Question

I have a template class that is only valid for couple of template parameters:

doIt.h:

// only int and float are valid T template <typename T> class doer { public:    void doIt(); } 

I want to hide the implementation inside the .cpp file (for faster compile and also because its proprietary):

doIt.cpp:

template <> void doer<T>::doIt()  {  /* how to do it */ } 

… and use it as follows: use.cpp:

int main( int, char** ) {    doer<int>::doIt() } 

The above fails to link because the implementation of void doer::doIt(void) was never in scope at the place where it was called.

I can force the code to be generated into doItv2.obj, as follows:

doIt_v2.cpp:

template <> void doer<T>::doIt()  {  /* how to do it */ }  doer<int> a;     doer<real> b; 

but this causes a variety of headaches (dynamic memory allocation before main is entered) and I actually don’t want to make an instance — I just want the object code for the template instantiations to be generated.

Any ideas?

Answer 1

See the article How to Organize Template Source Code. I think you are after the second method described there: explicit template instantiation.