[Interest] Advice on random program finish crash

[Nuno Santos]

Hi,

I have made the following modification and it seems not crashing anymore:

static Manager* gManager = 0;

Manager* Manager::sharedManager()
{
	QMutexLocker lock(&managerMutex);

	if (!gManager)
	{
		gManager = new Manager();
	}

	return gManager;
}

Does this seems a better approach?

Regards,

Nuno

> On 07 Jan 2015, at 10:30, Nuno Santos <nunosantos at imaginando.pt> wrote:
> 
> Hi Igor,
> 
> Ops… You are right, it is not static.
> 
> I have tried your suggestion but now it crashes everytime I close the app and I can’t even get a stack trace like before. If I run it on debug, it points me to assembler code. Not anything I can really point to.
> 
> Regards,
> 
> Nuno
> 
>> 
>> On 07 Jan 2015, at 10:19, Igor Mironchik <igor.mironchik at gmail.com <mailto:igor.mironchik at gmail.com>> wrote:
>> 
>> On Wed, 07 Jan 2015 13:01:32 +0300, Nuno Santos <nunosantos at imaginando.pt <mailto:nunosantos at imaginando.pt>> wrote:
>> 
>>> Yes,
>>> 
>>> int main(int argc, char **argv)
>>> {
>>>    QGuiApplication app(argc, argv);
>>> 
>>>    ...
>>> 
>>>    return app.exec();
>>> }
>> 
>> No. Here QGuiApplication is not static. Then in your app the situation is the next: QGuiApplication destroyes before your Manager. But any QObject-derived class must be created after QApplication and destroyed before QApplication. May be this is the reason of your crash.
>> 
>> Make QGuiApplication static. For example:
>> 
>> static QSharedPointer< QApplication > application( int argc = 0, char ** argv = 0 )
>> {
>> 	static QSharedPointer< QApplication > app(
>> 		new QApplication( argc, argv ) );
>> 
>> 	return app;
>> }
>> 
>> and in main()
>> 
>> QSharedPointer< QApplication > app = application( argc, argv );
>> 
>> before any QObject...
>> 
>>> 
>>> 
>>>> On 07 Jan 2015, at 09:54, Igor Mironchik <igor.mironchik at gmail.com <mailto:igor.mironchik at gmail.com>> wrote:
>>>> 
>>>> Hi, I have one question: is QApplication static too?
>>>> 
>>>> On Wed, 07 Jan 2015 12:32:21 +0300, Nuno Santos <nunosantos at imaginando.pt <mailto:nunosantos at imaginando.pt>>
>>>> wrote:
>>>> 
>>>>> Hi,
>>>>> 
>>>>> I’m having a problem with a random crash that not always happens. I
>>>>> would like to have your advice on how to find the origin of it.
>>>>> 
>>>>> This crash always happens on program exit and the stack trace is the
>>>>> following:
>>>>> 
>>>>> Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
>>>>> 0   org.qt-project.QtCore         	0x0000000109a03549
>>>>> QMutexPrivate::allocate() + 105
>>>>> 1   org.qt-project.QtCore         	0x0000000109a02d1c
>>>>> QBasicMutex::lockInternal(int) + 92
>>>>> 2   org.qt-project.QtCore         	0x0000000109a02c64 QMutex::lock() + 52
>>>>> 3   org.qt-project.QtCore         	0x0000000109a0b6fd
>>>>> QWaitCondition::wait(QMutex*, unsigned long) + 173
>>>>> 4   org.qt-project.QtCore         	0x0000000109a0aeae
>>>>> QThread::wait(unsigned long) + 110
>>>>> 5   org.qt-project.QtNetwork      	0x000000010a4870da
>>>>> QNetworkAccessManagerPrivate::~QNetworkAccessManagerPrivate() + 58
>>>>> 6   org.qt-project.QtNetwork      	0x000000010a48722e
>>>>> QNetworkAccessManagerPrivate::~QNetworkAccessManagerPrivate() + 14
>>>>> 7   org.qt-project.QtCore         	0x0000000109c3e7c7
>>>>> QObject::~QObject() + 1879
>>>>> 8   org.qt-project.QtNetwork      	0x000000010a483c16
>>>>> QNetworkAccessManager::~QNetworkAccessManager() + 262
>>>>> 
>>>>> The only particularity of this QNetworkAccessManager is the fact that it
>>>>> is instantiated on a class that is a singleton:
>>>>> 
>>>>> class Manager : public QObject
>>>>> {
>>>>> public:
>>>>> 
>>>>> 	static Manager* sharedManager();
>>>>> 
>>>>> 	...
>>>>> 
>>>>> 	QNetworkAccessManager* networkAccessManager();
>>>>> 
>>>>> 	...
>>>>> 
>>>>> protected:
>>>>> 
>>>>> 	Manager();
>>>>> 	~Manager();
>>>>> 
>>>>> 	...
>>>>> 	
>>>>> 	QNetworkAccessManager _networkAccessManager;
>>>>> };
>>>>> 
>>>>> 
>>>>> Manager* Manager::sharedManager()
>>>>> {
>>>>> 	QMutexLocker lock(&managerMutex);
>>>>> 	static Manager manager;
>>>>> 	return &manager;
>>>>> }
>>>>> 
>>>>> Manager::Manager() :
>>>>> 	_networkAccessManager()
>>>>> {
>>>>> 	...	
>>>>> }
>>>>> 
>>>>> Manager::~Manager()
>>>>> {
>>>>> 	
>>>>> }
>>>>> 
>>>>> Is there any obvious reason for this crash to happen randomly at program
>>>>> termination?
>>>>> 
>>>>> Thanks,
>>>>> 
>>>>> Regards,
>>>>> 
>>>>> Nuno Santos
>>>>> _______________________________________________
>>>>> Interest mailing list
>>>>> Interest at qt-project.org <mailto:Interest at qt-project.org>
>>>>> http://lists.qt-project.org/mailman/listinfo/interest
>>>> 
>>>> 
>>>> --
>>>> Best Regards,
>>>> Igor Mironchik.
>>>> _______________________________________________
>>>> Interest mailing list
>>>> Interest at qt-project.org <mailto:Interest at qt-project.org>
>>>> http://lists.qt-project.org/mailman/listinfo/interest
>>> 
>> 
>> 
>> -- 
>> Best Regards,
>> Igor Mironchik.
> 
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