Populating ${SRCS} from CMakeLists.txt in subdirectories

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)