On Sat, Sep 28, 2019 at 1:39 AM Marek Vojtko <marek.voj...@oxidegames.com> wrote:
> I agree that manually keeping track of transitive dependencies is a very > bad and error-prone idea. > > > > The ideal solution is the separate repositories, but I don’t think that’s > really feasible. > > > > The multi-root setup would work, but the ugly part of it is requiring an > “app*_root” directory for each application, which is needed to be able to > create a solution/makefile with only the application’s dependencies. When > compiling an app I don’t want to be compiling targets it does not depend > on, which is what would happen if I were to use the app*_root directory > directly. > Why would you build targets you don't depend upon in my original proposal? you certainly *include* them all in your project, but as long as you build your application target, only it's actual dependencies will be built. Of course, if you build the "all" target, everything will be built, but that could easily be avoided with EXCLUDE_FROM_ALL when adding the `components` subdirectory.😊 > > *From:* Avraham Shukron <avraham.shuk...@gmail.com> > *Sent:* Friday, September 27, 2019 5:23 PM > *To:* Marek Vojtko <marek.voj...@oxidegames.com> > *Cc:* cmake@cmake.org > *Subject:* Re: [CMake] Project Structure and add_subdirectory() > > > > I think option 2 (keeping track on transitive dependencies) should be out > of the question. > > It is bound to fail. > > > > Superbuild setup makes sense where all the components are part of a bigger > whole. > > But if each application may depend on a different "flavor" of a > dependency library, I think it should be reflected in your project > structure, E.g each application in a separate repository, with all the > dependencies as submodules. > > > > alternatively, you can create a multi-root setup, where you have a > project-root-directory for each application, with a top-level CMakeLists > that adds all the necessary subdirectories. > > This way, you get the best of all worlds: > > 1. Each component's source code is kept only once, and changes are > immediately affecting all products. > > 2. You can compile each application independently from one another. > > > > Consider the following structure: > > > > -top/ > > - app1_root/ > > - CMakeLists.txt > > - app2_root/ > > - CMakeLists.txt > > - app3_root/ > > - CMakeLists.txt > > - components/ > > - CMakeLists.txt > > - libA/ > > - libB/ > > - libC/ > > > > The only issue I can think of is that in each application's top-level > CMakeLists.txt you have to add_subdirectory(../components) and the ".." is > kind of ugly. > > Other than that I think it should work > > > > > > On Fri, Sep 27, 2019 at 7:00 PM Marek Vojtko <marek.voj...@oxidegames.com> > wrote: > > Using add_subdirectory() in a "superbuild" setup is straightforward: > Create a root CMakeLists.txt which calls add_subdirectory() on all > directories of your project and each target can then use > target_link_libraries() without worrying where the target came from. > > Unfortunately the "superbuild" setup also means that each target is > compiled exactly once, which means that you cannot change a target's build > environment per-application (e.g. preprocessor definitions that change the > sizes of stack arrays). > > If I need per-application control of its dependencies' build environment I > can have each application's CMakeLists.txt call add_subdirectory() for all > of its dependencies. However, that means that each application now has to > know all of its *transitive* dependencies and the application's > CMakeLists.txt has to be kept up-to-date with any changes in its dependency > tree, no matter how deep. So if AppA depends on LibA, which depends on > LibB, which depends on LibC. Not only does AppA's CMakeLists.txt have to > call add_subdirectory() on LibA, LibB, and LibC, but if LibC is modified to > depend on LibX, now AppA's CMakeLists.txt has to also be modified to call > add_subdirectory() on LibX. > > Having each target call add_subdirectory() on its own dependencies seems > silly, because that would create an insane number of duplicated targets. If > LibA depends on LibB and LibC, and both LibB and LibC depend on LibD, this > approach would result in both LibB and LibC calling add_subdirectory() on > LibD, creating the target twice, which would likely not compile. > > Are these my only two options? Either: > - use a superbuild to have CMake handle my transitive dependencies, but > give up per-application build environment changes, or > - track all transitive dependencies manually in each application's > CMakeLists.txt, but retain the ability to change the build environment per > application. > -- > > Powered by www.kitware.com > > Please keep messages on-topic and check the CMake FAQ at: > http://www.cmake.org/Wiki/CMake_FAQ > > Kitware offers various services to support the CMake community. For more > information on each offering, please visit: > > CMake Support: http://cmake.org/cmake/help/support.html > CMake Consulting: http://cmake.org/cmake/help/consulting.html > CMake Training Courses: http://cmake.org/cmake/help/training.html > > Visit other Kitware open-source projects at > http://www.kitware.com/opensource/opensource.html > > Follow this link to subscribe/unsubscribe: > https://cmake.org/mailman/listinfo/cmake > >
-- Powered by www.kitware.com Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Kitware offers various services to support the CMake community. For more information on each offering, please visit: CMake Support: http://cmake.org/cmake/help/support.html CMake Consulting: http://cmake.org/cmake/help/consulting.html CMake Training Courses: http://cmake.org/cmake/help/training.html Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Follow this link to subscribe/unsubscribe: https://cmake.org/mailman/listinfo/cmake
