linux-kernel - Re: [PATCH] coccinelle: misc: add swap script

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Date:   Wed, 17 Feb 2021 22:31:05 +0100 (CET)
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 swap script

> +@...ends on patch@
> +identifier tmp;
> +expression a, b;
> +type T;
> +@@
> +
> +(
> +- T tmp;
> +|
> +- T tmp = 0;
> +|
> +- T *tmp = NULL;
> +)
> +... when != tmp
> +- tmp = a;
> +- a = b;
> +- b = tmp;
> ++ swap(a, b);
> +... when != tmp

In this rule and the next one, if you remove the final ; from the b = tmp
line and from the swap line, and put it into context code afterwards, them
the generated code looks better on cases like fs/xfs/xfs_inode.c in the
function xfs_lock_two_inodes where two successive swap calls are
generated.

There are also some cases such as drivers/net/wireless/ath/ath5k/phy.c in
the function ath5k_hw_get_median_noise_floor where the swap code makes up
a whole if branch.  In this cases it would be good to remove the {}.

julia

> +
> +@...ends on patch@
> +identifier tmp;
> +expression a, b;
> +@@
> +
> +- tmp = a;
> +- a = b;
> +- b = tmp;
> ++ swap(a, b);
> +
> +@...ipt:python depends on report@
> +p << r.p;
> +@@
> +
> +coccilib.report.print_report(p[0], "WARNING opportunity for swap()")
> +
> +@...ipt:python depends on org@
> +p << r.p;
> +@@
> +
> +coccilib.org.print_todo(p[0], "WARNING opportunity for swap()")
> --
> 2.26.2
>
>