[Development] QML instantiation performance
Chris Adams
chris.adams at qinetic.com.au
Thu Dec 4 05:46:25 CET 2014
Hi Gunnar,
Can you get a backtrace which might help pinpoint what's causing it?
I've integrated the patch to 5.4, and it passed CI, so at least in the CI
environments it's not crashing, I think.
I don't have a windows 5.4 build to test against, currently, so I'm not
sure what could cause the problem.
Cheers,
Chris.
www.qinetic.com.au - Qt And QML User Experience Specialists
On Tue, Dec 2, 2014 at 8:26 PM, Gunnar Roth <gunnar.roth at gmx.de> wrote:
> Hi Chris,
> i tried your patch with 5.4rc1 as i am working on that.
>
> i get erros like
>
> nfig: Using QtTest library 5.4.0, Qt 5.4.0 (i386-little_endian-ilp32
> shared (dynamic) release build; by MSVC 2012)
>
> PASS : tst_librarymetrics_performance::initTestCase()
>
> QWARN : tst_librarymetrics_performance::compilation(001) item - empty)
> QQml_removeValueTypeProvider: was asked to remove provider 0x2b4c2ac but it
> was not found
>
> on each test case until it crashes after
>
> tst_librarymetrics_performance::instantiation_cached(014) item -
> initialised Item prop (with child)) QQml_removeValueTypeProvider: was asked
> to remove provider 0xf82c2ac but it was not found
>
>
>
>
> the patch i used is this:
> diff -r -U 5 -N -x doc -x test -x 'qquickrectangle*'
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/imports/qtquick2/plugin.cpp
> qtdeclarative\src/imports/qtquick2/plugin.cpp
> ---
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/imports/qtquick2/plugin.cpp
> 2014-11-24 16:01:09.000000000 +0100
> +++ qtdeclarative\src/imports/qtquick2/plugin.cpp 2014-12-01
> 17:28:57.174986000 +0100
> @@ -47,10 +47,15 @@
> {
> Q_ASSERT(QLatin1String(uri) == QLatin1String("QtQuick"));
> Q_UNUSED(uri);
> QQmlQtQuick2Module::defineModule();
> }
> +
> + ~QtQuick2Plugin()
> + {
> + QQmlQtQuick2Module::undefineModule();
> + }
> };
> //![class decl]
>
> QT_END_NAMESPACE
>
> diff -r -U 5 -N -x doc -x test -x 'qquickrectangle*'
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/qml/compiler/qqmltypecompiler.cpp
> qtdeclarative\src/qml/compiler/qqmltypecompiler.cpp
> ---
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/qml/compiler/qqmltypecompiler.cpp
> 2014-11-24 16:01:06.000000000 +0100
> +++ qtdeclarative\src/qml/compiler/qqmltypecompiler.cpp 2014-12-01
> 17:30:40.223986000 +0100
> @@ -1387,11 +1387,11 @@
> }
>
> if (!mo)
> continue;
>
> - static QQmlType *componentType =
> QQmlMetaType::qmlType(&QQmlComponent::staticMetaObject);
> + QQmlType *componentType =
> QQmlMetaType::qmlType(&QQmlComponent::staticMetaObject);
> Q_ASSERT(componentType);
>
> QmlIR::Object *syntheticComponent = pool->New<QmlIR::Object>();
> syntheticComponent->init(pool,
> compiler->registerString(QString::fromUtf8(componentType->typeName())),
> compiler->registerString(QString()));
> syntheticComponent->location = binding->valueLocation;
> diff -r -U 5 -N -x doc -x test -x 'qquickrectangle*'
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/qtquick2.cpp
> qtdeclarative\src/quick/qtquick2.cpp
> ---
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/qtquick2.cpp
> 2014-11-24 16:01:08.000000000 +0100
> +++ qtdeclarative\src/quick/qtquick2.cpp 2014-12-01 17:32:06.715986000
> +0100
