linux-kernel - Re: [PATCH] ubsan: don't mark __ubsan_handle_builtin

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Date:   Mon, 5 Feb 2018 12:02:21 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Nicolas Pitre <nico@...aro.org>, Andi Kleen <ak@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ubsan: don't mark __ubsan_handle_builtin_unreachable as
 noreturn



On 02/02/2018 06:47 PM, Arnd Bergmann wrote:
> 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]
> 

That's actually a bug in GCC. In GCC __ubsan_handle_builtin_unreachable declared
with 'noreturn' and 'const' attributes:

DEF_SANITIZER_BUILTIN(BUILT_IN_UBSAN_HANDLE_BUILTIN_UNREACHABLE,                                                                                                                                                    
                      "__ubsan_handle_builtin_unreachable",                                                                                                                                                         
                      BT_FN_VOID_PTR,                                                                                                                                                                               
                      ATTR_COLD_CONST_NORETURN_NOTHROW_LEAF_LIST)


But const attribute doesn't make any sense for function that returns void or doesn't return at all.
Given that gcc-8 has not released yet, it would be better to fix this bug there.