[Interest] Advice on random program finish crash

[Michael Sué]

Hi,
 
With this approach, the object will no longer be deleted at program exit, right? So there can be no crash on deletion anymore.
 
- Michael.
 
From: interest-bounces+sue=sf.mpg.de at qt-project.org [mailto:interest-bounces+sue=sf.mpg.de at qt-project.org] On Behalf Of Nuno Santos
Sent: Wednesday, January 07, 2015 1:16 PM
To: Igor Mironchik
Cc: Interests Qt
Subject: Re: [Interest] Advice on random program finish crash
 
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> wrote:
 
On Wed, 07 Jan 2015 13:01:32 +0300, Nuno Santos < <mailto:nunosantos at imaginando.pt> 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> 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>
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
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--
Best Regards,
Igor Mironchik.
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-- 
Best Regards,
Igor Mironchik.
 
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