linux-kernel - Re: [PATCH v2 1/2] compiler-clang.h: Add CLANG_VERSION and _

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Date:   Mon, 30 Jul 2018 16:25:54 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     akpm@...ux-foundation.org, arnd@...db.de, paul.burton@...s.com,
        christophe.leroy@....fr, shorne@...il.com,
        yamada.masahiro@...ionext.com, keescook@...omium.org,
        mingo@...nel.org, gregkh@...uxfoundation.org, tglx@...utronix.de,
        rdunlap@...radead.org, bp@...e.de, neilb@...e.com,
        linux-kernel@...r.kernel.org, aryabinin@...tuozzo.com,
        dwmw@...zon.co.uk, sandipan@...ux.vnet.ibm.com,
        linux@...musvillemoes.dk, paullawrence@...gle.com,
        andreyknvl@...gle.com, will.deacon@....com, ghackmann@...roid.com,
        stable@...r.kernel.org, ghackmann@...gle.com, mka@...omium.org,
        jpoimboe@...hat.com, wvw@...gle.com, avagin@...nvz.org
Subject: Re: [PATCH v2 1/2] compiler-clang.h: Add CLANG_VERSION and __diag
 macros

On Mon, Jul 30, 2018 at 02:34:11PM -0700, Nick Desaulniers wrote:
> These are needed for doing proper version checks, though feature
> detection via __has_attribute,  __has_builtin, and __has_feature should
> be preferred, see:
> https://clang.llvm.org/docs/LanguageExtensions.html#feature-checking-macros
> 
> Also adds __diag support, for generating compiler version specific
> _Pragma()'s.
> 
> __diag support based on commit 8793bb7f4a9d ("kbuild: add macro for
> controlling warnings to linux/compiler.h")
> 
> Cc: stable@...r.kernel.org # 4.17, 4.14, 4.9, 4.4
> Suggested-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Tested-and-reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
>  include/linux/compiler-clang.h | 19 +++++++++++++++++++
>  include/linux/compiler_types.h |  4 ++++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index 7087446c24c8..9442e07a361e 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -7,6 +7,10 @@
>   * for Clang compiler
>   */
>  
> +#define CLANG_VERSION (__clang_major__ * 10000	\
> +		       + __clang_minor__ * 100	\
> +		       + __clang_patchlevel__)
> +

I know this was done to be consistent with GCC_VERSION but certain
toolchains may set the patch level to the SVN revision (at least that's
what it appears to be) like AOSP's clang-4053586, which would make
CLANG_VERSION 350080. For this particular warning, it doesn't matter
since Clang has supported it since 2011 and Clang 5.0 isn't supported
in this tree anyways but maybe relying on just __clang_major__ below
is more ideal.

Other than that, patch functions just as it should.

>  #ifdef uninitialized_var
>  #undef uninitialized_var
>  #define uninitialized_var(x) x = *(&(x))
> @@ -46,3 +50,18 @@
>      __has_builtin(__builtin_sub_overflow)
>  #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
>  #endif
> +
> +#define __diag_str1(s) #s
> +#define __diag_str(s) __diag_str1(s)
> +#define __diag(s) _Pragma(__diag_str(clang diagnostic s))
> +#define __diag_CLANG_ignore ignored
> +#define __diag_CLANG_warn warning
> +#define __diag_CLANG_error error
> +#define __diag_CLANG(version, severity, s) \
> +	__diag_CLANG_ ## version(__diag_CLANG_ ## severity s)
> +
> +#if CLANG_VERSION >= 70000
> +#define __diag_CLANG_7(s) __diag(s)
> +#else
> +#define __diag_CLANG_7(s)
> +#endif
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index a8ba6b04152c..a04e6bd63476 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -279,6 +279,10 @@ struct ftrace_likely_data {
>  #define __diag_GCC(version, severity, string)
>  #endif
>  
> +#ifndef __diag_CLANG
> +#define __diag_CLANG(version, severity, string)
> +#endif
> +
>  #define __diag_push()	__diag(push)
>  #define __diag_pop()	__diag(pop)
>  
> -- 
> 2.18.0.345.g5c9ce644c3-goog
>