> @@ -192,7 +192,12 @@
> new QQmlQtQuick2DebugStatesDelegate);
> QQuickProfiler::initialize();
> }
> }
>
> +void QQmlQtQuick2Module::undefineModule()
> +{
> + QQuick_deinitializeProviders();
> +}
> +
> QT_END_NAMESPACE
>
> diff -r -U 5 -N -x doc -x test -x 'qquickrectangle*'
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/qtquick2_p.h
> qtdeclarative\src/quick/qtquick2_p.h
> ---
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/qtquick2_p.h
> 2014-11-24 16:01:07.000000000 +0100
> +++ qtdeclarative\src/quick/qtquick2_p.h 2014-12-01 17:32:46.839986000
> +0100
> @@ -40,10 +40,11 @@
>
> class Q_QUICK_PRIVATE_EXPORT QQmlQtQuick2Module
> {
> public:
> static void defineModule();
> + static void undefineModule();
> };
>
> QT_END_NAMESPACE
>
> #endif // QTQUICK2_P_H
> diff -r -U 5 -N -x doc -x test -x 'qquickrectangle*'
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/qtquickglobal_p.h
> qtdeclarative\src/quick/qtquickglobal_p.h
> ---
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/qtquickglobal_p.h
> 2014-11-24 16:01:08.000000000 +0100
> +++ qtdeclarative\src/quick/qtquickglobal_p.h 2014-12-01
> 17:33:21.893986000 +0100
> @@ -52,10 +52,11 @@
> #define Q_QUICK_PRIVATE_EXPORT Q_QUICK_EXPORT
>
> QT_BEGIN_NAMESPACE
>
> void QQuick_initializeProviders();
> +void QQuick_deinitializeProviders();
>
> Q_DECLARE_LOGGING_CATEGORY(DBG_TOUCH)
> Q_DECLARE_LOGGING_CATEGORY(DBG_MOUSE)
> Q_DECLARE_LOGGING_CATEGORY(DBG_FOCUS)
> Q_DECLARE_LOGGING_CATEGORY(DBG_DIRTY)
> diff -r -U 5 -N -x doc -x test -x 'qquickrectangle*'
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/util/qquickglobal.cpp
> qtdeclarative\src/quick/util/qquickglobal.cpp
> ---
> D:\Temp\qt-everywhere-opensource-src-5.4.0-rc\qtdeclarative\src/quick/util/qquickglobal.cpp
> 2014-11-24 16:01:08.000000000 +0100
> +++ qtdeclarative\src/quick/util/qquickglobal.cpp 2014-12-01
> 17:44:37.800986000 +0100
> @@ -980,6 +980,13 @@
> QQml_addValueTypeProvider(getValueTypeProvider());
> QQml_setColorProvider(getColorProvider());
> QQml_setGuiProvider(getGuiProvider());
> }
>
> +void QQuick_deinitializeProviders()
> +{
> + QQml_removeValueTypeProvider(getValueTypeProvider());
> + QQml_setColorProvider(0); // the only accessor is Q_AUTOTEST_EXPORT,
> so....
> + QQml_setGuiProvider(0);
> +}
> +
> QT_END_NAMESPACE
>
>
> *Gesendet:* Montag, 01. Dezember 2014 um 05:51 Uhr
> *Von:* "Chris Adams" <chris.adams at qinetic.com.au>
> *An:* "Simon Hausmann" <simon.hausmann at theqtcompany.com>
> *Cc:* "development at qt-project.org" <development at qt-project.org>
> *Betreff:* Re: [Development] QML instantiation performance
> See https://codereview.qt-project.org/#/c/101048/ - huge thanks to Matt
> Vogt for his help with debugging and fixing the issues.
> Juha, does that resolve the issues for you? Gunnar Roth, does that fix
> the issues on Windows? I haven't tested there.
>
> www.qinetic.com.au - Qt And QML User Experience Specialists
>
> On Mon, Dec 1, 2014 at 2:16 PM, Chris Adams <chris.adams at qinetic.com.au>
> wrote:
>>
>> The loop was due to the QtQuick2 plugin's defineModule() code
>> initializing the value type providers on load, but not deinitializing them
>> on dtor, resulting in future loads of that plugin adding the same ptr to
>> the linked list as the head's next ptr (so, cycle).
