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 86310385841C; Mon,  7 Feb 2022 17:46:46 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 86310385841C
From: "pdimov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/104426] New: -fsanitize=undefined causes constexpr failures
Date: Mon, 07 Feb 2022 17:46:46 +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: 12.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pdimov 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-104426-4@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
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Mon, 07 Feb 2022 17:46:46 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104426

            Bug ID: 104426
           Summary: -fsanitize=3Dundefined causes constexpr failures
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pdimov at gmail dot com
  Target Milestone: ---

The following program

```
struct category
{
    constexpr bool failed() const noexcept
    {
        return true;
    }
};

inline constexpr category s_cat;

struct condition
{
    category const* cat_;

    constexpr bool failed() const noexcept
    {
        if( cat_ )
        {
            return cat_->failed();
        }
        else
        {
            return false;
        }
    }
};

int main()
{
    constexpr condition cond{ &s_cat };
    static_assert( cond.failed() );
}
```

compiles without -fsanitize=3Dundefined (https://godbolt.org/z/Pn9M5ocfz), =
but
fails with it (https://godbolt.org/z/KKc8Tb9qe) with

```
<source>: In function 'int main()':
<source>:31:31: error: non-constant condition for static assertion
   31 |     static_assert( cond.failed() );
      |                    ~~~~~~~~~~~^~
<source>:31:31:   in 'constexpr' expansion of 'cond.condition::failed()'
<source>:17:13: error: '((& s_cat) !=3D 0)' is not a constant expression
   17 |         if( cat_ )
      |             ^~~~
```

This happens under all GCC versions starting from 7.

(The above is an extract from the test suite for
boost::system::error_condition.)=