From: Miguel Ojeda <ojeda@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>,
Peter Zijlstra <peterz@infradead.org>,
Miguel Ojeda <ojeda@kernel.org>,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: [PATCH] compiler_types: mark __compiletime_assert failure as __noreturn
Date: Thu, 14 Oct 2021 15:23:31 +0200 [thread overview]
Message-ID: <20211014132331.GA4811@kernel.org> (raw)
`__compiletime_assert` declares a fake `extern` function
which appears (to the compiler) to be called when the test fails.
Therefore, compilers may emit possibly-uninitialized warnings
in some cases, even if it will be an error anyway (for compilers
supporting the `error` attribute, e.g. GCC and Clang >= 14)
or a link failure (for those that do not, e.g. Clang < 14).
Annotating the fake function as `__noreturn` gives them
the information they need to avoid the warning,
e.g. see https://godbolt.org/z/x1v69jjYY.
Link: https://lore.kernel.org/llvm/202110100514.3h9CI4s0-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
include/linux/compiler_types.h | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index b6ff83a714ca..ca1a66b8cd2f 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -298,7 +298,13 @@ struct ftrace_likely_data {
#ifdef __OPTIMIZE__
# define __compiletime_assert(condition, msg, prefix, suffix) \
do { \
- extern void prefix ## suffix(void) __compiletime_error(msg); \
+ /* \
+ * __noreturn is needed to give the compiler enough \
+ * information to avoid certain possibly-uninitialized \
+ * warnings (regardless of the build failing). \
+ */ \
+ __noreturn extern void prefix ## suffix(void) \
+ __compiletime_error(msg); \
if (!(condition)) \
prefix ## suffix(); \
} while (0)
--
2.33.1
next reply other threads:[~2021-10-14 13:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-14 13:23 Miguel Ojeda [this message]
2021-10-14 15:01 ` [PATCH] compiler_types: mark __compiletime_assert failure as __noreturn Peter Zijlstra
2021-10-14 17:48 ` Nick Desaulniers
2021-10-14 18:33 ` Miguel Ojeda
2021-10-14 18:41 ` Miguel Ojeda
2021-10-14 18:55 ` Nick Desaulniers
2021-10-14 19:33 ` Miguel Ojeda
2021-10-15 7:55 ` Rasmus Villemoes
2021-10-15 8:11 ` Rasmus Villemoes
2021-10-15 12:36 ` Miguel Ojeda
2021-10-14 17:26 ` Nathan Chancellor
2021-10-14 17:36 ` Nick Desaulniers
2021-10-21 23:20 ` Miguel Ojeda
2021-12-02 6:12 ` Dan Carpenter
2021-12-02 6:24 ` Dan Carpenter
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