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From: "daniel at constexpr dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107129] New: [13 Regression] False positive
 -Wstringop-overflow warning with -O2 or -O3
Date: Mon, 03 Oct 2022 10:59:11 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: daniel at constexpr dot org
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107129

            Bug ID: 107129
           Summary: [13 Regression] False positive -Wstringop-overflow
                    warning with -O2 or -O3
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: daniel at constexpr dot org
  Target Milestone: ---

Created attachment 53652
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D53652&action=3Dedit
Reduced testcase

The attached testcase produces the following warning with GCC 13.0.0 202210=
02
(commit 3290dcf):

$ /opt/gcc-dev/bin/c++ -O2 -c test.cpp=20
test.cpp: In member function =E2=80=98void C::f()=E2=80=99:
test.cpp:39:33: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=3D]
   39 |                         c[i] =3D e(1.f - i, i);
      |                                ~^~~~~~~~~~~~
test.cpp:9:23: note: at offset 1 into destination object =E2=80=98C4::r=E2=
=80=99 of size 1
    9 |         unsigned char r;
      |=