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From: Alexandre Oliva <aoliva@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc(refs/users/aoliva/heads/testbase)] libstdc++: Constrain std::make_optional Date: Wed, 22 Jul 2020 07:50:53 +0000 (GMT) [thread overview] Message-ID: <20200722075053.EB5593890431@sourceware.org> (raw) https://gcc.gnu.org/g:bcfe4681f9be68f96f0610f30356510ff518806b commit bcfe4681f9be68f96f0610f30356510ff518806b Author: Jonathan Wakely <jwakely@redhat.com> Date: Mon Jul 6 21:54:12 2020 +0100 libstdc++: Constrain std::make_optional The standard rquires that std::make_optional is constrained similarly to the std::optional constructors, which our implementation fails to do. As a conforming extension this also adds a noexcept-specifier to each std::make_optional overload. libstdc++-v3/ChangeLog: * include/std/optional (make_optional): Add enable_if constraints and noexcept-specifier to each overload. * testsuite/20_util/optional/make_optional-2.cc: New test. Diff: --- libstdc++-v3/include/std/optional | 25 ++++-- .../testsuite/20_util/optional/make_optional-2.cc | 94 ++++++++++++++++++++++ 2 files changed, 111 insertions(+), 8 deletions(-) diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional index 785c434412d..24821f81d0f 100644 --- a/libstdc++-v3/include/std/optional +++ b/libstdc++-v3/include/std/optional @@ -1220,19 +1220,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION swap(optional<_Tp>&, optional<_Tp>&) = delete; template<typename _Tp> - constexpr optional<decay_t<_Tp>> + constexpr + enable_if_t<is_constructible_v<decay_t<_Tp>, _Tp>, + optional<decay_t<_Tp>>> make_optional(_Tp&& __t) - { return optional<decay_t<_Tp>> { std::forward<_Tp>(__t) }; } + noexcept(is_nothrow_constructible_v<optional<decay_t<_Tp>>, _Tp>) + { return optional<decay_t<_Tp>>{ std::forward<_Tp>(__t) }; } - template<typename _Tp, typename ..._Args> - constexpr optional<_Tp> + template<typename _Tp, typename... _Args> + constexpr + enable_if_t<is_constructible_v<_Tp, _Args...>, + optional<_Tp>> make_optional(_Args&&... __args) - { return optional<_Tp> { in_place, std::forward<_Args>(__args)... }; } + noexcept(is_nothrow_constructible_v<_Tp, _Args...>) + { return optional<_Tp>{ in_place, std::forward<_Args>(__args)... }; } - template<typename _Tp, typename _Up, typename ..._Args> - constexpr optional<_Tp> + template<typename _Tp, typename _Up, typename... _Args> + constexpr + enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, + optional<_Tp>> make_optional(initializer_list<_Up> __il, _Args&&... __args) - { return optional<_Tp> { in_place, __il, std::forward<_Args>(__args)... }; } + noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>) + { return optional<_Tp>{ in_place, __il, std::forward<_Args>(__args)... }; } // Hash. diff --git a/libstdc++-v3/testsuite/20_util/optional/make_optional-2.cc b/libstdc++-v3/testsuite/20_util/optional/make_optional-2.cc new file mode 100644 index 00000000000..65a1fc78d80 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/optional/make_optional-2.cc @@ -0,0 +1,94 @@ +// { 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 <optional> + +int i; + +struct Cont +{ + Cont() noexcept; + Cont(Cont&&) noexcept; + Cont(const Cont&); + Cont(int); + Cont(std::initializer_list<int>, int) noexcept; + Cont(std::initializer_list<int>, const char*); +}; +const Cont c{}; + +template<typename T, typename = void> + struct can_make_optional1 + : std::false_type + { }; + +template<typename T> + struct can_make_optional1<T, + std::void_t<decltype(std::make_optional(std::declval<T>()))>> + : std::true_type + { }; + +static_assert( can_make_optional1<int>::value ); +static_assert( noexcept(std::make_optional(1)) ); +static_assert( can_make_optional1<int&>::value ); +static_assert( noexcept(std::make_optional(i)) ); +static_assert( ! can_make_optional1<void>::value ); +static_assert( can_make_optional1<Cont>::value ); +static_assert( noexcept(std::make_optional(Cont{})) ); +static_assert( can_make_optional1<Cont>::value ); +static_assert( ! noexcept(std::make_optional(c)) ); + +template<typename T, typename Arg, typename = void> + struct can_make_optional2 + : std::false_type + { }; + +template<typename T, typename Arg> + struct can_make_optional2<T, Arg, + std::void_t<decltype(std::make_optional<T>(std::declval<Arg>()))>> + : std::true_type + { }; + +static_assert( can_make_optional2<int, int>::value ); +static_assert( noexcept(std::make_optional<int>(1)) ); +static_assert( can_make_optional2<int, int&>::value ); +static_assert( noexcept(std::make_optional(i)) ); +static_assert( ! can_make_optional2<void, void>::value ); +static_assert( can_make_optional2<Cont, Cont>::value ); +static_assert( noexcept(std::make_optional<Cont>({})) ); +static_assert( can_make_optional2<Cont, const Cont&>::value ); +static_assert( ! noexcept(std::make_optional(c)) ); +static_assert( can_make_optional2<Cont, int>::value ); +static_assert( ! noexcept(std::make_optional<Cont>(1)) ); + +template<typename T, typename Arg, typename = void> + struct can_make_optional3 + : std::false_type + { }; + +template<typename T, typename Arg> + struct can_make_optional3<T, Arg, + std::void_t<decltype(std::make_optional<T>({1,2}, std::declval<Arg>()))>> + : std::true_type + { }; + +static_assert( can_make_optional3<Cont, int>::value ); +static_assert( noexcept(std::make_optional<Cont>({1,2}, 1)) ); +static_assert( can_make_optional3<Cont, char*>::value ); +static_assert( ! noexcept(std::make_optional<Cont>({1,2}, "")) ); +static_assert( !can_make_optional3<Cont, int*>::value );
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