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c++cross-platformbuild-processcmakemodularity

CMAKE for modular c++ framework

I'm refactoring a large platform independent c++ framework so that it's libraries and execuables no longer have to be in the same directory (or even repository) and it is proving quite challenging. The framework was currently used only by me and it should now address our whole working group so I have to keep it as modular and as automatized as possible.

My basic structure looks like this

  • apps/
    • app1, app2, ...
  • libs/
    • core, lib1, lib2, ...
  • bin:
    • app1, app2, libcore, liblib1, liblib2, ... (on NIX)
    • app1.exe, app2.exe, core.dll, lib1.dll, lib2.dll, ... (on Windows)

Apps depend on libs, and all libs depend on the core lib. This all works fine in the same root directory and with the add_subdirectory mechanism.

Project dependencies were handeled by the order in which I was calling add_subdirectory: first libs (core being the first), then apps. Cmake was kind enough to set ${core_SOURCE_IR} to the respective directory and all binaries (libs and apps) were generated in the same directory.

What I need advice with is:

  • should I move to a find_package based approach (write for each lib and FindLib.cmake file)
  • how the apps and libs will find each other
  • where to put the binaries
  • how to pass along include directories of dependent targets
  • ExternalProject_Add ?

Thank you

Solution

  • First, you can add_subdirectory()es in any order without caring about dependencies. CMake handles them when all CMakeLists.txt are parsed.

    Second, if you wish any your lib or app to be buildable stand-alone, you certainly should use something like find_package(). It can be find_library() and find_file(lib.h) for simple cases.

    In this case after find_package() invocation you will have LIB_INCLUDE_DIRS, LIB_LIBRARY_DIRS, LIB_LIBRARIES variables defined, which can be passed to include_directories(), link_directories() and target_link_libraries() respectively. That's how apps will find libs.

    As for where to put binaries - in *NIX it's wide practice to place them into ${CMAKE_INSTALL_PREFIX}/bin.

    Please comment on this answer, if there is something unclear for you.