Re: [PATCH v2] rust: kbuild: rebuild if `.clippy.toml` changes

[Tamir Duberstein <tamird@gmail.com>]

On Tue, May 20, 2025 at 3:53 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> We rarely modify `.clippy.toml`, but currently we do not rebuild if that
> happens, thus it is easy to miss possible changes in lints.
>
> Thus rebuild in case of changes.
>
> Cc: stable@vger.kernel.org
> Reported-by: Tamir Duberstein <tamird@gmail.com>
> Closes: https://github.com/Rust-for-Linux/linux/issues/1151
> Fixes: 7d56786edcbd ("rust: introduce `.clippy.toml`")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
>  rust/Makefile | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index 3aca903a7d08..107299c32065 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -57,6 +57,10 @@ rustdoc_test_quiet=--test-args -q
>  rustdoc_test_kernel_quiet=>/dev/null
>  endif
>
> +ifeq ($(KBUILD_CLIPPY),1)
> +       clippy_toml := $(srctree)/.clippy.toml
> +endif
> +
>  core-cfgs = \
>      --cfg no_fp_fmt_parse
>
> @@ -405,11 +409,12 @@ quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
>                 --crate-name $(patsubst lib%.$(libmacros_extension),%,$(notdir $@)) $<
>
>  # Procedural macros can only be used with the `rustc` that compiled it.
> -$(obj)/$(libmacros_name): $(src)/macros/lib.rs FORCE
> +$(obj)/$(libmacros_name): $(src)/macros/lib.rs $(clippy_toml) FORCE
>         +$(call if_changed_dep,rustc_procmacro)
>
>  $(obj)/$(libpin_init_internal_name): private rustc_target_flags = --cfg kernel
> -$(obj)/$(libpin_init_internal_name): $(src)/pin-init/internal/src/lib.rs FORCE
> +$(obj)/$(libpin_init_internal_name): $(src)/pin-init/internal/src/lib.rs \
> +    $(clippy_toml) FORCE
>         +$(call if_changed_dep,rustc_procmacro)
>
>  quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@
> @@ -495,7 +500,8 @@ endif
>
>  $(obj)/compiler_builtins.o: private skip_gendwarfksyms = 1
>  $(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
> -$(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
> +$(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o \
> +    $(clippy_toml) FORCE
>         +$(call if_changed_rule,rustc_library)
>
>  $(obj)/pin_init.o: private skip_gendwarfksyms = 1

This is only changing 3 targets, right? libmacros, libpin_init, and
compiler_builtins. Can you help me understand why only these need to
change? Is it because these are leaf nodes in the graph?

The `rusttest` target wouldn't rebuild properly, I think? Is it
possible to apply this rule to all rust targets, rather than
individual ones?