Port QModelIndex to new comparison helper macros
Use Milian's asTuple() trick and compareThreeWayMulti(). The pointer variable presents a challenge, because, like op<, op<=> cannot order unrelated pointer values. Trying to is UB; one is supposed to use std::less and std::compare_three_way instead, but, you guessed it, less<tuple<T*>> uses op< to compare the tuples, which, in turn uses op< on the T* member, causing UB. [ChangeLog][QtCore][QtCompare] Added a Qt::totally_ordered_wrapper class whose relational operators use the std ordering types. Use it to wrap the pointers when doing the comparison to avoid UB. This allows a smooth migration once we depend on C++20 and class authors start using lhs.asTuple() <=> rhs.asTuple() or even start to =default op<=>. The wrapper type is robust against all these transformations. Update QModelIndex comparison documentation part. Task-number: QTBUG-117660 Change-Id: I126b2ebff458800134ed6e774a389d85d76a395f Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
This commit is contained in:
Marc Mutz
Tatiana Borisova
parent
5fe166ab41
commit
ece36a7394
@ -559,9 +559,103 @@ constexpr Qt::strong_ordering compareThreeWay(Enum lhs, Enum rhs) noexcept
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{
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return compareThreeWay(qToUnderlying(lhs), qToUnderlying(rhs));
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}
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} // namespace Qt
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namespace QtOrderingPrivate {
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template <typename Head, typename...Tail, std::size_t...Is>
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constexpr std::tuple<Tail...> qt_tuple_pop_front_impl(const std::tuple<Head, Tail...> &t,
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std::index_sequence<Is...>) noexcept
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{
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return std::tuple<Tail...>(std::get<Is + 1>(t)...);
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}
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template <typename Head, typename...Tail>
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constexpr std::tuple<Tail...> qt_tuple_pop_front(const std::tuple<Head, Tail...> &t) noexcept
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{
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return qt_tuple_pop_front_impl(t, std::index_sequence_for<Tail...>{});
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}
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template <typename LhsHead, typename...LhsTail, typename RhsHead, typename...RhsTail>
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constexpr auto compareThreeWayMulti(const std::tuple<LhsHead, LhsTail...> &lhs, // ie. not empty
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const std::tuple<RhsHead, RhsTail...> &rhs) noexcept
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{
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static_assert(sizeof...(LhsTail) == sizeof...(RhsTail),
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// expanded together below, but provide a nicer error message:
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"The tuple arguments have to have the same size.");
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using Qt::compareThreeWay;
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using R = std::common_type_t<
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decltype(compareThreeWay(std::declval<LhsHead>(), std::declval<RhsHead>())),
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decltype(compareThreeWay(std::declval<LhsTail>(), std::declval<RhsTail>()))...
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>;
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const auto &l = std::get<0>(lhs);
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const auto &r = std::get<0>(rhs);
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static_assert(noexcept(compareThreeWay(l, r)),
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"This function requires all relational operators to be noexcept.");
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const auto res = compareThreeWay(l, r);
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if constexpr (sizeof...(LhsTail) > 0) {
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if (is_eq(res))
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return R{compareThreeWayMulti(qt_tuple_pop_front(lhs), qt_tuple_pop_front(rhs))};
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}
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return R{res};
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}
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} //QtOrderingPrivate
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namespace Qt {
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// A wrapper class that adapts the wrappee to use the strongly-ordered
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// <functional> function objects for implementing the relational operators.
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// Mostly useful to avoid UB on pointers (which it currently mandates P to be),
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// because all the comparison helpers (incl. std::compare_three_way on
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// std::tuple<T*>!) will use the language-level operators.
