[libc++] Take 2: Implement LWG 3158
Summary: LWG 3158 marks the allocator_arg_t constructor of std::tuple as conditionnally explicit based on whether the default constructors of the tuple's members are explicitly default constructible. This was previously committed as r372778 and reverted in r372832 due to the commit breaking LLVM's build in C++14 mode. This issue has now been addressed. Reviewers: mclow.lists Subscribers: christof, jkorous, dexonsmith, libcxx-commits Tags: #libc Differential Revision: https://reviews.llvm.org/D65232 llvm-svn: 373092
This commit is contained in:
Louis Dionne
parent
7ca15ba73f
commit
59e26308e6
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@ -500,20 +500,22 @@ class _LIBCPP_TEMPLATE_VIS tuple
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struct _CheckArgsConstructor<true, _Dummy>
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{
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template <class ..._Args>
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static constexpr bool __enable_implicit_default() {
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struct __enable_implicit_default
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// In C++03, there's no way to implement the resolution of LWG2510.
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#ifdef _LIBCPP_CXX03_LANG
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return true;
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: true_type
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#else
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return __all<__is_implicitly_default_constructible<_Args>::value...>::value;
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: __all<__is_implicitly_default_constructible<_Args>::value...>
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#endif
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}
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{ };
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template <class ..._Args>
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static constexpr bool __enable_explicit_default() {
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return __all<is_default_constructible<_Args>::value...>::value
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&& !__enable_implicit_default<_Args...>();
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}
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struct __enable_explicit_default
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: integral_constant<bool,
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__all<is_default_constructible<_Args>::value...>::value &&
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!__enable_implicit_default<_Args...>::value
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>
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{ };
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template <class ..._Args>
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static constexpr bool __enable_explicit() {
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@ -653,14 +655,14 @@ class _LIBCPP_TEMPLATE_VIS tuple
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public:
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template <bool _Dummy = true, _EnableIf<
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_CheckArgsConstructor<_Dummy>::template __enable_implicit_default<_Tp...>()
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_CheckArgsConstructor<_Dummy>::template __enable_implicit_default<_Tp...>::value
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, void*> = nullptr>
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_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
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tuple()
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_NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
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template <bool _Dummy = true, _EnableIf<
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_CheckArgsConstructor<_Dummy>::template __enable_explicit_default<_Tp...>()
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_CheckArgsConstructor<_Dummy>::template __enable_explicit_default<_Tp...>::value
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, void*> = nullptr>
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explicit _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
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tuple()
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@ -669,12 +671,12 @@ public:
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tuple(tuple const&) = default;
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tuple(tuple&&) = default;
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template <class _AllocArgT, class _Alloc, bool _Dummy = true, class = _EnableIf<
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template <class _AllocArgT, class _Alloc, bool _Dummy = true, _EnableIf<
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_And<
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_IsSame<allocator_arg_t, _AllocArgT>,
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__dependent_type<is_default_constructible<_Tp>, _Dummy>...
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typename _CheckArgsConstructor<_Dummy>::template __enable_implicit_default<_Tp...>
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>::value
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>
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, void*> = nullptr
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>
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_LIBCPP_INLINE_VISIBILITY
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tuple(_AllocArgT, _Alloc const& __a)
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@ -683,6 +685,20 @@ public:
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typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
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__tuple_types<_Tp...>()) {}
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template <class _AllocArgT, class _Alloc, bool _Dummy = true, _EnableIf<
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_And<
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_IsSame<allocator_arg_t, _AllocArgT>,
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typename _CheckArgsConstructor<_Dummy>::template __enable_explicit_default<_Tp...>
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>::value
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, void*> = nullptr
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>
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explicit _LIBCPP_INLINE_VISIBILITY
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tuple(_AllocArgT, _Alloc const& __a)
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: __base_(allocator_arg_t(), __a,
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__tuple_indices<>(), __tuple_types<>(),
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typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
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__tuple_types<_Tp...>()) {}
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template <bool _Dummy = true,
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typename enable_if
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<
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@ -0,0 +1,33 @@
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++98, c++03
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// <tuple>
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// template <class... Types> class tuple;
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// template <class Alloc>
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// explicit(see-below) tuple(allocator_arg_t, const Alloc& a);
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// Make sure we get the explicit-ness of the constructor right.
