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Make it possible to put QObject tracked with QWeakPointer inside QSharedPointer

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Do that by keeping the QWeakPointer that track QObject independent of
the ones that track QSharedPointer.

QSharedPointer do not touch the sharedRefCount in QObjectPrivate anymore

When converting a QWeakPointer constructed from a QObject to a
QSharedPointer, it will display a warning saying one should not do that.

Task-number: QTBUG-22622
Change-Id: I3595e3e7401702410776c458687ab357ad9366ab
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
This commit is contained in:
Olivier Goffart 2011-12-23 17:13:05 +01:00 committed by Qt by Nokia
parent 281673e5d3
commit 497622cafe
3 changed files with 44 additions and 25 deletions
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28
src/corelib/tools/qsharedpointer.cpp
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@ -1226,24 +1226,22 @@ QT_BEGIN_NAMESPACE
/*!
\internal
This function is called for a just-created QObject \a obj, to enable
the use of QSharedPointer and QWeakPointer.
the use of QSharedPointer and QWeakPointer in the future.
*/
void QtSharedPointer::ExternalRefCountData::setQObjectShared(const QObject *, bool)
{}
When QSharedPointer is active in a QObject, the object must not be deleted
directly: the lifetime is managed by the QSharedPointer object. In that case,
the deleteLater() and parent-child relationship in QObject only decrease
the strong reference count, instead of deleting the object.
/*!
\internal
This function is called when a QSharedPointer is created from a QWeakPointer
We check that the QWeakPointer was really created from a QSharedPointer, and
not from a QObject.
*/
void QtSharedPointer::ExternalRefCountData::setQObjectShared(const QObject *obj, bool)
void QtSharedPointer::ExternalRefCountData::checkQObjectShared(const QObject *)
{
Q_ASSERT(obj);
QObjectPrivate *d = QObjectPrivate::get(const_cast<QObject *>(obj));
if (d->sharedRefcount.load() != 0)
qFatal("QSharedPointer: pointer %p already has reference counting", obj);
d->sharedRefcount.store(this);
// QObject decreases the refcount too, so increase it up
weakref.ref();
if (strongref.load() < 0)
qWarning("QSharedPointer: cannot create a QSharedPointer from a QObject-tracking QWeakPointer");
}
QtSharedPointer::ExternalRefCountData *QtSharedPointer::ExternalRefCountData::getAndRef(const QObject *obj)

8
src/corelib/tools/qsharedpointer_impl.h
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@ -192,7 +192,9 @@ namespace QtSharedPointer {
#ifndef QT_NO_QOBJECT
Q_CORE_EXPORT static ExternalRefCountData *getAndRef(const QObject *);
Q_CORE_EXPORT void setQObjectShared(const QObject *, bool enable);
Q_CORE_EXPORT void checkQObjectShared(const QObject *);
#endif
inline void checkQObjectShared(...) { }
inline void setQObjectShared(...) { }
};
// sizeof(ExternalRefCount) = 12 (32-bit) / 16 (64-bit)
@ -432,10 +434,12 @@ namespace QtSharedPointer {
tmp = o->strongref.load(); // failed, try again
}
if (tmp > 0)
if (tmp > 0) {
o->weakref.ref();
else
} else {
o->checkQObjectShared(actual);
o = 0;
}
}
qSwap(d, o);

33
tests/auto/corelib/tools/qsharedpointer/tst_qsharedpointer.cpp
View File

@ -76,6 +76,7 @@ private slots:
void upCast();
void qobjectWeakManagement();
void noSharedPointerFromWeakQObject();
void sharedPointerFromQObjectWithWeak();
void weakQObjectFromSharedPointer();
void objectCast();
void differentPointers();
@ -692,12 +693,34 @@ void tst_QSharedPointer::noSharedPointerFromWeakQObject()
QObject obj;
QWeakPointer<QObject> weak(&obj);
QSharedPointer<QObject> strong = weak.toStrongRef();
QVERIFY(strong.isNull());
{
QTest::ignoreMessage(QtWarningMsg , "QSharedPointer: cannot create a QSharedPointer from a QObject-tracking QWeakPointer");
QSharedPointer<QObject> strong = weak.toStrongRef();
QVERIFY(strong.isNull());
}
{
QTest::ignoreMessage(QtWarningMsg , "QSharedPointer: cannot create a QSharedPointer from a QObject-tracking QWeakPointer");
QSharedPointer<QObject> strong = weak;
QVERIFY(strong.isNull());
}
QCOMPARE(weak.data(), &obj);
// if something went wrong, we'll probably crash here
}
void tst_QSharedPointer::sharedPointerFromQObjectWithWeak()
{
QObject *ptr = new QObject;
QWeakPointer<QObject> weak = ptr;
{
QSharedPointer<QObject> shared(ptr);
QVERIFY(!weak.isNull());
QCOMPARE(shared.data(), ptr);
QCOMPARE(weak.data(), ptr);
}
QVERIFY(weak.isNull());
}
void tst_QSharedPointer::weakQObjectFromSharedPointer()
{
// this is the inverse of the above: you're allowed to create a QWeakPointer
@ -1767,12 +1790,6 @@ void tst_QSharedPointer::invalidConstructs_data()
<< "Data *ptr = 0;\n"
"QWeakPointer<Data> weakptr(ptr);\n";
QTest::newRow("shared-pointer-from-unmanaged-qobject")
<< &QTest::QExternalTest::tryRunFail
<< "QObject *ptr = new QObject;\n"
"QWeakPointer<QObject> weak = ptr;\n" // this makes the object unmanaged
"QSharedPointer<QObject> shared(ptr);\n";
QTest::newRow("shared-pointer-implicit-from-uninitialized")
<< &QTest::QExternalTest::tryCompileFail
<< "Data *ptr = 0;\n"