Re: [PATCH 5/9] extrawarn: enable format and stringop overflow warnings in W=1

[Masahiro Yamada <masahiroy@kernel.org>]

On Sat, Aug 12, 2023 at 10:50 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> The stringop and format warnings got disabled globally when they were
> newly introduced in commit bd664f6b3e376 ("disable new gcc-7.1.1 warnings
> for now"), 217c3e0196758 ("disable stringop truncation warnings for now")
> and 5a76021c2eff7 ("gcc-10: disable 'stringop-overflow' warning for now").
>
> In all cases, the sentiment at the time was that the warnings are
> useful, and we actually addressed a number of real bugs based on
> them, but we never managed to eliminate them all because even the
> build bots using W=1 builds only see the -Wstringop-truncation
> warnings that are enabled at that level.
>
> Move these into the W=1 section to give them a larger build coverage
> and actually eliminate them over time.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  scripts/Makefile.extrawarn | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 87bfe153198f1..ec528972371fa 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -16,8 +16,6 @@ KBUILD_CFLAGS += -Werror=strict-prototypes
>  KBUILD_CFLAGS += -Wno-format-security
>  KBUILD_CFLAGS += -Wno-trigraphs
>  KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
> -KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
> -KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
>  KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
>
>  ifneq ($(CONFIG_FRAME_WARN),0)
> @@ -56,9 +54,6 @@ KBUILD_CFLAGS += -Wno-pointer-sign
>  # globally built with -Wcast-function-type.
>  KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
>
> -# We'll want to enable this eventually, but it's not going away for 5.7 at least
> -KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
> -
>  # Another good warning that we'll want to enable eventually
>  KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
>
> @@ -111,6 +106,9 @@ KBUILD_CFLAGS += -Wmissing-include-dirs
>  KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
>  KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
>  KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
> +KBUILD_CFLAGS += $(call cc-option, -Wformat-overflow)
> +KBUILD_CFLAGS += $(call cc-option, -Wformat-truncation)


These are redundant because -Wall implies
-Wformat-overflow and -Wformat-truncation
according to the GCC manual.




-- 
Best Regards
Masahiro Yamada