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References: <20240519211235.589325-1-ojeda@kernel.org> <20240519211235.589325-2-ojeda@kernel.org>
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From: Masahiro Yamada <masahiroy@kernel.org>
Date: Tue, 21 May 2024 13:14:41 +0900
Message-ID: <CAK7LNATPx2wTEM=KDmGtcH8vVTB4suOhh-CUQKP54F8wtPWDiw@mail.gmail.com>
Subject: Re: [PATCH 2/3] kbuild: rust: apply `CONFIG_WERROR` to all Rust targets
To: Miguel Ojeda <ojeda@kernel.org>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>, Alex Gaynor <alex.gaynor@gmail.com>, 
	Nathan Chancellor <nathan@kernel.org>, Nicolas Schier <nicolas@fjasle.eu>, Boqun Feng <boqun.feng@gmail.com>, 
	Gary Guo <gary@garyguo.net>, =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, 
	Benno Lossin <benno.lossin@proton.me>, Andreas Hindborg <a.hindborg@samsung.com>, 
	Alice Ryhl <aliceryhl@google.com>, linux-kbuild@vger.kernel.org, 
	rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, 
	patches@lists.linux.dev
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On Mon, May 20, 2024 at 6:12=E2=80=AFAM Miguel Ojeda <ojeda@kernel.org> wro=
te:
>
> Make all Rust code (i.e. not just kernel code) respect `CONFIG_WERROR`,
> so that we keep everything warning clean.


Rust started to do something different from C.


KBUILD_HOSTCFLAGS is not affected by any CONFIG option.

The reason is because HOSTCC is needed for building Kconfig.
If the flags for HOSTCC is changed by a CONFIG option,
it would be a chicken-egg problem.
Also, some host programs might be compiled even
without .config at all. (e.g. scripts/unifdef)


I know Rust will not become a part of the core infrastructure
of the build system, but IMHO, host programs should not be
affected by any CONFIG option.

I do not like this patch.


>
> In particular, this affects targets in `rust/` (`RUSTDOC H`, `RUSTC TL`,
> `RUSTDOC T`, `RUSTC T` and `RUSTC P`), plus host programs and any others
> we may add later.
>
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
> This one requires the `rusttest` warning cleanup at
> https://lore.kernel.org/rust-for-linux/20240519210735.587323-1-ojeda@kern=
el.org/
>
>  Makefile                   | 4 ++--
>  scripts/Makefile.extrawarn | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index fba567a55607..2d0ea441cb9c 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -469,7 +469,7 @@ export rust_common_flags :=3D --edition=3D2021 \
>
>  KBUILD_HOSTCFLAGS   :=3D $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(H=
OSTCFLAGS)
>  KBUILD_HOSTCXXFLAGS :=3D -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
> -KBUILD_HOSTRUSTFLAGS :=3D $(rust_common_flags) -O -Cstrip=3Ddebuginfo \
> +KBUILD_HOSTRUSTFLAGS =3D $(rust_common_flags) -O -Cstrip=3Ddebuginfo \
>                         -Zallow-features=3D $(HOSTRUSTFLAGS)
>  KBUILD_HOSTLDFLAGS  :=3D $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
>  KBUILD_HOSTLDLIBS   :=3D $(HOST_LFS_LIBS) $(HOSTLDLIBS)
> @@ -560,7 +560,7 @@ KBUILD_CFLAGS +=3D -fno-PIE
>  KBUILD_CFLAGS +=3D -fno-strict-aliasing
>
>  KBUILD_CPPFLAGS :=3D -D__KERNEL__
> -KBUILD_RUSTFLAGS :=3D $(rust_common_flags) \
> +KBUILD_RUSTFLAGS =3D $(rust_common_flags) \
>                     -Cpanic=3Dabort -Cembed-bitcode=3Dn -Clto=3Dn \
>                     -Cforce-unwind-tables=3Dn -Ccodegen-units=3D1 \
>                     -Csymbol-mangling-version=3Dv0 \
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 48114e91c386..990890821889 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -26,8 +26,8 @@ endif
>
>  KBUILD_CPPFLAGS-$(CONFIG_WERROR) +=3D -Werror
>  KBUILD_CPPFLAGS +=3D $(KBUILD_CPPFLAGS-y)
> -KBUILD_RUSTFLAGS-$(CONFIG_WERROR) +=3D -Dwarnings
> -KBUILD_RUSTFLAGS +=3D $(KBUILD_RUSTFLAGS-y)
> +rust_common_flags-$(CONFIG_WERROR) +=3D -Dwarnings
> +rust_common_flags +=3D $(rust_common_flags-y)
>
>  KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) +=3D -Wno-array-bounds
>
> --
> 2.45.1


--
Best Regards

Masahiro Yamada