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From: Julia Lawall <julia.lawall@inria.fr>
To: Joe Perches <joe@perches.com>
Cc: Giuseppe Scrivano <gscrivan@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Julia Lawall <julia.lawall@lip6.fr>,
	Andy Whitcroft <apw@shadowen.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	cocci <cocci@systeme.lip6.fr>
Subject: Re: [Cocci] coccinelle: Convert comma to semicolons (was Re: [PATCH] checkpatch: Add test for comma use that should be semicolon)
Date: Thu, 20 Aug 2020 10:33:33 +0200 (CEST)
Message-ID: <alpine.DEB.2.22.394.2008201021400.2524@hadrien> (raw)
In-Reply-To: <b0fd63e4b379eda69ee85ab098353582b8c054bb.camel@perches.com>



On Wed, 19 Aug 2020, Joe Perches wrote:

> On Wed, 2020-08-19 at 14:22 -0700, Joe Perches wrote:
> > There are commas used as statement terminations that should typically
> > have used semicolons instead.  Only direct assignments or use of a single
> > function or value on a single line are detected by this test.
> >
> > e.g.:
> > 	foo = bar(),		/* typical use is semicolon not comma */
> > 	bar = baz();
> >
> > Add an imperfect test to detect these comma uses.
> >
> > No false positives were found in testing, but many types of false negatives
> > are possible.
> >
> > e.g.:
> > 	foo = bar() + 1,	/* comma use, but not direct assignment */
> > 	bar = baz();
>
> Hi.
>
> I recently added a test for this condition to linux's checkpatch.
>
> A similar coccinelle script might be:
>
> $ cat comma.cocci
> @@
> expression e1;
> expression e2;
> @@
>
> 	e1
> -	,
> +	;
> 	e2;
> $
>
> This works reasonably well but it has several false positives
> for declarations like:
>
> $ spatch --sp-file comma.cocci mm/huge_memory.c
> diff -u -p a/huge_memory.c b/huge_memory.c
> --- a/huge_memory.c
> +++ b/huge_memory.c
> @@ -2778,7 +2778,7 @@ static unsigned long deferred_split_scan
>  	struct pglist_data *pgdata = NODE_DATA(sc->nid);
>  	struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
>  	unsigned long flags;
> -	LIST_HEAD(list), *pos, *next;
> +	LIST_HEAD(list), *pos; *next;
>  	struct page *page;
>  	int split = 0;
> $
>
> Any script improvement suggestions?

I have a bunch of variations of this that are more complicated than I
would have expected.  One shorter variant that I have is:

@@
expression e1,e2;
statement S;
@@

 S
 e1
-,
+;
  (<+... e2 ...+>);

This will miss cases where the first statement is the comma thing.  But I
think it is possible to improve this now.  I will check.

thanks,
julia
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Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200818184107.f8af232fb58b17160c570874@linux-foundation.org>
     [not found] ` <3bf27caf462007dfa75647b040ab3191374a59de.camel@perches.com>
2020-08-19 23:07   ` Joe Perches
2020-08-20  8:33     ` Julia Lawall [this message]
2020-08-20 16:52       ` Joe Perches
2020-08-20 17:03         ` Julia Lawall
2020-08-20 17:28           ` Joe Perches
2020-08-22  1:08           ` Joe Perches
2020-08-22  3:35             ` Valdis Klētnieks
2020-08-22  5:30               ` Joe Perches
2020-08-22  7:07                 ` Julia Lawall
2020-09-24 20:19                   ` Thomas Gleixner
2020-09-24 20:21                     ` Julia Lawall
2020-09-24 20:33                     ` Joe Perches
2020-09-24 21:53                       ` Thomas Gleixner
2020-09-24 22:23                         ` Joe Perches
2020-09-25 17:06                           ` Julia Lawall
2020-09-25 17:26                             ` Joe Perches
2020-09-26 19:11                               ` Valdis Klētnieks
2020-09-27 17:08                           ` Julia Lawall
2020-09-27 17:45                             ` Joe Perches
2020-09-27 19:35                               ` Julia Lawall

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