[Cocci] problems with typecasts

[Julia Lawall]

> > cast_expr(r,pe):
> >     unary_expr(r,pe)                      { $1 }
> >   | lp=TOPar t=ctype rp=TCPar e=cast_expr(r,pe)
> >       { Ast0.wrap(Ast0.Cast (P.clt2mcode "(" lp, t,
> > 			     P.clt2mcode ")" rp, e)) }
> >
> >   
> 
> Coccinelle 0.1.5 is what I'm using and it has the code you posted.
> 
> cast_expr(r,pe):
>     unary_expr(r,pe)                      { $1 }
>   | lp=TOPar t=ctype rp=TCPar e=cast_expr(r,pe)
>       { Ast0.wrap(Ast0.Cast (P.clt2mcode "(" lp, t,
>                              P.clt2mcode ")" rp, e)) }

OK, I still think something is wrong with cast and volatile, but I will 
let you try it first; perhaps 0.1.5 is more up to date than I thought.


> 
> >> - Reads outside an assignment are not matched (the if clause).
> >>     
> >
> > This is because you have a eg *b = a;.  If you drop the semicolon, it 
> > should work
> >   
> 
> I tried this and failed.
> @@
> expression a;
> volatile uint8_t *b;
> @@
> - a = *b
> + a = readb(b)
> 
> still does not match
> if ((*bios & 0x80) == 0) {      // it's busy
>     while ((*bios & 0x80) == 0) ;
> }
> 
> That's probably because I also match the equal sign. I'd rather avoid
> creating a separate semantic patch for every possible formula containing
> a read access to *bios.
> Is it possible to tell Coccinelle to just match on read accesses? Or
> maybe a right-hand-side expression?

OK, I didn't look at the if code carefully enough.  Since you have the 
rule for writes first, in the rule for reads, you should be able to just 
match *b.  Coccinelle applies the first rule to the whole file, then the 
second rule, etc.

julia