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QMetaType: fix QMetaTypes for non-const references

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Namely, they shouldn't be supported. Even trying to create such a type
(as in QMetaType::fromType<int &>()) should fail, because for the
purposes of the meta type, they are not the same.

However, they were being registered in the meta objects' meta type list
as a mistake since commit cb43aaca11
("Introduce QMetaObject::metaType"), including for output parameters in
D-Bus remote objects' meta objects. despite the comment saying "type id
not available".

[ChangeLog][Potentially Source-incompatible Changes] Made meta types for
non-const references fail to compile. Previously, QMetaType::fromType
allowed this to compile, but returned the meta type for the base type,
which was incorrect. Const references are understood to be the same as
the base type.

[ChangeLog][Important Behavior Changes] The meta type for non-const
reference parameters in extracted methods (signals, slots, etc.) is no
longer available in QMetaMethod. This used to be the case in Qt 4.x and
5.x, but due to a mistake in Qt 6.0-6.3, QMetaMethod would incorrectly
report the base (non-reference) type. Additionally, both the reference
and the non-reference types may have been reported in different APIs.

Pick-to: 6.4
Change-Id: I36b24183fbd041179f2ffffd1702384d2b64a5f9
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
This commit is contained in:
Thiago Macieira 2022-07-15 22:31:56 -07:00
parent 7211771c64
commit 2d0c31e7d9
2 changed files with 20 additions and 10 deletions
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28
src/corelib/kernel/qmetatype.h
View File

@ -843,7 +843,11 @@ namespace QtPrivate
} // namespace detail
template <typename T, typename ODR_VIOLATION_PREVENTER>
struct is_complete : detail::is_complete_helper<T, ODR_VIOLATION_PREVENTER>::type {};
struct is_complete : detail::is_complete_helper<std::remove_reference_t<T>, ODR_VIOLATION_PREVENTER>::type {};
template <typename T> struct MetatypeDecay { using type = T; };
template <typename T> struct MetatypeDecay<const T> { using type = T; };
template <typename T> struct MetatypeDecay<const T &> { using type = T; };
template<typename T>
struct IsPointerToTypeDerivedFromQObject
@ -2478,12 +2482,6 @@ QT_FOR_EACH_STATIC_CORE_POINTER(QT_METATYPE_DECLARE_EXTERN_TEMPLATE_ITER)
QT_FOR_EACH_STATIC_CORE_TEMPLATE(QT_METATYPE_DECLARE_EXTERN_TEMPLATE_ITER)
#undef QT_METATYPE_DECLARE_EXTERN_TEMPLATE_ITER
#endif
template<typename T>
constexpr const QMetaTypeInterface *qMetaTypeInterfaceForType()
{
using Ty = std::remove_cv_t<std::remove_reference_t<T>>;
return &QMetaTypeInterfaceWrapper<Ty>::metaType;
}
template<typename T>
struct qRemovePointerLike
@ -2510,14 +2508,26 @@ struct TypeAndForceComplete
using ForceComplete = ForceComplete_;
};
template<typename T>
constexpr const QMetaTypeInterface *qMetaTypeInterfaceForType()
{
using Ty = typename MetatypeDecay<T>::type;
return &QMetaTypeInterfaceWrapper<Ty>::metaType;
}
template<typename Unique, typename TypeCompletePair>
constexpr const QMetaTypeInterface *qTryMetaTypeInterfaceForType()
{
using T = typename TypeCompletePair::type;
using ForceComplete = typename TypeCompletePair::ForceComplete;
using Ty = std::remove_cv_t<std::remove_reference_t<T>>;
using Ty = typename MetatypeDecay<T>::type;
using Tz = qRemovePointerLike_t<Ty>;
if constexpr (!is_complete<Tz, Unique>::value && !ForceComplete::value) {
if constexpr (ForceComplete::value) {
return &QMetaTypeInterfaceWrapper<Ty>::metaType;
} else if constexpr (std::is_reference_v<Tz>) {
return nullptr;
} else if constexpr (!is_complete<Tz, Unique>::value) {
return nullptr;
} else {
return &QMetaTypeInterfaceWrapper<Ty>::metaType;

2
src/dbus/qdbusmetaobject.cpp
View File

@ -477,8 +477,8 @@ void QDBusMetaObjectGenerator::write(QDBusMetaObject *obj)
// Output parameters are references; type id not available
typeName = QMetaType(type).name();
typeName.append('&');
type = QMetaType::UnknownType;
}
Q_ASSERT(type != QMetaType::UnknownType);
int typeInfo;
if (!typeName.isEmpty())
typeInfo = IsUnresolvedType | strings.enter(typeName);