Re: [Development] [Qt-5.6] leak of QtSharedPointer::ExternalRefCountData objects

[Liang Jian]

I have submited a patch to fix this issue:
https://codereview.qt-project.org/#/c/141311/

On Mon, Nov 16, 2015 at 11:01 PM, Liang Jian  wrote:

> The allocated QV4::QObjectWrapper object hold a QPointer which track
> 'instance', it seems that it should be destroyed with 
> QObjectWrapper::destroyObject()
> to properly destruct the QPointer in it in QV4::MemoryManager::sweep().
> But when sweep() is being called it couldn't find the QObjectWrapper
> object created before which will make the QPointer in it not destructed
> properly.
>
> On Sun, Nov 15, 2015 at 11:58 PM, Liang Jian 
> wrote:
>
>> After some further investigation I can now confirm that one of the
>> leak is caused by the following code in QQmlObjectCreator::createInstance(),
>> qqmlobjectcreator.cpp:
>>
>> *sharedState->allJavaScriptObjects = QV4::QObjectWrapper::wrap(v4,
>> instance);
>>
>>   ++sharedState->allJavaScriptObjects;
>>
>>
>> But the reason is still unknown
>>
>>
>>
>> On Sun, Nov 15, 2015 at 10:19 PM, Liang Jian 
>> wrote:
>>
>>>   Hello everyone, I checkout qt 5.6 branch yesterday in my windows
>>> 10 x64 machine, I build it and run my program and see many leaks. Then I
>>> use C++ Memory Validator to find the source of the leaks, I can now
>>> confirm the leaked objects are QtSharedPointer::ExternalRefCountData which
>>> are created in QQmlObjectCreator::createInstance(), qqmlobjectcreator.cpp
>>> Line 1049, below is the call stack printed by C++ Memory Validator:
>>>
>>>Qt5Cored.dll  QtSharedPointer::ExternalRefCountData::getAndRef :
>>> [d:\qt5\qtbase\src\corelib\tools\qsharedpointer.cpp Line 1337]
>>>
>>>Qt5Qmld.dll  QWeakPointer::QWeakPointer :
>>> [d:\qt5\qtbase\src\corelib\tools\qsharedpointer_impl.h Line 706]
>>>
>>>Qt5Qmld.dll  QPointer::QPointer :
>>> [d:\qt5\qtbase\src\corelib\kernel\qpointer.h Line 65]
>>>
>>>Qt5Qmld.dll  QQmlObjectCreator::createInstance :
>>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 1049]
>>> 1044 : QQmlData *ddata = QQmlData::get(instance,
>>> /*create*/true);
>>> 1045 : ddata->rootObjectInCreation = true;
>>> 1046 :
>>> sharedState->rootContext->isRootObjectInCreation = false;
>>> 1047 : }
>>> 1048 :
>>> 1049 : sharedState->allCreatedObjects.push(instance);
>>> 1050 : } else {
>>> 1051 : Q_ASSERT(typeRef->component);
>>> 1052 : Q_QML_OC_PROFILE(sharedState->profiler,
>>> profiler.update(typeRef->component->fileName(),
>>> 1053 : context->url(), obj->location.line,
>>> obj->location.column));
>>> 1054 : if
>>> (typeRef->component->compilationUnit->data->isSingleton())
>>>Qt5Qmld.dll  QQmlObjectCreator::create :
>>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 197]
>>>
>>>Qt5Qmld.dll  QQmlComponentPrivate::beginCreate :
>>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 863]
>>>
>>>Qt5Qmld.dll  QQmlComponent::beginCreate :
>>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 812]
>>>
>>>Qt5Qmld.dll  QQmlComponent::create :
>>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 772]
>>>
>>>Qt5Quickd.dll  QQuickView::continueExecute :
>>> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 486]
>>>
>>>Qt5Quickd.dll  QQuickViewPrivate::execute :
>>> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 127]
>>>
>>>Qt5Quickd.dll  QQuickView::setSource :
>>> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 256]
>>>
>>>
>>> All the leaked QtSharedPointer::ExternalRefCountData objects are
>>> allocated in the line
>>> sharedState->allCreatedObjects.push(instance);
>>> then some other code path will also use QPointer (contained in some
>>> structures allocated by v4mm) to track the same object 'instance' and I
>>> guess the QPointer wasn't properly destructed which will cause the 
>>> QtSharedPointer::ExternalRefCountData
>>> not deleted.
>>> I have investigated this issue for nearly one day, but I can't find
>>> which code cause the leak, this is a non-trivial leak, I hope somebody can
>>> help to find the source of the leak. thanks!
>>>
>>>
>>
>
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Re: [Development] [Qt-5.6] leak of QtSharedPointer::ExternalRefCountData objects

