tree:   git://git.cmpxchg.org/linux-mmotm.git master
head:   065f1d86a58cc88249cd8371b29a57c97483753a
commit: dac5c7cf6c6a30d263f120ade36c36b974db01e0 [318/427] signal: use BUILD_BUG() instead of _NSIG_WORDS_is_unsupported_size()
config: xtensa-common_defconfig (attached as .config)
reproduce:
  wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
  chmod +x ~/bin/make.cross
  git checkout dac5c7cf6c6a30d263f120ade36c36b974db01e0
  # save the attached .config to linux build tree
  make.cross ARCH=xtensa 

All error/warnings:

   In file included from arch/xtensa/kernel/signal.c:18:0:
   include/linux/signal.h: In function 'sigisemptyset':
>> include/linux/signal.h:79:3: error: implicit declaration of function 'BUILD_BUG' [-Werror=implicit-function-declaration]
      BUILD_BUG();
      ^
   cc1: some warnings being treated as errors

vim +/BUILD_BUG +79 include/linux/signal.h

    73				set->sig[1] | set->sig[0]) == 0;
    74		case 2:
    75			return (set->sig[1] | set->sig[0]) == 0;
    76		case 1:
    77			return set->sig[0] == 0;
    78		default:
  > 79			BUILD_BUG();
    80			return 0;
    81		}
    82	}

---
0-DAY kernel build testing backend              Open Source Technology Center
http://lists.01.org/mailman/listinfo/kbuild                 Intel Corporation