On 25/02/20 12:40 +0000, Jonathan Wakely wrote:
The std::move and std::move_backward algorithms dispatch to the std::__memmove helper when appropriate. That function uses a pointer-to-const for the source values, preventing them from being moved. The two callers of that function have the same problem.Rather than altering __memmove and its callers to work with const or non-const source pointers, this takes a more conservative approach of casting away the const at the point where we want to do a move assignment. This relies on the fact that we only use __memmove when the type is trivially copyable, so we know the move assignment doesn't alter the source anyway. PR libstdc++/93872 * include/bits/stl_algobase.h (__memmove): Cast away const before doing move assignment. * testsuite/25_algorithms/move/93872.cc: New test. * testsuite/25_algorithms/move_backward/93872.cc: New test.
Oops, I forgot to 'git add' one of the new tests. Tested x86_64-linux, committed to master.
commit 6de946e65c9558515a2c31be76853ae7653d4fc9 Author: Jonathan Wakely <[email protected]> Date: Tue Feb 25 12:42:03 2020 +0000 libstdc++: Add test accidentally left out of previous commit * testsuite/25_algorithms/move_backward/93872.cc: Add test left out of previous commit. diff --git a/libstdc++-v3/testsuite/25_algorithms/move_backward/93872.cc b/libstdc++-v3/testsuite/25_algorithms/move_backward/93872.cc new file mode 100644 index 00000000000..69774fa86c6 --- /dev/null +++ b/libstdc++-v3/testsuite/25_algorithms/move_backward/93872.cc @@ -0,0 +1,39 @@ +// 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/>. + +// { dg-options "-std=gnu++2a" } +// { dg-do compile { target c++2a } } + +#include <algorithm> + +struct X +{ + X() = default; + + X(const X&) = delete; + X& operator=(const X&) = delete; + + X(X&&) = default; + X& operator=(X&&) = default; +}; + +void +test01() +{ + X a[2], b[2]; + std::move_backward(std::begin(a), std::end(a), std::begin(b)); +}
