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Diffstat (limited to 'src/corelib/global/q20memory.h')
| -rw-r--r-- | src/corelib/global/q20memory.h | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/src/corelib/global/q20memory.h b/src/corelib/global/q20memory.h new file mode 100644 index 0000000000..008f4ddeb2 --- /dev/null +++ b/src/corelib/global/q20memory.h @@ -0,0 +1,93 @@ +// Copyright (C) 2023 The Qt Company Ltd. +// Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com> +// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only + +#ifndef Q20MEMORY_H +#define Q20MEMORY_H + +#include <QtCore/qtconfigmacros.h> + +#include <memory> + +#include <type_traits> +#include <utility> + +// +// W A R N I N G +// ------------- +// +// This file is not part of the Qt API. Types and functions defined in this +// file can reliably be replaced by their std counterparts, once available. +// You may use these definitions in your own code, but be aware that we +// will remove them once Qt depends on the C++ version that supports +// them in namespace std. There will be NO deprecation warning, the +// definitions will JUST go away. +// +// If you can't agree to these terms, don't use these definitions! +// +// We mean it. +// + +QT_BEGIN_NAMESPACE + +// like std::construct_at (but not whitelisted for constexpr) +namespace q20 { +#ifdef __cpp_lib_constexpr_dynamic_alloc +using std::construct_at; +#else +template <typename T, + typename... Args, + typename Enable = std::void_t<decltype(::new (std::declval<void *>()) T(std::declval<Args>()...))> > +T *construct_at(T *ptr, Args && ... args) +{ + return ::new (const_cast<void *>(static_cast<const volatile void *>(ptr))) + T(std::forward<Args>(args)...); +} +#endif // __cpp_lib_constexpr_dynamic_alloc +} // namespace q20 + + +namespace q20 { +// like std::to_address +#ifdef __cpp_lib_to_address +using std::to_address; +#else +// http://eel.is/c++draft/pointer.conversion +template <typename T> +constexpr T *to_address(T *p) noexcept { + // http://eel.is/c++draft/pointer.conversion#1: + // Mandates: T is not a function type. + static_assert(!std::is_function_v<T>, "to_address must not be used on function types"); + return p; +} + +template <typename Ptr, typename std::enable_if_t<!std::is_pointer_v<Ptr>, bool> = true> +constexpr auto to_address(const Ptr &ptr) noexcept; // fwd declared + +namespace detail { + // http://eel.is/c++draft/pointer.conversion#3 + template <typename Ptr, typename = void> + struct to_address_helper { + static auto get(const Ptr &ptr) noexcept + { return q20::to_address(ptr.operator->()); } + }; + template <typename Ptr> + struct to_address_helper<Ptr, std::void_t< + decltype(std::pointer_traits<Ptr>::to_address(std::declval<const Ptr&>())) + >> + { + static auto get(const Ptr &ptr) noexcept + { return std::pointer_traits<Ptr>::to_address(ptr); } + }; +} // namespace detail + +template <typename Ptr, typename std::enable_if_t<!std::is_pointer_v<Ptr>, bool>> +constexpr auto to_address(const Ptr &ptr) noexcept +{ return detail::to_address_helper<Ptr>::get(ptr); } + +#endif // __cpp_lib_to_address +} // namespace q20 + +QT_END_NAMESPACE + +#endif /* Q20MEMORY_H */ |