From: Luca Coelho <luca@coelho.fi>
To: Julia Lawall <julia.lawall@lip6.fr>
Cc: cocci@systeme.lip6.fr, backports@vger.kernel.org,
johannes.berg@intel.com, felipe.balbi@intel.com
Subject: Re: Weird problem trying to match code inside a function
Date: Tue, 11 Sep 2018 14:22:44 +0300 [thread overview]
Message-ID: <9ff5075ecd90926d1e47060f0309cd2c0e531ba2.camel@coelho.fi> (raw)
In-Reply-To: <alpine.DEB.2.20.1809111059590.3671@hadrien>
On Tue, 2018-09-11 at 11:05 +0200, Julia Lawall wrote:
>
> On Tue, 11 Sep 2018, Luca Coelho wrote:
>
> > Hi Julia,
> >
> > I bumped in to another weird problem. I'm trying to match some
> > code
> > inside a function that has a specific struct as a parameter, but I
> > can't get it to work.
> >
> > This is cocci code I tried first:
> >
> > http://pastebin.coelho.fi/6f8f346822a7c99e.txt
> >
> > And this is the file I'm trying to match:
> >
> > http://pastebin.coelho.fi/f73f542932add1c6.txt
> >
> > The led activate op changed from being a function that returns void
> > to
> > one that returns int and I had to backport that.
> >
> > The strange thing is that if I have only the first rule, it works
> > fine,
> > but when I add the second rule it fails.
>
> I didn't look at the code in detail, but there is a restriction on
> metavariables that are not position variables that are inherited from
> one
> rule to another. Such metavariables have to have only one value. If
> there is more than one possible value, the original match fails
> completely.
>
> For example, if you do:
>
> @r@
> expression E;
> @@
>
> f();
> ...
> -g(E);
>
> This will do the right thing for:
>
> f();
> if (x)
> g(3);
> else g(4);
>
> But if you do:
>
> @r@
> expression E;
> @@
>
> f();
> ...
> -g(E);
>
> @@
> expression r.E;
> @@
>
> - xxx(E);
>
> Then nothing will happen at all. Because in the first rule, it is
> not
> able to find a unique binding for E.
>
> A solution can be:
>
> @r@
> expression E;
> position p;
> @@
>
> f();
> ...
> g(E@p);
>
> @s@
> position r.p;
> expression E;
> @@
>
> - g(E@p);
>
> @@
> expression s.E;
> @@
>
> - xxx(E);
>
> Position metavariable can take on many values, even if they are
> inherited.
Ah, I think this explains the problem.
I tried to add the position thing in my rules, but I didn't succeed.
I'll have to try again at some other time. My rules without matching
inside a function work fine, so I'll leave with that for now.
Thanks!
--
Luca.
--
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prev parent reply other threads:[~2018-09-11 16:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-11 8:08 Weird problem trying to match code inside a function Luca Coelho
2018-09-11 9:05 ` Julia Lawall
2018-09-11 11:22 ` Luca Coelho [this message]
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