CMake - Check if a higher level directory exists

Question

I'm new to CMake and I tried to do this in my root CMakeLists.txt :

set(HAVE_MY_SDK   OFF)

if(IS_DIRECTORY "${PROJECT_SOURCE_DIR}../Libs/A")
    if(EXISTS "${PROJECT_SOURCE_DIR}../Libs/A/CMakeLists.txt")
        set (HAVE_MY_SDK   ON)
    endif()
endif()

Currently, CMake is just avoiding the instruction, leaving HAVE_MY_SDK in a OFF status. Is it possible to check an higher level directory with CMake ? Or maybe doing it with an indirect method

Answer 1

I think you're just missing a / after ${PROJECT_SOURCE_DIR}.

Out of completeness here is the code I use for this (note that if (EXISTS ...) needs full paths):

get_filename_component(_fullpath "${_dir}" REALPATH)
if (EXISTS "${_fullpath}" AND EXISTS "${_fullpath}/CMakeLists.txt")
    ...

And here inside my extended add_subdirectory() version (including a "add once guard"):

function(my_add_subdirectory _dir)
    get_filename_component(_fullpath "${_dir}" REALPATH)
    if (EXISTS "${_fullpath}" AND EXISTS "${_fullpath}/CMakeLists.txt")
        get_property(_included_dirs GLOBAL PROPERTY GlobalAddSubdirectoryOnceIncluded)
        list(FIND _included_dirs "${_fullpath}" _used_index)
        if (${_used_index} EQUAL -1)
            set_property(GLOBAL APPEND PROPERTY GlobalAddSubdirectoryOnceIncluded "${_fullpath}")
            add_subdirectory(${_dir} ${ARGN})
        endif()
    else()
        message(WARNING "my_add_subdirectory: Can't find ${_fullpath}/CMakeLists.txt")
    endif()
endfunction(my_add_subdirectory)