| Message ID | 1550722418-9189-1-git-send-email-yamada.masahiro@socionext.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig | expand |
On Thu, Feb 21, 2019 at 01:13:38PM +0900, Masahiro Yamada wrote: > Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched > various false positives: > > - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building > with -Os") turned off this option for -Os. > > - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning > for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for > CONFIG_PROFILE_ALL_BRANCHES > > - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning > for "make W=1"") turned off this option for GCC < 4.9 > Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 > > I think this looks better by shifting the logic from Makefile to Kconfig. > I agree! > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> > --- > > Makefile | 10 +++------- > init/Kconfig | 17 +++++++++++++++++ > kernel/trace/Kconfig | 1 + > 3 files changed, 21 insertions(+), 7 deletions(-) > > diff --git a/Makefile b/Makefile > index 1bb0535..b21aa2e3 100644 > --- a/Makefile > +++ b/Makefile > @@ -656,17 +656,13 @@ KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context) > > ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE > KBUILD_CFLAGS += $(call cc-option,-Oz,-Os) > -KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,) > -else > -ifdef CONFIG_PROFILE_ALL_BRANCHES > -KBUILD_CFLAGS += -O2 $(call cc-disable-warning,maybe-uninitialized,) > else > KBUILD_CFLAGS += -O2 > endif > -endif > > -KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \ > - $(call cc-disable-warning,maybe-uninitialized,)) > +ifdef CONFIG_CC_DISABLE_WARN_MAYBE_UNINITIALIZED > +KBUILD_CFLAGS += -Wno-maybe-uninitialized > +endif > > # Tell gcc to never replace conditional load with a non-conditional one > KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) > diff --git a/init/Kconfig b/init/Kconfig > index c9386a3..1f05a88 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -26,6 +26,22 @@ config CLANG_VERSION > config CC_HAS_ASM_GOTO > def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) > > +config CC_HAS_WARN_MAYBE_UNINITIALIZED > + def_bool $(cc-option,-Wmaybe-uninitialized) > + help > + GCC >= 4.7 supports this option. > + > +config CC_DISABLE_WARN_MAYBE_UNINITIALIZED > + bool > + depends on CC_HAS_WARN_MAYBE_UNINITIALIZED > + default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 > + help > + GCC's -Wmaybe-uninitialized is not reliable by definition. > + Lots of false positive warnings are produced in some cases. > + > + If this option is enabled, -Wno-maybe-uninitialzed is passed > + to the compiler to suppress maybe-uninitialized warnings. > + > config CONSTRUCTORS > bool > depends on !UML > @@ -1113,6 +1129,7 @@ config CC_OPTIMIZE_FOR_PERFORMANCE > > config CC_OPTIMIZE_FOR_SIZE > bool "Optimize for size" > + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives > help > Enabling this option will pass "-Os" instead of "-O2" to > your compiler resulting in a smaller kernel. > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index fa8b1fe..8bd1d6d 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -370,6 +370,7 @@ config PROFILE_ANNOTATED_BRANCHES > config PROFILE_ALL_BRANCHES > bool "Profile all if conditionals" if !FORTIFY_SOURCE > select TRACE_BRANCH_PROFILING > + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives > help > This tracer profiles all branch conditions. Every if () > taken in the kernel is recorded whether it hit or miss. > -- > 2.7.4 >
On Thu, Feb 21, 2019 at 5:14 AM Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > > Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched > various false positives: > > - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building > with -Os") turned off this option for -Os. > > - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning > for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for > CONFIG_PROFILE_ALL_BRANCHES > > - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning > for "make W=1"") turned off this option for GCC < 4.9 > Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 > > I think this looks better by shifting the logic from Makefile to Kconfig. