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References: <20230109204520.539080-1-ojeda@kernel.org> <20230109204520.539080-4-ojeda@kernel.org>
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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Thu, 12 Jan 2023 14:28:36 +0900
Message-ID: <CAK7LNARuGz=oFukWH4g=7zg1EbWP9rxpVXPgPrJBKHzLQW4N1Q@mail.gmail.com>
Subject: Re: [PATCH 4/6] kbuild: rust_is_available: check if the script was
 invoked from Kbuild
To:     Miguel Ojeda <ojeda@kernel.org>
Cc:     linux-kbuild@vger.kernel.org,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev, Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>
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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