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From: Arnd Bergmann <arnd@arndb.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: "the arch/x86 maintainers" <x86@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andi Kleen <ak@linux.intel.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>
Subject: Re: [PATCH 01/17] kbuild: Disable -Waddress-of-packed-member for gcc 9
Date: Fri, 22 Mar 2019 14:58:51 +0100	[thread overview]
Message-ID: <CAK8P3a31L6ddJ1JPpygHqeVspExv7eaKWsLQ5pb+T8LAF2Zjtw@mail.gmail.com> (raw)
In-Reply-To: <20190321220009.29334-2-andi@firstfloor.org>

On Thu, Mar 21, 2019 at 11:00 PM Andi Kleen <andi@firstfloor.org> wrote:
>
> From: Andi Kleen <ak@linux.intel.com>
>
> This warning is very noisy in a default build with gcc 9.
> Move it into W=2 only.
>
> Cc: arnd@arndb.de
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>

I think W=2 is too aggressive. On many architectures, this finds
real bugs and the false positives tend to be trivial to fix
(by removing the bogus __packed annotation), which improves
the generated code in the process.

Moving it to W=1 for the moment is probably fine, but ideally
I think we should fix the kernel to behave according to the
C standard.

      Arnd

> ---
>  Makefile                   | 1 +
>  scripts/Makefile.extrawarn | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 71c2c482e2a2..78efbb172991 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -676,6 +676,7 @@ KBUILD_CFLAGS       += $(call cc-disable-warning,frame-address,)
>  KBUILD_CFLAGS  += $(call cc-disable-warning, format-truncation)
>  KBUILD_CFLAGS  += $(call cc-disable-warning, format-overflow)
>  KBUILD_CFLAGS  += $(call cc-disable-warning, int-in-bool-context)
> +KBUILD_CFLAGS  += $(call cc-disable-warning, address-of-packed-member)
>
>  ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
>  KBUILD_CFLAGS  += $(call cc-option,-Oz,-Os)
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 768306add591..ed974a0f4a47 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -43,6 +43,7 @@ warning-2 += $(call cc-option, -Wmissing-field-initializers)
>  warning-2 += $(call cc-option, -Wsign-compare)
>  warning-2 += $(call cc-option, -Wmaybe-uninitialized)
>  warning-2 += $(call cc-option, -Wunused-macros)
> +warning-2 += $(call cc-option, -Waddress-of-packed-member)
>
>  warning-3 := -Wbad-function-cast
>  warning-3 += -Wcast-qual
> --
> 2.20.1
>

  reply	other threads:[~2019-03-22 13:59 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-21 21:59 Fixes and cleanup from LTO tree Andi Kleen
2019-03-21 21:59 ` [PATCH 01/17] kbuild: Disable -Waddress-of-packed-member for gcc 9 Andi Kleen
2019-03-22 13:58   ` Arnd Bergmann [this message]
2019-03-22 16:31     ` Andi Kleen
2019-03-22 16:39     ` Peter Zijlstra
2019-03-22 16:57       ` Arnd Bergmann
2019-03-22 16:58       ` Andi Kleen
2019-03-25 16:27         ` David Laight
2019-04-01  1:04     ` Masahiro Yamada
2019-03-21 21:59 ` [PATCH 02/17] x86, lto: Mark all top level asm statements as .text Andi Kleen
2019-03-26 17:03   ` Thomas Gleixner
2019-03-26 21:38     ` Andi Kleen
2019-03-26 22:25       ` Thomas Gleixner
2019-03-27  0:55         ` Andi Kleen
2019-03-27  1:08           ` Andi Kleen
2019-03-27 14:20           ` Thomas Gleixner
2019-03-27 14:39             ` Ingo Molnar
2019-03-27 14:59             ` Andi Kleen
2019-03-27 15:08               ` Thomas Gleixner
2019-03-27 15:45                 ` Andi Kleen
2019-03-27 19:08                   ` Thomas Gleixner
2019-03-27 20:40                     ` Andi Kleen
2019-03-27 21:55                       ` Thomas Gleixner
2019-03-27 22:29                         ` Andi Kleen
2019-03-27 22:50                           ` Thomas Gleixner
2019-04-02  8:54                             ` Thomas Gleixner
2019-03-21 21:59 ` [PATCH 03/17] x86: Don't inline __const_udelay Andi Kleen
2019-03-21 21:59 ` [PATCH 04/17] init: Add __noreorder and mark initcalls __noreorder Andi Kleen
2019-03-21 21:59 ` [PATCH 05/17] Use C version for SYSCALL_ALIAS Andi Kleen
2019-03-21 21:59 ` [PATCH 06/17] locking/core: Mark spinlocks noinline when inline spinlocks are disabled Andi Kleen
2019-03-21 21:59 ` [PATCH 07/17] amdkfd: Fix extern declaration Andi Kleen
2019-03-21 22:00 ` [PATCH 08/17] x86/speculation: Fix __initconst in bugs.c Andi Kleen
2019-03-26 17:24   ` Thomas Gleixner
2019-03-21 22:00 ` [PATCH 09/17] x86/kvm: Make steal_time visible Andi Kleen
2019-03-21 22:00 ` [PATCH 10/17] delta: Fix buffer overrun in delta_ipc_open Andi Kleen
2019-04-01 13:37   ` Hugues FRUCHET
2019-04-01 16:54     ` Andi Kleen
2019-04-02  9:56       ` Hugues FRUCHET
2019-03-21 22:00 ` [PATCH 11/17] x86/kprobes: Make trampoline_handler global and visible Andi Kleen
2019-03-23  9:45   ` Masami Hiramatsu
2019-03-23 14:35     ` Andi Kleen
2019-03-25  1:53       ` Masami Hiramatsu
2019-03-21 22:00 ` [PATCH 12/17] afs: Avoid section confusion in CM_NAME Andi Kleen
2019-03-21 22:00 ` [PATCH 13/17] ASoC: AMD: Fix incorrect extern Andi Kleen
2019-03-21 22:00 ` [PATCH 14/17] crypto: Don't mark AES tables const and cacheline_aligned Andi Kleen
2019-03-26  8:42   ` Rasmus Villemoes
2019-03-26 18:30     ` Andi Kleen
2019-03-21 22:00 ` [PATCH 15/17] x86/hyperv: Make hv_vcpu_is_preempted visible Andi Kleen
2019-03-26  8:15   ` Yi Sun
2019-03-21 22:00 ` [PATCH 16/17] x86/xen: Mark xen_vcpu_stolen as __visible Andi Kleen
2019-03-21 22:00 ` [PATCH 17/17] dm: Fix const confusion in dm Andi Kleen
2019-03-22  8:34 ` [PATCH 12/17] afs: Avoid section confusion in CM_NAME David Howells
2019-03-26 17:00 ` Fixes and cleanup from LTO tree Thomas Gleixner

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