[kbuild-all] Re: drivers/pinctrl/bcm/pinctrl-bcm2835.c:412:14: warning: variable 'group' is used uninitialized whenever 'for' loop exits because its condition is false

On Tue, Dec 14, 2021 at 10:44:28PM +0800, kernel test robot wrote: > Hi Jason, > > FYI, the error/warning still remains. > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: 5472f14a37421d1bca3dddf33cabd3bd6dbefbbc > commit: 29d45a642d4ea8de7e89b57f856046df7c3b219f pinctrl: bcm2835: Replace BUG with BUG_ON > date: 5 months ago > config: mips-randconfig-c004-20211214 (https://download.01.org/0day-ci/archive/20211214/202112142208.QW0tVv0m-lk...) > compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project b6a2ddb6c8ac29412b1361810972e15221fa021c) > 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... > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > git fetch --no-tags linus master > git checkout 29d45a642d4ea8de7e89b57f856046df7c3b219f > # save the config file to linux build tree > mkdir build_dir > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash drivers/pinctrl/bcm/ > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <lkp(a)intel.com&gt; > > All warnings (new ones prefixed by >>): > > >> drivers/pinctrl/bcm/pinctrl-bcm2835.c:412:14: warning: variable 'group' is used uninitialized whenever 'for' loop exits because its condition is false [-Wsometimes-uninitialized] > for (i = 0; i < BCM2835_NUM_IRQS; i++) { > ^~~~~~~~~~~~~~~~~~~~ > drivers/pinctrl/bcm/pinctrl-bcm2835.c:423:10: note: uninitialized use occurs here > switch (group) { > ^~~~~ > drivers/pinctrl/bcm/pinctrl-bcm2835.c:412:14: note: remove the condition if it is always true > for (i = 0; i < BCM2835_NUM_IRQS; i++) { > ^~~~~~~~~~~~~~~~~~~~ > drivers/pinctrl/bcm/pinctrl-bcm2835.c:409:11: note: initialize the variable 'group' to silence this warning > int group; > ^ > = 0 > 1 warning generated. It seems like MIP's __BUG_ON() makes it harder for clang to figure out that 'i == BCM2835_NUM_IRQS' will make the kernel panic, which is the only way that the loop exits because the condition is false. I am not really sure of a way to fix this other than just reverting that change or changing the BUG_ON() to WARN_ON().