make testShell crashes

[Albert Astals Cid]

Since Qt 5.3 make testShell is crashing

Find out why

[Albert Astals Cid (aacid)]

When compiled with debug i'm getting
ASSERT: "context() && engine()" in file qml/qqmlboundsignal.cpp, line 190

[Daniel d'Andrada (dandrader)]

I get the very same crash when trying to run lp:~unity-team/unity8/mirCompositor.
So that bug is blocking the "Rotating Shell" feature because right now, as a work around this bug, we have disabled it, which magically makes the bug go away.

[Michael Terry (mterry)]

I looked into this briefly over the weekend. I just wanted to see if I could stop the crash by disabling a little bit of qml, so I could at least test parts of the shell for other branches.

It seems like the error is in the Dash's GenericScopeView's sectionDelegate being set to a ListItems.Header.

If ListItems.Header doesn't have any height (no child items and no declared height), it doesn't crash. If you comment out some of the code in ListViewWithPageHeader::setSectionDelegate and ListViewWithPageHeader::getSectionItem, it doesn't crash.

But I figure digging more than that involved more knowledge of Qml than I have, at least to figure it out in a reasonable amount of time.

[Albert Astals Cid (aacid)]

Upstream bug report https://bugreports.qt-project.org/browse/QTBUG-39966

[Albert Astals Cid (aacid)]

My naive patch upstream that fixes it (not sure it may break a billion other things) https://codereview.qt-project.org/#/c/88717/

[Daniel d'Andrada (dandrader)]

@mterry

I went through the same exercise last week with lp:~unity-team/unity8/mirCompositor. I found out that you by commenting out *arbitrary* parts of the QML code you can make it go away. Or even moving code from one file to the other (so that the end resulting qml tree is still exactly the same). My conclusion is that trying to pinpoint some piece of QML code as "the one bit that causes the crash" is simply misleading.

[Albert Astals Cid (aacid)]

IRC comment from upstream: "that's probably not The Right Thing<TM> but I'm not 100% sure which object should retain it. So, I'd keep that patch around in your repo and replace it with whatever Simon comes up with"

Simon is on holidays until 17th.

[Albert Astals Cid (aacid)]

There's also more crashes besides this one fixed in qtdeclarative, i'll link the branches as i have them

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity8 - 7.90+14.10.20140703.1-0ubuntu1

---------------
unity8 (7.90+14.10.20140703.1-0ubuntu1) utopic; urgency=low

  [ Michał Sawicz ]
  * Initial code for a payment button widget, to handle purchasing apps
    from the click scope.

  [ Nick Dedekind ]
  * Moved [Message]MenuItemFacotory from Unity.Indicators plugin to qml
    folder.

  [ Albert Astals ]
  * EasingCurve: Initialize members
  * Fix valgrind warning by not emitting reset on model destructor That
    won't be supported until Qt 5.4 More info at https://bugreports.qt-
    project.org/browse/QTBUG-39780 Warning was ==16693== Invalid read of
    size 8 ==16693== at 0x72B19A0: QQmlContext::isValid() const
    (qqmlcontext.cpp:231) ==16693== by 0x736C82B:
    QQmlDelegateModelPrivate::emitChanges() (qqmldelegatemodel.cpp:1412)
    ==16693== by 0x7372AE6: QQmlDelegateModel::_q_modelReset()
    (qqmldelegatemodel.cpp:1463) ==16693== by 0x7397224:
    QQmlDelegateModel::qt_static_metacall(QObject*, QMetaObject::Call,
    int, void**) (moc_qqmldelegatemodel_p.cpp:196) ==16693== by
    0x739769E: QQmlDelegateModel::qt_metacall(QMetaObject::Call, int,
    void**) (moc_qqmldelegatemodel_p.cpp:292) ==16693== by 0x66379CC:
    QMetaObject::activate(QObject*, int, int, void**) (in
    /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.3.0) ==16693== by
    0x65AEEFD: QAbstractItemModel::endResetModel() (in /usr/lib/x86_64-
    linux-gnu/libQt5Core.so.5.3.0) ==16693== by 0x23461EFD:
    FakeIndicatorsModel::unload() (fakeindicatorsmodel.cpp:53) ==16693==
    by 0x23461E13: FakeIndicatorsModel::~FakeIndicatorsModel()
    (fakeindicatorsmodel.cpp:34) ==16693== by 0x2345C073:
    QQmlPrivate::QQmlElement<FakeIndicatorsModel>::~QQmlElement() (in
    /home/tsdgeos_work/phablet/unity8/investigate_test_shell_crash/build
    dir/tests/mocks/Unity/Indicators/libIndicatorsFakeQml.so) ==16693==
    by 0x2345C0A3:
    QQmlPrivate::QQmlElement<FakeIndicatorsModel>::~QQmlElement()
    (qqmlprivate.h:106) ==16693== by 0x663636B:
    QObjectPrivate::deleteChildren() (in /usr/lib/x86_64-linux-
    gnu/libQt5Core.so.5.3.0) ==16693== Address 0x1862d448 is 8 bytes
    inside a block of size 16 free'd ==16693== at 0x4C2C2BC: operator
    delete(void*) (vg_replace_malloc.c:503) ==16693== by 0x72B21B8:
    QQmlContextData::destroy() (qqmlcontext.cpp:647) ==16693== by
    0x7293458: QQmlPrivate::qdeclarativeelement_destructor(QObject*)
    (qqmlengine.cpp:612) ==16693== by 0x6C0CADD:
    QQmlPrivate::QQmlElement<QQuickItem>::~QQmlElement()
    (qqmlprivate.h:105) ==16693== by 0x663636B:
    QObjectPrivate::deleteChildren() (in /usr/lib/x86_64-linux-
    gnu/libQt5Core.so.5.3.0) ==16693== by 0x663F0EB: QObject::~QObject()
    (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.3.0) ==16693== by
    0x6BF64B5: QQuickItem::~QQuickItem() (qquickitem.cpp:2064) ==16693==
    by 0x6C0CAE5: QQmlPrivate::QQmlElement<QQuickItem>::~QQmlElement()
    (qqmlprivate.h:106) ==16693== by 0x663636B:
    QObjectPrivate::deleteChildren() (in /usr/lib/x86_64-linux-
    gnu/libQt5Core.so.5.3.0) ==16693== by 0x663F0EB: QObject::~QObject()
    (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.3.0) ==16693== by
    0x6BF64...