>> The attached diff fixes that issue, but has unmasked at least one further
>> crash which also seems related to the qmlClearTypeRegistrations function.
>>
>> I'll see if I can trace it further, and push something to Gerrit later in
>> the week.
>>
>> Cheers,
>> Chris.
>>
>> www.qinetic.com.au - Qt And QML User Experience Specialists
>>
>> On Fri, Nov 28, 2014 at 5:39 PM, Simon Hausmann <
>> simon.hausmann at theqtcompany.com> wrote:
>>>
>>> On Friday 28. November 2014 12.20.29 Chris Adams wrote:
>>> > Hi,
>>> >
>>> > No worries. Interestingly, when I ran the benchmark against 5.3, I
>>> found
>>> > that it hangs after performing several tests.
>>> >
>>> > Before each test, the benchmark will clear the QML type registrations
>>> to
>>> > ensure that the cached compiled type data isn't re-used during the run,
>>> > tainting the results. It appears that if the call to
>>> > qmlClearTypeRegistrations() is commented out, the benchmark runs all
>>> the
>>> > way through (but obviously, with tainted / useless results). With that
>>> > call left in, it hangs, with CPU spinning at 100%, while trying to
>>> load a
>>> > component:
>>> >
>>> > (gdb) t a a bt
>>> >
>>> > Thread 290 (Thread 0x7fffee1ba700 (LWP 14829)):
>>> > #0 0x00007fffec1f7c56 in QQuickValueTypeProvider::create
>>> > (this=0x7fffec7b3980 <getValueTypeProvider()::valueTypeProvider>,
>>> > type=1037, v=
>>> > @0x7fffee1b9080: 0x0) at util/qquickglobal.cpp:404
>>> > #1 0x00007ffff795813f in QQmlValueTypeProvider::createValueType
>>> > (this=0x7fffec7b3980 <getValueTypeProvider()::valueTypeProvider>,
>>> type=1037)
>>> > at qml/qqmlglobal.cpp:67
>>> > #2 0x00007ffff7914d41 in (anonymous
>>> > namespace)::QQmlValueTypeFactoryImpl::createValueType (
>>> > this=0x7ffff7dd7340 <(anonymous
>>> > namespace)::Q_QGS_factoryImpl::innerFunction()::holder>, t=1037) at
>>> > qml/qqmlvaluetype.cpp:121
>>> > #3 0x00007ffff7914e21 in (anonymous
>>> > namespace)::QQmlValueTypeFactoryImpl::valueType (
>>> > this=0x7ffff7dd7340 <(anonymous
>>> > namespace)::Q_QGS_factoryImpl::innerFunction()::holder>, idx=1037) at
>>> > qml/qqmlvaluetype.cpp:137
>>> > #4 0x00007ffff7915006 in QQmlValueTypeFactory::valueType (idx=1037) at
>>> > qml/qqmlvaluetype.cpp:169
>>> > #5 0x00007ffff7767d09 in QQmlPropertyValidator::validateObject
>>> > (this=0x7fffee1b9580, objectIndex=0, instantiatingBinding=0x0,
>>> > populatingValueTypeGroupProperty=false) at
>>> > compiler/qqmltypecompiler.cpp:1912
>>> > #6 0x00007ffff7766c6f in QQmlPropertyValidator::validate
>>> > (this=0x7fffee1b9580) at compiler/qqmltypecompiler.cpp:1730
>>> > #7 0x00007ffff775f676 in QQmlTypeCompiler::compile
>>> (this=0x7fffee1b96f0)
>>> > at compiler/qqmltypecompiler.cpp:265
>>> > #8 0x00007ffff7904370 in QQmlTypeData::compile (this=0x7dc4b0) at
