Ndtyjky

I have an issue with a repository not having its CMakeLists in the root directory, namely https://github.com/lz4/lz4
The CMakeLists.txt is in the subfolder contrib/cmake_unofficial.

I already checked similar questions on SO (Is it possible to have cmake build file (CMakeLists.txt) not in root in CLion, cmake - CMakeLists.txt is not in root folder (but is included in source)), but they only provide alternatives, and not a solution applicable to my situation.

Heres the cmake module I came up with:

if(ENABLE_LZ4)

    message(STATUS "Using LZ4.")

    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DENABLE_LZ4")



    # Enable ExternalProject CMake module

    include(ExternalProject)



    set(LZ4_SOURCE_DIR ${CMAKE_CURRENT_BINARY_DIR}/lz4)

    set(LZ4_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/lib)

    # Download and install lz4

    ExternalProject_Add(

        lz4

        GIT_REPOSITORY https://github.com/lz4/lz4.git

        GIT_TAG dev

        SOURCE_DIR ${LZ4_SOURCE_DIR}

        BINARY_DIR ${LZ4_BINARY_DIR}

        INSTALL_COMMAND ""

        CMAKE_ARGS

            ${LZ4_SOURCE_DIR}/contrib/cmake_unofficial

            -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}

    )



    # Get lz4 source and binary directories from CMake project

    ExternalProject_Get_Property(lz4 source_dir binary_dir)



    # Create a liblz4 target to be used as a dependency by the program

    add_library(liblz4 IMPORTED SHARED GLOBAL)

    add_dependencies(liblz4 lz4)



    include_directories(

        ${LZ4_SOURCE_DIR}/lib

    )

    set(LZ4_LIB ${LZ4_BINARY_DIR}/liblz4.so)

else()

    message(STATUS "Not using LZ4.")

    set(LZ4_LIB "")

endif()

Here the complete error output:

[  0%] Performing update step for 'lz4'

Current branch dev is up to date.

[  1%] Performing configure step for 'lz4'

CMake Error: The source directory "/****/build/lz4" does not appear to contain CMakeLists.txt.

Specify --help for usage, or press the help button on the CMake GUI.

CMakeFiles/lz4.dir/build.make:105: recipe for target 'lz4-prefix/src/lz4-stamp/lz4-configure' failed

make[2]: *** [lz4-prefix/src/lz4-stamp/lz4-configure] Error 1

CMakeFiles/Makefile2:72: recipe for target 'CMakeFiles/lz4.dir/all' failed

make[1]: *** [CMakeFiles/lz4.dir/all] Error 2

Makefile:94: recipe for target 'all' failed

make: *** [all] Error 2

I tried adding the path 'contrib/cmake_unofficial' to the CMAKE_ARGS variable (as seen in the module above), but it does not work (seems to be ignored?).

I also tried using PATCH_COMMAND to copy the CMakeLists.txt to the root before the build starts, but the relative paths of the file get messed up.
In other words, i need the cmake command to be called to build the library to be : cmake contrib/cmake_unofficial.

I also tried using CONFIGURE_COMMAND for this, but keep getting a file not found error for some reason (even though the path is correct).
The module has some other issues too, but I'm only interested in the non-root CMakeLists.

Thanks in advance!

ExternalProject separates download and source directories:

• 
  DOWNLOAD_DIR - a directory where downloading step is performed


• 
  SOURCE_DIR - a directory used as a source one when configuration step is performed

When use git for extract the project, note that git clone is called from the download directory, where it creates new directory with a project sources.

set(LZ4_DOWNLOAD_DIR ${CMAKE_CURRENT_BINARY_DIR}/lz4)

# Set a source dir based on the download one.

set(LZ4_SOURCE_DIR ${LZ4_DOWNLOAD_DIR}/lz4/contrib/cmake_unofficial)

set(LZ4_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/lib)

# Download and install lz4

ExternalProject_Add(

    lz4

    DOWNLOAD_DIR ${LZ4_DOWNLOAD_DIR} # Set download directory explicitely

    GIT_REPOSITORY https://github.com/lz4/lz4.git

    GIT_TAG dev

    SOURCE_DIR ${LZ4_SOURCE_DIR}

    BINARY_DIR ${LZ4_BINARY_DIR}

    ...

)

Probably not the correct way to do it, but this seems to work for me.
I used the CONFIGURE_COMMAND to call cmake on the correct directory.
Then use BUILD_COMMAND to call make
So essentially, it breaks down to this:

ExternalProject_Add(

    lz4

    GIT_REPOSITORY https://github.com/lz4/lz4.git

    GIT_TAG dev

    SOURCE_DIR ${LZ4_SOURCE_DIR}

    BINARY_DIR ${LZ4_BINARY_DIR}

    CONFIGURE_COMMAND cmake ${LZ4_SOURCE_DIR}/contrib/cmake_unofficial

    BUILD_COMMAND make

    INSTALL_COMMAND ""

    CMAKE_ARGS

        -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}

)