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> I like how this cleans up the logic and documents it better. I've had my own plans to move this (and most other conditional warning options) into a header file using the KBUILD_WARN() infrastructure, but never got around to doing that. I still think that's what we want eventually, but in the meantime your patch seems fine as well. Also, I see that your patch keeps the existing logic, which is good, but we may want to refine this a little afterwards: - we may want to turn off -Wuninitialized for gcc-4.6 and gcc-4.7 instead of turning off -Wmaybe-uninitialized as we do in the later compilers. - the proposed CC_OPTIMIZE_FOR_DEBUGGING may need the same workaround as CC_OPTIMZE_FOR_SIZE. - For clang, we may want to /not/ turn off -Wmaybe-uninitialized in all cases. I haven't tried build with with 'clang -Oz -Wmaybe-uninitialized', but if the number of false positives is small enough, we could decide to just leave that on. Arnd
On Thu, Feb 21, 2019 at 6:23 PM Arnd Bergmann <arnd@arndb.de> wrote: > > On Thu, Feb 21, 2019 at 5:14 AM Masahiro Yamada > <yamada.masahiro@socionext.com> wrote: > > > > Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched > > various false positives: > > > > - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building > > with -Os") turned off this option for -Os. > > > > - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning > > for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for > > CONFIG_PROFILE_ALL_BRANCHES > > > > - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning > > for "make W=1"") turned off this option for GCC < 4.9 > > Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 > > > > I think this looks better by shifting the logic from Makefile to Kconfig. > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > I like how this cleans up the logic and documents it better. > I've had my own plans to move this (and most other conditional warning > options) into a header file using the KBUILD_WARN() infrastructure, but > never got around to doing that. I still think that's what we want eventually, > but in the meantime your patch seems fine as well. > > Also, I see that your patch keeps the existing logic, which is good, > but we may want to refine this a little afterwards: > > - we may want to turn off -Wuninitialized for gcc-4.6 and gcc-4.7 > instead of turning off -Wmaybe-uninitialized as we do in the later > compilers. Ah, right. I can do that if it is worthwhile. But, I'd rather want to raise the minimum compiler version than taking care of old compilers. (We will do it eventually.) > - the proposed CC_OPTIMIZE_FOR_DEBUGGING may need the > same workaround as CC_OPTIMZE_FOR_SIZE. I know this. First, my patch took care of CC_OPTIMIZE_FOR_DEBUGGING as well. But, CC_OPTIMIZE_FOR_DEBUGGING was rejected. (https://patchwork.kernel.org/patch/10744541/) So, I dropped this. > - For clang, we may want to /not/ turn off -Wmaybe-uninitialized > in all cases. I haven't tried build with with 'clang -Oz > -Wmaybe-uninitialized', but if the number of false positives is small > enough, we could decide to just leave that on. Does clang recognize -Wmaybe-uninitialized? I am using Clang I built a few days ago. masahiro@pug:~$ clang --version clang version 9.0.0 (http://llvm.org/git/clang.git b492883ea31e2046d5725126318911465bc1374f) (http://llvm.org/git/llvm.git 03a15eec9ef44798cd5c57b4ed6a63e62b2c1db6) Target: x86_64-unknown-linux-gnu Thread model: posix InstalledDir: /home/masahiro/toolchains/clang-latest/bin masahiro@pug:~$ clang -x c /dev/null -Wmaybe-uninitialized -c -o /dev/null warning: unknown warning option '-Wmaybe-uninitialized'; did you mean '-Wuninitialized'? [-Wunknown-warning-option] 1 warning generated. > Arnd
