On Thu, Jul 20, 2017 at 10:17 AM, gregkh <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, Jul 20, 2017 at 09:24:21AM +0200, Arnd Bergmann wrote: >> On Wed, Jul 19, 2017 at 11:50 PM, <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: >> > ------------------------------------------------------ >> > From: Arnd Bergmann <arnd@xxxxxxxx> >> > Subject: kbuild: disable -Wformat-truncation warnings by default >> > >> > With x86 allmodconfig, we currently get 233 -Wformat-truncation warnings, >> > which makes the entire warnings rather useless. >> > >> > This turns off the warning by default, unless we specify W=1 or higher >> > >> > Link: http://lkml.kernel.org/r/20170714120720.906842-2-arnd@xxxxxxxx >> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> >> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> > --- >> > >> > scripts/Makefile.extrawarn | 3 +++ >> > 1 file changed, 3 insertions(+) >> > >> > diff -puN scripts/Makefile.extrawarn~kbuild-disable-wformat-truncation-warnings-by-default scripts/Makefile.extrawarn >> > --- a/scripts/Makefile.extrawarn~kbuild-disable-wformat-truncation-warnings-by-default >> > +++ a/scripts/Makefile.extrawarn >> > @@ -67,5 +67,8 @@ KBUILD_CFLAGS += $(call cc-disable-warni >> > KBUILD_CFLAGS += $(call cc-disable-warning, sign-compare) >> > KBUILD_CFLAGS += $(call cc-disable-warning, format-zero-length) >> > KBUILD_CFLAGS += $(call cc-disable-warning, uninitialized) >> > +else >> > +# noisy gcc-7 warnings >> > +KBUILD_CFLAGS += $(call cc-option,-Wformat-truncation=0) >> > endif >> > endif >> >> Hi Andrew, Linus, Greg, >> >> I noticed that Linus has made a similar patch in 4.13-rc1, commit bd664f6b3e37 >> ("disable new gcc-7.1.1 warnings for now"), and it completely disables three >> warnings (format-truncation, format-overflow and int-in-bool-context). >> >> Obviously there is no point in having both, so let's talk about what we >> want for 4.13, stable-backports and for future kernels, I'll then send those >> patches. Here is my first suggestion: >> >> - enable all three warnings with "make W=1" in 4.13, but leave them >> disabled by default. >> - backport Linus' patch, plus the follow-up for W=1 to stable kernels, >> to allow stable kernels to build cleanly > > I don't care which of these, I'll take whatever is in Linus's tree. > > And I'll go backport that patch now as I'm getting annoyed by the > warnings at the moment... Yes, that's what I meant here, the follow-up obviously has to be agreed on before that can be backported. Let me know what other warnings you see on the stable kernels after backporting the bd664f6b3e37 patch, I can help identify the fixes that went into mainline to address those if you want. >> - backport the patches that address any other gcc-7 warnings, as >> well as those that are not obvious false-positives to stable kernels > > I'll do that as well, as I notice them go by. > >> - In 4.14+, use my version above and address all int-in-bool-context >> and format-overflow warnings, but only use -Wformat-truncation >> with make W=1. > > I don't really care about this, as long as we are not forced to do > "silly things" like some of the patches seemed to do :) Sure, I understand that from the previous feedback, and for a couple of patches I found better workarounds (that improve the code while fixing the warning, rather than adding hacks). I also reported two of them in gcc bugzilla already, one was decided to be invalid: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81484 the other one looks valid, but possibly hard to fix: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81483 When I go through the remaining patches again, I'll have a look at what others might be incorrect warnings that should be fixed in gcc, or which ones can be fixed in a better way. I just wanted to first make sure that there is no fundamental objections to enabling the warnings in future kernels (at whichever W= level) at all. Arnd