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SubjectRe: [PATCH] compiler_types: mark __compiletime_assert failure as __noreturn
On Thu, Oct 14, 2021 at 6:25 AM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> `__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.

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>
> 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
>
>


--
Thanks,
~Nick Desaulniers

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