On Tue, Apr 30, 2019 at 11:46:44AM +0200, Arnd Bergmann wrote: > On Tue, Apr 30, 2019 at 11:33 AM Nathan Chancellor > <natechancellor@xxxxxxxxx> wrote: > > On Tue, Apr 30, 2019 at 09:16:50AM +0200, Arnd Bergmann wrote: > > > On Tue, Apr 30, 2019 at 3:01 AM Nathan Chancellor > > > <natechancellor@xxxxxxxxx> wrote: > > > > > > > > This is Clang's version of GCC's -Wmaybe-uninitialized. Up to this > > > > point, it has not been used because -Wuninitialized has been disabled, > > > > which also turns off -Wsometimes-uninitialized, meaning that we miss out > > > > on finding some bugs [1]. In my experience, it appears to be more > > > > accurate than GCC and catch some things that GCC can't. > > > > > > > > All of these warnings have now been fixed in -next across arm, arm64, > > > > and x86_64 defconfig/allyesconfig so this should be enabled for everyone > > > > to prevent more from easily creeping in. > > > > > > > > As of next-20190429: > > > > > > > > $ git log --oneline --grep="sometimes-uninitialized" | wc -l > > > > 45 > > > > > > > > [1]: https://lore.kernel.org/lkml/86649ee4-9794-77a3-502c-f4cd10019c36@xxxxxx/ > > > > > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/381 > > > > Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > > > > --- > > > > > > > > Masahiro, I am not sure how you want to handle merging this with regards > > > > to all of the patches floating around in -next but I wanted to send this > > > > out to let everyone know this is ready to be turned on. > > > > > > > > Arnd, are there many remaning -Wsometimes-uninitialized warnings in > > > > randconfigs? > > > > > > No, I don't see any with the patches that I submitted. I haven't checked > > > if there are any that still need to get merged into linux-next though. > > > > > > > diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn > > > > index 768306add591..f4332981ea85 100644 > > > > --- a/scripts/Makefile.extrawarn > > > > +++ b/scripts/Makefile.extrawarn > > > > @@ -72,5 +72,6 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format) > > > > KBUILD_CFLAGS += $(call cc-disable-warning, sign-compare) > > > > KBUILD_CFLAGS += $(call cc-disable-warning, format-zero-length) > > > > KBUILD_CFLAGS += $(call cc-disable-warning, uninitialized) > > > > +KBUILD_CFLAGS += $(call cc-option, -Wsometimes-uninitialized) > > > > endif > > > > endif > > > > > > This doesn't look right. Shouldn't you remove the line that turns off > > > -Wuninitilized > > > instead of adding only -Wsometimes-uninitialized? > > > > Well, there are still some outstanding issues with -Wuninitialized > > right? Like with DECLARE_WAIT_QUEUE_HEAD_ONSTACK? I'd rather not > > add warnings to the build but if you feel strongly, we could turn it on > > then fix them after. > > Ah, I thought they were all fixed, as I don't see any remaining warnings > in my tree. It seems that I never send this workaround for > DECLARE_WAIT_QUEUE_HEAD_ONSTACK: > > diff --git a/include/linux/wait.h b/include/linux/wait.h > index 5f3efabc36f4..cbe1ea0fce84 100644 > --- a/include/linux/wait.h > +++ b/include/linux/wait.h > @@ -68,8 +68,15 @@ extern void __init_waitqueue_head(struct > wait_queue_head *wq_head, const char *n > } while (0) > > #ifdef CONFIG_LOCKDEP > -# define __WAIT_QUEUE_HEAD_INIT_ONSTACK(name) \ > - ({ init_waitqueue_head(&name); name; }) > +# define __WAIT_QUEUE_HEAD_INIT_ONSTACK(name) { > \ > + .lock = __SPIN_LOCK_UNLOCKED(name.lock), > \ > + .head = ({ > \ > + static struct lock_class_key __key; > \ > + lockdep_set_class_and_name(&(name).lock, &__key, # > name); \ > + (struct list_head){ &(name).head, &(name).head }; > \ > + }), > \ > +} > + > # define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name) \ > struct wait_queue_head name = __WAIT_QUEUE_HEAD_INIT_ONSTACK(name) > #else > > Are there any others you see? > > Arnd After applying that diff by hand and another patch that was accepted but not in -next (https://lore.kernel.org/lkml/20190325125147.1436083-1-arnd@xxxxxxxx/), I see three other warnings: arm, arm64, and x86_64 allyesconfig: drivers/net/wireless/rsi/rsi_91x_sdio.c:940:43: error: variable 'data' is uninitialized when used here [-Werror,-Wuninitialized] https://github.com/ClangBuiltLinux/linux/issues/464 x86 allyesconfig: mm/kasan/common.c:490:40: error: variable 'tag' is uninitialized when used here [-Werror,-Wuninitialized] https://github.com/ClangBuiltLinux/linux/issues/465 drivers/misc/sgi-xp/xpc_partition.c:73:14: error: variable 'buf' is uninitialized when used within its own initialization [-Werror,-Wuninitialized] https://github.com/ClangBuiltLinux/linux/issues/466 These shouldn't be difficult to fix then we can turn both uninitialized warnings. Please let me know if you have any input with regards to fixing them, I am going to try to look at them later today. Nathan
