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Date:   Wed, 7 Nov 2018 12:55:17 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc:     linux-kernel@vger.kernel.org, Olof Johansson <olof@lixom.net>,
        Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v2] ubsan: don't mark __ubsan_handle_builtin_unreachable
 as noreturn
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On Wed,  7 Nov 2018 17:45:16 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:

> From: Arnd Bergmann <arnd@arndb.de>
> 
> gcc-8 complains about the prototype for this function:
> 
> lib/ubsan.c:432:1: error: ignoring attribute 'noreturn' in declaration of a built-in function '__ubsan_handle_builtin_unreachable' because it conflicts with attribute 'const' [-Werror=attributes]
> 
> This is actually a GCC's bug. In GCC internals
> __ubsan_handle_builtin_unreachable() declared with both 'noreturn' and
> 'const' attributes instead of only 'noreturn':
>    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84210
> 
> Workaround this by removing the noreturn attribute.
> 
> ...
>
> --- a/lib/ubsan.c
> +++ b/lib/ubsan.c
> @@ -427,8 +427,7 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
>  EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
>  
>  
> -void __noreturn
> -__ubsan_handle_builtin_unreachable(struct unreachable_data *data)
> +void __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
>  {
>  	unsigned long flags;

This code has been here since 2016 and presumably people will want to
build older kernels with newer gcc's.  So I'll add cc:stable, OK?