[CMake] Beginner's Question: Organizing Projects

[John Drescher]

On Thu, Oct 28, 2010 at 8:23 AM, Dominik Gabi <dkgispam at gmail.com> wrote:
> On Wed, 2010-10-27 at 10:54 -0500, Ryan Pavlik wrote:
>> On Wed, Oct 27, 2010 at 9:04 AM, Rolf Eike Beer <eike at sf-mail.de> wrote:
>> >> Thanks. The way I understand this is that now instead of
>> >>
>> >> include_directories(${GTKMM_INCLUDE_DIRS})
>> >>
>> >> i would write something like
>> >>
>> >> include_directories(${GTKMM_INCLUDE_DIRS})
>> >> # and at the end of the file
>> >> set(INCLUDE_DIRECTORIES ${INCLUDE_DIRECTORIES} PARENT_SCOPE)
>> >>
>> >> ? I'd do the same with the LINK_DIRECTORIES, LINK_LIBRARIES property and
>> >> for all other libraries?
>> >
>> > Don't set LINK_DIRECTORIES and LINK_LIBRARIES. When you are a beginner
>> > probably every usage of them is wrong.
>> >
>> > You simply do
>> >
>> > TARGET_LINK_LIBRARIES(mytarget ${GTK_LIBRARIES}) (or however that is called)
>> >
>> > The only thing you need to "export upwards" in this case would be the
>> > GTK_LIBRARIES variable.
>> >
>> > Eike
>>
>> This is good advice, however, in most cases, since you're using
>> pkgconfig directly (which is not the recommended way), that will cause
>> more failure.  Best thing to do is to create/find a cmake module for
>> each of those packages, that might use pkgconfig for help finding the
>> library, but that doesn't just use what it returns verbatim.
>>
>> Ryan
>>
>
> As it turns out, my problems are probably not cmake related. Thanks for
> the help anyway.
>
> Maybe it's my limited understanding of C++. So here's the problem. The
> project structure is as before. I've got a ui directory that uses
> classes from the geometry directory. I've set up a simple test class in
> the geometry directory that I use in some file in ui.
>
> // Test.h
> class Test
> {
>        public:
>                static void test();
> };
>
> // Test.cpp
> #include "Test.h"
> #include <iostream>
> void Test::test()
> {
>        std::cout << "Hello World!" << std::endl;
> }
>
> With these two files it works perfectly fine. Everything compiles, links
> and runs without problems. Unfortunately, as soon as I add templates the
> situation is different:
>
> // Test.h
> template<class T>
> class Test
> {
> public:
> static void test();
> };
>
> // Test.cpp
> #include "Test.h"
> #include <iostream>
> template<class T>
> void Test<T>::test()
> {
> std::cout << "Hello World!" << std::endl;
> }
>
> results in the following error (I've left out the name spaces above for
> clarity):
>
> dominik at DMac:Pixels$ make
> Scanning dependencies of target Ui
> [ 33%] Building CXX object ui/CMakeFiles/Ui.dir/MainWindow.cpp.o
> Linking CXX static library libUi.a
> [ 33%] Built target Ui
> [ 66%] Built target Geometry
> Linking CXX executable Pixels
> ui/libUi.a(MainWindow.cpp.o): In function
> `UI::MainWindow::start_application(int, char**)':
> MainWindow.cpp:(.text+0x9e1): undefined reference to
> `GE::Test<double>::test()'
> collect2: ld returned 1 exit status
> make[2]: *** [Pixels] Error 1
> make[1]: *** [CMakeFiles/Pixels.dir/all] Error 2
> make: *** [all] Error 2
>
> I don't get it, can anyone explain this to me?
>

Start reading here:

http://stackoverflow.com/questions/115703/storing-c-template-function-definitions-in-a-cpp-file

John