From: Michal Hocko <mhocko@kernel.org>
To: Nick Desaulniers <nick.desaulniers@gmail.com>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org,
mgorman@techsingularity.net, vbabka@suse.cz, minchan@kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [Patch v2] mm/vmscan: fix unsequenced modification and access warning
Date: Wed, 31 May 2017 17:21:51 +0200 [thread overview]
Message-ID: <20170531152151.GT27783@dhcp22.suse.cz> (raw)
In-Reply-To: <20170526044343.autu63rpfigbzhyi@lostoracle.net>
On Thu 25-05-17 21:43:43, Nick Desaulniers wrote:
> On Tue, May 16, 2017 at 10:27:46AM +0200, Michal Hocko wrote:
> > I guess it is worth reporting this to clang bugzilla. Could you take
> > care of that Nick?
>
> >From https://bugs.llvm.org//show_bug.cgi?id=33065#c5
> it seems that this is indeed a sequence bug in the previous version of
> this code and not a compiler bug. You can read that response for the
> properly-cited wording but my TL;DR/understanding is for the given code:
>
> struct foo bar = {
> .a = (c = 0),
> .b = c,
> };
>
> That the compiler is allowed to reorder the initializations of bar.a and
> bar.b, so what the value of c here might not be what you expect.
This is interesting because what I hear from our gcc people is something
different. I am not in a possition to argue here, though.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2017-05-31 15:21 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-10 6:53 [PATCH] mm/vmscan: fix unsequenced modification and access warning Nick Desaulniers
2017-05-10 7:15 ` Michal Hocko
2017-05-10 8:27 ` [Patch v2] " Nick Desaulniers
2017-05-10 8:38 ` Michal Hocko
2017-05-16 8:27 ` Michal Hocko
2017-05-17 3:01 ` Nick Desaulniers
2017-05-26 4:43 ` Nick Desaulniers
2017-05-31 15:21 ` Michal Hocko [this message]
2017-05-10 8:46 ` [PATCH] " Nick Desaulniers
2017-05-10 9:25 ` Michal Hocko
2017-05-10 15:40 ` [Patch v3] " Nick Desaulniers
2018-03-21 21:37 ` [PATCH] " Nick Desaulniers
2018-03-22 9:50 ` Michal Hocko
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