename Objct>
void List<Objct>::Add( Objct *o )
{
int i =5;
Node<Objct> *nnode = new Node<Objct>(o);
if ( o->key < i )
std::cout << "Ok" << std::endl;
}
main.cpp
#include <iostream>
#include "A.h"
#include "List.h"
int main()
{
A *magazyn = new A();
magazyn->NewObj(6);
}
makefile
CC=g++
CFLAGS=-c -Wall -pedantic
program: List.o A.o main.o
$(CC) List.o A.o main.o -o program
A.o: A.cpp List.h
$(CC) $(CFLAGS) A.cpp
List.o: List.cpp
$(CC) $(CFLAGS) List.cpp
main.o: main.cpp A.h
$(CC) $(CFLAGS) main.cpp
