linux-kernel - Re: [PATCH] coccinelle: misc: add excluded

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Date:   Fri, 4 Sep 2020 22:39:16 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Denis Efremov <efremov@...ux.com>
cc:     cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coccinelle: misc: add excluded_middle.cocci script



On Wed, 2 Sep 2020, Denis Efremov wrote:

> Check for "!A || A && B" condition. It's equivalent to
> "!A || B" condition.
>
> Signed-off-by: Denis Efremov <efremov@...ux.com>
> ---
>  scripts/coccinelle/misc/excluded_middle.cocci | 40 +++++++++++++++++++
>  1 file changed, 40 insertions(+)
>  create mode 100644 scripts/coccinelle/misc/excluded_middle.cocci
>
> diff --git a/scripts/coccinelle/misc/excluded_middle.cocci b/scripts/coccinelle/misc/excluded_middle.cocci
> new file mode 100644
> index 000000000000..1b8c20f13966
> --- /dev/null
> +++ b/scripts/coccinelle/misc/excluded_middle.cocci
> @@ -0,0 +1,40 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +///
> +/// Condition "!A || A && B" is equalent to "!A || B".

As was noted, there is a spelling mistake here.

> +///
> +// Confidence: High
> +// Copyright: (C) 2020 Denis Efremov ISPRAS
> +// Options: --no-includes --include-headers
> +
> +virtual patch
> +virtual context
> +virtual org
> +virtual report
> +
> +@r depends on !patch@
> +expression A, B;
> +position p;
> +@@
> +
> +* !A || (A && B)@p

In org mode, the token with the position variable gets highlighted in
color.  It would be more meaningful to put the position variable on the &&
operator.

> +
> +@...ends on patch@
> +expression A, B;
> +@@
> +
> +  !A ||
> +-      (A &&
> +             B
> +-      )

I found it better to say

- (A && B)
+ B

There are some cases where B should be moved one space to the left and by
removing B and adding it back again that will happen.  I didn't see any
case where the result was less good.

> +@...ipt:python depends on report@
> +p << r.p;
> +@@
> +
> +coccilib.report.print_report(p[0], "WARNING condition !A || A && B is equivalent to !A || B")
> +
> +@...ipt:python depends on org@
> +p << r.p;
> +@@
> +
> +coccilib.org.print_todo(p[0], "WARNING condition !A || A && B is equivalent to !A || B")

I'm not sure that you need the word condition, but up to you.

julia