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[libc++] Implement std::experimental::observer_ptr
This patch adds std::experimental::observer_ptr (n4282) and also fixes LWG2516. Co-Authored-By: Louis Dionne <[email protected]> Differential Revision: https://reviews.llvm.org/D63230
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‎libcxx/docs/Status/Cxx17Issues.csv‎

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"`2441 <https://wg21.link/LWG2441>`__","Exact-width atomic typedefs should be provided","Oulu","|Complete|",""
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"`2451 <https://wg21.link/LWG2451>`__","[fund.ts.v2] optional should 'forward' T's implicit conversions","Oulu","|Nothing To Do|",""
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"`2509 <https://wg21.link/LWG2509>`__","[fund.ts.v2] any_cast doesn't work with rvalue reference targets and cannot move with a value target","Oulu","|Complete|",""
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"`2516 <https://wg21.link/LWG2516>`__","[fund.ts.v2] Public ""exposition only"" members in observer_ptr","Oulu","",""
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"`2516 <https://wg21.link/LWG2516>`__","[fund.ts.v2] Public ""exposition only"" members in observer_ptr","Oulu","|Complete|","18.0"
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"`2542 <https://wg21.link/LWG2542>`__","Missing const requirements for associative containers","Oulu","",""
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"`2549 <https://wg21.link/LWG2549>`__","Tuple EXPLICIT constructor templates that take tuple parameters end up taking references to temporaries and will create dangling references","Oulu","|Complete|",""
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"`2550 <https://wg21.link/LWG2550>`__","Wording of unordered container's clear() method complexity","Oulu","|Complete|",""

‎libcxx/include/CMakeLists.txt‎

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experimental/iterator
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experimental/list
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experimental/map
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experimental/memory
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experimental/memory_resource
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experimental/propagate_const
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experimental/regex

‎libcxx/include/__std_clang_module‎

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#include <experimental/iterator>
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#include <experimental/list>
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#include <experimental/map>
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#include <experimental/memory>
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#include <experimental/memory_resource>
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#include <experimental/propagate_const>
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#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)

