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Diffstat (limited to 'src/corelib/global/q20type_traits.h')
| -rw-r--r-- | src/corelib/global/q20type_traits.h | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/src/corelib/global/q20type_traits.h b/src/corelib/global/q20type_traits.h new file mode 100644 index 0000000000..63a453daca --- /dev/null +++ b/src/corelib/global/q20type_traits.h @@ -0,0 +1,81 @@ +// Copyright (C) 2021 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 Q20TYPE_TRAITS_H +#define Q20TYPE_TRAITS_H + +#include <QtCore/qcompilerdetection.h> +#include <QtCore/qsystemdetection.h> +#include <QtCore/qtconfigmacros.h> + +// +// 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. +// + +#include <type_traits> + +QT_BEGIN_NAMESPACE + +namespace q20 { +// like std::is_constant_evaluated +#ifdef __cpp_lib_is_constant_evaluated +using std::is_constant_evaluated; +#define QT_SUPPORTS_IS_CONSTANT_EVALUATED +#else +constexpr bool is_constant_evaluated() noexcept +{ +#ifdef Q_OS_INTEGRITY + // Integrity complains "calling __has_builtin() from a constant expression". + // Avoid the __has_builtin check until we know what's going on. + return false; +#elif __has_builtin(__builtin_is_constant_evaluated) || \ + (defined(Q_CC_MSVC_ONLY) /* >= 1925, but we require 1927 in qglobal.h */) +# define QT_SUPPORTS_IS_CONSTANT_EVALUATED + return __builtin_is_constant_evaluated(); +#else + return false; +#endif +} +#endif // __cpp_lib_is_constant_evaluated +} + +namespace q20 { +// like std::remove_cvref(_t) +#ifdef __cpp_lib_remove_cvref +using std::remove_cvref; +using std::remove_cvref_t; +#else +template <typename T> +using remove_cvref = std::remove_cv<std::remove_reference_t<T>>; +template <typename T> +using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<T>>; +#endif // __cpp_lib_remove_cvref +} + +namespace q20 { +// like std::type_identity(_t) +#ifdef __cpp_lib_type_identity +using std::type_identity; +using std::type_identity_t; +#else +template <typename T> +struct type_identity { using type = T; }; +template <typename T> +using type_identity_t = typename type_identity<T>::type; +#endif // __cpp_lib_type_identity +} + +QT_END_NAMESPACE + +#endif /* Q20TYPE_TRAITS_H */ |