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Possible memory leak in QNetworkAccessManager
Hi, I'm running this simple code in valgrind and it finds some memory leaks. Where am I wrong? I'm using Qt5.0.2 shipped with Ubuntu Linux 13.04 64bit
As you can see, I do delete the reply using deleteLater and qApp is quit with a proper delay, just to be completely sure that everything went as expected.
Valgrind output is:
valgrind --leak-check=yes ./TestNetworkBug
==31550== LEAK SUMMARY:
==31550== definitely lost: 1,904 bytes in 26 blocks
==31550== indirectly lost: 2,601 bytes in 22 blocks
==31550== possibly lost: 0 bytes in 0 blocks
==31550== still reachable: 25,100 bytes in 605 blocks
==31550== suppressed: 0 bytes in 0 blocks
Thanks in advance,
int main(int argc, char *argv)
QCoreApplication a(argc, argv);
Tester tester(&a); QObject::connect(&tester, SIGNAL(readyToQuit()), &a, SLOT(quit())); QTimer::singleShot(1000, &tester, SLOT(get())); return a.exec();
class Tester : public QObject
explicit Tester(QObject *parent = 0);
void finished(QNetworkReply *reply);
QNetworkAccessManager * manager;
#endif // TESTER_H
Tester::Tester(QObject parent) :
manager = new QNetworkAccessManager(this);
connect(manager, SIGNAL(finished(QNetworkReply)), this, SLOT(finished(QNetworkReply*)));
qDebug() << "~Tester";
qDebug() << "Posting request";
manager->get( QNetworkRequest( QUrl(QString("http://www.google.it"))) );
void Tester::finished(QNetworkReply *reply)
qDebug() << "Getting reply";
QTimer::singleShot(1000, this, SIGNAL(readyToQuit()));
Valgrind is known to produce false positives for some Qt classes.
I'm not sure setting the application as the parent for your Tester object is a good idea.
Anyway, please try with newer Qt version.
same with Qt 5.2.1
==312== LEAK SUMMARY:
==312== definitely lost: 1,640 bytes in 24 blocks
==312== indirectly lost: 4,191 bytes in 41 blocks
==312== possibly lost: 0 bytes in 0 blocks
==312== still reachable: 26,700 bytes in 608 blocks
==312== suppressed: 0 bytes in 0 blocks
On a side note: why shouldn't be a good idea to set qApp as the parent for a object? In this particular case, it makes no difference to set or not to set a parent for my Tester instance. But, in this case:
Tester * tester = new Tester(&a);
the idea is to let qApp call tester's destructor.
Isn't it correct?
In your case, you are creating the Tester object on a stack. So I guessed it will be first deleted by QApplication (after quit() is called), and then the standard out-of-scope deletion will be attempted. So it might be that this is what Valgrind reports as a leak here.
Since you say that it makes no difference, I guess I was wrong.
I think your guess is more than correct, but in real life it actually makes no difference.
On a side note, I would have expected a "double free or corruption" error, with a core-dump. But maybe I'm quite going off-topic here...