[Bug c++/60284] New: Default-initialization without user-provided constructor allowed

[Bug c++/60284] New: Default-initialization without user-provided constructor allowed

[potswa at mac dot com]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60284

            Bug ID: 60284
           Summary: Default-initialization without user-provided
                    constructor allowed
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: potswa at mac dot com

This declaration is ill-formed according to the last sentence of [dcl.init]
§8.5/7, "If a program calls for the default initialization of an object of a
const-qualified type T, T shall be a class type with a user-provided default
constructor":

struct a {} const o;

There is actually a very nice diagnostic implemented by r179170 and PR42844,
but it's only activated when the class has an uninitialized member, per the
notes of CWG DR 253. However those notes aren't normative and Clang diagnoses
the error, http://stackoverflow.com/q/21900237/153285 .
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From: "petr.kmoch at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/60285] std::list<T>::insert(position, x) does not accept const_iterator position
Date: Thu, 20 Feb 2014 08:53:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`285

--- Comment #1 from Petr Kmoch <petr.kmoch at gmail dot com> ---
Created attachment 32177
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id2177&actioníit
gcc -v output when building test case

[Bug c++/60284] [DR 253] Default-initialization without user-provided constructor allowed

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60284

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |SUSPENDED
   Last reconfirmed|                            |2014-02-20
            Summary|Default-initialization      |[DR 253]
                   |without user-provided       |Default-initialization
                   |constructor allowed         |without user-provided
                   |                            |constructor allowed
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is by design, because as DR 253 shows, the normative standard is flawed.

[Bug c++/60284] [DR 253] Default-initialization without user-provided constructor allowed

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60284

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|SUSPENDED                   |NEW

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
From cwg253
(https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#253):
[Adopted at the November, 2016 meeting as part of paper P0490R0.]


But I can't tell if it was a adopted as a defect report or just implemented as
part of C++17.