linux-kernel - Re: [PATCH] ASoC: wcd934x: Remove some unnecessary NULL checks

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Message-ID: <20200205102238.GG3897@sirena.org.uk>
Date:   Wed, 5 Feb 2020 10:22:38 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] ASoC: wcd934x: Remove some unnecessary NULL checks

On Tue, Feb 04, 2020 at 12:32:15PM -0700, Nathan Chancellor wrote:
> On Tue, Feb 04, 2020 at 10:00:39AM +0000, Mark Brown wrote:

> > I'm not convincd this is a sensible warning, at the use site a
> > pointer to an array in a struct looks identical to an array
> > embedded in the struct so it's not such a bad idea to check and
> > refactoring of the struct could easily introduce problems.

> Other static checkers like smatch will warn about this as well (since I
> am sure that is how Dan Carpenter found the same issue in the wcd9335
> driver). Isn't an antipattern in the kernel to do things "just in
> case we do something later"? There are plenty of NULL checks removed
> from the kernel because they do not do anything now.

I'm not convinced it is an antipattern - adding the checks would
be a bit silly but with the way C works the warnings feel like
false positives.  If the compiler were able to warn about missing
NULL checks in the case where the thing in the struct is a
pointer I'd be a lot happier with this.

> I'd be fine with changing the check to something else that keeps the
> same logic but doesn't create a warning; I am not exactly sure what that
> would be because that is more of a specific driver logic thing, which I
> am not familiar with.

I've queued the change to be applied since it's shuts the
compiler up but I'm really not convinced the compiler is helping
here.

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