[Liang Jian]

The allocated QV4::QObjectWrapper object hold a QPointer which track
'instance', it seems that it should be destroyed with
QObjectWrapper::destroyObject()
to properly destruct the QPointer in it in QV4::MemoryManager::sweep(). But
when sweep() is being called it couldn't find the QObjectWrapper object
created before which will make the QPointer in it not destructed properly.

On Sun, Nov 15, 2015 at 11:58 PM, Liang Jian  wrote:

> After some further investigation I can now confirm that one of the
> leak is caused by the following code in QQmlObjectCreator::createInstance(),
> qqmlobjectcreator.cpp:
>
> *sharedState->allJavaScriptObjects = QV4::QObjectWrapper::wrap(v4,
> instance);
>
>   ++sharedState->allJavaScriptObjects;
>
>
> But the reason is still unknown
>
>
>
> On Sun, Nov 15, 2015 at 10:19 PM, Liang Jian 
> wrote:
>
>>   Hello everyone, I checkout qt 5.6 branch yesterday in my windows 10
>> x64 machine, I build it and run my program and see many leaks. Then I use C++
>> Memory Validator to find the source of the leaks, I can now confirm the
>> leaked objects are QtSharedPointer::ExternalRefCountData which are created
>> in QQmlObjectCreator::createInstance(), qqmlobjectcreator.cpp Line 1049,
>> below is the call stack printed by C++ Memory Validator:
>>
>>Qt5Cored.dll  QtSharedPointer::ExternalRefCountData::getAndRef :
>> [d:\qt5\qtbase\src\corelib\tools\qsharedpointer.cpp Line 1337]
>>
>>Qt5Qmld.dll  QWeakPointer::QWeakPointer :
>> [d:\qt5\qtbase\src\corelib\tools\qsharedpointer_impl.h Line 706]
>>
>>Qt5Qmld.dll  QPointer::QPointer :
>> [d:\qt5\qtbase\src\corelib\kernel\qpointer.h Line 65]
>>
>>Qt5Qmld.dll  QQmlObjectCreator::createInstance :
>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 1049]
>> 1044 : QQmlData *ddata = QQmlData::get(instance,
>> /*create*/true);
>> 1045 : ddata->rootObjectInCreation = true;
>> 1046 :
>> sharedState->rootContext->isRootObjectInCreation = false;
>> 1047 : }
>> 1048 :
>> 1049 : sharedState->allCreatedObjects.push(instance);
>> 1050 : } else {
>> 1051 : Q_ASSERT(typeRef->component);
>> 1052 : Q_QML_OC_PROFILE(sharedState->profiler,
>> profiler.update(typeRef->component->fileName(),
>> 1053 : context->url(), obj->location.line,
>> obj->location.column));
>> 1054 : if
>> (typeRef->component->compilationUnit->data->isSingleton())
>>Qt5Qmld.dll  QQmlObjectCreator::create :
>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 197]
>>
>>Qt5Qmld.dll  QQmlComponentPrivate::beginCreate :
>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 863]
>>
>>Qt5Qmld.dll  QQmlComponent::beginCreate :
>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 812]
>>
>>Qt5Qmld.dll  QQmlComponent::create :
>> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 772]
>>
>>Qt5Quickd.dll  QQuickView::continueExecute :
>> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 486]
>>
>>Qt5Quickd.dll  QQuickViewPrivate::execute :
>> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 127]
>>
>>Qt5Quickd.dll  QQuickView::setSource :
>> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 256]
>>
>>
>> All the leaked QtSharedPointer::ExternalRefCountData objects are
>> allocated in the line
>> sharedState->allCreatedObjects.push(instance);
>> then some other code path will also use QPointer (contained in some
>> structures allocated by v4mm) to track the same object 'instance' and I
>> guess the QPointer wasn't properly destructed which will cause the 
>> QtSharedPointer::ExternalRefCountData
>> not deleted.
>> I have investigated this issue for nearly one day, but I can't find
>> which code cause the leak, this is a non-trivial leak, I hope somebody can
>> help to find the source of the leak. thanks!
>>
>>
>
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Re: [Development] [Qt-5.6] leak of QtSharedPointer::ExternalRefCountData objects

