[Bug c++/66583] New: incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[Bug c++/66583] New: incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[jens.maurer at gmx dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66583

            Bug ID: 66583
           Summary: incorrect implicitly-defined move constructor for
                    class with anonymous union and NSDMI
           Product: gcc
           Version: 5.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jens.maurer at gmx dot net
  Target Milestone: ---

The following code wrongly prints 0 instead of the correct 1:

$ g++ -std=c++11 union.cc 
$ ./a.out 
0

(reproducible with both 4.9.2 and 5.1.0)


#include <algorithm>
#include <iostream>

struct A {
  A() { };
  A(const A&) { }
};

struct B {
  union {
    int m_1 = 0;
    int m_2;
  };
  A dummy;
};

int main()
{
  B b;
  b.m_1 = 1;
  B c(std::move(b));
  std::cout << c.m_1 << std::endl;
}


The assembly code for B::B(B&&) when compiling unoptimized has this (x86-64):

        movl    (%rdx), %edx
        movl    %edx, (%rax)

Until here, we correctly copy the object representation of the anonymous union
(12.8p16).

        movq    -8(%rbp), %rax
        movl    $0, (%rax)

And then we seem to evaluate the non-static data member initializer for m_1,
which is (obviously) wrong.

[Bug c++/66583] incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66583

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
The problem seems to exists for the current head gcc HEAD 6.0.0 20150617
(experimental) as well.
>From gcc-bugs-return-489337-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Jun 18 17:09:06 2015
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From: "jason at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/66585] [5/6 Regression] Internal compiler error when initialize field with lambda
Date: Thu, 18 Jun 2015 17:09:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf585

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org

[Bug c++/66583] incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66583

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2015-10-21
                 CC|                            |jason at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
     Ever confirmed|0                           |1

[Bug c++/66583] incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66583

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Wed Oct 21 02:24:08 2015
New Revision: 229108

URL: https://gcc.gnu.org/viewcvs?rev=229108&root=gcc&view=rev
Log:
        PR c++/66583

        * init.c (innermost_aggr_scope): New.
        (build_field_list): Change uses_unions_p to uses_unions_or_anon_p.
        (sort_mem_initializers): Handle initializers for entire anonymous
        aggregates.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/anon-union1.C
    trunk/gcc/testsuite/g++.dg/ext/anon-struct7.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/init.c

[Bug c++/66583] incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66583

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Wed Oct 21 09:27:18 2015
New Revision: 229122

URL: https://gcc.gnu.org/viewcvs?rev=229122&root=gcc&view=rev
Log:
        PR c++/66583

        * init.c (innermost_aggr_scope): New.
        (sort_mem_initializers): Use it.

Added:
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp0x/anon-union1.C
Modified:
    branches/gcc-5-branch/gcc/cp/ChangeLog
    branches/gcc-5-branch/gcc/cp/init.c

[Bug c++/66583] incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66583

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |5.3

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 5.3/6.

[Bug c++/66583] incorrect implicitly-defined move constructor for class with anonymous union and NSDMI

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66583

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |akju at mailinator dot com

--- Comment #5 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
*** Bug 68051 has been marked as a duplicate of this bug. ***