[CMake] Build one target with multiple subdirectories

[James Bigler]

Hi,

The problem with using SUBDIR is that variables will get scoped to the 
subdirectory and not automatically available in the parent.  There are 
two ways around this.

The method I use heralds from CMake 1.8.  You simply include the 
CMakeLists.txt files directly, thus putting everything in the same scope:

INCLUDE(subdir1/CMakeLists.txt)
INCLUDE(subdir2/CMakeLists.txt)

ADD_LIBRARY(irgendwas
             hello.cpp
             ${subdir_1_SRCS}
             ${subdir_2_SRCS}
             )

In subdir1/CMakeLists.txt

SET(subdir_1_SRCS
     subdir1/hello1.cpp
     subdir1/hello2.cpp
     )

In subdir2/CMakeLists.txt

SET(subdir_2_SRCS
     subdir2/hello3.cpp
     subdir2/hello4.cpp
     )

The other option is to get the value using GET_DIRECTORY_PROPERTY (note 
the following code may or may not work, because I don't have a concrete 
example of it):

GET_DIRECTORY_PROPERTY(subdir_1_SOURCES DIRECTORY subdir1
                        DEFINITION subdir_1_SOURCES)

This looks like an example of using GET_DIRECTORY_PROPERTY:
http://public.kitware.com/pipermail/cmake-commits/2006-October/000303.html

James

Michael Hammer wrote:
> Hi!
> 
> I would like to add a library and the sources are distributed in 
> different directories, something like the following example:
> 
> / CmakeLists.txt
>  hello.cpp
>  subdir1 / hello1.cpp
>            hello2.cpp
>            CMakeLists.txt
>  subdir2 / hello3.cpp
>            hello4.cpp
>            CMakeLists.txt
> 
> In the CMakeLists.txt of subdir1 I would write:
> 
> set( subdir1_SOURCES
>     hello1.cpp
>     hello2.cpp )
> 
> similar in subdir2
> 
> set( subdir2_SOURCES
>     hello3.cpp
>     hello4.cpp )
> 
> in /CMakeLists.txt I would add something like that:
> 
> add_subdirectory(subdir1)
> add_subdirectory(subdir2)
> 
> add_library( irgendwas
>             hello.cpp
>             subdir_1/${subdir1_SOURCES}
>             subdir_2/${subdir2_SOURCES} )
> 
> Unfortunately this doesn't work ;) CMake doesn't set the variables 
> subdirx_SOURCES by calling add_subdirectory. The next problem I see is 
> the add_library statement. In subdir1_SOURCES there is a necessary path 
> prefix (subdir1/, subdir2/) missing - I am really not sure if I can add 
> the prefix the way I have done it here (obviously not ;)).
> 
> Perhaps someone can help? I am sure there is a "good" or "accurate" way 
> to do this - thanks a lot.
> 
> Michael
>