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SubjectRe: [PATCH v3 1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS
On Thu, Oct 13, 2022 at 03:01:17AM +0900, Masahiro Yamada wrote:
> CONFIG_WERROR turns warnings into errors, which happens only for *.c
> files because -Werror is added to KBUILD_CFLAGS.
>
> Adding it to KBUILD_CPPFLAGS makes more sense because preprocessors
> understand the -Werror option.
>
> For example, you can put a #warning directive in any preprocessed code.
>
> warning: #warning "this is a warning message" [-Wcpp]
>
> If -Werror is added, it is promoted to an error.
>
> error: #warning "this is a warning message" [-Werror=cpp]
>
> This commit moves -Werror to KBUILD_CPPFLAGS so it works in the same way
> for *.c, *.S, *.lds.S or whatever needs preprocessing.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
>
> (no changes since v1)
>
> Makefile | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 85a63a1d29b3..790760d26ea0 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -859,7 +859,8 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong
>
> KBUILD_CFLAGS += $(stackp-flags-y)
>
> -KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
> +KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
> +KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
> KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
>
> KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
> --
> 2.34.1
>
>

For what it's worth, this is going to break 32-bit ARM builds with clang
plus the integrated assembler due to
https://github.com/ClangBuiltLinux/linux/issues/1315:

clang-16: error: argument unused during compilation: '-march=armv7-a' [-Werror,-Wunused-command-line-argument]

Ultimately, I want -Wunused-command-line-argument to be an error anyways
(https://github.com/ClangBuiltLinux/linux/issues/1587) but it would be
nice to get these cleaned up before this goes in.

Cheers,
Nathan

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