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

Static member have to be declared in the class but defined in the unit (cpp file) where it is really located.

The only exception is in case the class is template: in this case you have to define the member outside the class, but you have to provide it too with the class declaration, in the header file.