CUDA linker error with template class

Question

Using CUDA 5.0 on ubuntu with gcc/g++ 4.6, I\'m getting errors when linking against CUDA code with templates.

cu_array.cu:

#include \"cu_array.hpp\"
         


        

Answer 1

You haven't instantiated the class in the compilation unit where it is defined, so the compiler doesn't emit any code for the class member function, and linkage fails. This isn't specific to CUDA, this greedy style of instantiation is the compilation/linkage model g++ uses, and lots of people get caught out by it.

As you have found already, the simplest solution is to include everything into the same compilation unit, and the problem disappears.

Otherwise if you explicitly instantiate CuArray::CuArray at the bottom of cu_array.cu like this:

template CuArray<float>::CuArray(unsigned int);

the compiler will emit code where it would otherwise not, and the linkage problem will be fixed. You will need to instantiate every class function for every type you want to use elsewhere in the code to make this approach work.