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kbuild: rust_is_available: add check for bindgen invocation
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`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 <[email protected]>
Link: https://lore.kernel.org/rust-for-linux/CAKwvOdm5JT4wbdQQYuW+RT07rCi6whGBM2iUAyg8A1CmLXG6Nw@mail.gmail.com/
Reported-by: François Valenduc <[email protected]>
Closes: Rust-for-Linux#934
Reported-by: Alexandru Radovici <[email protected]>
Closes: Rust-for-Linux#921
Reported-by: Matthew Leach <[email protected]>
Closes: https://lore.kernel.org/rust-for-linux/[email protected]/
Fixes: 78521f3 ("scripts: add `rust_is_available.sh`")
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Reviewed-by: Masahiro Yamada <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>
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ojeda committed Aug 9, 2023
1 parent aac284b commit 52cae7f
Showing 1 changed file with 21 additions and 1 deletion.
22 changes: 21 additions & 1 deletion scripts/rust_is_available.sh
Original file line number Diff line number Diff line change
Expand Up @@ -106,8 +106,28 @@ 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.
bindgen_libclang_output=$( \
LC_ALL=C "$BINDGEN" $(dirname $0)/rust_is_available_bindgen_libclang.h 2>&1 >/dev/null
) || bindgen_libclang_code=$?
if [ -n "$bindgen_libclang_code" ]; then
echo >&2 "***"
echo >&2 "*** Running '$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 \
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