>>> > qml/qqmltypeloader.cpp:2341
>>> > #9 0x00007ffff7903081 in QQmlTypeData::done (this=0x7dc4b0) at
>>> > qml/qqmltypeloader.cpp:2164
>>> > #10 0x00007ffff78fc2b0 in QQmlDataBlob::tryDone (this=0x7dc4b0) at
>>> > qml/qqmltypeloader.cpp:615
>>> > #11 0x00007ffff78fdf56 in QQmlDataLoader::setData (this=0x7d5b48,
>>> > blob=0x7dc4b0, d=...) at qml/qqmltypeloader.cpp:1208
>>> > #12 0x00007ffff78fde44 in QQmlDataLoader::setData (this=0x7d5b48,
>>> > blob=0x7dc4b0, file=0x7fffee1b9910) at qml/qqmltypeloader.cpp:1190
>>> > #13 0x00007ffff78fd683 in QQmlDataLoader::loadThread (this=0x7d5b48,
>>> > blob=0x7dc4b0) at qml/qqmltypeloader.cpp:1068
>>> > #14 0x00007ffff78fcb03 in QQmlDataLoaderThread::loadThread
>>> (this=0x751b90,
>>> > b=0x7dc4b0) at qml/qqmltypeloader.cpp:816
>>> > #15 0x00007ffff7908121 in void
>>> > QQmlThread::callMethodInThread<QQmlDataBlob*, QQmlDataBlob*,
>>> > QQmlDataLoaderThread>(void (QQmlDataLoaderThread::*)(QQmlDataBlob*),
>>> > QQmlDataBlob* const&)::I::call(QQmlThread*) (this=0x7dc7b0,
>>> thread=0x751b90)
>>> > at
>>> >
>>> /home/chriadam/Code/qt/qt5/qtbase/include/QtQml/5.3.2/QtQml/private/../../..
>>> > /../../../qtdeclarative/src/qml/qml/ftw/qqmlthread_p.h:160 #16
>>> > 0x00007ffff7973eee in QQmlThreadPrivate::threadEvent (this=0x729cd0) at
>>> > qml/ftw/qqmlthread.cpp:198
>>> > #17 0x00007ffff7973c76 in QQmlThreadPrivate::event (this=0x729cd0,
>>> > e=0x7dc7e0) at qml/ftw/qqmlthread.cpp:136
>>> > #18 0x00007ffff6619936 in QCoreApplicationPrivate::notify_helper
>>> > (this=0x60be80, receiver=0x729cd0, event=0x7dc7e0) at
>>> > kernel/qcoreapplication.cpp:1052
>>> > #19 0x00007ffff6619618 in QCoreApplication::notify
>>> (this=0x7fffffffdd10,
>>> > receiver=0x729cd0, event=0x7dc7e0) at kernel/qcoreapplication.cpp:997
>>> > #20 0x00007ffff6c7a83c in QGuiApplication::notify (this=0x7fffffffdd10,
>>> > object=0x729cd0, event=0x7dc7e0) at kernel/qguiapplication.cpp:1477
>>> > #21 0x00007ffff6619522 in QCoreApplication::notifyInternal
>>> > (this=0x7fffffffdd10, receiver=0x729cd0, event=0x7dc7e0) at
>>> > kernel/qcoreapplication.cpp:935
>>> > #22 0x00007ffff661d0af in QCoreApplication::sendEvent
>>> (receiver=0x729cd0,
>>> > event=0x7dc7e0)
>>> > at
>>> ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:237
>>> > #23 0x00007ffff661a7ed in QCoreApplicationPrivate::sendPostedEvents
>>> > (receiver=0x0, event_type=0, data=0x6ce920) at
>>> > kernel/qcoreapplication.cpp:1539
>>> > #24 0x00007ffff668bf85 in QEventDispatcherUNIX::processEvents
>>> > (this=0x7fffe0183690, flags=...) at
>>> kernel/qeventdispatcher_unix.cpp:587
>>> > #25 0x00007ffff66162c2 in QEventLoop::processEvents
>>> (this=0x7fffee1b9dd0,
>>> > flags=...) at kernel/qeventloop.cpp:136
>>> > #26 0x00007ffff6616583 in QEventLoop::exec (this=0x7fffee1b9dd0,
>>> flags=...)
