linux-kernel - Re: [PATCH RFC] Coccinelle: Check for return not matching function signature

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Date:	Tue, 5 May 2015 18:00:35 +0200
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Michal Marek <mmarek@...e.cz>, cocci@...teme.lip6.fr,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] Coccinelle: Check for return not matching function
	signature

On Tue, 05 May 2015, Julia Lawall wrote:

> > +@...ch@
> > +identifier f,ret;
> > +position p;
> > +type T1,T2;
> > +@@
> > +
> > +T1 f(...) {
> > + T2 ret;
> > +<+...
> > +* return@p ret
> > +;
> > +...+>
> > +}
> 
> Given the number of results, it may seem surprising, but I think that you
> are actually missing a lot of results.  Becaue you require that ret be the
> first variable that is declared in the function.  Also, you require that
> ret be an identifier.  If you want to keep the restriction about being an
> identifier, you could put:
> 
> @match exists@
> type T1,T2;
> idexpression T2 ret;
> identifier f;
> @@
> 
> T1 f(...) {
> <+...
> return@p ret;
> ...+>
> }
>

this is depressing - I now like by wrong solution even more ...
unfortunately you are right - I missed most - its now at 25146
 
> If you don't care about the identifier constraint, then you can just put
> T2 ret.  Note also the addition of exists.  There is a problem if only one
> path has this property.  Another thing you can do is the following:
> 
> @match exists@
> type T1,T2;
  idexpression T1 ok;
> idexpression T2 ret;
> identifier f;
  position p;
> @@
> 
> T1 f(...) {
> <+...
> (
> return ok;
> |
> return@p ret;
> )
> ...+>
> }
> 
> Then Coccinelle will find the cases where the types are wrong, rather than
> requiring a test in python.
> 
> (I haven't tested any of this)

also works - I had naively expected this to be faster - but it does not
seem to be.

will check results did not expect 10% of the kernel functions
to have missmatching return types in atleast one of their paths.

thx!
hofrat
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