When input_iterator<_Out> isn't satisfied, we need to avoid substituting into iter_value_t<_Out> because the latter isn't necessarily well-formed in that case. To that end, this patch rewrites the problematic condition in ranges::unique_copy into a nested requirement which has the correct short-circuiting behavior.
Tested on x86_64-pc-linux-gnu, does this look OK? libstdc++-v3/ChangeLog: * include/bits/ranges_algo.h (__unique_copy_fn::operator()): Rewrite the constexpr if conjunction into a nested requirement for sake of short-circuiting. * testsuite/25_algorithms/unique_copy/100770.cc: New test. --- libstdc++-v3/include/bits/ranges_algo.h | 5 +-- .../25_algorithms/unique_copy/100770.cc | 33 +++++++++++++++++++ 2 files changed, 36 insertions(+), 2 deletions(-) create mode 100644 libstdc++-v3/testsuite/25_algorithms/unique_copy/100770.cc diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h index cda3042c11f..ce4719d5642 100644 --- a/libstdc++-v3/include/bits/ranges_algo.h +++ b/libstdc++-v3/include/bits/ranges_algo.h @@ -1432,8 +1432,9 @@ namespace ranges } return {__next, std::move(++__result)}; } - else if constexpr (input_iterator<_Out> - && same_as<iter_value_t<_Iter>, iter_value_t<_Out>>) + else if constexpr (requires { requires (input_iterator<_Out> + && same_as<iter_value_t<_Iter>, + iter_value_t<_Out>>); }) { *__result = *__first; while (++__first != __last) diff --git a/libstdc++-v3/testsuite/25_algorithms/unique_copy/100770.cc b/libstdc++-v3/testsuite/25_algorithms/unique_copy/100770.cc new file mode 100644 index 00000000000..ea49eb46a18 --- /dev/null +++ b/libstdc++-v3/testsuite/25_algorithms/unique_copy/100770.cc @@ -0,0 +1,33 @@ +// Copyright (C) 2021 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 } } + +// PR libstdc++/100770 + +#include <algorithm> +#include <sstream> + +int main() { + std::istringstream str("42 42 42"); + extern std::ostream out; + std::ranges::unique_copy( + std::istream_iterator<int>(str), + std::istream_iterator<int>(), + std::ostream_iterator<int>(out, " ")); +} -- 2.32.0.rc0