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Date: Tue, 20 Jul 2021 13:56:51 -0700
From: Nick Desaulniers <ndesaulniers@...gle.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Miguel Ojeda <ojeda@...nel.org>,
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 Tue, Jul 20, 2021 at 12:07 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> 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__)
>
> ?
Yes. :-X
>
> > +# 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) \
> >
--
Thanks,
~Nick Desaulniers
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