So put the source code in the header file?
That is the common solution. The other solution as mentioned is to do something like:
template GENERIC_STACK< int >;
in the source to force implementation of a specific version of the template. (I believe I have that correct, rarely implement a full class that way, just members.)
PS. this is not a good idea in general, putting the code in the header to be generated at compile time is better than forcing a compile time generation of the entire class.