reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging.git/commit/?id=068e2e1754d7c9e92e07c8332b2b64673b4989cc
        git remote add groeck-staging https://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging.git
        git fetch --no-tags groeck-staging testing
        git checkout 068e2e1754d7c9e92e07c8332b2b64673b4989cc
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash lib/