Re: Possible code defects: macros and precedence

Julia Lawall
2016-09-21T05:04:33Z

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On Tue, 20 Sep 2016, Joe Perches wrote:

> On Tue, 2016-09-20 at 15:14 +0200, Julia Lawall wrote:
> > The semantic patch below finds a binary operator in a macro and a binary
> > operator in the use of the macro, and checks if the priority of the
> > operator in the macro is higher (lower number) than the priority of the
> > operator in the use.  If this is the case, it adds parentheses in the use,
> > which is not what one wants, but serves to show where the problem is.
> >
> > It doesn't turn up anything, except an occurrence of (u32)-1, which
> > Coccinelle parses as a subtraction, due to not having any nearby evidence
> > that u32 is a type.
> >
> > I didn't make any special effort on the include files, which means that
> > only local include files and ones with the same name as the C file are
> > taken into account.  I can try with more aggressive include options.
> >
> > This only works with the github version of Coccinelle, as it required
> > quite a lot of improvement to the treatmern of #define.
> >
> > julia
> >
> > @initialize:ocaml@
> > @@
> >
> > let binoptbl =
> >     [("*",3);("/",3);("%",3);
>
> Shouldn't bitwise negation (~) and not (!) be added at 3?
>
> ("~",3);("!",3);

My semantic patch only covers binary operators at the moment, so I didn't
put the complete table.

I can extend it.

julia

>
> >       ("+",4);("-",4);
> >       ("<<",5);(">>",5);
> >       ("<",6);(">",6);("<=",6);(">=",6);
> >       ("==",7);("!=",7);
> >       ("&",8);
> >       ("^",9);
> >       ("|",10);
> >       ("&&",11);
> >       ("||",12)]
> >
> > @r@
> > identifier i,j;
> > identifier list[n] is;
> > binary operator b;
> > expression e;
> > @@
> >
> > #define i(is,j,...) (<+... \(j b e \| e b j\) ...+>)
> >
> > @s@
> > identifier r.i;
> > expression list[r.n] es;
> > binary operator b1;
> > expression e1,e2;
> > position p;
> > @@
> >
> > >  i@p(es,e1 b1 e2,...)
> >
> > @script:ocaml@
> > _p << s.p;
> > b << r.b;
> > b1 << s.b1;
> > @@
> >
> > try
> >   let p1 = List.assoc b binoptbl in
> >   let p2 = List.assoc b1 binoptbl in
> >   if p1 >= p2 then Coccilib.include_match false
> > with Not_found -> ()
> >
> > @@
> > identifier r.i;
> > expression list[r.n] es;
> > expression e;
> > position s.p;
> > @@
> >
> > i@p(es,
> > +(
> > e
> > +)
> > ,...)
> >
>