Why won't my C++ program link when my class has static members?

Question

I have a little class called Stuff that I want to store things in. These things are a list of type int. Throughout my code in whatever classes I use I want to be able to a

Answer 1

Stuff::things is only declared, but it is not defined.

please use:

// Stuff.cpp
#include "Stuff.h"

std::list Stuff::things;

Added: it is also a good practice to protect your header files against multiple inclusion:

// Stuff.h
#ifndef STUFF_H_
#define STUFF_H_

#include 

class Stuff {
    public:
       static std::list things;
};

#endif