linux-kernel - Re: [PATCH 3/3] Kbuild: use -std=gnu11 for KBUILD

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Message-ID: <CA+icZUWCTuVeohWvePhxYY3WC9xAYSy9nP1xQQf=tFH_mWDCNQ@mail.gmail.com>
Date:   Wed, 2 Mar 2022 23:14:10 +0100
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Marco Elver <elver@...gle.com>,
        Jani Nikula <jani.nikula@...el.com>,
        David Sterba <dsterba@...e.com>, Alex Shi <alexs@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-kbuild@...r.kernel.org, llvm@...ts.linux.dev,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] Kbuild: use -std=gnu11 for KBUILD_USERCFLAGS

On Wed, Mar 2, 2022 at 10:47 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> As we change the C language standard for the kernel from gnu89 to
> gnu11, it makes sense to also update the version for user space
> compilation.
>

Overdue.

Can you point me to a lore link where I can easily fetch the full 3/3
v3 patchset?

I would like to give this a try on x86-64 with my latest kernel-config
(based on the latest kernel-config v5.17-rc5 from Debian/unstable).

What Linux source base do I need?
Is Linux v5.17-rc6 good enough (patchset applicable) for testing?

Thanks, Arnd.

Regards,
- Sedat -

> Some users have older native compilers than what they use for
> kernel builds, so I considered using gnu99 as the default version
> for wider compatibility with gcc-4.6 and earlier.
>
> However, testing with older compilers showed that we already require
> HOSTCC version 5.1 as well because a lot of host tools include
> linux/compiler.h that uses __has_attribute():
>
>   CC      tools/objtool/exec-cmd.o
> In file included from tools/include/linux/compiler_types.h:36:0,
>                  from tools/include/linux/compiler.h:5,
>                  from exec-cmd.c:2:
> tools/include/linux/compiler-gcc.h:19:5: error: "__has_attribute" is not defined [-Werror=undef]
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 37ef6a555dcd..7c9be7f1ccd4 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -432,7 +432,7 @@ HOSTCXX     = g++
>  endif
>
>  export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
> -                           -O2 -fomit-frame-pointer -std=gnu89 \
> +                           -O2 -fomit-frame-pointer -std=gnu11 \
>                             -Wdeclaration-after-statement
>  export KBUILD_USERLDFLAGS :=
>
> --
> 2.29.2
>