Question

I have been struggling with this for quite a while, and my adventures with cmake have only resulted in hackish solutions that I am pretty sure are not correct.

I created a library that consists of several files, as follows:

-libfolder
  -codepart1folder
    -CMakeLists.txt
    -codepart1.cpp
    -codepart1.hpp
  -codepart2folder
  -codepart3folder
  -lib.cpp
  -lib.hpp
  -CMakeLists.txt

I wrote a CMakeLists file to compile the library (after some experimentation), and I can generate a lib.a file. Now I would like to include this code as a library in other projects, and access it through the interface in lib.hpp. What is the best way to do this, in terms of directory structure, and what I need to put into CMakeLists.txt in my root project?

My current attempt has been to add -libfolder as a subfolder to my current project, and add the commands:

include_directories(${PROJECT_SOURCE_DIR}/libfolder)
link_directories(${PROJECT_BINARY_DIR}/libfolder)
add_subdirectory(libfolder)
target_link_libraries(project lib)

When I run make, the library compiles fine, but when project.cpp compiles, it complains that it cannot find codepart1.hpp (which is included in lib.hpp, included from project.cpp).

I suspect that this is the wrong way about doing this, but I cannot wade through the CMake documentation and find a good tutorial on setting up projects like this. Please help, CMake gurus!

Answer 1

Ok, so after consulting a coworker of mine who is a CMake guru, it seems CMake does not have support for what I am trying to do, leaving one with 3 options:

1. Add all of the dependencies to the parent projects CMakeLists.txt – not very clean, but it will get the thing to work. You’ll have to do this for every project you add the code to, and go back and fix things if your library changes.

2. clean up your library headers. This is done through some compiler hackery. The idea is to forward-declare every class, and use only pointers or boost::shared_ptr, and then include the dependencies only in the cpp file. That way you can build the cpp file using all the findpackage stuff, and you get the bonus of being able to use the lib by only including the header and linking to the library.

3. Look into build systems. Having portable code and fast code compilation with complex dependencies is not a solved problem! From my investigations it turned out to be quite complicated. I ended up adopting my coworkers build system which he created himself in cmake, using things he picked up from Google.