[Liang Jian]

After some further investigation I can now confirm that one of the leak
is caused by the following code in QQmlObjectCreator::createInstance(),
qqmlobjectcreator.cpp:

*sharedState->allJavaScriptObjects = QV4::QObjectWrapper::wrap(v4,
instance);

  ++sharedState->allJavaScriptObjects;


But the reason is still unknown



On Sun, Nov 15, 2015 at 10:19 PM, Liang Jian  wrote:

>   Hello everyone, I checkout qt 5.6 branch yesterday in my windows 10
> x64 machine, I build it and run my program and see many leaks. Then I use C++
> Memory Validator to find the source of the leaks, I can now confirm the
> leaked objects are QtSharedPointer::ExternalRefCountData which are created
> in QQmlObjectCreator::createInstance(), qqmlobjectcreator.cpp Line 1049,
> below is the call stack printed by C++ Memory Validator:
>
>Qt5Cored.dll  QtSharedPointer::ExternalRefCountData::getAndRef :
> [d:\qt5\qtbase\src\corelib\tools\qsharedpointer.cpp Line 1337]
>
>Qt5Qmld.dll  QWeakPointer::QWeakPointer :
> [d:\qt5\qtbase\src\corelib\tools\qsharedpointer_impl.h Line 706]
>
>Qt5Qmld.dll  QPointer::QPointer :
> [d:\qt5\qtbase\src\corelib\kernel\qpointer.h Line 65]
>
>Qt5Qmld.dll  QQmlObjectCreator::createInstance :
> [d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 1049]
> 1044 : QQmlData *ddata = QQmlData::get(instance,
> /*create*/true);
> 1045 : ddata->rootObjectInCreation = true;
> 1046 :
> sharedState->rootContext->isRootObjectInCreation = false;
> 1047 : }
> 1048 :
> 1049 : sharedState->allCreatedObjects.push(instance);
> 1050 : } else {
> 1051 : Q_ASSERT(typeRef->component);
> 1052 : Q_QML_OC_PROFILE(sharedState->profiler,
> profiler.update(typeRef->component->fileName(),
> 1053 : context->url(), obj->location.line,
> obj->location.column));
> 1054 : if
> (typeRef->component->compilationUnit->data->isSingleton())
>Qt5Qmld.dll  QQmlObjectCreator::create :
> [d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 197]
>
>Qt5Qmld.dll  QQmlComponentPrivate::beginCreate :
> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 863]
>
>Qt5Qmld.dll  QQmlComponent::beginCreate :
> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 812]
>
>Qt5Qmld.dll  QQmlComponent::create :
> [d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 772]
>
>Qt5Quickd.dll  QQuickView::continueExecute :
> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 486]
>
>Qt5Quickd.dll  QQuickViewPrivate::execute :
> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 127]
>
>Qt5Quickd.dll  QQuickView::setSource :
> [d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 256]
>
>
> All the leaked QtSharedPointer::ExternalRefCountData objects are
> allocated in the line
> sharedState->allCreatedObjects.push(instance);
> then some other code path will also use QPointer (contained in some
> structures allocated by v4mm) to track the same object 'instance' and I
> guess the QPointer wasn't properly destructed which will cause the 
> QtSharedPointer::ExternalRefCountData
> not deleted.
> I have investigated this issue for nearly one day, but I can't find
> which code cause the leak, this is a non-trivial leak, I hope somebody can
> help to find the source of the leak. thanks!
>
>
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[Development] [Qt-5.6] leak of QtSharedPointer::ExternalRefCountData objects

