On Fri, 16 Dec 2016, Thomas Adam wrote:
> On Fri, Dec 16, 2016 at 08:21:35PM +0100, Julia Lawall wrote:
> > The problem for the vset function is that a pattern like
> >
> > A
> > ...
> >
> > requires that there be no A along all paths leaving from the matched A.
> > Your code matching the first pattern is in a loop, so obviously there is
> > at least one path that reaches A again. So the rule doesn't match. If
> > you want to consider the region until A optionally occurs again, then you
> > can write:
> >
> > A
> > ...
> > ?A
> >
> > The ? makes it optional.
>
> Ah. I think I understand that, Julia. If I blindly modify the strdup rule to
> this:
>
> T = strdup(...);
> + if (T == NULL)
> + pkg_emit_errno("strdup", __func__);
> ?... when != (T == NULL)
> ? when != (T != NULL)
The ? doesn't go on the ... line. I'm rather surprised that that would
parse, even. Your line in the A position is T = strdup(...);. So you
need to put another copy of that at the end of the rule with ? in front
of it. So that it stops when it comes to that again.
julia
>
> And then run:
>
> spatch --in-place --sp-file ~/unchecked_malloc.cocci libpkg/pkg.c
>
> This now captures the other remaining strdup() calls which were going
> undetected. However, as a side-effect of this, the matching rule is adding in
> the same NULL checks for function calls which already has them; hence a
> doubling-up.
>
> I appreciate I've just blindly followed your advice; could you perhaps
> elaborate (and educate me) as to the correct way to ammend this rule?
>
> Thanks.
>
> Thomas
>
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