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 28CF33858C52; Wed, 11 Oct 2023 15:59:41 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 28CF33858C52
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1697039981;
	bh=JhbPvgDtIr3fF2P/asHNgPQsCP1wFLYGIYS3MjTSmkA=;
	h=From:To:Subject:Date:From;
	b=wAeCRYtS9QP8WX6678sj3Q8wo1BxEilSr1aqAjV9+RBebKbRGVzBcKinlU+ynBSk5
	 OtPQLXj/nj8z7++f+u+29ffJPFTB0GJzs2JNagol59raTlHYwfO4xcSoNh2OBe4dAN
	 CiD4nx8X1GxJuPt3mBZkTmYey2kitn7XsbrynjUM=
From: "vlad at solidsands dot nl" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/111773] New: Inconsistent optimization of replaced operator
 new()
Date: Wed, 11 Oct 2023 15:59:40 +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: 13.2.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: vlad at solidsands dot nl
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-111773-4@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=3D111773

            Bug ID: 111773
           Summary: Inconsistent optimization of replaced operator new()
           Product: gcc
           Version: 13.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vlad at solidsands dot nl
  Target Milestone: ---

#include <new>
#include <cstdint>
#include <cstdio>

int a[10];
void* operator new(std::size_t) {
    return a;
}

int main() {
    int* p =3D static_cast<int*>(::operator new(sizeof(int)));

    std::ptrdiff_t x =3D a - p;

    printf("%ld %d", x, x =3D=3D 0);

    return 0;
}


Here, GCC with -O1 optimizes 'x' to 0 and 'x =3D=3D 0' to false at the same=
 time.

Compiler explorer link: https://godbolt.org/z/4Y3eeY56r

---
Also, possibly related:

#include <new>

void* operator new(std::size_t sz)
{
    throw std::bad_alloc{};
}

int main()
{
    int* p1 =3D static_cast<int*>(::operator new(sizeof(int)));

    return 10;
}

Here, again with -O1, terminate is not called, and the program returned
successfully. However, the program returned 0 instead of 10.

Compiler explorer link: https://godbolt.org/z/9oczTzP7s=