From:   Andrea Righi <andrea.righi@canonical.com>
To:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>
Cc:     Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        bjorn3_gh@protonmail.com, Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, rust-for-linux@vger.kernel.org,
        llvm@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: [PATCH] rust: allow to use INIT_STACK_ALL_ZERO
Date:   Fri, 10 Feb 2023 18:22:03 +0100
Message-Id: <20230210172203.101331-1-andrea.righi@canonical.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

With CONFIG_INIT_STACK_ALL_ZERO enabled, bindgen is passing
-ftrivial-auto-var-init=zero to clang, that triggers the following:

  error: '-ftrivial-auto-var-init=zero' hasn't been enabled; enable it at your own peril for benchmarking purpose only with '-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang'

This flag should be dropped in clang-17, but at the moment it seems more
reasonable to add it to the bindgen CFLAGS to prevent the error above.

In this way we can enable CONFIG_INIT_STACK_ALL_ZERO with CONFIG_RUST
without triggering any build error.

Link: https://reviews.llvm.org/D125142
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 rust/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/rust/Makefile b/rust/Makefile
index ff70c4c916f8..5e26db07a1dc 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -267,7 +267,8 @@ BINDGEN_TARGET		:= $(BINDGEN_TARGET_$(SRCARCH))
 # All warnings are inhibited since GCC builds are very experimental,
 # many GCC warnings are not supported by Clang, they may only appear in
 # some configurations, with new GCC versions, etc.
-bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET)
+bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET) \
+			-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
 
 bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \
 	$(bindgen_extra_c_flags)
-- 
2.37.2