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  1. Qt
  2. QTBUG-73196

QVariant::isNull returns true after successfully downcasting a non-null Value

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Details

    • Bug
    • Resolution: Done
    • P2: Important
    • 5.14.0 Alpha
    • 5.11.3
    • Core: Containers and Algorithms
    • None
    • Linux 4.19.12 on Debian Buster/Testing.
    • All
    • 758151d077536eb8fe2cd1a3252dec5619b9789f (qt/qtbase/dev)

    Description

      When storing a QObject derived class T in a QVariant as QObject* and then trying to cast it to T*, QVariant::isNull returns true even though the value can be received via QVariant::value<T*>()

      Full testcase:

      // Put this testcase in tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
// Function: void tst_QVariant::qvariant_cast_QObject_derived()
 QObject *object = new CustomQObjectDerivedNoMetaType(this);
 QVariant data = QVariant::fromValue(object);
 QVERIFY(data.canConvert<CustomQObjectDerivedNoMetaType*>());
 QVERIFY(data.convert(qMetaTypeId<CustomQObjectDerivedNoMetaType*>()));
 QCOMPARE(data.value<CustomQObjectDerivedNoMetaType*>(), object);
 QCOMPARE(data.isNull(), false); //fails here. Code above runs fine

      I think this is a pretty serious bug, since the wrong value of isNull will cause subsequent QVariant calls to fail (e.g. QVariant::save).

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            thiago Thiago Macieira
            dreamcooled Mr Dreamcooled
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            Dates

              Created:
              Updated:
              Resolved:

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