https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96003
--- Comment #25 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #24)
> I see. Yes, if the types are unrelated, that would be a likely bug. I
> think could and should be diagnosed by the C++ front end, by some more
> targeted warning than -Wnonnull (as requested in pr38557).
>
> But I didn't actually mean to write that test case in comment #20 (I forgot
> to derive one class from the other). The following is what I meant where
> the -Wnonnull is strictly a false positive because of the test. It can be
> avoided by casting *p to C& which might be argued (as I do in comment #17)
> makes the code clearer, but if this is a common idiom we could try to
> suppress the warning in these cases as well. Do you see this pattern a lot?
I see the pattern in libyui-3.12.2 package.
>
> struct A { virtual ~A (); };
> struct C: A { virtual ~C (); void f (); };
>
> void g (A *p)
> {
> if (dynamic_cast<C*>(p))
> dynamic_cast<C*>(p)->f (); // -Wnonnull
>
> /* Avoid like so:
> if (dynamic_cast<C*>(p))
> dynamic_cast<C&>(*p)->f (); */
dynamic_cast<C&>(*p).f (); */
works for me as a workaround of the issue.
