| Message ID | CAFk2RUbYNFUtBa4e4-_FK1WNbpQpkq36mTZrMppxasL6Kn9HqA@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | libstdc++: std::variant with multiple identical types assignment fail to compile [PR91807] | expand |
On Wed, 1 Jul 2020 at 20:46, Ville Voutilainen <ville.voutilainen@gmail.com> wrote: > > Looks like just a small thinko. We construct a temporary and move-construct > from it, but we should construct the temporary with the right index. > > OK for trunk and gcc-10 if full tests pass? > > 2020-07-01 Ville Voutilainen <ville.voutilainen@gmail.com> > > PR libstdc++/91807 > * include/std/variant > (_Copy_assign_base::operator=(const _Copy_assign_base&): > Do the move-construction from a temporary so that the temporary > is constructed with an explicit index. > * testsuite/20_util/variant/91807.cc: New. And sure, s/move-construction/move-assignment/.
On Wed, 1 Jul 2020 at 21:09, Ville Voutilainen
<ville.voutilainen@gmail.com> wrote:
> And sure, s/move-construction/move-assignment/.
And with dg-options.
2020-07-01 Ville Voutilainen <ville.voutilainen@gmail.com>
PR libstdc++/91807
* include/std/variant
(_Copy_assign_base::operator=(const _Copy_assign_base&):
Do the move-assignment from a temporary so that the temporary
is constructed with an explicit index.
* testsuite/20_util/variant/91807.cc: New.
On 01/07/20 23:32 +0300, Ville Voutilainen via Libstdc++ wrote: >On Wed, 1 Jul 2020 at 21:09, Ville Voutilainen ><ville.voutilainen@gmail.com> wrote: >> And sure, s/move-construction/move-assignment/. > >And with dg-options. OK for master and gcc-10, thanks. Does it apply cleanly to gcc-9 too?
On Wed, 1 Jul 2020 at 23:53, Jonathan Wakely <jwakely@redhat.com> wrote: > > On 01/07/20 23:32 +0300, Ville Voutilainen via Libstdc++ wrote: > >On Wed, 1 Jul 2020 at 21:09, Ville Voutilainen > ><ville.voutilainen@gmail.com> wrote: > >> And sure, s/move-construction/move-assignment/. > > > >And with dg-options. > > OK for master and gcc-10, thanks. > > Does it apply cleanly to gcc-9 too? Yes. I managed to misremember where the new variant implementation landed and misread the bug title/version, so backporting there, too.
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant index c9504914365..eb3d6779205 100644 --- a/libstdc++-v3/include/std/variant +++ b/libstdc++-v3/include/std/variant @@ -611,7 +611,8 @@ namespace __variant this->_M_destructive_copy(__rhs_index, __rhs_mem); else __variant_cast<_Types...>(*this) - = variant<_Types...>(__rhs_mem); + = variant<_Types...>(std::in_place_index<__rhs_index>, + __rhs_mem); } } else diff --git a/libstdc++-v3/testsuite/20_util/variant/91807.cc b/libstdc++-v3/testsuite/20_util/variant/91807.cc new file mode 100644 index 00000000000..ddede7c9b32 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/variant/91807.cc @@ -0,0 +1,34 @@ +// { dg-do compile { target c++17 } } + +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +#include <variant> + +struct me_data { + me_data() = default; + + me_data(const me_data &) {}; + me_data(me_data &&) noexcept {}; + me_data& operator=(const me_data &) = default; +}; + +int main() { + std::variant<me_data, me_data> v1, v2; + + v2 = v1; +}
Looks like just a small thinko. We construct a temporary and move-construct from it, but we should construct the temporary with the right index. OK for trunk and gcc-10 if full tests pass? 2020-07-01 Ville Voutilainen <ville.voutilainen@gmail.com> PR libstdc++/91807 * include/std/variant (_Copy_assign_base::operator=(const _Copy_assign_base&): Do the move-construction from a temporary so that the temporary is constructed with an explicit index. * testsuite/20_util/variant/91807.cc: New.