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 BE0613854551; Fri, 18 Nov 2022 21:19:50 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org BE0613854551
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1668806390;
	bh=G7Q6fpz8cE73iIh0CQy5sR5ykLJv72M0DUREyaPxHis=;
	h=From:To:Subject:Date:From;
	b=YObFMpBXs4pVwbAr/6n4F5+90+LsmHwMBJM/7gV9qkdmONyhotsDVV4jkvfwsI4yC
	 ZyNR10s/QOJN2XSJNes0+hxhrwPm9DvTc18qu8L83gc3rRNA08/hi1FEttHA8+wyh1
	 YN8dq8CmVqCLfpQ8PUGDPKE7FBmeT1vj9HjL7zqo=
From: "nightstrike at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107754] New: Confusing -Warray-bounds warning with strcpy
Date: Fri, 18 Nov 2022 21:19:50 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 12.2.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: nightstrike at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-107754-4@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=3D107754

            Bug ID: 107754
           Summary: Confusing -Warray-bounds warning with strcpy
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nightstrike at gmail dot com
  Target Milestone: ---

Metabug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3Dwarray-bounds

// Compile with GCC 12.2.0 with -O2:
//    warning: =E2=80=98strcpy=E2=80=99 offset 0 is out of the bounds [0, 0=
] [-Warray-bounds]
// no warning without -O2

struct Inst;
struct Class { int offset; };

static struct Class * classFoo; // No problem without static here

struct Foo
{
   unsigned int a;   // no problem if commented out
   char bar[1024];
};

void setFoo(struct Inst * this, const char * value)
{
   struct Foo * ptr =3D (struct Foo *)(this ? (((char *)this) + classFoo->o=
ffset)
: 0);
   __builtin_strcpy(ptr->bar, value);
}


$ gcc-12 -c -O2 -Warray-bounds a.c -o /dev/null
a.c: In function 'setFoo':
a.c:19:4: warning: '__builtin_strcpy' offset 0 is out of the bounds [0, 0]
[-Warray-bounds]
   19 |    __builtin_strcpy(ptr->bar, value);
      |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=