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Message-ID: <7c7d1639-7997-265e-aa77-ebe3d2fa05e6@kernel.org>
Date: Tue, 20 Jul 2021 12:07:23 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Nick Desaulniers <ndesaulniers@...gle.com>,
Miguel Ojeda <ojeda@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Ard Biesheuvel <ardb@...nel.org>,
Marco Elver <elver@...gle.com>, Will Deacon <will@...nel.org>,
Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
Arvind Sankar <nivedita@...m.mit.edu>,
Sami Tolvanen <samitolvanen@...gle.com>,
Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
clang-built-linux@...glegroups.com
Subject: Re: [PATCH] compiler_attributes.h: move __compiletime_{error|warning}
On 7/20/2021 11:04 AM, Nick Desaulniers wrote:
> I'm working on adding support for __attribute__((__error__(""))) and
> __attribute__((__warning__(""))) to Clang. To make use of these in
> __compiletime_error and __compiletime_warning (as used by BUILD_BUG and
> friends) for newer clang and detect/fallback for older versions of
> clang, move these to compiler_attributes.h and guard them with
> __has_attribute preprocessor guards.
>
> Link: https://reviews.llvm.org/D106030
> Link: https://bugs.llvm.org/show_bug.cgi?id=16428
> Link: https://github.com/ClangBuiltLinux/linux/issues/1173
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> Note that this feature hasn't landed yet in clang! I expect it to land
> in clang-13 though soon. We can still move this in anticipation of the
> feature landing, though perhaps the versions might not be precise if it
> slips to clang-14 (though I don't anticipate that).
>
> include/linux/compiler-gcc.h | 3 ---
> include/linux/compiler_attributes.h | 30 ++++++++++++++++++++++++++---
> include/linux/compiler_types.h | 6 ------
> 3 files changed, 27 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index cb9217fc60af..21c36b69eb06 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -43,9 +43,6 @@
>
> #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
>
> -#define __compiletime_warning(message) __attribute__((__warning__(message)))
> -#define __compiletime_error(message) __attribute__((__error__(message)))
> -
> #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
> #define __latent_entropy __attribute__((latent_entropy))
> #endif
> diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
> index 2487be0e7199..5f474b593425 100644
> --- a/include/linux/compiler_attributes.h
> +++ b/include/linux/compiler_attributes.h
> @@ -30,14 +30,16 @@
> # define __GCC4_has_attribute___assume_aligned__ 1
> # define __GCC4_has_attribute___copy__ 0
> # define __GCC4_has_attribute___designated_init__ 0
> +# define __GCC4_has_attribute___error__ 1
> # define __GCC4_has_attribute___externally_visible__ 1
> +# define __GCC4_has_attribute___fallthrough__ 0
> # define __GCC4_has_attribute___no_caller_saved_registers__ 0
> -# define __GCC4_has_attribute___noclone__ 1
> # define __GCC4_has_attribute___no_profile_instrument_function__ 0
> -# define __GCC4_has_attribute___nonstring__ 0
> # define __GCC4_has_attribute___no_sanitize_address__ 1
> # define __GCC4_has_attribute___no_sanitize_undefined__ 1
> -# define __GCC4_has_attribute___fallthrough__ 0
> +# define __GCC4_has_attribute___noclone__ 1
> +# define __GCC4_has_attribute___nonstring__ 0
> +# define __GCC4_has_attribute___warning__ 1
> #endif
>
> /*
> @@ -137,6 +139,17 @@
> # define __designated_init
> #endif
>
> +/*
> + * Optional: only supported since clang >= 13.0
> + *
> + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
> + */
> +#if __has_attribute(__error__)
> +# define __compiletime_error(msg) __attribute__((__error__(msg)))
> +#else
> +# define __compiletime_error(msg)
> +#endif
> +
> /*
> * Optional: not supported by clang
> *
> @@ -298,6 +311,17 @@
> */
> #define __must_check __attribute__((__warn_unused_result__))
>
> +/*
> + * Optional: only supported since clang >= 13.0
> + *
> + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
> + */
> +#if __has_attribute(warning)
Should this be
#if __has_attribute(__warning__)
?
> +# define __compiletime_warning(msg) __attribute__((__warning__(msg)))
> +#else
> +# define __compiletime_warning(msg)
> +#endif
> +
> /*
> * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
> * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index e4ea86fc584d..b6ff83a714ca 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -294,12 +294,6 @@ struct ftrace_likely_data {
> #ifndef __compiletime_object_size
> # define __compiletime_object_size(obj) -1
> #endif
> -#ifndef __compiletime_warning
> -# define __compiletime_warning(message)
> -#endif
> -#ifndef __compiletime_error
> -# define __compiletime_error(message)
> -#endif
>
> #ifdef __OPTIMIZE__
> # define __compiletime_assert(condition, msg, prefix, suffix) \
>
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