>>> > at kernel/qeventloop.cpp:212
>>> > #27 0x00007ffff63a46ce in QThread::exec (this=0x729cd0) at
>>> > thread/qthread.cpp:511
>>> > #28 0x00007ffff7973ce7 in QQmlThreadPrivate::run (this=0x729cd0) at
>>> > qml/ftw/qqmlthread.cpp:149
>>> > #29 0x00007ffff63ab9c9 in QThreadPrivate::start (arg=0x729cd0) at
>>> > thread/qthread_unix.cpp:345
>>> > ---Type <return> to continue, or q <return> to quit---
>>> > #30 0x00007ffff54aa182 in start_thread (arg=0x7fffee1ba700) at
>>> > pthread_create.c:312
>>> > #31 0x00007ffff5b1530d in clone () at
>>> > ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
>>> >
>>> > Thread 2 (Thread 0x7fffef01f700 (LWP 14532)):
>>> > #0 0x00007ffff5b07fbd in poll () at
>>> ../sysdeps/unix/syscall-template.S:81
>>> > #1 0x00007ffff16d6b72 in poll (__timeout=-1, __nfds=1,
>>> > __fds=0x7fffef01ecc0) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
>>> > #2 _xcb_conn_wait (c=c at entry=0x658740, cond=cond at entry=0x658780,
>>> > vector=vector at entry=0x0, count=count at entry=0x0) at
>>> ../../src/xcb_conn.c:447
>>> > #3 0x00007ffff16d864f in xcb_wait_for_event (c=0x658740) at
>>> > ../../src/xcb_in.c:622
>>> > #4 0x00007ffff0cb5a79 in QXcbEventReader::run (this=0x6663a0) at
>>> > qxcbconnection.cpp:1043
>>> > #5 0x00007ffff63ab9c9 in QThreadPrivate::start (arg=0x6663a0) at
>>> > thread/qthread_unix.cpp:345
>>> > #6 0x00007ffff54aa182 in start_thread (arg=0x7fffef01f700) at
>>> > pthread_create.c:312
>>> > #7 0x00007ffff5b1530d in clone () at
>>> > ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
>>> >
>>> > Thread 1 (Thread 0x7ffff7fca7c0 (LWP 14524)):
>>> > #0 pthread_cond_wait@@GLIBC_2.3.2 () at
>>> > ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>>> > #1 0x00007ffff63ad096 in QWaitConditionPrivate::wait (this=0x6b6d00,
>>> > time=18446744073709551615) at thread/qwaitcondition_unix.cpp:136
>>> > #2 0x00007ffff63ace69 in QWaitCondition::wait (this=0x729d48,
>>> > mutex=0x729d40, time=18446744073709551615) at
>>> > thread/qwaitcondition_unix.cpp:208
>>> > #3 0x00007ffff79747ba in QQmlThreadPrivate::wait (this=0x729cd0) at
>>> > qml/ftw/qqmlthread.cpp:64
>>> > #4 0x00007ffff7974409 in QQmlThread::internalCallMethodInThread
>>> > (this=0x751b90, message=0x7dc7b0) at qml/ftw/qqmlthread.cpp:319
>>> > #5 0x00007ffff790817c in QQmlThread::callMethodInThread<QQmlDataBlob*,
>>> > QQmlDataBlob*, QQmlDataLoaderThread> (this=0x751b90, Member=
>>> > (void (QQmlDataLoaderThread::*)(QQmlDataLoaderThread * const,
>>> > QQmlDataBlob *)) 0x7ffff78fcadc
>>> > <QQmlDataLoaderThread::loadThread(QQmlDataBlob*)>,
>>> > arg=@0x7fffffffce00: 0x7dc4b0)
>>> > at
>>> >
>>> /home/chriadam/Code/qt/qt5/qtbase/include/QtQml/5.3.2/QtQml/private/../../..
