[CMake] modularizing, specifying dependencies in a project

[Geogin Varghese]

This works.

Have pushed changes to the repo here:
https://github.com/vargheseg/test

Thank you

On Wed, Jan 3, 2018 at 8:16 PM, Robert Maynard
<robert.maynard at kitware.com> wrote:
> You will want to use add_subdirectory instead of include in the root
> CMakeLists.txt and remove all include statements from ModA and ModB
>
> It total the changes needed to get everything to work are:
>
> diff --git a/CMakeLists.txt b/CMakeLists.txt
> index e611a37..b6968c1 100644
> --- a/CMakeLists.txt
> +++ b/CMakeLists.txt
> @@ -1,8 +1,9 @@
>  cmake_minimum_required(VERSION 3.0)
>  project(test_project)
>
> -include(${CMAKE_CURRENT_LIST_DIR}/ModA/CMakeLists.txt)
> -include(${CMAKE_CURRENT_LIST_DIR}/ModB/CMakeLists.txt)
> +add_subdirectory(ModA)
> +add_subdirectory(ModB)
> +add_subdirectory(ModC)
>
>  add_executable(main main.cpp)
>  target_link_libraries(main
> diff --git a/ModA/CMakeLists.txt b/ModA/CMakeLists.txt
> index 87128d8..4931be6 100644
> --- a/ModA/CMakeLists.txt
> +++ b/ModA/CMakeLists.txt
> @@ -1,5 +1,4 @@
> -include(${CMAKE_CURRENT_LIST_DIR}/../ModC/CMakeLists.txt)
> -add_library(ModA  $CMAKE_CURRENT_LIST_DIR}/a.cpp)
> +add_library(ModA a.cpp)
>  target_link_libraries(ModA
>         PRIVATE
>           ModC)
> diff --git a/ModB/CMakeLists.txt b/ModB/CMakeLists.txt
> index 3a31be9..7f83856 100644
> --- a/ModB/CMakeLists.txt
> +++ b/ModB/CMakeLists.txt
> @@ -1,4 +1,3 @@
> -include(${CMAKE_CURRENT_LIST_DIR}/../ModC/CMakeLists.txt)
>
>  add_library(ModB b.cpp)
>  target_link_libraries(ModB
>
> On Wed, Jan 3, 2018 at 1:46 PM, Geogin Varghese <geogin at gmail.com> wrote:
>> Hello,
>>
>> Recently came across these presentations on cmake:
>>
>> Using Modern CMake Patterns to Enforce a Good Modular Design
>> (https://www.youtube.com/watch?v=bsXLMQ6WgIk)
>> Effective CMake
>> (https://www.youtube.com/watch?v=eC9-iRN2b04)
>>
>> They encourage using target_* command variants for scripting
>> CMakeLists.txt.
>>
>> What would be the recommended way of writing build scripts for a
>> repository structured as below. The application is compiled from three
>> modules with a dependency among the modules as in the ascii diagram.
>>
>> Is it possible to distribute compile info, such that each submodule has
>> a CMakeLists.txt that describes sources, include and link dependencies needed
>> to compile that module.
>>
>> ---------------------------------------
>> .
>> ├── main.cpp
>> ├── ModA
>> ├── ModB
>> ├── ModC
>>
>> Dependency relation:
>> --------------------
>>        +--------+
>>     +->+main.cpp+<-+
>>     |  +--------+  |
>>     |              |
>>     |              |
>>     |              |
>>   +----+        +----+
>>   |ModA|        |ModB|
>>   +----+        +----+
>>     ^              ^
>>     |              |
>>     |    +----+    |
>>     +----+ModC+----+
>>          +----+
>>
>> ModA <- ModC: Module A
>>  depends on Module C
>> ---------------------------------------
>>
>> My naive effort to do this can be found here:
>> https://github.com/vargheseg/test
>>
>> The problem I run into is with describing the dependency relation
>> between ModA, ModB and ModC.
>>
>> Details:
>> .
>> ├── CMakeLists.txt
>> ├── main.cpp
>> ├── ModA
>> │   ├── a.cpp
>> │   └── CMakeLists.txt
>> ├── ModB
>> │   ├── b.cpp
>> │   └── CMakeLists.txt
>> ├── ModC
>> │   ├── c.cpp
>> │   └── CMakeLists.txt
>>
>> - CMakeLists.txt in the child directories describe compilation
>>   information for that directory.
>> - The top level directory includes the CMakeLists.txt from
>>   subdirectories.
>> - Cmake buildfile generation fails because the way I set things up; the
>>   top level CMakeLists.txt ends up including ModC/CMakeLists.txt twice.
>>
>> ---
>> CMakeLists.txt
>> ---
>>  cmake_minimum_required(VERSION 3.0)
>>  project(test_project)
>>
>>  include(${CMAKE_CURRENT_LIST_DIR}/ModA/CMakeLists.txt)
>>  include(${CMAKE_CURRENT_LIST_DIR}/ModB/CMakeLists.txt)
>>
>>  add_executable(main main.cpp)
>>  target_link_libraries(main PRIVATE ModA ModB)
>>
>>
>> ---
>> ModA/CMakeLists.txt
>> ---
>>  include(${CMAKE_CURRENT_LIST_DIR}/../ModC/CMakeLists.txt)
>>  add_library(ModA  $CMAKE_CURRENT_LIST_DIR}/a.cpp)
>>  target_link_libraries(ModA PRIVATE ModC)
>>
>>
>> ---
>> ModB/CMakeLists.txt
>> ---
>>  include(${CMAKE_CURRENT_LIST_DIR}/../ModC/CMakeLists.txt)
>>  add_library(ModB b.cpp)
>>  target_link_libraries(ModB
>>          PRIVATE
>>          ModC)
>>
>> Is this way of structuring a project a supported use case?
>> --
>>
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