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.
# version 3.11 or later of CMake needed later for installing GoogleTest # so let's require it now. Cmakeminimumrequired(VERSION 3.11-3.18) project( VscodeCmakeHello VERSION 0.1 DESCRIPTION 'Small CMake example built with VSCode') addsubdirectory(hello) # look in hello subdirectory for CMakeLists.txt to process addsubdirectory(apps) # look. CMake is an open-source, cross-platform family of tools designed to build, test and package software. CMake is used to control the software compilation process using simple platform and compiler independent configuration files, and generate native makefiles and workspaces that can be used in the compiler environment of your choice.
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. So in your example:
-top/
- app1 /
- CMakeLists.txt
- app1_root/
- CMakeLists.txt
- app2/
- CMakeLists.txt
- app2_root/
- CMakeLists.txt
- app3/
- CMakeLists.txt
- app3_root/
- CMakeLists.txt
- components/
- CMakeLists.txt
- libA/
- libB/
- libC/
And developers would have to CMake the app*_root directories and then open solutions / run makefiles generated for the individual apps. Not terrible, but definitely not intuitive. But thank you for sharing that, I haven’t thought of that ?
From: Avraham Shukron <[hidden email]>
Sent: Friday, September 27, 2019 5:23 PM
To: Marek Vojtko <[hidden email]>
Cc:[hidden email]
Subject: Re: [CMake] Project Structure and add_subdirectory()
Sent: Friday, September 27, 2019 5:23 PM
To: Marek Vojtko <[hidden email]>
Cc:[hidden email]
Subject: Re: [CMake] Project Structure and add_subdirectory()
Cmake Add_subdirectory C
I think option 2 (keeping track on transitive dependencies) should be out of the question.
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.
Cmake Add_subdirectory Example
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/
- CMakeLists.txt
- CMakeLists.txt
- CMakeLists.txt
- CMakeLists.txt
- libB/
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.
On Fri, Sep 27, 2019 at 7:00 PM Marek Vojtko <[hidden email]> 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
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
My scenario is as follows.
I have an example folder with 20+ examples in it. Each example is separated into it’s own sub-folder with it’s own
CMakeLists.txt
file, source/include folder, etc.I have a top level
CMakeLists.txt
file under Examples
. That file is basically a bunch of add_subdirectory()
calls to all the Ex#
subdirectories.I had a case where I ran
The compile for Ex2 failed, but everything else succeeded. As anti-luck would have it I wasn’t watching the compile so I didn’t see the error message/failure scroll by.
Nothing in the final screen of output from the
cmake
command made me think that I had any failures earlier on, so I started to do next step action. Which eventually lead me to finding out that Ex2 actually failed to compile.I know that I could have done the command
after running
cmake --build .
, however that’s not really a common practice when working with the cli. It is for scripts, but not manual CLI interaction.Is there a method, a pattern, or a practice that I can use so that
cmake
will display a summary or some indicate of a failure at the end?