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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/104492] [12 Regression] Bogus dangling pointer
 warning at -O3
Date: Fri, 11 Feb 2022 00:49:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104492

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|c++                         |middle-end
            Summary|Bogus dangling pointer      |[12 Regression] Bogus
                   |warning (dangling pointer   |dangling pointer warning at
                   |to =E2=80=98candidates=E2=80=99 may be used |-O3
                   |[-Werror=3Ddangling-pointer=3D] |
                   |)                           |
     Ever confirmed|0                           |1
             Blocks|                            |104077
   Last reconfirmed|                            |2022-02-11
           Keywords|                            |diagnostic
                 CC|                            |msebor at gcc dot gnu.org

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning is issued for the if condition in the basic block below:

<bb 28> [local count: 1014686340]:
# _106 =3D PHI <&MEM <const struct QLatin1String[1]> [(void *)&candidates +
16B](26), &candidates(27)>
<L14>:
_274 =3D _106;
__pred =3D{v} {CLOBBER(eol)};
_17 =3D _274;
__pred =3D{v} {CLOBBER(eol)};
candidates =3D{v} {CLOBBER(eol)};=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20
<<< clobber
s =3D{v} {CLOBBER(eol)};
D.169975 =3D{v} {CLOBBER(eol)};
if (&MEM <const struct QLatin1String[1]> [(void *)&candidates + 16B] !=3D _=
17)=20=20
<<< -Wdangling-pointer
  goto <bb 30>; [5.50%]
else
  goto <bb 29>; [94.50%]


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104077
[Bug 104077] bogus/missing -Wdangling-pointer=