Messages in this thread | | | Date | Thu, 14 Oct 2021 10:26:27 -0700 | From | Nathan Chancellor <> | Subject | Re: [PATCH] compiler_types: mark __compiletime_assert failure as __noreturn |
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On Thu, Oct 14, 2021 at 03:23:31PM +0200, Miguel Ojeda 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. > > 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>
Reviewed-by: Nathan Chancellor <nathan@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 >
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