[Bug c++/46103] New: [c++0x] moving from std::array copies the elements

[Bug c++/46103] New: [c++0x] moving from std::array copies the elements

[marc.glisse at normalesup dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

           Summary: [c++0x] moving from std::array copies the elements
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: marc.glisse@normalesup.org


Hello,

this is probably another "not implemented yet" (although the status page seems
to say that this is done), but I noticed that moving from:
struct A { Type t; };
properly moves t while moving from:
struct B { Type t[1]; };
copies t[0] (this is the case for std::array).

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-10-20 21:10:27 UTC ---
so this would demonstrate the problem?

struct MoveOnly {
  MoveOnly(const MoveOnly&) = delete;
  MoveOnly(MoveOnly&&) { }
  MoveOnly() = default;
};

struct A {
  MoveOnly mo[1];
};

int main() {
  A a;
  A aa = static_cast<A&&>(a);
}

(I haven't checked whether this is valid, or is meant to be implemented yet in
g++)

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[marc.glisse at normalesup dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

--- Comment #2 from marc.glisse at normalesup dot org 2010-10-20 21:30:22 UTC ---
(In reply to comment #1)
> so this would demonstrate the problem?
[snip example]

Yes, precisely.

> I haven't checked whether this is valid

I looked at N3126 around 12.8.17.

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2010-10-20 23:26:33 UTC ---
What if implicitly-defined move-constructors go away again? If I understand
correctly that the bits we are missing are part of the recent work on implicit
moves and the Committee ends up returning to something similar to what we had
before (I didn't follow the pre-meeting exchanges in detail, but seems well
possible, see n3153) maybe we don't have to do much here in GCC ;) Looks like
we should suspend this PR pending the resolution of those thorny issues...

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[marc.glisse at normalesup dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

--- Comment #4 from marc.glisse at normalesup dot org 2010-10-21 05:36:58 UTC ---
Adding an explicit A(A&&)=default; doesn't help, so I don't think this is
related to the implicit stuff. More like a missing piece of code telling the
compiler how to move from an array.

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2010-10-21 09:32:12 UTC ---
Ok, let's add Jason in CC.

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2010.10.22 13:52:19
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> 2010-10-22 18:37:46 UTC ---
Author: jason
Date: Fri Oct 22 18:37:41 2010
New Revision: 165849

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=165849
Log:
    PR c++/46103
    * init.c (build_vec_init): Handle memberwise move.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/implicit10.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/init.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2010-10-22 20:55:59 UTC ---
Fixed.

[Bug c++/46103] [c++0x] moving from std::array copies the elements

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46103

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yacwroy at gmail dot com

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-11-22 12:54:04 UTC ---
*** Bug 46600 has been marked as a duplicate of this bug. ***