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// This is LWG 3158.
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#include <tuple>
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#include <memory>
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struct ExplicitDefault { explicit ExplicitDefault() { } };
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std::tuple<ExplicitDefault> explicit_default_test() {
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return {std::allocator_arg, std::allocator<int>()}; // expected-error {{chosen constructor is explicit in copy-initialization}}
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}
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int main(int, char**) {
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return 0;
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}
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@ -13,7 +13,7 @@
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// template <class... Types> class tuple;
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// template <class Alloc>
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// tuple(allocator_arg_t, const Alloc& a);
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// explicit(see-below) tuple(allocator_arg_t, const Alloc& a);
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// NOTE: this constructor does not currently support tags derived from
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// allocator_arg_t because libc++ has to deduce the parameter as a template
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@ -358,7 +358,7 @@
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<tr><td><a href="https://wg21.link/LWG3182">3182</a></td><td>Specification of <tt>Same</tt> could be clearer</td><td>Kona</td><td></td></tr>
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<tr><td></td><td></td><td></td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG2899">2899</a></td><td><tt>is_(nothrow_)move_constructible</tt> and <tt>tuple</tt>, <tt>optional</tt> and <tt>unique_ptr</tt></td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG2899">2899</a></td><td><tt>is_(nothrow_)move_constructible</tt> and <tt>tuple</tt>, <tt>optional</tt> and <tt>unique_ptr</tt></td><td>Cologne</td><td>Complete</td></tr>
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<tr><td><a href="https://wg21.link/LWG3055">3055</a></td><td><tt>path::operator+=(<i>single-character</i>)</tt> misspecified</td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG3158">3158</a></td><td><tt>tuple(allocator_arg_t, const Alloc&)</tt> should be conditionally explicit</td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG3169">3169</a></td><td><tt>ranges</tt> permutation generators discard useful information</td><td>Cologne</td><td></td></tr>
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@ -61,7 +61,7 @@
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<tr><th>Issue #</th><th>Has P/R</th><th>Issue Name</th><th>Meeting</th><th>Status</th></tr>
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<tr><td><a href="https://wg21.link/LWG2899">2899</a></td><td>Yes</td><td><tt>is_(nothrow_)move_constructible</tt> and <tt>tuple</tt>, <tt>optional</tt> and <tt>unique_ptr</tt></td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG3055">3055</a></td><td>Yes</td><td><tt>path::operator+=(<i>single-character</i>)</tt> misspecified</td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG3158">3158</a></td><td>Yes</td><td><tt>tuple(allocator_arg_t, const Alloc&)</tt> should be conditionally explicit</td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG3158">3158</a></td><td>Yes</td><td><tt>tuple(allocator_arg_t, const Alloc&)</tt> should be conditionally explicit</td><td>Cologne</td><td>Complete</td></tr>
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<tr><td><a href="https://wg21.link/LWG3169">3169</a></td><td>Yes</td><td><tt>ranges</tt> permutation generators discard useful information</td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG3183">3183</a></td><td>Yes</td><td>Normative permission to specialize Ranges variable templates</td><td>Cologne</td><td></td></tr>
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<tr><td><a href="https://wg21.link/LWG3184">3184</a></td><td>Yes</td><td>Inconsistencies in <tt>bind_front</tt> wording</td><td>Cologne</td><td></td></tr>
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@ -95,7 +95,6 @@
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<ul>
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<li>2899 - Louis</li>
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<li>3055 - Eric?</li>
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<li>3158 - Louis</li>
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<li>3169 - We don't do ranges yet</li>
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<li>3183 - We don't do ranges yet</li>
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<li>3184 - We don't do bind_front yet</li>
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