On Thu, Feb 21, 2019 at 10:45 AM Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > On Thu, Feb 21, 2019 at 6:23 PM Arnd Bergmann <arnd@arndb.de> wrote: > > On Thu, Feb 21, 2019 at 5:14 AM Masahiro Yamada > > <yamada.masahiro@socionext.com> wrote: > > > > I like how this cleans up the logic and documents it better. > > I've had my own plans to move this (and most other conditional warning > > options) into a header file using the KBUILD_WARN() infrastructure, but > > never got around to doing that. I still think that's what we want eventually, > > but in the meantime your patch seems fine as well. > > > > Also, I see that your patch keeps the existing logic, which is good, > > but we may want to refine this a little afterwards: > > > > - we may want to turn off -Wuninitialized for gcc-4.6 and gcc-4.7 > > instead of turning off -Wmaybe-uninitialized as we do in the later > > compilers. > > Ah, right. > > I can do that if it is worthwhile. > > But, I'd rather want to raise the minimum compiler version > than taking care of old compilers. > (We will do it eventually.) I was hoping that with gcc-4.6 being the minimum version, we could actually get all supported compilers to produce clean builds on all configurations, possibly at the cost of just turning off all unreliable warning options on older compilers. I don't mind regularly raising the minimum version, but I would also wait several years before I'd consider gcc-4.9 a good choice for the minimum, and all older versions have problems here. > Does clang recognize -Wmaybe-uninitialized? > > I am using Clang I built a few days ago. > > > masahiro@pug:~$ clang --version > clang version 9.0.0 (http://llvm.org/git/clang.git > b492883ea31e2046d5725126318911465bc1374f) > (http://llvm.org/git/llvm.git > 03a15eec9ef44798cd5c57b4ed6a63e62b2c1db6) > Target: x86_64-unknown-linux-gnu > Thread model: posix > InstalledDir: /home/masahiro/toolchains/clang-latest/bin > > masahiro@pug:~$ clang -x c /dev/null -Wmaybe-uninitialized -c -o /dev/null > warning: unknown warning option '-Wmaybe-uninitialized'; did you mean > '-Wuninitialized'? [-Wunknown-warning-option] > 1 warning generated. Ah, that's right. I also see -Wconditional-uninitialized and -Wsometimes-uninitialized, but they are something different again. Arnd
On Wed, Feb 20, 2019 at 8:14 PM Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > > Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched > various false positives: > > - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building > with -Os") turned off this option for -Os. > > - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning > for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for > CONFIG_PROFILE_ALL_BRANCHES > > - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning > for "make W=1"") turned off this option for GCC < 4.9 > Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 > > I think this looks better by shifting the logic from Makefile to Kconfig. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> I verified that mainline+this patch did not regression arm64 allyesconfig clang build. Tested-by: Nick Desaulniers <ndesaulniers@google.com> Thanks for the patch! Would you mind adding a link tag to: Link: https://github.com/ClangBuiltLinux/linux/issues/350 > --- > > Makefile | 10 +++------- > init/Kconfig | 17 +++++++++++++++++ > kernel/trace/Kconfig | 1 + > 3 files changed, 21 insertions(+), 7 deletions(-) > > diff --git a/Makefile b/Makefile > index 1bb0535..b21aa2e3 100644 > --- a/Makefile > +++ b/Makefile > @@ -656,17 +656,13 @@ KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context) > > ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE > KBUILD_CFLAGS += $(call cc-option,-Oz,-Os) > -KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,) > -else > -ifdef CONFIG_PROFILE_ALL_BRANCHES > -KBUILD_CFLAGS += -O2 $(call cc-disable-warning,maybe-uninitialized,) > else > KBUILD_CFLAGS += -O2 > endif > -endif > > -KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \ > - $(call cc-disable-warning,maybe-uninitialized,)) > +ifdef CONFIG_CC_DISABLE_WARN_MAYBE_UNINITIALIZED > +KBUILD_CFLAGS += -Wno-maybe-uninitialized > +endif > > # Tell gcc to never replace conditional load with a non-conditional one > KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) > diff --git a/init/Kconfig b/init/Kconfig > index c9386a3..1f05a88 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -26,6 +26,22 @@ config CLANG_VERSION > config CC_HAS_ASM_GOTO > def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) > > +config CC_HAS_WARN_MAYBE_UNINITIALIZED > + def_bool $(cc-option,-Wmaybe-uninitialized) > + help > + GCC >= 4.7 