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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/99251] [11 Regression] inconsistent -Wnonnull warning
 behaviour with dynamic_cast
Date: Wed, 24 Feb 2021 17:12:27 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99251

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |95507
   Last reconfirmed|                            |2021-02-24
           Keywords|                            |diagnostic
            Summary|Strange -Wnonnull warning   |[11 Regression]
                   |behaviour with dynamic_cast |inconsistent -Wnonnull
                   |                            |warning behaviour with
                   |                            |dynamic_cast
     Ever confirmed|0                           |1
                 CC|                            |msebor at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
We discussed this instance of the warning in pr98646 and decided that even
though issuing it for an access to the result of dynamic_cast was strictly a
false positive when the operand was guaranteed to be nonnull by a prior tes=
t,
the workaround to cast to a reference rather than a pointer was simple enou=
gh
and made the intent clearer:

  return dynamic_cast<cl2 &>(*p).i();

But the inconsistency exhibited in this test case is not a good thing
(enclosing the cast in parentheses certainly shouldn't make a difference) a=
nd
suggests the decision should be revisited.  The warning for the dynamic_cast
should either be issued consistently or not at all.  Let me look into it.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95507
[Bug 95507] [meta-bug] bogus/missing -Wnonnull=