Populating ${SRCS} from CMakeLists.txt in subdirec

Question

I currently define a ${SRCS} variable in the CMakeLists.txt file in my projects root directory, listing every source file required for my executable:

SET (SRCS main.cpp
          dir1/file1.cpp
          dir1/file2.cpp
          dir2/file3.cpp
          dir2/file4.cpp)

How can I distribute this list across the CMakeLists.txt files in each of the subdirectories? That is:

CMakeLists.txt
    Adds main.cpp to SRCS and subdirectories dir1 and dir2

dir1/CMakeLists.txt
    Adds file1.cpp, file2.cpp to SRCS

dir2/CMakeLists.txt
    Adds file3.cpp, file4.cpp to SRCS

Answer 1

It's best to hide all the details of setting up the variable SRCS in a CMake macro. The macro can then be called in all the project CMake list files to add sources.

In the CMakeLists.txt in the project root folder, add the following macro definition:

macro (add_sources)
    file (RELATIVE_PATH _relPath "${PROJECT_SOURCE_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}")
    foreach (_src ${ARGN})
        if (_relPath)
            list (APPEND SRCS "${_relPath}/${_src}")
        else()
            list (APPEND SRCS "${_src}")
        endif()
    endforeach()
    if (_relPath)
        # propagate SRCS to parent directory
        set (SRCS ${SRCS} PARENT_SCOPE)
    endif()
endmacro()

add_sources(main.cpp)
add_subdirectory(dir1)
add_subdirectory(dir2)

message(STATUS "${SRCS}")

The macro first computes the path of the source file relative to the project root for each argument. If the macro is invoked from inside a project sub directory the new value of the variable SRCS needs to be propagated to the parent folder by using the PARENT_SCOPE option.

In the sub directories, you can simply add a macro call, e.g. in dir1/CMakeLists.txt add:

add_sources(file1.cpp file2.cpp)

And in dir2/CMakeLists.txt add:

add_sources(file3.cpp file4.cpp)

Answer 2

A similar macro like the one suggested by sakra was posted on the CMake mailing list by Michael Wild [1]. It uses global properties instead of propagating a variable upwards.

[1] http://www.cmake.org/pipermail/cmake/2010-March/035992.html

Answer 3

In dir1/CMakeLists.txt put this:

set(SRCS ${SRCS} file1.cpp PARENT_SCOPE)

If that wouldn't work, the only solution is to

set(DIR1_SRCS "file1.cpp" PARENT_SCOPE)

and then in ./CMakeLists.txt

set(SRCS ${DIR1_SRCS} ${DIR2_SRCS})