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 21999385DC1A; Sat, 16 Jan 2021 08:30:56 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 21999385DC1A
From: "m.krause@tu-harburg.de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/98704] New: coroutine_handle::done() == false after
 promise's unhandled_exception() has thrown
Date: Sat, 16 Jan 2021 08:30:55 +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: 11.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: m.krause@tu-harburg.de
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
 attachments.created
Message-ID: <bug-98704-4@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: Sat, 16 Jan 2021 08:30:56 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98704

            Bug ID: 98704
           Summary: coroutine_handle::done() =3D=3D false after promise's
                    unhandled_exception() has thrown
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: m.krause@tu-harburg.de
  Target Milestone: ---

Created attachment 49981
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D49981&action=3Dedit
Reproducer

[dcl.fct.def.coroutine]/14 says: "If the evaluation of the expression
promise.unhandled_exception() exits via an exception, the coroutine is
considered suspended at the final suspend point". So, after this exception =
has
propagated to the caller, I expect that the coroutine_handle's done() funct=
ion
returns true (because of [coroutine.handle.observers]/3 "Returns: true if t=
he
coroutine is suspended at its final suspend point, otherwise false").

However, the compiler for which I am reporting this makes done() return fal=
se
in this situation. See the attached example code (my expectation is 1 inste=
ad
of 0 in the final two lines of output).

By the way, gcc 10.2, gcc trunk, clang 10.0.0, clang trunk, msvc 14.28 all
behave in this way. See the short discussion on Slack Cpplang #coroutines
starting on 02-Jan-2021. A fix for msvc is already underway:
https://developercommunity.visualstudio.com/content/problem/1305540/corouti=
ne-handledone-false-after-promises-unhandle.html=