Extern templates

A template specialization can be explicitly declared as a way to suppress multiple instantiations. For example:

 
    #include "MyVector.h"
    extern template class MyVector<int>; // Suppresses implicit instantiation below --
                    // MyVector<int> will be explicitly instantiated elsewhere
    void foo(MyVector<int>& v)
    {
        // use the vector in here
    }

The “elsewhere” might look something like this:

 
    #include "MyVector.h"
    template class MyVector<int>; // Make MyVector available to clients (e.g., of the shared library

This is basically a way of avoiding significant redundant work by the compiler and linker.