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

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Message-ID: <20200205155006.GA21667@ubuntu-x2-xlarge-x86>
Date:   Wed, 5 Feb 2020 08:50:06 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Mark Brown <broonie@...nel.org>
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 Wed, Feb 05, 2020 at 10:22:38AM +0000, Mark Brown wrote:
> 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.

Yes, that would definitely be nice. I am not entirely sure that this is
possible with clang due to its architecture but I am far from a clang
internal expert.

> > 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.

Thank you :)

Cheers,
Nathan