‎libcxx/include/experimental/memory‎

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// -*- C++ -*-
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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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#ifndef _LIBCPP_EXPERIMENTAL_MEMORY
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#define _LIBCPP_EXPERIMENTAL_MEMORY
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/*
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experimental/memory synopsis
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namespace std::experimental::inline fundamentals_v2 {
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template <class W> class observer_ptr {
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public:
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using element_type = W;
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using pointer = add_pointer_t<W>; // exposition-only
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using reference = add_lvalue_reference_t<W>; // exposition-only
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// default ctor
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constexpr observer_ptr() noexcept;
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// pointer-accepting ctors
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constexpr observer_ptr(nullptr_t) noexcept;
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constexpr explicit observer_ptr(pointer) noexcept;
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// copying ctors (in addition to compiler-generated copy ctor)
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template <class W2> constexpr observer_ptr(observer_ptr<W2>) noexcept;
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// observers
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constexpr pointer get() const noexcept;
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constexpr reference operator*() const;
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constexpr pointer operator->() const noexcept;
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constexpr explicit operator bool() const noexcept;
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// conversions
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constexpr explicit operator pointer() const noexcept;
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// modifiers
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constexpr pointer release() noexcept;
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constexpr void reset(pointer = nullptr) noexcept;
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constexpr void swap(observer_ptr&) noexcept;
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};
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}
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*/
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#include <__functional/hash.h>
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#include <__functional/operations.h>
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#include <__type_traits/add_lvalue_reference.h>
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#include <__type_traits/add_pointer.h>
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#include <__type_traits/common_type.h>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/is_convertible.h>
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#include <cstddef>
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#include <experimental/__config>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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#ifdef _LIBCPP_ENABLE_EXPERIMENTAL
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_LIBCPP_BEGIN_NAMESPACE_LFTS_V2
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# if _LIBCPP_STD_VER >= 17
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template <class _Wp>
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class observer_ptr {
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public:
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using element_type = _Wp;
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// constructors
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_LIBCPP_HIDE_FROM_ABI constexpr observer_ptr() noexcept : __ptr_(nullptr) {}
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_LIBCPP_HIDE_FROM_ABI constexpr observer_ptr(nullptr_t) noexcept : __ptr_(nullptr) {}
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_LIBCPP_HIDE_FROM_ABI constexpr explicit observer_ptr(element_type* __p) noexcept : __ptr_(__p) {}
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template <class _W2, class = __enable_if_t<is_convertible<_W2*, _Wp*>::value>>
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_LIBCPP_HIDE_FROM_ABI constexpr observer_ptr(observer_ptr<_W2> __other) noexcept : __ptr_(__other.get()) {}
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// observers
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_LIBCPP_HIDE_FROM_ABI constexpr element_type* get() const noexcept { return __ptr_; }
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_LIBCPP_HIDE_FROM_ABI constexpr add_lvalue_reference_t<_Wp> operator*() const { return *__ptr_; }
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_LIBCPP_HIDE_FROM_ABI constexpr element_type* operator->() const noexcept { return __ptr_; }
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_LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return __ptr_ != nullptr; }
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// conversions
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_LIBCPP_HIDE_FROM_ABI constexpr explicit operator element_type*() const noexcept { return __ptr_; }
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// modifiers
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_LIBCPP_HIDE_FROM_ABI constexpr void reset(element_type* __p = nullptr) noexcept { __ptr_ = __p; }
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_LIBCPP_HIDE_FROM_ABI constexpr void swap(observer_ptr& __other) noexcept {
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observer_ptr __tmp = __other;
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__other = *this;
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*this = __tmp;
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}
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_LIBCPP_HIDE_FROM_ABI constexpr element_type* release() noexcept {
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observer_ptr __p;
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__p.swap(*this);
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return __p.get();
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}
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private:
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element_type* __ptr_;
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};
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// specializations
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template <class _Wp>
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_LIBCPP_HIDE_FROM_ABI constexpr void swap(observer_ptr<_Wp>& __a, observer_ptr<_Wp>& __b) noexcept {
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__a.swap(__b);
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}
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template <class _Wp>
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_LIBCPP_HIDE_FROM_ABI observer_ptr<_Wp> make_observer(_Wp* __ptr) noexcept {
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return observer_ptr<_Wp>{__ptr};
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}
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template <class _W1, class _W2>
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_LIBCPP_HIDE_FROM_ABI bool operator==(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
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return __a.get() == __b.get();
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}
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template <class _W1, class _W2>
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_LIBCPP_HIDE_FROM_ABI bool operator!=(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
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return !(__a == __b);
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}
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template <class _Wp>
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_LIBCPP_HIDE_FROM_ABI bool operator==(observer_ptr<_Wp> __p, nullptr_t) {
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return !__p;
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}
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template <class _Wp>
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_LIBCPP_HIDE_FROM_ABI bool operator==(nullptr_t, observer_ptr<_Wp> __p) {
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return !__p;
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}
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template <class _Wp>
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_LIBCPP_HIDE_FROM_ABI bool operator!=(observer_ptr<_Wp> __p, nullptr_t) {
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return (bool)__p;
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}
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template <class _Wp>
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_LIBCPP_HIDE_FROM_ABI bool operator!=(nullptr_t, observer_ptr<_Wp> __p) {
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return (bool)__p;
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}
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template <class _W1, class _W2>
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_LIBCPP_HIDE_FROM_ABI bool operator<(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
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return std::less<typename std::common_type<_W1*, _W2*>::type>()(__a.get(), __b.get());
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}
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template <class _W1, class _W2>
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_LIBCPP_HIDE_FROM_ABI bool operator>(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
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return __b < __a;
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}
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template <class _W1, class _W2>
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_LIBCPP_HIDE_FROM_ABI bool operator<=(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
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return !(__a > __b);
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}
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template <class _W1, class _W2>
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_LIBCPP_HIDE_FROM_ABI bool operator>=(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
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return !(__a < __b);
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}
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# endif // _LIBCPP_STD_VER >= 17
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_LIBCPP_END_NAMESPACE_LFTS_V2
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_LIBCPP_BEGIN_NAMESPACE_STD
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// hash
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# if _LIBCPP_STD_VER >= 17
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template <class _Tp>
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struct hash<experimental::observer_ptr<_Tp>> {
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_LIBCPP_HIDE_FROM_ABI size_t operator()(const experimental::observer_ptr<_Tp>& __ptr) const noexcept {
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return hash<_Tp*>()(__ptr.get());
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}
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};
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# endif // _LIBCPP_STD_VER >= 17
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_ENABLE_EXPERIMENTAL
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#endif /* _LIBCPP_EXPERIMENTAL_MEMORY */

‎libcxx/include/module.modulemap.in‎

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header "experimental/map"
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export *
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}
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module memory {
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header "experimental/memory"
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export *
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}
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module memory_resource {
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header "experimental/memory_resource"
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export *

‎libcxx/test/libcxx/transitive_includes/cxx03.csv‎

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experimental/list list
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experimental/map experimental/memory_resource
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experimental/map map
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experimental/memory cstddef
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experimental/memory cstdint
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experimental/memory cstring
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experimental/memory limits
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experimental/memory_resource atomic
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experimental/memory_resource climits
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experimental/memory_resource concepts

‎libcxx/test/libcxx/transitive_includes/cxx11.csv‎

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experimental/list list
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experimental/map experimental/memory_resource
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experimental/map map
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experimental/memory cstddef
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experimental/memory cstdint
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experimental/memory cstring
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experimental/memory limits
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experimental/memory_resource atomic
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experimental/memory_resource climits
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experimental/memory_resource concepts

‎libcxx/test/libcxx/transitive_includes/cxx14.csv‎

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experimental/list list
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experimental/map experimental/memory_resource
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experimental/map map
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experimental/memory cstddef
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experimental/memory cstdint
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experimental/memory cstring
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experimental/memory limits
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experimental/memory_resource atomic
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experimental/memory_resource climits
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experimental/memory_resource concepts

‎libcxx/test/libcxx/transitive_includes/cxx17.csv‎

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experimental/list list
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experimental/map experimental/memory_resource
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experimental/map map
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experimental/memory cstddef
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experimental/memory cstdint
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experimental/memory cstring
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experimental/memory limits
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experimental/memory_resource atomic
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experimental/memory_resource climits
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experimental/memory_resource concepts

‎libcxx/test/libcxx/transitive_includes/cxx20.csv‎

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experimental/list list
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experimental/map experimental/memory_resource
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experimental/map map
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experimental/memory cstddef
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experimental/memory cstdint
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experimental/memory cstring
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experimental/memory limits
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experimental/memory_resource atomic
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experimental/memory_resource climits
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experimental/memory_resource concepts

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