linux-kernel - Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

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Message-ID: <FB827022-C732-432A-8F31-734C88EBF7A4@zytor.com>
Date:   Fri, 17 Mar 2017 16:50:19 -0700
From:   hpa@...or.com
To:     Michael Davidson <md@...gle.com>, Michal Marek <mmarek@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Shaohua Li <shli@...nel.org>
CC:     Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>, x86@...nel.org,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-raid@...r.kernel.org
Subject: Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

On March 16, 2017 5:15:16 PM PDT, Michael Davidson <md@...gle.com> wrote:
>Suppress clang warnings about potential unaliged accesses
>to members in packed structs. This gets rid of almost 10,000
>warnings about accesses to the ring 0 stack pointer in the TSS.
>
>Signed-off-by: Michael Davidson <md@...gle.com>
>---
> arch/x86/Makefile | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>index 894a8d18bf97..7f21703c475d 100644
>--- a/arch/x86/Makefile
>+++ b/arch/x86/Makefile
>@@ -128,6 +128,11 @@ endif
>         KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
> endif
> 
>+ifeq ($(cc-name),clang)
>+# Suppress clang warnings about potential unaligned accesses.
>+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
>+endif
>+
> ifdef CONFIG_X86_X32
> 	x32_ld_ok := $(call try-run,\
> 			/bin/echo -e '1: .quad 1b' | \

Why conditional on clang?
-- 
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