1219dbcd12
Construction from nullptr wasn't, before, because it was using the QPointer(T*) constructor, which cannot be constexpr. Add a constexpr QPointer(std::nullptr_t) constructor to enable this use-case. This requires to mark the (T*) constructor as Q_WEAK_OVERLOAD, otherwise legacy construction from a literal 0 would be ambiguous. No documentation changes needed, as the set of valid expressions (apart from constinit'ing) has not changed. Mention the nullptr ctor, though, without \since. Add a test to confirm that contruction from derived still works. Change-Id: If9d5281f6eca0c408a69f03fecba64a70a0c9cf0 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
130 lines
3.8 KiB
C++
130 lines
3.8 KiB
C++
// Copyright (C) 2016 The Qt Company Ltd.
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// 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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#ifndef QPOINTER_H
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#define QPOINTER_H
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#include <QtCore/qsharedpointer.h>
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#include <QtCore/qtypeinfo.h>
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#ifndef QT_NO_QOBJECT
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QT_BEGIN_NAMESPACE
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class QVariant;
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template <class T>
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class QPointer
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{
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static_assert(!std::is_pointer<T>::value, "QPointer's template type must not be a pointer type");
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template <typename X>
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using if_convertible = std::enable_if_t<std::is_convertible_v<X*, T*>, bool>;
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template <typename X>
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friend class QPointer;
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using QObjectType =
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typename std::conditional<std::is_const<T>::value, const QObject, QObject>::type;
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QWeakPointer<QObjectType> wp;
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public:
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Q_NODISCARD_CTOR
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QPointer() noexcept = default;
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Q_NODISCARD_CTOR
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constexpr QPointer(std::nullptr_t) noexcept : QPointer{} {}
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Q_WEAK_OVERLOAD
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Q_NODISCARD_CTOR
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inline QPointer(T *p) : wp(p, true) { }
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// compiler-generated copy/move ctor/assignment operators are fine!
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// compiler-generated dtor is fine!
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template <typename X, if_convertible<X> = true>
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Q_NODISCARD_CTOR
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QPointer(QPointer<X> &&other) noexcept
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: wp(std::exchange(other.wp, nullptr).internalData(), true) {}
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template <typename X, if_convertible<X> = true>
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Q_NODISCARD_CTOR
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QPointer(const QPointer<X> &other) noexcept
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: wp(other.wp.internalData(), true) {}
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template <typename X, if_convertible<X> = true>
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QPointer &operator=(const QPointer<X> &other) noexcept
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{
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QPointer(other).swap(*this);
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return *this;
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}
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template <typename X, if_convertible<X> = true>
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QPointer &operator=(QPointer<X> &&other) noexcept
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{
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QPointer(std::move(other)).swap(*this);
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return *this;
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}
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#ifdef Q_QDOC
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// Stop qdoc from complaining about missing function
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~QPointer();
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#endif
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inline void swap(QPointer &other) noexcept { wp.swap(other.wp); }
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inline QPointer<T> &operator=(T* p)
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{ wp.assign(static_cast<QObjectType*>(p)); return *this; }
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T* data() const noexcept
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{ return static_cast<T*>(wp.internalData()); }
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T* get() const noexcept
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{ return data(); }
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T* operator->() const noexcept
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{ return data(); }
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T& operator*() const noexcept
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{ return *data(); }
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operator T*() const noexcept
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{ return data(); }
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bool isNull() const noexcept
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{ return wp.isNull(); }
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void clear() noexcept
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{ wp.clear(); }
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friend void swap(QPointer &lhs, QPointer &rhs) noexcept
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{ lhs.swap(rhs); }
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#define DECLARE_COMPARE_SET(T1, A1, T2, A2) \
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friend bool operator==(T1, T2) noexcept \
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{ return A1 == A2; } \
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friend bool operator!=(T1, T2) noexcept \
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{ return A1 != A2; }
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#define DECLARE_TEMPLATE_COMPARE_SET(T1, A1, T2, A2) \
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template <typename X> \
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friend bool operator==(T1, T2) noexcept \
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{ return A1 == A2; } \
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template <typename X> \
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friend bool operator!=(T1, T2) noexcept \
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{ return A1 != A2; }
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DECLARE_TEMPLATE_COMPARE_SET(const QPointer &p1, p1.data(), const QPointer<X> &p2, p2.data())
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DECLARE_TEMPLATE_COMPARE_SET(const QPointer &p1, p1.data(), X *ptr, ptr)
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DECLARE_TEMPLATE_COMPARE_SET(X *ptr, ptr, const QPointer &p2, p2.data())
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DECLARE_COMPARE_SET(const QPointer &p1, p1.data(), std::nullptr_t, nullptr)
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DECLARE_COMPARE_SET(std::nullptr_t, nullptr, const QPointer &p2, p2.data())
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#undef DECLARE_COMPARE_SET
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#undef DECLARE_TEMPLATE_COMPARE_SET
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};
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template <class T> Q_DECLARE_TYPEINFO_BODY(QPointer<T>, Q_RELOCATABLE_TYPE);
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template<typename T>
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QPointer<T>
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qPointerFromVariant(const QVariant &variant)
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{
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const auto wp = QtSharedPointer::weakPointerFromVariant_internal(variant);
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return QPointer<T>{qobject_cast<T*>(QtPrivate::EnableInternalData::internalData(wp))};
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}
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QT_END_NAMESPACE
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#endif // QT_NO_QOBJECT
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#endif // QPOINTER_H
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