reproduce (this is a W=1 build):
        git remote add trace https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
        git fetch trace for-next
        git checkout trace/for-next
        b4 shazam https://lore.kernel.org/r/176071774097.175601.10233017390618260565.stgit@devnote2
        # apt-get install sparse
        # sparse version: v0.6.4-71-g610d841d

        # 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=i386 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=i386 SHELL=/bin/bash kernel/