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

[Ard Biesheuvel]

On Sat, 1 Nov 2025 at 17:36, Nathan Chancellor <nathan at kernel.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 at kernel.org>
> Closes: https://lore.kernel.org/20251030-meerjungfrau-getrocknet-7b46eacc215d@brauner/
> Signed-off-by: Nathan Chancellor <nathan at kernel.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 at kernel.org>