From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id B45683858C33; Fri, 31 Mar 2023 11:55:02 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B45683858C33
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1680263702;
	bh=BF5qR4j1raUv6rVCXeq5EwwDPcyXX7wLcfBhpbfzPE4=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=Ih5wQH72mQHmrNoV8mjWj7RI5KUlGoeDb6JbD+H+e82ZPlp5ay3X6wL4NDyUVduBb
	 u+Y0DpHKHYnnEUMRKlFPPVHkEkpkjZ67ZI8kLWK2ylTynNRYJa5oDs2V9qcPlZLMc4
	 RDX7rioXrAG0vpbzitpiDr9cxcPT/Eb0Dsw/hbBM=
From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107087] [12/13 Regression]
 bits/stl_algobase.h:431: warning: 'void* __builtin_memcpy(void*, const void*,
 unsigned int)' reading between 8 and 2147483644 bytes from a region of size 4
 [-Wstringop-overread]
Date: Fri, 31 Mar 2023 11:55:02 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: diagnostic, missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: redi at gcc dot gnu.org
X-Bugzilla-Status: REOPENED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 12.3
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-107087-4-C9EsxSKRvN@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-107087-4@http.gcc.gnu.org/bugzilla/>
References: <bug-107087-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107087

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This prevents the warning:

--- a/libstdc++-v3/include/bits/cow_string.h
+++ b/libstdc++-v3/include/bits/cow_string.h
@@ -911,13 +911,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       ///  null-termination.
       size_type
       size() const _GLIBCXX_NOEXCEPT
-      { return _M_rep()->_M_length; }
+      {
+#if _GLIBCXX_FULLY_DYNAMIC_STRING =3D=3D 0 && __OPTIMIZE__
+       if (_M_rep() =3D=3D &_S_empty_rep() && _M_rep()->_M_length !=3D 0)
+         __builtin_unreachable();
+#endif
+       return _M_rep()->_M_length;
+      }

       ///  Returns the number of characters in the string, not including a=
ny
       ///  null-termination.
       size_type
       length() const _GLIBCXX_NOEXCEPT
-      { return _M_rep()->_M_length; }
+      {
+#if _GLIBCXX_FULLY_DYNAMIC_STRING =3D=3D 0 && __OPTIMIZE__
+       if (_M_rep() =3D=3D &_S_empty_rep() && _M_rep()->_M_length !=3D 0)
+         __builtin_unreachable();
+#endif
+       return _M_rep()->_M_length;
+      }

       ///  Returns the size() of the largest possible %string.
       size_type=