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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/98646] [11 Regression] A static_cast confuses -Wnonnull,
 causing false positives
Date: Mon, 18 Jan 2021 19:13:14 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98646

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I don't see how either TREE_NO_WARNING or some magic call would help.
Because the user can also write:
// PR c++/98646
// { dg-do compile }
// { dg-options "-Wnonnull" }

struct B { void foo (); };
struct D : B { void show (); };

void
D::show ()
{
  constexpr D *p =3D nullptr;
  if (p)
    p->foo ();
}

and that also warns and IMNSHO should not.

We should warn for:
struct B { void foo (); };
struct D : B { void show (); };

void
D::show ()
{
  constexpr D *p =3D nullptr;
  p->foo ();
}

So, the problem is IMHO that the warning about passing NULL to this is
misplaced, it shouldn't be done in the FEs, but later when there was at lea=
st
some chance of dead code removal.=