| 1 | // Copyright (C) 2023 The Qt Company Ltd. |
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| 2 | // Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com> |
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| 3 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
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| 4 | |
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| 5 | #ifndef Q20MEMORY_H |
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| 6 | #define Q20MEMORY_H |
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| 7 | |
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| 8 | #include <QtCore/qtconfigmacros.h> |
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| 9 | |
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| 10 | #include <memory> |
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| 11 | |
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| 12 | #include <QtCore/q20type_traits.h> |
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| 13 | #include <utility> |
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| 14 | |
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| 15 | // |
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| 16 | // W A R N I N G |
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| 17 | // ------------- |
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| 18 | // |
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| 19 | // This file is not part of the Qt API. Types and functions defined in this |
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| 20 | // file can reliably be replaced by their std counterparts, once available. |
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| 21 | // You may use these definitions in your own code, but be aware that we |
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| 22 | // will remove them once Qt depends on the C++ version that supports |
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| 23 | // them in namespace std. There will be NO deprecation warning, the |
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| 24 | // definitions will JUST go away. |
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| 25 | // |
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| 26 | // If you can't agree to these terms, don't use these definitions! |
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| 27 | // |
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| 28 | // We mean it. |
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| 29 | // |
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| 30 | |
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| 31 | QT_BEGIN_NAMESPACE |
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| 32 | |
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| 33 | // like std::construct_at (but not whitelisted for constexpr) |
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| 34 | namespace q20 { |
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| 35 | #ifdef __cpp_lib_constexpr_dynamic_alloc |
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| 36 | using std::construct_at; |
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| 37 | #else |
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| 38 | template <typename T, |
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| 39 | typename... Args, |
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| 40 | typename Enable = std::void_t<decltype(::new (std::declval<void *>()) T(std::declval<Args>()...))> > |
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| 41 | T *construct_at(T *ptr, Args && ... args) |
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| 42 | { |
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| 43 | return ::new (const_cast<void *>(static_cast<const volatile void *>(ptr))) |
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| 44 | T(std::forward<Args>(args)...); |
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| 45 | } |
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| 46 | #endif // __cpp_lib_constexpr_dynamic_alloc |
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| 47 | } // namespace q20 |
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| 48 | |
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| 49 | // like std::make_unique_for_overwrite (excl. C++23-added constexpr) |
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| 50 | namespace q20 { |
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| 51 | #ifdef __cpp_lib_smart_ptr_for_overwrite |
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| 52 | using std::make_unique_for_overwrite; |
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| 53 | #else |
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| 54 | // https://eel.is/c++draft/unique.ptr.create#6 |
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| 55 | template <typename T> |
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| 56 | std::enable_if_t<!std::is_array_v<T>, std::unique_ptr<T>> |
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| 57 | make_unique_for_overwrite() |
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| 58 | // https://eel.is/c++draft/unique.ptr.create#7 |
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| 59 | { return std::unique_ptr<T>(new T); } |
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| 60 | |
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| 61 | // https://eel.is/c++draft/unique.ptr.create#8 |
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| 62 | template <typename T> |
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| 63 | std::enable_if_t<q20::is_unbounded_array_v<T>, std::unique_ptr<T>> |
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| 64 | make_unique_for_overwrite(std::size_t n) |
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| 65 | // https://eel.is/c++draft/unique.ptr.create#9 |
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| 66 | { return std::unique_ptr<T>(new std::remove_extent_t<T>[n]); } |
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| 67 | |
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| 68 | // https://eel.is/c++draft/unique.ptr.create#10 |
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| 69 | template <typename T, typename...Args> |
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| 70 | std::enable_if_t<q20::is_bounded_array_v<T>> |
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| 71 | make_unique_for_overwrite(Args&&...) = delete; |
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| 72 | |
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| 73 | #endif // __cpp_lib_smart_ptr_for_overwrite |
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| 74 | } // namespace q20 |
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| 75 | |
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| 76 | namespace q20 { |
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| 77 | // like std::to_address |
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| 78 | #ifdef __cpp_lib_to_address |
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| 79 | using std::to_address; |
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| 80 | #else |
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| 81 | // http://eel.is/c++draft/pointer.conversion |
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| 82 | template <typename T> |
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| 83 | constexpr T *to_address(T *p) noexcept { |
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| 84 | // http://eel.is/c++draft/pointer.conversion#1: |
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| 85 | // Mandates: T is not a function type. |
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| 86 | static_assert(!std::is_function_v<T>, "to_address must not be used on function types" ); |
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| 87 | return p; |
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| 88 | } |
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| 89 | |
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| 90 | template <typename Ptr, typename std::enable_if_t<!std::is_pointer_v<Ptr>, bool> = true> |
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| 91 | constexpr auto to_address(const Ptr &ptr) noexcept; // fwd declared |
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| 92 | |
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| 93 | namespace detail { |
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| 94 | // http://eel.is/c++draft/pointer.conversion#3 |
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| 95 | template <typename Ptr, typename = void> |
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| 96 | struct to_address_helper { |
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| 97 | static auto get(const Ptr &ptr) noexcept |
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| 98 | { return q20::to_address(ptr.operator->()); } |
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| 99 | }; |
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| 100 | template <typename Ptr> |
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| 101 | struct to_address_helper<Ptr, std::void_t< |
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| 102 | decltype(std::pointer_traits<Ptr>::to_address(std::declval<const Ptr&>())) |
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| 103 | >> |
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| 104 | { |
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| 105 | static auto get(const Ptr &ptr) noexcept |
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| 106 | { return std::pointer_traits<Ptr>::to_address(ptr); } |
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| 107 | }; |
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| 108 | } // namespace detail |
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| 109 | |
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| 110 | template <typename Ptr, typename std::enable_if_t<!std::is_pointer_v<Ptr>, bool>> |
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| 111 | constexpr auto to_address(const Ptr &ptr) noexcept |
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| 112 | { return detail::to_address_helper<Ptr>::get(ptr); } |
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| 113 | |
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| 114 | #endif // __cpp_lib_to_address |
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| 115 | } // namespace q20 |
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| 116 | |
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| 117 | QT_END_NAMESPACE |
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| 118 | |
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| 119 | #endif /* Q20MEMORY_H */ |
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| 120 | |
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