linux-kernel - Re: [PATCH] coccinelle: misc: remove "complex return code" warnings

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Message-ID: <20151001174718.GJ4284@localhost>
Date:	Thu, 1 Oct 2015 13:47:18 -0400
From:	Johan Hovold <johan@...nel.org>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	Johan Hovold <johan@...nel.org>, Michal Marek <mmarek@...e.com>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	linux-kernel@...r.kernel.org, cocci@...teme.lip6.fr
Subject: Re: [PATCH] coccinelle: misc: remove "complex return code" warnings

On Thu, Oct 01, 2015 at 07:20:10AM +0200, Julia Lawall wrote:
> On Wed, 30 Sep 2015, Johan Hovold wrote:
> 
> > This effectively reverts 932058a5d5f9 ("coccinelle: misc: semantic patch
> > to delete overly complex return code processing").
> > 
> > There can be both symmetry and readability reasons for not wanting to do
> > the final function call as part of the return statement and to maintain
> > a clear separation of success and error paths.
> > 
> > Since this is in no way mandated by the coding standard, let's just
> > remove this semantic patch to avoid having "clean up" patches being
> > posted over and over in response to these Coccinelle warnings.
> 
> What do you mean by "posted"?  Are you referring to 0-day build testing 
> or individual usage of make coccicheck?  Maybe it would make sense to 
> remove the semantic patch from 0-day build testing but leave it in the 
> kernel, perhaps removing the < 0 case because that one in practice doesn't 
> seem to turn up much that is useful?

Individuals running coccicheck on in-kernel code and posting patches to
"fix warnings", where the end result is not necessarily an improvement.

But I don't think these warnings should be enabled for 0-day build
testing either as it is should be up to the author to decide what style
to prefer in each case.

> Perhaps it could also be improved to detect a previous != 0 case and then 
> not return a warning.  On some functions, this change can make some nice 
> simplifications.

Yes, that would at least improve things.

I don't think warnings should be generated at all for the following
code:

{
	int ret;

	ret = init_a(...);
	if (ret)
		return ret;

	ret = init_b(...);
	if (ret)
		return ret;

	return 0;
}

as it is (at least to me) preferred over:

{
	int ret;

	ret = init_a(...);
	if (ret)
		return ret;

	return init_b(...);
}

for symmetry and readability reasons (e.g. I don't have to look at
init_b to figure out what the functions returns). And with a long
parameter list to init_b with line breaks, this would look even worse.

But either way, it should be up to the author of the code to decide what
style to use.

Thanks,
Johan
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