[Liang Jian]

  Hello everyone, I checkout qt 5.6 branch yesterday in my windows 10
x64 machine, I build it and run my program and see many leaks. Then I use C++
Memory Validator to find the source of the leaks, I can now confirm the
leaked objects are QtSharedPointer::ExternalRefCountData which are created
in QQmlObjectCreator::createInstance(), qqmlobjectcreator.cpp Line 1049,
below is the call stack printed by C++ Memory Validator:

   Qt5Cored.dll  QtSharedPointer::ExternalRefCountData::getAndRef :
[d:\qt5\qtbase\src\corelib\tools\qsharedpointer.cpp Line 1337]

   Qt5Qmld.dll  QWeakPointer::QWeakPointer :
[d:\qt5\qtbase\src\corelib\tools\qsharedpointer_impl.h Line 706]

   Qt5Qmld.dll  QPointer::QPointer :
[d:\qt5\qtbase\src\corelib\kernel\qpointer.h Line 65]

   Qt5Qmld.dll  QQmlObjectCreator::createInstance :
[d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 1049]
1044 : QQmlData *ddata = QQmlData::get(instance,
/*create*/true);
1045 : ddata->rootObjectInCreation = true;
1046 : sharedState->rootContext->isRootObjectInCreation
= false;
1047 : }
1048 :
1049 : sharedState->allCreatedObjects.push(instance);
1050 : } else {
1051 : Q_ASSERT(typeRef->component);
1052 : Q_QML_OC_PROFILE(sharedState->profiler,
profiler.update(typeRef->component->fileName(),
1053 : context->url(), obj->location.line,
obj->location.column));
1054 : if
(typeRef->component->compilationUnit->data->isSingleton())
   Qt5Qmld.dll  QQmlObjectCreator::create :
[d:\qt5\qtdeclarative\src\qml\qml\qqmlobjectcreator.cpp Line 197]

   Qt5Qmld.dll  QQmlComponentPrivate::beginCreate :
[d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 863]

   Qt5Qmld.dll  QQmlComponent::beginCreate :
[d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 812]

   Qt5Qmld.dll  QQmlComponent::create :
[d:\qt5\qtdeclarative\src\qml\qml\qqmlcomponent.cpp Line 772]

   Qt5Quickd.dll  QQuickView::continueExecute :
[d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 486]

   Qt5Quickd.dll  QQuickViewPrivate::execute :
[d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 127]

   Qt5Quickd.dll  QQuickView::setSource :
[d:\qt5\qtdeclarative\src\quick\items\qquickview.cpp Line 256]


All the leaked QtSharedPointer::ExternalRefCountData objects are
allocated in the line
sharedState->allCreatedObjects.push(instance);
then some other code path will also use QPointer (contained in some
structures allocated by v4mm) to track the same object 'instance' and I
guess the QPointer wasn't properly destructed which will cause the
QtSharedPointer::ExternalRefCountData
not deleted.
I have investigated this issue for nearly one day, but I can't find
which code cause the leak, this is a non-trivial leak, I hope somebody can
help to find the source of the leak. thanks!
___
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