From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Julien Grall <julien.grall@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [Xen-devel] Ping: [PATCH v2] dom0-build: fix build with clang5
Date: Wed, 15 Jan 2020 10:56:37 +0100 [thread overview]
Message-ID: <20200115095637.GI11756@Air-de-Roger> (raw)
In-Reply-To: <91d9f45c-e0e1-a01c-d812-2dd3345fff48@suse.com>
On Fri, Dec 20, 2019 at 05:26:34PM +0100, Jan Beulich wrote:
> On 17.07.2019 08:47, Jan Beulich wrote:
> > With non-empty CONFIG_DOM0_MEM clang5 produces
> >
> > dom0_build.c:344:24: error: use of logical '&&' with constant operand [-Werror,-Wconstant-logical-operand]
> > if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
> > ^ ~~~~~~~~~~~~~~~~~~
> > dom0_build.c:344:24: note: use '&' for a bitwise operation
> > if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
> > ^~
> > &
> > dom0_build.c:344:24: note: remove constant to silence this warning
> > if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
> > ~^~~~~~~~~~~~~~~~~~~~~
> > 1 error generated.
> >
> > Obviously neither of the two suggestions are an option here. Oddly
> > enough swapping the operands of the && helps, while e.g. casting or
> > parenthesizing doesn't. Another workable variant looks to be the use of
> > !! on the constant.
> >
> > Signed-off-by: Jan Beulich <jbeulich@suse.com>
> > ---
> > v2: Also adjust the Arm incarnation of the same construct.
> > ---
> > I'm open to going the !! or yet some different route (but not really the
> > suggested strlen() one). No matter which one we choose, I'm afraid it is
> > going to remain guesswork what newer (and future) versions of clang will
> > choke on.
>
> I guess the disagreement on how to exactly address the issue has
> stalled this. But I think we should rather have _some_ (e.g.
> this) solution in the repo, than continue to ship versions which
> don't build. People wanting to beautify the code further could
> then submit incremental patches.
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
I'm not providing a RB because this is all guesswork, so it doesn't
feel appropriate to review something that's based on undocumented
compiler behavior.
Another option would be to pass -Wconstant-logical-operand but that
would prevent caching some licit issues.
Thanks, Roger.
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next prev parent reply other threads:[~2020-01-15 9:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 6:47 [Xen-devel] [PATCH v2] dom0-build: fix build with clang5 Jan Beulich
2019-07-29 10:05 ` Julien Grall
2019-07-29 11:36 ` Jan Beulich
2019-12-20 16:26 ` [Xen-devel] Ping: " Jan Beulich
2020-01-11 16:27 ` Julien Grall
2020-01-15 9:56 ` Roger Pau Monné [this message]
2020-01-15 10:00 ` Roger Pau Monné
2020-01-15 10:18 ` Jan Beulich
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