Hi Thomas, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 7cca308cfdc0725363ac5943dca9dcd49cc1d2d5 commit: 396c7d94c3bbe07ae00c9f694a5c731878843038 MIPS: alchemy: Fix build breakage, if TOUCHSCREEN_WM97XX is disabled date: 11 months ago config: mips-randconfig-r016-20210903 (attached as .config) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 1104e3258b5064e7110cc297e2cec60ac9acfc0a) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install mips cross compiling tool for clang build # apt-get install binutils-mips-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=396c7d94c3bbe07ae00c9f694a5c731878843038 git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout 396c7d94c3bbe07ae00c9f694a5c731878843038 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot All warnings (new ones prefixed by >>): >> arch/mips/boot/compressed/dbg.c:12:13: warning: no previous prototype for function 'putc' [-Wmissing-prototypes] void __weak putc(char c) ^ arch/mips/boot/compressed/dbg.c:12:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __weak putc(char c) ^ static >> arch/mips/boot/compressed/dbg.c:16:6: warning: no previous prototype for function 'puts' [-Wmissing-prototypes] void puts(const char *s) ^ arch/mips/boot/compressed/dbg.c:16:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void puts(const char *s) ^ static >> arch/mips/boot/compressed/dbg.c:26:6: warning: no previous prototype for function 'puthex' [-Wmissing-prototypes] void puthex(unsigned long long val) ^ arch/mips/boot/compressed/dbg.c:26:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void puthex(unsigned long long val) ^ static 3 warnings generated. -- >> arch/mips/boot/compressed/uart-alchemy.c:4:6: warning: no previous prototype for function 'putc' [-Wmissing-prototypes] void putc(char c) ^ arch/mips/boot/compressed/uart-alchemy.c:4:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void putc(char c) ^ static 1 warning generated. vim +/putc +12 arch/mips/boot/compressed/dbg.c 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 11 e52dd9fc6b9e0c Wu Zhangjin 2010-01-26 @12 void __weak putc(char c) 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 13 { 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 14 } 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 15 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 @16 void puts(const char *s) 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 17 { 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 18 char c; 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 19 while ((c = *s++) != '\0') { 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 20 putc(c); 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 21 if (c == '\n') 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 22 putc('\r'); 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 23 } 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 24 } 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 25 1b93b3c3e94be2 Wu Zhangjin 2009-10-14 @26 void puthex(unsigned long long val) :::::: The code at line 12 was first introduced by commit :::::: e52dd9fc6b9e0c17b220bd38371ff15032a1a155 MIPS: Simplify the weak annotation with __weak :::::: TO: Wu Zhangjin :::::: CC: Ralf Baechle --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org