linux-kernel - Re: [PATCH] kbuild: Add '-fms-extensions' to areas with dedicated CFLAGS

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Message-ID: <CAMj1kXGy8s7Cc=aycKymv2d5wEZFL5J5_HxWyMb-QYDXkUrU9Q@mail.gmail.com>
Date: Sat, 1 Nov 2025 17:55:37 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, 
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>, Helge Deller <deller@....de>, 
	Madhavan Srinivasan <maddy@...ux.ibm.com>, Michael Ellerman <mpe@...erman.id.au>, 
	Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, 
	Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Sven Schnelle <svens@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev, 
	linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
	linux-s390@...r.kernel.org, linux-efi@...r.kernel.org, llvm@...ts.linux.dev, 
	Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH] kbuild: Add '-fms-extensions' to areas with dedicated CFLAGS

On Sat, 1 Nov 2025 at 17:36, Nathan Chancellor <nathan@...nel.org> wrote:
>
> This is a follow up to commit c4781dc3d1cf ("Kbuild: enable
> -fms-extensions") but in a separate change due to being substantially
> different from the initial submission.
>
> There are many places within the kernel that use their own CFLAGS
> instead of the main KBUILD_CFLAGS, meaning code written with the main
> kernel's use of '-fms-extensions' in mind that may be tangentially
> included in these areas will result in "error: declaration does not
> declare anything" messages from the compiler.
>
> Add '-fms-extensions' to all these areas to ensure consistency, along
> with -Wno-microsoft-anon-tag to silence clang's warning about use of the
> extension that the kernel cares about using. parisc does not build with
> clang so it does not need this warning flag. LoongArch does not need it
> either because -W flags from KBUILD_FLAGS are pulled into cflags-vdso.
>
> Reported-by: Christian Brauner <brauner@...nel.org>
> Closes: https://lore.kernel.org/20251030-meerjungfrau-getrocknet-7b46eacc215d@brauner/
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> I am taking the original '-fms-extensions' change [1] via a shared
> branch in kbuild [2] so I would appreciate acks. I plan to finalize that
> branch so that other maintainers can safely pull it on Thursday.
>
> [1]: https://git.kernel.org/kbuild/c/c4781dc3d1cf0e017e1f290607ddc56cfe187afc
> [2]: https://git.kernel.org/kbuild/l/kbuild-ms-extensions
> ---
>  arch/arm64/kernel/vdso32/Makefile     | 3 ++-
>  arch/loongarch/vdso/Makefile          | 2 +-
>  arch/parisc/boot/compressed/Makefile  | 2 +-
>  arch/powerpc/boot/Makefile            | 3 ++-
>  arch/s390/Makefile                    | 3 ++-
>  arch/s390/purgatory/Makefile          | 3 ++-
>  arch/x86/Makefile                     | 4 +++-
>  arch/x86/boot/compressed/Makefile     | 7 +++++--
>  drivers/firmware/efi/libstub/Makefile | 4 ++--
>  9 files changed, 20 insertions(+), 11 deletions(-)
>

Acked-by: Ard Biesheuvel <ardb@...nel.org>