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//
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template <typename P>
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class totally_ordered_wrapper
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{
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static_assert(std::is_pointer_v<P>);
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using T = std::remove_pointer_t<P>;
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P ptr;
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public:
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explicit constexpr totally_ordered_wrapper(P p) : ptr(p) {}
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constexpr P get() const noexcept { return ptr; }
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constexpr P operator->() const noexcept { return get(); }
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constexpr T& operator*() const noexcept { return *get(); }
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explicit constexpr operator bool() const noexcept { return get(); }
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private:
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friend constexpr auto compareThreeWay(const totally_ordered_wrapper &lhs, const totally_ordered_wrapper &rhs) noexcept
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{ return Qt::compareThreeWay(lhs.ptr, rhs.ptr); }
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#define MAKE_RELOP(Ret, op, Op) \
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friend constexpr Ret operator op (const totally_ordered_wrapper &lhs, const totally_ordered_wrapper &rhs) noexcept \
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{ return std:: Op {}(lhs.ptr, rhs.ptr); } \
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friend constexpr Ret operator op (const totally_ordered_wrapper &lhs, const P &rhs) noexcept \
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{ return std:: Op {}(lhs.ptr, rhs ); } \
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friend constexpr Ret operator op (const P &lhs, const totally_ordered_wrapper &rhs) noexcept \
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{ return std:: Op {}(lhs, rhs.ptr); } \
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friend constexpr Ret operator op (const totally_ordered_wrapper &lhs, std::nullptr_t) noexcept \
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{ return std:: Op {}(lhs.ptr, nullptr); } \
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friend constexpr Ret operator op (std::nullptr_t, const totally_ordered_wrapper &rhs) noexcept \
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{ return std:: Op {}(nullptr, rhs.ptr); } \
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/* end */
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MAKE_RELOP(bool, ==, equal_to<P>)
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MAKE_RELOP(bool, !=, not_equal_to<P>)
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MAKE_RELOP(bool, < , less<P>)
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MAKE_RELOP(bool, <=, less_equal<P>)
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MAKE_RELOP(bool, > , greater<P>)
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MAKE_RELOP(bool, >=, greater_equal<P>)
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#ifdef __cpp_lib_three_way_comparison
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MAKE_RELOP(auto, <=>, compare_three_way)
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#endif
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#undef MAKE_RELOP
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};
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} //Qt
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QT_END_NAMESPACE
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#endif // QCOMPAREHELPERS_H
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@ -1158,6 +1158,7 @@ void QAbstractItemModel::resetInternalData()
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\ingroup model-view
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\compares strong
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This class is used as an index into item models derived from
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QAbstractItemModel. The index is used by item views, delegates, and
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@ -1328,24 +1329,22 @@ void QAbstractItemModel::resetInternalData()
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*/
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/*!
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\fn bool QModelIndex::operator==(const QModelIndex &other) const
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\fn bool QModelIndex::operator==(const QModelIndex &lhs, const QModelIndex &rhs)
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Returns \c{true} if this model index refers to the same location as the
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\a other model index; otherwise returns \c{false}.
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Returns \c{true} if \a lhs model index refers to the same location as the
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\a rhs model index; otherwise returns \c{false}.
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The internal data pointer, row, column, and model values are used when
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comparing with another model index.
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*/
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/*!
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\fn bool QModelIndex::operator!=(const QModelIndex &other) const
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\fn bool QModelIndex::operator!=(const QModelIndex &lhs, const QModelIndex &rhs)
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Returns \c{true} if this model index does not refer to the same location as
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the \a other model index; otherwise returns \c{false}.
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Returns \c{true} if \a lhs model index does not refer to the same location as
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the \a rhs model index; otherwise returns \c{false}.
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*/
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/*!
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\fn QModelIndex QModelIndex::parent() const
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@ -4124,10 +4123,10 @@ bool QAbstractListModel::dropMimeData(const QMimeData *data, Qt::DropAction acti
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*/
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/*!
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\fn bool QModelIndex::operator<(const QModelIndex &other) const
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\fn bool QModelIndex::operator<(const QModelIndex &lhs, const QModelIndex &rhs)
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\since 4.1
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Returns \c{true} if this model index is smaller than the \a other
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Returns \c{true} if \a lhs model index is smaller than the \a rhs
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model index; otherwise returns \c{false}.
