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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/100370] [11/12 Regression] Incorrect warning for placement
 new
Date: Mon, 03 May 2021 16:48:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100370

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |100399
   Last reconfirmed|                            |2021-05-03
      Known to fail|                            |11.1.0
             Status|UNCONFIRMED                 |NEW
                 CC|                            |msebor at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Confirmed.  The false positive here is the result of trying to avoid other
false positives for unions and not considering that the pointer might point=
 to
space that's larger than that.  Like the false negative in pr100307 comment=
 2
(AKA pr100325), this would also be prevented by running -Wplacement-new lat=
er,
when the program is in SSA form, rather than from the front end.

  if (code =3D=3D COMPONENT_REF)
    {
      tree ref =3D TREE_OPERAND (ptr, 0);
      if (TREE_CODE (TREE_TYPE (ref)) =3D=3D UNION_TYPE)
        /* In accesses through union types consider the entire unions
           rather than just their members.  */
        ostype =3D 0;


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100399
[Bug 100399] bogus/missing -Wplacement-new=