linux-kernel - Re: [PATCH] kbuild: remove cc-option switch from -Wframe-larger-than=

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Date:   Sun, 16 Feb 2020 13:07:02 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] kbuild: remove cc-option switch from -Wframe-larger-than=

On Sun, Feb 16, 2020 at 7:20 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> This CONFIG option was added by commit 35bb5b1e0e84 ("Add option to
> enable -Wframe-larger-than= on gcc 4.4"). At that time, the cc-option
> check was needed.

Indeed, the oldest version of GCC 4.4 on godbolt.org; GCC 4.4.7 supports it.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> According to Documentation/process/changes.rst, the current minimal
> supported version of GCC is 4.6, so you can assume GCC supports it.
> Clang supports it as well.
>
> Remove the cc-option switch and redundant comments.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  Makefile          | 2 +-
>  lib/Kconfig.debug | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 84b71845c43f..8f15926b83bb 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -728,7 +728,7 @@ KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,) \
>  endif
>
>  ifneq ($(CONFIG_FRAME_WARN),0)
> -KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
> +KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
>  endif
>
>  stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 69def4a9df00..fb6b93ffdf77 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -266,7 +266,7 @@ config ENABLE_MUST_CHECK
>           attribute warn_unused_result" messages.
>
>  config FRAME_WARN
> -       int "Warn for stack frames larger than (needs gcc 4.4)"
> +       int "Warn for stack frames larger than"
>         range 0 8192
>         default 2048 if GCC_PLUGIN_LATENT_ENTROPY
>         default 1280 if (!64BIT && PARISC)
> @@ -276,7 +276,6 @@ config FRAME_WARN
>           Tell gcc to warn at build time for stack frames larger than this.
>           Setting this too low will cause a lot of warnings.
>           Setting it to 0 disables the warning.
> -         Requires gcc 4.4
>
>  config STRIP_ASM_SYMS
>         bool "Strip assembler-generated symbols during link"
> --
> 2.17.1
>

-- 
Thanks,
~Nick Desaulniers