[Cocci] coccinelle: Convert comma to semicolons (was Re: [PATCH] checkpatch: Add test for comma use that should be semicolon)

[Joe Perches]

(forwarding on to kernel-janitors/mentees and kernelnewbies)

Just fyi for anyone that cares:

A janitorial task for someone might be to use Julia's coccinelle
script below to convert the existing instances of commas that
separate statements into semicolons.

https://lore.kernel.org/lkml/alpine.DEB.2.22.394.2008201856110.2524@hadrien/

On Thu, 2020-08-20 at 19:03 +0200, Julia Lawall wrote:
> > > 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.
> > 
> > Hi Julia.
> > 
> > Right, thanks, this adds a dependency on a statement
> > before the expression.  Any stragglers would be easily
> > found using slightly different form.
> > There are not very many of these in linux kernel.
> > 
> > Another nicety would be to allow the s/,/;/ conversion to
> > find both b and c in this sequence:
> > 	a = 1;
> > 	b = 2,
> > 	c = 3,
> > 	d = 4;
> > without running the script multiple times.
> > There are many dozen uses of this style in linux kernel.
> > 
> > I tried variants of adding a comma after the e2 expression,
> > but cocci seems to have parsing problems with:
> > 
> > @@
> > expression e1;
> > expression e2;
> > @@
> > 	e1
> > -	,
> > +	;
> > 	e2,
> 
> This doesn't work because it's not a valid expression.
> 
> The problem is solved by doing:
> 
>   e1
> - ,
> + ;
>   e2
>   ... when any
> 
> But that doesn't work in the current version of Coccinelle.  I have fixed
> the problem, though and it will work shortly.
> 
> > I do appreciate that coccinelle adds braces for multiple
> > expression comma use after an if.
> > 
> > i.e.:
> > 	if (foo)
> > 		a = 1, b = 2;
> > becomes
> > 	if (foo) {
> > 		a = 1; b = 2;
> > 	}
> 
> I wasn't sure what was wanted for such things.  Should b = 2 now be on a
> separate line?
> 
> I took the strategy of avoiding the problem and leaving those cases as is.
> That also solves the LIST_HEAD problem.  But if it is wanted to change
> these commas under ifs, then that is probably possible too.
> 
> My current complete solution is as follows.  The first rule avoids changing
> commas in macros, where thebody of the macro is just an expression.  The
> second rule uses position variables to ensure that the two expression are
> on different lines.
> 
> @r@
> expression e1,e2;
> statement S;
> position p;
> @@
> 
> e1 , at S@p e2;
> 
> @@
> expression e1,e2;
> position p1;
> position p2 :
>     script:ocaml(p1) { not((List.hd p1).line_end = (List.hd p2).line) };
> statement S;
> position r.p;
> @@
> 
> e1 at p1
> -, at S@p
> +;
> e2 at p2
> ... when any
> 
> The generated patch is below.
> 
> julia
> 
> diff -u -p a/drivers/reset/hisilicon/reset-hi3660.c b/drivers/reset/hisilicon/reset-hi3660.c
> --- a/drivers/reset/hisilicon/reset-hi3660.c
> +++ b/drivers/reset/hisilicon/reset-hi3660.c
> @@ -89,7 +89,7 @@ static int hi3660_reset_probe(struct pla
>  		return PTR_ERR(rc->map);
>  	}
> 
> -	rc->rst.ops = &hi3660_reset_ops,
> +	rc->rst.ops = &hi3660_reset_ops;
>  	rc->rst.of_node = np;
>  	rc->rst.of_reset_n_cells = 2;
>  	rc->rst.of_xlate = hi3660_reset_xlate;

The rest of the changes are in the link above...