linux-kernel - Re: [PATCH] platform/x86: thinkpad_acpi: Fix bitwise vs. logical warning

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Message-ID: <CAKwvOd=wGjd_L1703Y9Kngcr9-_wTvcRLToiydXYkR=S_9xWDw@mail.gmail.com>
Date:   Mon, 18 Oct 2021 13:14:05 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Henrique de Moraes Holschuh <hmh@....eng.br>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        ibm-acpi-devel@...ts.sourceforge.net,
        platform-driver-x86@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        llvm@...ts.linux.dev, Tor Vic <torvic9@...lbox.org>
Subject: Re: [PATCH] platform/x86: thinkpad_acpi: Fix bitwise vs. logical warning

On Mon, Oct 18, 2021 at 12:41 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Mon, Oct 18, 2021 at 8:34 AM Nick Desaulniers
> <ndesaulniers@...gle.com> wrote:
> >
> > LGTM, thanks for the patch! I guess this would be the first
> > "interesting" case this warning has found in kernel sources?
>
> The patch looks obviously correct (tm), but I'm not convinced that the
> warning is actually all that interesting.
>
> The thing is, using bitwise operators for booleans is _exactly_ the
> same as using logical ones as long as there are no side effects.

Right, the patch that added the warning explicitly checks for side effects.
https://reviews.llvm.org/D108003
https://lore.kernel.org/lkml/20211018193101.2340261-1-nathan@kernel.org/
is another example that I would point to in favor of the error.
-- 
Thanks,
~Nick Desaulniers