>>> > /../../../qtdeclarative/src/qml/qml/ftw/qqmlthread_p.h:163 #6
>>> > 0x00007ffff78fc7ab in QQmlDataLoaderThread::load (this=0x751b90,
>>> > b=0x7dc4b0) at qml/qqmltypeloader.cpp:761
>>> > #7 0x00007ffff78fcebb in QQmlDataLoader::load (this=0x7d5b48,
>>> > blob=0x7dc4b0, mode=QQmlDataLoader::PreferSynchronous) at
>>> > qml/qqmltypeloader.cpp:936
>>> > #8 0x00007ffff78ffe95 in QQmlTypeLoader::getType (this=0x7d5b48,
>>> url=...,
>>> > mode=QQmlDataLoader::PreferSynchronous) at qml/qqmltypeloader.cpp:1606
>>> > #9 0x00007ffff78dedb0 in QQmlComponentPrivate::loadUrl (this=0x7cb9b0,
>>> > newUrl=..., mode=QQmlComponent::PreferSynchronous) at
>>> > qml/qqmlcomponent.cpp:691
>>> > #10 0x00007ffff78deaba in QQmlComponent::loadUrl (this=0x7fffffffd0a0,
>>> > url=...) at qml/qqmlcomponent.cpp:648
>>> > #11 0x00000000004040e0 in
>>> tst_librarymetrics_performance::compilation() ()
>>> > #12 0x00007ffff66256c1 in QMetaMethod::invoke (this=0x7fffffffd3b0,
>>> > object=0x7fffffffdd20, connectionType=Qt::DirectConnection,
>>> > returnValue=...,
>>> > val0=..., val1=..., val2=..., val3=..., val4=..., val5=...,
>>> val6=...,
>>> > val7=..., val8=..., val9=...) at kernel/qmetaobject.cpp:2169
>>> > #13 0x00007ffff6624b99 in QMetaObject::invokeMethod
>>> (obj=0x7fffffffdd20,
>>> > member=0x7a3ba0 "compilation", type=Qt::DirectConnection, ret=...,
>>> > val0=...,
>>> > val1=..., val2=..., val3=..., val4=..., val5=..., val6=...,
>>> val7=...,
>>> > val8=..., val9=...) at kernel/qmetaobject.cpp:1464
>>> > #14 0x00007ffff73d6c21 in QMetaObject::invokeMethod
>>> (obj=0x7fffffffdd20,
>>> > member=0x7a3ba0 "compilation", type=Qt::DirectConnection, val0=...,
>>> > val1=...,
>>> > val2=..., val3=..., val4=..., val5=..., val6=..., val7=...,
>>> val8=...,
>>> > val9=...) at
>>> ../../include/QtCore/../../src/corelib/kernel/qobjectdefs.h:399
>>> > #15 0x00007ffff73d26d4 in QTest::qInvokeTestMethodDataEntry
>>> (slot=0x7a3ba0
>>> > "compilation") at qtestcase.cpp:1890
>>> > #16 0x00007ffff73d2f64 in QTest::qInvokeTestMethod (slotName=0x7a4d48
>>> > "compilation()", data=0x0) at qtestcase.cpp:2015
>>> > #17 0x00007ffff73d3a81 in QTest::qInvokeTestMethods
>>> > (testObject=0x7fffffffdd20) at qtestcase.cpp:2242
>>> > #18 0x00007ffff73d4047 in QTest::qExec (testObject=0x7fffffffdd20,
>>> argc=1,
>>> > argv=0x7fffffffde38) at qtestcase.cpp:2475
>>> > #19 0x00000000004025c4 in main ()
>>> >
>>> > It appears that the QQuickValueTypeProvider instances are continuously
>>> > recreated (spinning at 100% and locking the incubator thread, which the
>>> > main thread is waiting on). Lars or Simon, are you able to guess what
>>> > might cause this issue? The implementation of
>>> qmlClearTypeRegistrations
>>> > seems fairly straightforward, but my memory of the complexities of
>>> value
>>> > type providers is hazy.
>>>
>>> Something looks fishy there :)
>>>
>>> The backtrace makes sense, but it shouldn't repeatedly end up in there.
>>> The
>>> last line number in question is a return statement for me. What is it in
>>> your
>>> source tree?
>>>
>>> Can you try to step and see where the loop header is?
>>>
>>> Simon
>>
>> _______________________________________________ Development mailing
> list Development at qt-project.org
> http://lists.qt-project.org/mailman/listinfo/development
>
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