QSqlDatabase open crashes application

Kaluss

Hello,
got problem with QSqlDatabase:

Code is simple:
try{
db.open()
}
catch(...){
std::cout << "Something is wrong";
}

Of corse I got db fully configured and is everything ok if I got internet connection (remote database) but if not the application carshes. No exception no nothing?

Does anybody know where is the problem?

BR
Tom

Kaluss

If I change host name to non valid it also crashes...

Db config looks ike:

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");

db.setHostName( "host" );
db.setDatabaseName( "dbName" );
db.setUserName( "username" );
db.setPassword( "password" );

SGaist

Hi,

What version of Qt ? On what OS ?

Kaluss

Qt 5.5
Windows 8.1

Kaluss

As I checked in debug mode got segmentation fault from open() function.

Could I do something with that or it's a bug and I have to find different way to work with databases ?

SGaist

What is the stack trace ?

Kaluss

0 QMYSQLDriver::open qsql_mysql.cpp 1320 0x6ad85e22
1 QSqlDatabase::open C:/QtNew/5.5/mingw492_32/bin/Qt5Sqld.dll 835 0x6794482e
2 main main.cpp 21 0x401756

Crashes on line:
mysql_set_character_set(d->mysql, "utf8");

SGaist

What version of MySQL do you have installed ?

Kaluss

I have to mention that use of 32 bit MySQL on 64 bit machine is determinated by using mingw32. Otherwise I couldn't compile mysql driver.

szergejbubka

Any progress? I have this issue too on Linux 64bit with Qt 5.5. With Qt 5.4.2 it works as expected, open() returns false. How could I help in fixing or finding a solution/workaround?

SebastianS

I am facing the same issue with Windows 7 64bit, MySQL 5.6 32bit, Qt 5.5 mingw. With Qt 5.4.1 it worked without any problem.

SGaist

Same stack trace ?

szergejbubka

The stack trace on Linux:

0	__GI_____strtoul_l_internal	strtol_l.c	298	0x7ffff5b229d7	
1	mysql_get_server_version			0x7fffdc8e41bc	
2	mysql_set_character_set			0x7fffdc8e4b92	
3	??			0x7fffdcc7d18e	
4	QSqlDatabase::open()			0x7ffff6b1d954	
5	UpdateVerifier::getUpdate(QString, int, QString, QString, QString, QString, int)			0x41aadc	
6	main	main.cpp	23	0x408b1d

SGaist

Are you using any special parameters to setup the connection ?

szergejbubka

No special parameters. Here is my code:

    QString dbName = "mydb";
    {
        QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL", dbName);
        db.setHostName(databaseUrl);
        db.setPort(databasePort);
        db.setDatabaseName(databaseName);
        db.setUserName(databaseUsername);
        db.setPassword(databasePassword);
//        db.setConnectOptions("MYSQL_OPT_CONNECT_TIMEOUT=5");

        if(db.open() == false)
            qDebug("Cannot access update database");
        else {
            QSqlQuery query = QSqlQuery(db);
            ...
        }
    }

    QSqlDatabase::removeDatabase(dbName);

The crash is in open() with the same stack trace independently of using the timeout option or not. But I found something, that might help. If I turn off my wifi on my laptop, it crashes immediately. On the other hand, if the wifi is on, and I unplug the network cable from my router, it still crashes, but just after 20 seconds (which is not 5, as I would expect from the timeout option, but this might be another issue). In either case there was no connection to the remote mysql server. So there is a difference in behavior when there is a network interface and when no network interface exists.

mcosta

Hi and welcome to devnet,

could be related to this?? https://bugreports.qt.io/browse/QTBUG-47452

SGaist

@mcosta might be indeed

@szergejbubka It would be great if you could apply the following patch: https://codereview.qt-project.org/#/c/123488/ and test again

szergejbubka

This patch solved the crash on Linux.

Thanks.

SebastianS

How can I apply this patch on windows?

Here is my stack trace:

0	load_defaults			0x5fff84c8	
1	load_defaults			0x5fff8700	
2	mysql_get_server_version			0x5ff8f60c	
3	QMYSQLDriver::open	C:/Qt/Qt5.5.0/5.5/mingw492_32/plugins/sqldrivers/qsqlmysqld.dll	1328	0x6ad85e6b	
4	QSqlDatabase::open	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Sqld.dll	835	0xa87482e	
5	FirstTimeWizard::checkDatabaseSettings	firsttimewizard.cpp	318	0x42bff6	
6	FirstTimeWizard::qt_static_metacall	moc_firsttimewizard.cpp	99	0x43170d	
7	QMetaObject::activate	C:/Users/Thor/Pers/build-Mars-Desktop_Qt_5_5_0_MinGW_32bit-Debug/debug/Qt5Cored.dll	3718	0x6b906d5f	
8	QMetaObject::activate	C:/Users/Thor/Pers/build-Mars-Desktop_Qt_5_5_0_MinGW_32bit-Debug/debug/Qt5Cored.dll	3583	0x6b9066a4	
9	QAbstractButton::clicked	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	303	0xb16616f	
10	QAbstractButtonPrivate::emitClicked	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	534	0xaf26de9	
11	QAbstractButtonPrivate::click	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	527	0xaf26d84	
12	QAbstractButton::mouseReleaseEvent	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	1132	0xaf28083	
13	QWidget::event	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	8665	0xae63f21	
14	QAbstractButton::event	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	1089	0xaf27ef8	
15	QPushButton::event	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	673	0xafb571e	
16	QApplicationPrivate::notify_helper	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	3717	0xae2f3f1	
17	QApplication::notify	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	3277	0xae2d513	
18	QCoreApplication::notifyInternal	C:/Users/Thor/Pers/build-Mars-Desktop_Qt_5_5_0_MinGW_32bit-Debug/debug/Qt5Cored.dll	965	0x6b8de86a	
19	QCoreApplication::sendSpontaneousEvent	C:/Qt/Qt5.5.0/5.5/mingw492_32/bin/Qt5Widgetsd.dll	227	0xb193ce5	
...	<Mehr>

and here is the code:

    QSqlDatabase datab = QSqlDatabase::addDatabase("QMYSQL", "test");
    datab.setHostName(leHost->text());
    datab.setPort(lePort->text().toInt());
    datab.setDatabaseName("testname");
    datab.setUserName(leUser->text().trimmed());
    datab.setPassword(lePass->text());

    if (datab.open()) {
        ...
    }
    else
    {
        ...
    }

SGaist

It boils down to: get the sources of Qt 5 and apply the diff, then just build the plugin