QSqlDatabase::addDatabase cause crash???

nyaruko

I have the following code which is called by many threads using a thread pool:

 @QByteArray PureImageCache::GetImageFromCache(MapType::Types type, Point pos, int zoom)

 {   

       lock.lockForRead();

      QByteArray ar;

      if(gtilecache.isEmpty()|gtilecache.isNull())

      return ar;

QString dir=gtilecache;
Mcounter.lock();
qlonglong id=++ConnCounter;
Mcounter.unlock();

    QString db=dir+"Data.qmdb";
    {
        QSqlDatabase cn;

        cn = QSqlDatabase::addDatabase("QSQLITE",QString::number(id));

        cn.setDatabaseName(db);
        cn.setConnectOptions("QSQLITE_ENABLE_SHARED_CACHE");
        if(cn.open())
        {
            QSqlQuery query(cn);
            query.exec&#40;QString("SELECT Tile FROM TilesData WHERE id = (SELECT id FROM Tiles WHERE X=%1 AND Y=%2 AND Zoom=%3 AND Type=%4&#41;").arg(pos.X()).arg(pos.Y()).arg(zoom).arg((int) type));
            query.next();
            if(query.isValid())
            {
                ar=query.value(0).toByteArray();
                //qDebug()<<"Got";
            }else{
                //qDebug()<<"Miss";
            }
            cn.close();
        }
    }
    QSqlDatabase::removeDatabase(QString::number(id));
lock.unlock();
return ar;

}@

However, I have met one crash (not every time) right after I call the:

cn = QSqlDatabase::addDatabase("QSQLITE",QString::number(id));

function. And the call stack says the error is:

Debug Assertion Failed!
File:f:\dd\vctools\crt_bld\self_x86\crt\src\dbgdel.cpp
Line: 52
Expression:_BLOCK_TYPE_IS_VALID(pHead->nBlockUse)

Is there any thing in my code that is not multithread safe? I am not familiar with the Qt Sql part, can anyone give some suggestions?

SGaist

Hi and welcome to devnet,

One thing that is not correct is that you don't release the lock after if(gtilecache.isEmpty()|gtilecache.isNull())

nyaruko

Thanks for that. I have asked some of my friends and now there would be some deeper thoughts about this problem, would you like to have a look?
http://qt-project.org/forums/viewthread/49170/

[quote author="SGaist" date="1414800164"]Hi and welcome to devnet,

One thing that is not correct is that you don't release the lock after if(gtilecache.isEmpty()|gtilecache.isNull())[/quote]