Re: [PATCH 4/6] kbuild: rust_is_available: check if the script was invoked from Kbuild

Masahiro Yamada
2023-01-12T05:29:19Z

On Tue, Jan 10, 2023 at 5:46 AM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> Sometimes [1] users may attempt to setup the Rust support by
> checking what Kbuild does and they end up finding out about
> `scripts/rust_is_available.sh`. Inevitably, they run the script
> directly, but unless they setup the required variables,
> the result of the script is not meaningful.
>
> We could add some defaults to the variables, but that could be
> confusing for those that may override the defaults (compared
> to their kernel builds), and `$CC` would not be a simple default
> in any case.
>
> Therefore, instead, print a warning when the script detects
> the user may be invoking it, by testing `$MAKEFLAGS`.
>
> Link: https://lore.kernel.org/oe-kbuild-all/Y6r4mXz5NS0+HVXo@zn.tnic/ [1]
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
> scripts/rust_is_available.sh | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
> index cd87729ca3bf..0c082a248f15 100755
> --- a/scripts/rust_is_available.sh
> +++ b/scripts/rust_is_available.sh
> @@ -35,6 +35,16 @@ print_docs_reference()
> warning=0
> trap 'if [ $? -ne 0 ] || [ $warning -ne 0 ]; then print_docs_reference; fi' EXIT
>
> +# Check whether the script was invoked from Kbuild.
> +if [ -z "${MAKEFLAGS+x}" ]; then
> + echo >&2 "***"
> + echo >&2 "*** This script is intended to be called from Kbuild."
> + echo >&2 "*** Please use the 'rustavailable' target to call it instead."
> + echo >&2 "*** Otherwise, the results may not be meaningful."
> + echo >&2 "***"
> + warning=1
> +fi

I do not like this.
We do not need to cater to every oddity.

Checking MAKEFLAGS is too much.

You can check RUSTC/BINDGEN/CC if you persist in this.

diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
index a6f84dd2f71c..524aee03384a 100755
--- a/scripts/rust_is_available.sh
+++ b/scripts/rust_is_available.sh
@@ -34,7 +34,7 @@ warning=0
trap 'if [ $? -ne 0 ] || [ $warning -ne 0 ]; then
print_docs_reference; fi' EXIT

# Check that the Rust compiler exists.
-if ! command -v "$RUSTC" >/dev/null; then
+if ! command -v "${RUSTC:?RUSTC is not set}" >/dev/null; then
echo >&2 "***"
echo >&2 "*** Rust compiler '$RUSTC' could not be found."
echo >&2 "***"
@@ -42,7 +42,7 @@ if ! command -v "$RUSTC" >/dev/null; then
fi

# Check that the Rust bindings generator exists.
-if ! command -v "$BINDGEN" >/dev/null; then
+if ! command -v "${BINDGEN:?BINDGEN is not set}" >/dev/null; then
echo >&2 "***"
echo >&2 "*** Rust bindings generator '$BINDGEN' could not be found."
echo >&2 "***"
@@ -150,7 +150,7 @@ fi
#
# In the future, we might be able to perform a full version check, see
# https://github.com/rust-lang/rust-bindgen/issues/2138.
-cc_name=$($(dirname $0)/cc-version.sh "$CC" | cut -f1 -d' ')
+cc_name=$($(dirname $0)/cc-version.sh ${CC:?CC is not set} | cut -f1 -d' ')
if [ "$cc_name" = Clang ]; then
clang_version=$( \
LC_ALL=C "$CC" --version 2>/dev/null \

--
Best Regards
Masahiro Yamada