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The less than calculation is not directly useful to developers - the way that indexes
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@ -5,11 +5,14 @@
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#ifndef QABSTRACTITEMMODEL_H
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#define QABSTRACTITEMMODEL_H
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#include <QtCore/qcompare.h>
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#include <QtCore/qhash.h>
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#include <QtCore/qlist.h>
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#include <QtCore/qobject.h>
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#include <QtCore/qvariant.h>
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#include <tuple>
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QT_REQUIRE_CONFIG(itemmodel);
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QT_BEGIN_NAMESPACE
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@ -138,19 +141,16 @@ public:
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inline QVariant data(int role = Qt::DisplayRole) const;
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inline void multiData(QModelRoleDataSpan roleDataSpan) const;
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inline Qt::ItemFlags flags() const;
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constexpr inline const QAbstractItemModel *model() const noexcept { return m; }
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constexpr inline const QAbstractItemModel *model() const noexcept { return m.get(); }
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constexpr inline bool isValid() const noexcept { return (r >= 0) && (c >= 0) && (m != nullptr); }
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constexpr inline bool operator==(const QModelIndex &other) const noexcept
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{ return (other.r == r) && (other.i == i) && (other.c == c) && (other.m == m); }
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constexpr inline bool operator!=(const QModelIndex &other) const noexcept
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{ return !(*this == other); }
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constexpr inline bool operator<(const QModelIndex &other) const noexcept
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{
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return r < other.r
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|| (r == other.r && (c < other.c
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|| (c == other.c && (i < other.i
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|| (i == other.i && std::less<const QAbstractItemModel *>()(m, other.m))))));
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}
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private:
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constexpr auto asTuple() const noexcept { return std::tie(r, c, i, m); }
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friend constexpr bool comparesEqual(const QModelIndex &lhs, const QModelIndex &rhs) noexcept
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{ return lhs.asTuple() == rhs.asTuple(); }
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friend constexpr Qt::strong_ordering compareThreeWay(const QModelIndex &lhs, const QModelIndex &rhs) noexcept
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{ return QtOrderingPrivate::compareThreeWayMulti(lhs.asTuple(), rhs.asTuple()); }
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Q_DECLARE_STRONGLY_ORDERED_LITERAL_TYPE(QModelIndex)
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private:
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inline QModelIndex(int arow, int acolumn, const void *ptr, const QAbstractItemModel *amodel) noexcept
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: r(arow), c(acolumn), i(reinterpret_cast<quintptr>(ptr)), m(amodel) {}
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@ -158,7 +158,7 @@ private:
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: r(arow), c(acolumn), i(id), m(amodel) {}
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int r, c;
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quintptr i;
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const QAbstractItemModel *m;
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Qt::totally_ordered_wrapper<const QAbstractItemModel *> m;
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};
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Q_DECLARE_TYPEINFO(QModelIndex, Q_RELOCATABLE_TYPE);
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@ -993,7 +993,7 @@ void tst_QAbstractItemModel::complexChangesWithPersistent()
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void tst_QAbstractItemModel::modelIndexComparisons()
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{
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QTestPrivate::testEqualityOperatorsCompile<QModelIndex>();
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QTestPrivate::testAllComparisonOperatorsCompile<QModelIndex>();
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QTestPrivate::testEqualityOperatorsCompile<QPersistentModelIndex>();
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QTestPrivate::testEqualityOperatorsCompile<QPersistentModelIndex, QModelIndex>();
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@ -1006,6 +1006,9 @@ void tst_QAbstractItemModel::modelIndexComparisons()
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QT_TEST_EQUALITY_OPS(mi11, mi11, true);
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QT_TEST_EQUALITY_OPS(mi11, mi22, false);
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QT_TEST_ALL_COMPARISON_OPS(mi11, mi11, Qt::strong_ordering::equal);
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QT_TEST_ALL_COMPARISON_OPS(mi11, mi22, Qt::strong_ordering::less);
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QT_TEST_ALL_COMPARISON_OPS(mi22, mi11, Qt::strong_ordering::greater);
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QT_TEST_EQUALITY_OPS(pmi11, pmi11, true);
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QT_TEST_EQUALITY_OPS(pmi11, pmi22, false);
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QT_TEST_EQUALITY_OPS(pmi11, mi11, true);
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