6.7.6 Referencing Static Variables and Static Functions

Within a template definition, the compiler does not support referencing an object or function that is declared static at global scope or in a namespace. If multiple instances are generated, the One-Definition Rule (C++ standard section 3.2) is violated, because each instance refers to a different object. The usual failure indication is missing symbols at link time.

If you want a single object to be shared by all template instantiations, then make the object a nonstatic member of a named namespace. If you want a different object for each instantiation of a template class, then make the object a static member of the template class. If you want a different object for each instantiation of a template function, then make the object local to the function.