[CMake] Undefined symbols when header file with code is included

[Nicholas Kinar]

>
> I believe that this should be sufficient to let CMake know that my 
> header file is in this particular directory, but when I run the 
> generated makefile, I receive the following error:
>
> Undefined symbols:
>   "void util::load_matrix<double>(std::basic_string<char, 
> std::char_traits<char>, std::allocator<char> >, 
> TNT::Array2D<double>*)", referenced from:
>       run_test()    in model.cpp.o
> ld: symbol(s) not found
> collect2: ld returned 1 exit status
> make[2]: *** [model] Error 1
> make[1]: *** [CMakeFiles/model.dir/all] Error 2
> make: *** [all] Error 2
> Matilda-2:FDTD-model-1 nicholaskinar$
>
> What am I doing wrong, and what do I have to modify to let CMake link 
> my header file with the output executable?  I am building my project 
> on UNIX (Mac OS X and Linux) systems using CMake 2.8.2.
>

My mistake; linking with code contained in a header file actually works 
quite well in CMake.  Just as the error says, the problem was due to an 
undefined symbol.  In the file my_util.h, I changed

template <class T>
         void load_matrix(std::string fileName, TNT::Array2D<double> *M)

to

void load_matrix(std::string fileName, TNT::Array2D<T> *M)

I was then able to successfully compile and link my program.

Nicholas