On Thu, 14 Feb 2019, Michael Stefaniuc wrote:
> On 2/14/19 10:38 PM, Julia Lawall wrote:
> >
> >
> > On Thu, 14 Feb 2019, Michael Stefaniuc wrote:
> >
> >> Hello,
> >>
> >> I have this trivial script to remove useless casts to self:
> >> @ disable drop_cast @
> >> type T;
> >> T E;
> >> @@
> >> - (T)
> >> E
> >>
> >> It works but I'm hitting false positives when the code casts away
> >> qualifiers for field types. Please see the attached test case:
> >> - Good: Cast is kept in foo()
> >> - Bad: Cast is dropped in baz()
> >>
> >> Applying the generated diff will lead to a gcc warning:
> >> $ gcc -c qualifier.c
> >> qualifier.c: In function ‘baz’:
> >> qualifier.c:12:12: warning: return discards ‘const’ qualifier from
> >> pointer target type [-Wdiscarded-qualifiers]
> >> return &b->i;
> >> ^~~~~
> >>
> >> I tried disabling the optional_qualifier iso but that has no effect:
> >> - Not needed for the foo() case
> >> - No effect for the baz() case
> >>
> >> I even tried prepending an alternation with "const T good;" but the cast
> >> still gets removed.
> >
> > The following is better, but not perfect, in that it requires that the
> > const thing have type pointer to a structure. It could be possible to
> > explicitly consider more type patterns.
> Well, it doesn't fixes the problem that the qualifier is not propagated
> from the struct to its fields. Code like this isn't matched with or
> without the cocci modification.
>
> const int *zzz(const struct bar *b)
> {
> return (const int *)&b->i;
> }
>
> That's because "&b->i" has the type of just "int*" instead of the
> correct "const int*".
OK. I can change it in the way that is suggested. In the short term, you
can add another case to the disjunction, ie - (const T), to reduce the
number of false positives.
julia
>
> bye
> michael
>
> >
> > @disable drop_cast@
> > type T,T1;
> > T E;
> > identifier i;
> > const struct i *c;
> > @@
> >
> > (
> > c
> > |
> > - (T)
> > E
> > )
> >
> > julia
> >
>
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