supports this option. > + > +config CC_DISABLE_WARN_MAYBE_UNINITIALIZED > + bool > + depends on CC_HAS_WARN_MAYBE_UNINITIALIZED > + default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 > + help > + GCC's -Wmaybe-uninitialized is not reliable by definition. > + Lots of false positive warnings are produced in some cases. > + > + If this option is enabled, -Wno-maybe-uninitialzed is passed > + to the compiler to suppress maybe-uninitialized warnings. > + > config CONSTRUCTORS > bool > depends on !UML > @@ -1113,6 +1129,7 @@ config CC_OPTIMIZE_FOR_PERFORMANCE > > config CC_OPTIMIZE_FOR_SIZE > bool "Optimize for size" > + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives > help > Enabling this option will pass "-Os" instead of "-O2" to > your compiler resulting in a smaller kernel. > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index fa8b1fe..8bd1d6d 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -370,6 +370,7 @@ config PROFILE_ANNOTATED_BRANCHES > config PROFILE_ALL_BRANCHES > bool "Profile all if conditionals" if !FORTIFY_SOURCE > select TRACE_BRANCH_PROFILING > + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives > help > This tracer profiles all branch conditions. Every if () > taken in the kernel is recorded whether it hit or miss. > -- > 2.7.4 >
On Fri, Feb 22, 2019 at 9:53 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Wed, Feb 20, 2019 at 8:14 PM Masahiro Yamada > <yamada.masahiro@socionext.com> wrote: > > > > Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched > > various false positives: > > > > - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building > > with -Os") turned off this option for -Os. > > > > - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning > > for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for > > CONFIG_PROFILE_ALL_BRANCHES > > > > - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning > > for "make W=1"") turned off this option for GCC < 4.9 > > Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 > > > > I think this looks better by shifting the logic from Makefile to Kconfig. > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > I verified that mainline+this patch did not regression arm64 > allyesconfig clang build. > Tested-by: Nick Desaulniers <ndesaulniers@google.com> > Thanks for the patch! Would you mind adding a link tag to: > Link: https://github.com/ClangBuiltLinux/linux/issues/350 I added the tags, and applied to linux-kbuild. > > --- > > > > Makefile | 10 +++------- > > init/Kconfig | 17 +++++++++++++++++ > > kernel/trace/Kconfig | 1 + > > 3 files changed, 21 insertions(+), 7 deletions(-) > > > > diff --git a/Makefile b/Makefile > > index 1bb0535..b21aa2e3 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -656,17 +656,13 @@ KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context) > > > > ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE > > KBUILD_CFLAGS += $(call cc-option,-Oz,-Os) > > -KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,) > > -else > > -ifdef CONFIG_PROFILE_ALL_BRANCHES > > -KBUILD_CFLAGS += -O2 $(call cc-disable-warning,maybe-uninitialized,) > > else > > KBUILD_CFLAGS += -O2 > > endif > > -endif > > > > -KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \ > > - $(call cc-disable-warning,maybe-uninitialized,)) > > +ifdef CONFIG_CC_DISABLE_WARN_MAYBE_UNINITIALIZED > > +KBUILD_CFLAGS += -Wno-maybe-uninitialized > > +endif > > > > # Tell gcc to never replace conditional load with a non-conditional one > > KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) > > diff --git a/init/Kconfig b/init/Kconfig > > index c9386a3..1f05a88 100644 > > --- a/init/Kconfig > > +++ b/init/Kconfig > > @@ -26,6 +26,22 @@ config CLANG_VERSION > > config CC_HAS_ASM_GOTO > > def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) > > > > +config CC_HAS_WARN_MAYBE_UNINITIALIZED > > + def_bool $(cc-option,-Wmaybe-uninitialized) > > + help > > + GCC >= 4.7 supports this option. > > + > > +config CC_DISABLE_WARN_MAYBE_UNINITIALIZED > > + bool > > + depends on CC_HAS_WARN_MAYBE_UNINITIALIZED > > + default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 > > + help > > + GCC's -Wmaybe-uninitialized is not reliable by definition. > > + Lots