1 files changed, 77 insertions, 0 deletions
diff --git a/src/corelib/tools/qfunctionaltools_impl.h b/src/corelib/tools/qfunctionaltools_impl.h
new file mode 100644
index 0000000000..0942d5fe7d
--- /dev/null
+++ b/src/corelib/tools/qfunctionaltools_impl.h
@@ -0,0 +1,77 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#if 0
+#pragma qt_sync_skip_header_check
+#pragma qt_sync_stop_processing
+#endif
+
+#ifndef QFUNCTIONALTOOLS_IMPL_H
+#define QFUNCTIONALTOOLS_IMPL_H
+
+#include <QtCore/qtconfigmacros.h>
+
+#include <type_traits>
+#include <utility>
+
+QT_BEGIN_NAMESPACE
+
+namespace QtPrivate {
+
+namespace detail {
+
+#define FOR_EACH_CVREF(op) \
+    op(&) \
+    op(const &) \
+    op(&&) \
+    op(const &&) \
+    /* end */
+
+
+template <typename Object, typename = void>
+struct StorageByValue
+{
+    Object o;
+#define MAKE_GETTER(cvref) \
+    constexpr Object cvref object() cvref noexcept \
+    { return static_cast<Object cvref>(o); }
+    FOR_EACH_CVREF(MAKE_GETTER)
+#undef MAKE_GETTER
+};
+
+template <typename Object, typename Tag = void>
+struct StorageEmptyBaseClassOptimization : Object
+{
+    StorageEmptyBaseClassOptimization() = default;
+    StorageEmptyBaseClassOptimization(Object &&o)
+        : Object(std::move(o))
+    {}
+    StorageEmptyBaseClassOptimization(const Object &o)
+        : Object(o)
+    {}
+
+#define MAKE_GETTER(cvref) \
+    constexpr Object cvref object() cvref noexcept \
+    { return static_cast<Object cvref>(*this); }
+    FOR_EACH_CVREF(MAKE_GETTER)
+#undef MAKE_GETTER
+};
+} // namespace detail
+
+template <typename Object, typename Tag = void>
+using CompactStorage = typename std::conditional_t<
+        std::conjunction_v<
+            std::is_empty<Object>,
+            std::negation<std::is_final<Object>>
+        >,
+        detail::StorageEmptyBaseClassOptimization<Object, Tag>,
+        detail::StorageByValue<Object, Tag>
+    >;
+
+} // namespace QtPrivate
+
+#undef FOR_EACH_CVREF
+
+QT_END_NAMESPACE
+
+#endif // QFUNCTIONALTOOLS_IMPL_H