linux-kernel - [PATCH] rust: warn when using libclang >=19.1 with bindgen <0.70

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Message-ID: <20241030-bindgen-libclang-warn-v1-1-3a7ba9fedcfe@google.com>
Date: Wed, 30 Oct 2024 13:40:55 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH] rust: warn when using libclang >=19.1 with bindgen <0.70

When testing a clang upgrade with Rust Binder, I encountered a build
failure caused by bindgen not translating some symbols related to
tracepoints. This was caused by commit 2e770edd8ce1 ("[libclang] Compute
the right spelling location") changing the behavior of a function
exposed by libclang. Bindgen fixed the regression in commit 600f63895f73
("Use clang_getFileLocation instead of clang_getSpellingLocation").

However, the regression fix is only available in bindgen versions 0.70.0
or later. This means that when older bindgen versions are used with new
versions of libclang, bindgen may do the wrong thing, which could lead
to a build failure.

I encountered the bug with some header files related to tracepoints, but
it could also cause build failures in other circumstances. Thus, always
emit a warning when using an old bindgen with a new libclang so that
other people do not have to spend time chasing down the same bug as me.

If you encounter this warning, it is recommended that you upgrade
bindgen to 0.70 or later.

Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 scripts/rust_is_available.sh | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
index 5262c56dd674..30695612a0d7 100755
--- a/scripts/rust_is_available.sh
+++ b/scripts/rust_is_available.sh
@@ -225,6 +225,18 @@ if [ "$bindgen_libclang_cversion" -lt "$bindgen_libclang_min_cversion" ]; then
 	exit 1
 fi

+if [ "$bindgen_libclang_cversion" -ge 190100 ] && [ "$rust_bindings_generator_cversion" -lt 7000 ]; then
+	echo >&2 "***"
+	echo >&2 "*** You're using libclang version 19.1+ together with a version of the"
+	echo >&2 "*** Rust bindings generator '$BINDGEN' from before version 0.70. This"
+	echo >&2 "*** combination has a known bug that may lead to build failures."
+	echo >&2 "*** (https://github.com/rust-lang/rust-bindgen/pull/2824)"
+	echo >&2 "***   Your bindgen version:  $rust_bindings_generator_version"
+	echo >&2 "***   Your libclang version: $bindgen_libclang_version"
+	echo >&2 "***"
+	warning=1
+fi
+
 # If the C compiler is Clang, then we can also check whether its version
 # matches the `libclang` version used by the Rust bindings generator.
 #

---
base-commit: 81983758430957d9a5cb3333fe324fd70cf63e7e
change-id: 20241030-bindgen-libclang-warn-cebf97ea3506

Best regards,
-- 
Alice Ryhl <aliceryhl@...gle.com>