linux-kernel - Re: [PATCH 02/18] rust: kbuild: introduce `core-flags` and `core-skip

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Message-ID: <8e58087b-17e6-4362-93f9-f9aaac6c4476@nvidia.com>
Date: Mon, 10 Nov 2025 11:18:03 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>
Cc: Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org,
 linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
 patches@...ts.linux.dev
Subject: Re: [PATCH 02/18] rust: kbuild: introduce `core-flags` and
 `core-skip_flags`

On 11/10/25 1:50 AM, Miguel Ojeda wrote:
> In the next commits we are introducing `*-{cfgs,skip_flags,flags}`
> variables for other crates.
> 
> Thus do so here for `core`, which simplifies a bit the `Makefile`
> (including the next commit) and makes it more consistent.
> 
> This means we stop passing `-Wrustdoc::unescaped_backticks` to `rustc`
> and `-Wunreachable_pub` to `rustdoc`, i.e. we skip more, which is fine
> since it shouldn't have an effect.
> 
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
> ---
>  rust/Makefile | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/rust/Makefile b/rust/Makefile
> index 3e545c1a0ff4..a001aae0da9d 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -60,11 +60,20 @@ rustdoc_test_quiet=--test-args -q
>  rustdoc_test_kernel_quiet=>/dev/null
>  endif
>  
> -core-cfgs = \
> +core-cfgs := \

I agree that switching to ":=" for this kind of Makefile variable
is a good move. However, it should be mentioned in the commit log
so that it doesn't look like it was accidentally introduced.


thanks,
-- 
John Hubbard

>      --cfg no_fp_fmt_parse
>  
>  core-edition := $(if $(call rustc-min-version,108700),2024,2021)
>  
> +core-skip_flags := \
> +    --edition=2021 \
> +    -Wunreachable_pub \
> +    -Wrustdoc::unescaped_backticks
> +
> +core-flags := \
> +    --edition=$(core-edition) \
> +    $(core-cfgs)
> +
>  # `rustdoc` did not save the target modifiers, thus workaround for
>  # the time being (https://github.com/rust-lang/rust/issues/144521).
>  rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-allow-abi-mismatch=fixed-x18)
> @@ -125,8 +134,8 @@ rustdoc-macros: $(src)/macros/lib.rs rustdoc-clean FORCE
>  
>  # Starting with Rust 1.82.0, skipping `-Wrustdoc::unescaped_backticks` should
>  # not be needed -- see https://github.com/rust-lang/rust/pull/128307.
> -rustdoc-core: private skip_flags = --edition=2021 -Wrustdoc::unescaped_backticks
> -rustdoc-core: private rustc_target_flags = --edition=$(core-edition) $(core-cfgs)
> +rustdoc-core: private skip_flags = $(core-skip_flags)
> +rustdoc-core: private rustc_target_flags = $(core-flags)
>  rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs rustdoc-clean FORCE
>  	+$(call if_changed,rustdoc)
>  
> @@ -508,9 +517,9 @@ $(obj)/helpers/helpers.o: $(src)/helpers/helpers.c $(recordmcount_source) FORCE
>  $(obj)/exports.o: private skip_gendwarfksyms = 1
>  
>  $(obj)/core.o: private skip_clippy = 1
> -$(obj)/core.o: private skip_flags = --edition=2021 -Wunreachable_pub
> +$(obj)/core.o: private skip_flags = $(core-skip_flags)
>  $(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym))
> -$(obj)/core.o: private rustc_target_flags = --edition=$(core-edition) $(core-cfgs)
> +$(obj)/core.o: private rustc_target_flags = $(core-flags)
>  $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs \
>      $(wildcard $(objtree)/include/config/RUSTC_VERSION_TEXT) FORCE
>  	+$(call if_changed_rule,rustc_library)