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From: Nathan Sidwell <nathan@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc/devel/c++-modules] libstdc++: Define converting assignment operator for std::move_iterator Date: Thu, 25 Jun 2020 14:27:25 +0000 (GMT) [thread overview] Message-ID: <20200625142725.D6F12386F83C@sourceware.org> (raw) https://gcc.gnu.org/g:733167f9d5ca5b9417559b7362d91e967be95a01 commit 733167f9d5ca5b9417559b7362d91e967be95a01 Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Jun 9 22:16:24 2020 +0100 libstdc++: Define converting assignment operator for std::move_iterator As clarified by LWG 3265, std::move_iterator is supposed to have an assignment operator that converts from a different specialization of std::move_iterator, which performs an assignment. That has always been missing from libstdc++, so assigning a different type actually performs a converting construction, then an assignment. This is non-conforming for the (fairly contrived) case where the converting assignment is well-formed but the converting construction is not. * include/bits/stl_iterator.h (move_iterator::operator=): Define. * testsuite/24_iterators/move_iterator/dr3265.cc: New test. Diff: --- libstdc++-v3/include/bits/stl_iterator.h | 8 ++++ .../testsuite/24_iterators/move_iterator/dr3265.cc | 51 ++++++++++++++++++++++ 2 files changed, 59 insertions(+) diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h index 72907813bf5..6d2d19eb068 100644 --- a/libstdc++-v3/include/bits/stl_iterator.h +++ b/libstdc++-v3/include/bits/stl_iterator.h @@ -1307,6 +1307,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION move_iterator(const move_iterator<_Iter>& __i) : _M_current(__i.base()) { } + template<typename _Iter> + _GLIBCXX17_CONSTEXPR + move_iterator& operator=(const move_iterator<_Iter>& __i) + { + _M_current = __i.base(); + return *this; + } + #if __cplusplus <= 201703L _GLIBCXX17_CONSTEXPR iterator_type base() const diff --git a/libstdc++-v3/testsuite/24_iterators/move_iterator/dr3265.cc b/libstdc++-v3/testsuite/24_iterators/move_iterator/dr3265.cc new file mode 100644 index 00000000000..05327e979ac --- /dev/null +++ b/libstdc++-v3/testsuite/24_iterators/move_iterator/dr3265.cc @@ -0,0 +1,51 @@ +// 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-do compile { target c++11 } } + +#include <iterator> + +struct Iter +{ + using iterator_category = std::forward_iterator_tag; + using value_type = int; + using pointer = int*; + using reference = int&; + using difference_type = std::ptrdiff_t; + + Iter(); + + // Construction from int* is not valid: + Iter(int*) = delete; + + // Assignment from int* is valid: + Iter& operator=(int*); + + Iter& operator++(); + Iter operator++(int); + int& operator*() const; + int* operator->() const; + + template<int N> friend bool operator==(Iter, Iter); +}; + +void test01() +{ + std::move_iterator<Iter> m; + int i = 0; + m = std::make_move_iterator(&i); // Should use assignment not construction +}
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