Re: [PATCH 3/6] kbuild: rust_is_available: add check for `bindgen` invocation

[Boqun Feng]

On Mon, Jan 09, 2023 at 09:45:17PM +0100, Miguel Ojeda wrote:
> `scripts/rust_is_available.sh` calls `bindgen` with a special
> header in order to check whether the `libclang` version in use
> is suitable.
> 
> However, the invocation itself may fail if, for instance, `bindgen`
> cannot locate `libclang`. This is fine for Kconfig (since the
> script will still fail and therefore disable Rust as it should),
> but it is pretty confusing for users of the `rustavailable` target
> given the error will be unrelated:
> 
>     ./scripts/rust_is_available.sh: 21: arithmetic expression: expecting primary: "100000 *  + 100 *  + "
>     make: *** [Makefile:1816: rustavailable] Error 2
> 
> Instead, run the `bindgen` invocation independently in a previous
> step, saving its output and return code. If it fails, then show
> the user a proper error message. Otherwise, continue as usual
> with the saved output.
> 
> Since the previous patch we show a reference to the docs, and
> the docs now explain how `bindgen` looks for `libclang`,
> thus the error message can leverage the documentation, avoiding
> duplication here (and making users aware of the setup guide in
> the documentation).
> 
> Reported-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Reported-by: fvalenduc (@fvalenduc)

Per Documentation/process/maintainer-tip.rst, the "Reported-by" tag does
require "Name <mailaddress>" format. Given we already have the GitHub
issue link, I wonder whether it's better we ask for the reporter's
email address (and real name) for the "Reported-by" field, and if they
prefer to not providing one, we just don't use the "Reported-by" tag
since we still have the GitHub issue link for their contribution.

Thoughts?

Regards,
Boqun

> Reported-by: Alexandru Radovici <msg4alex@xxxxxxxxx>
> Link: https://lore.kernel.org/rust-for-linux/CAKwvOdm5JT4wbdQQYuW+RT07rCi6whGBM2iUAyg8A1CmLXG6Nw@xxxxxxxxxxxxxx/
> Link: https://github.com/Rust-for-Linux/linux/issues/934
> Link: https://github.com/Rust-for-Linux/linux/pull/921
> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> ---
>  scripts/rust_is_available.sh | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
> index c907cf881c2c..cd87729ca3bf 100755
> --- a/scripts/rust_is_available.sh
> +++ b/scripts/rust_is_available.sh
> @@ -108,8 +108,29 @@ if [ "$rust_bindings_generator_cversion" -gt "$rust_bindings_generator_min_cvers
>  fi
>  
>  # Check that the `libclang` used by the Rust bindings generator is suitable.
> +#
> +# In order to do that, first invoke `bindgen` to get the `libclang` version
> +# found by `bindgen`. This step may already fail if, for instance, `libclang`
> +# is not found, thus inform the user in such a case.
> +set +e
> +bindgen_libclang_output=$(LC_ALL=C "$BINDGEN" $(dirname $0)/rust_is_available_bindgen_libclang.h 2>&1 >/dev/null)
> +bindgen_libclang_code=$?
> +set -e
> +if [ $bindgen_libclang_code -ne 0 ]; then
> +	echo >&2 "***"
> +	echo >&2 "*** Running '$BINDGEN' to check the libclang version (used by the Rust"
> +	echo >&2 "*** bindings generator) failed with code $bindgen_libclang_code. This may be caused by"
> +	echo >&2 "*** a failure to locate libclang. See output and docs below for details:"
> +	echo >&2 "***"
> +	echo >&2 "$bindgen_libclang_output"
> +	echo >&2 "***"
> +	exit 1
> +fi
> +
> +# `bindgen` returned successfully, thus use the output to check that the version
> +# of the `libclang` found by the Rust bindings generator is suitable.
>  bindgen_libclang_version=$( \
> -	LC_ALL=C "$BINDGEN" $(dirname $0)/rust_is_available_bindgen_libclang.h 2>&1 >/dev/null \
> +	echo "$bindgen_libclang_output" \
>  		| grep -F 'clang version ' \
>  		| grep -oE '[0-9]+\.[0-9]+\.[0-9]+' \
>  		| head -n 1 \
> -- 
> 2.39.0
>