linux-kernel - Re: [cocci] [PATCH net-next 1/2] scripts/coccinelle: Find PTR

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Message-ID: <7522bdc8-1379-d516-d1fd-f7835453f23@inria.fr>
Date: Sun, 28 Sep 2025 14:23:40 +0200 (CEST)
From: Julia Lawall <julia.lawall@...ia.fr>
To: Gal Pressman <gal@...dia.com>
cc: Markus Elfring <Markus.Elfring@....de>, Tariq Toukan <tariqt@...dia.com>, 
    cocci@...ia.fr, Alexei Lazar <alazar@...dia.com>, 
    Andrew Lunn <andrew+netdev@...n.ch>, 
    "David S. Miller" <davem@...emloft.net>, 
    Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
    Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
    LKML <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org, 
    linux-rdma@...r.kernel.org, Leon Romanovsky <leon@...nel.org>, 
    Mark Bloch <mbloch@...dia.com>, Nicolas Palix <nicolas.palix@...g.fr>, 
    Richard Cochran <richardcochran@...il.com>, 
    Saeed Mahameed <saeedm@...dia.com>
Subject: Re: [cocci] [PATCH net-next 1/2] scripts/coccinelle: Find PTR_ERR()
 to %pe candidates

> >> +@r@
> >> +expression ptr;
> >> +constant fmt;
> >> +position p;
> >> +identifier print_func;
> >> +@@
> >> +* print_func(..., fmt, ..., PTR_ERR@p(ptr), ...)
> >
> > How do you think about to use the metavariable type “format list”?
>
> I did find "format list" in the documentation, but spatch fails when I
> try to use it.

I would suggest constant char[] fmt.

format is for the case where you want to specify something about the %d
%s, etc in the string.

> > Would it matter to restrict expressions to pointer expressions?
>
> I tried changing 'expression ptr;' -> 'expression *ptr;', but then it
> didn't find anything. Am I doing it wrong?

expression *ptr should be a valid metavariable declaration.  But
Coccinelle needs to have enough information to know that something is a
pointer.  If you have code like a->b and you don't have the definition of
the structure type of a, then it won't know the type of a->b.  More
information about types is available if you use options like
--recursive-includes, but then treatment of every C file will entail
parsing lots of header files, which could make things very slow.  So you
have to consider whether the information that the thing is a pointer is
really necessary to what you are trying to do.

> >> +@...ipt:python depends on r && org@
> >
> > I guess that such an SmPL dependency specification can be simplified a bit.
>
> You mean drop the depends on r?
>
> >
> >
> >> +p << r.p;

Since you have r.p, the rule will only be applied if r has succeeded and
furthermore if p has a value.  So depends on r is not necessary.

julia

> >> +@@
> >> +coccilib.org.print_todo(p[0], "WARNING: Consider using %pe to print PTR_ERR()")
> >
> > I suggest to reconsider the implementation detail once more
> > if the SmPL asterisk functionality fits really to the operation modes “org” and “report”.
> >
> > The operation mode “context” can usually work also without an extra position variable,
> > can't it?
>
> Can you please explain?
>