[CMake] Forcing a target to be built if another target is built

[Job Noorman]

I'm not sure I completely understand what you mean but I think your 
suggestion would be to list *all* needed subdirectories in the active 
project. This is not what a want. The active project simply lists its 
*direct* dependencies (via target_link_libraries) and CMake then figures 
out all the needed transitive dependencies.

Please correct me if i missed your point :-)


On 15/05/18 23:29, Robert Maynard wrote:
>
> Have you thought about not doing anything in the root CMakeLists for 
> your testing directories but instead inside the active project you use 
> add_subdirectory ( it supports relative paths to handle directories 
> not physically nested inside it ).
>
> On Wed, May 9, 2018 at 8:56 AM Job Noorman <job at noorman.info 
> <mailto:job at noorman.info>> wrote:
>
>     Hi all,
>
>     We have a large codebase consisting of 200+ modules. Each module is
>     defined in its own subdirectory and compiled as a static library.
>
>     These modules are not final products on their own but are combined to
>     create "projects". We have about 15 projects that all use a subset of
>     the modules to implement their functionality. The projects are
>     independent in the sense that they cannot be built together; when
>     running cmake, we select the project to build.
>
>     To ensure that only the modules that are needed by the selected
>     project
>     are built, we took the following approach: all modules have a common
>     root directory which is included using add_subdirectory with the
>     EXCLUDE_FROM_ALL flag. Then, the current project's root directory is
>     added without this flag. This ensures that the targets defined by the
>     project and the modules that they need (but no other) are added to
>     the
>     build system. This works very well and is much nicer than having to
>     define options for all optional modules to be able to disable them.
>
>     There is one catch, however: each module defines an executable
>     that runs
>     its unit tests. What should happen is that if a module is built by a
>     project, its unit tests are also built. However, there seems to be no
>     way to define this relationship in CMake. What we would like to
>     express
>     is that "if library A is built, then executable ATest should also be
>     built". Since ATest obviously links against A, we cannot use
>     add_dependencies(A ATest) since this creates a circular dependency
>     between an executable and a library.
>
>     Note that the "option" approach briefly mentioned above would
>     allow us
>     to express this but this would be completely unwieldy in our case.
>
>     Is there currently a way in CMake to express this relation between a
>     library and an executable?
>
>     If not, would the following suggestion make sense?: A target property
>     "INTERFACE_DEPENDENCIES" could be added that would set the
>     MANUALLY_ADDED_DEPENDENCIES target property of dependents. Setting
>     this
>     property on A with ATest as value would then solve my problem
>     (note that
>     I proposed adding this property for a different use case here:
>     https://gitlab.kitware.com/cmake/cmake/issues/14633).
>
>     Regards,
>     Job
>
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