of false positive warnings are produced in some cases. > > + > > + If this option is enabled, -Wno-maybe-uninitialzed is passed > > + to the compiler to suppress maybe-uninitialized warnings. > > + > > config CONSTRUCTORS > > bool > > depends on !UML > > @@ -1113,6 +1129,7 @@ config CC_OPTIMIZE_FOR_PERFORMANCE > > > > config CC_OPTIMIZE_FOR_SIZE > > bool "Optimize for size" > > + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives > > help > > Enabling this option will pass "-Os" instead of "-O2" to > > your compiler resulting in a smaller kernel. > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > > index fa8b1fe..8bd1d6d 100644 > > --- a/kernel/trace/Kconfig > > +++ b/kernel/trace/Kconfig > > @@ -370,6 +370,7 @@ config PROFILE_ANNOTATED_BRANCHES > > config PROFILE_ALL_BRANCHES > > bool "Profile all if conditionals" if !FORTIFY_SOURCE > > select TRACE_BRANCH_PROFILING > > + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives > > help > > This tracer profiles all branch conditions. Every if () > > taken in the kernel is recorded whether it hit or miss. > > -- > > 2.7.4 > > > > > -- > Thanks, > ~Nick Desaulniers
diff --git a/Makefile b/Makefile index 1bb0535..b21aa2e3 100644 --- a/Makefile +++ b/Makefile @@ -656,17 +656,13 @@ KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context) ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE KBUILD_CFLAGS += $(call cc-option,-Oz,-Os) -KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,) -else -ifdef CONFIG_PROFILE_ALL_BRANCHES -KBUILD_CFLAGS += -O2 $(call cc-disable-warning,maybe-uninitialized,) else KBUILD_CFLAGS += -O2 endif -endif -KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \ - $(call cc-disable-warning,maybe-uninitialized,)) +ifdef CONFIG_CC_DISABLE_WARN_MAYBE_UNINITIALIZED +KBUILD_CFLAGS += -Wno-maybe-uninitialized +endif # Tell gcc to never replace conditional load with a non-conditional one KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) diff --git a/init/Kconfig b/init/Kconfig index c9386a3..1f05a88 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -26,6 +26,22 @@ config CLANG_VERSION config CC_HAS_ASM_GOTO def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) +config CC_HAS_WARN_MAYBE_UNINITIALIZED + def_bool $(cc-option,-Wmaybe-uninitialized) + help + GCC >= 4.7 supports this option. + +config CC_DISABLE_WARN_MAYBE_UNINITIALIZED + bool + depends on CC_HAS_WARN_MAYBE_UNINITIALIZED + default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 + help + GCC's -Wmaybe-uninitialized is not reliable by definition. + Lots of false positive warnings are produced in some cases. + + If this option is enabled, -Wno-maybe-uninitialzed is passed + to the compiler to suppress maybe-uninitialized warnings. + config CONSTRUCTORS bool depends on !UML @@ -1113,6 +1129,7 @@ config CC_OPTIMIZE_FOR_PERFORMANCE config CC_OPTIMIZE_FOR_SIZE bool "Optimize for size" + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives help Enabling this option will pass "-Os" instead of "-O2" to your compiler resulting in a smaller kernel. diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index fa8b1fe..8bd1d6d 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -370,6 +370,7 @@ config PROFILE_ANNOTATED_BRANCHES config PROFILE_ALL_BRANCHES bool "Profile all if conditionals" if !FORTIFY_SOURCE select TRACE_BRANCH_PROFILING + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives help This tracer profiles all branch conditions. Every if () taken in the kernel is recorded whether it hit or miss.
Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched various false positives: - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building with -Os") turned off this option for -Os. - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for CONFIG_PROFILE_ALL_BRANCHES - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning for "make W=1"") turned off this option for GCC < 4.9 Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 I think this looks better by shifting the logic from Makefile to Kconfig. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- Makefile | 10 +++------- init/Kconfig | 17 +++++++++++++++++ kernel/trace/Kconfig | 1 + 3 files changed, 21 insertions(+), 7 deletions(-)