QSqlDatabase: QMYSQL driver not loaded / Build MySQL Plugin

[SGaist]

Hi and welcome to devnet,

Your code is wrong, you are creating an invalid QSqlDatabase object on the heap and then you call a static function on it.

Please take a look at QSqlDatabase's detailed documentation. There's an example there on how to do the setup and connection.

[RalfSchaefer]

@SGaist Thanks for your help!! That's it. Now all works fine for me!

[fikou1335]

Hi SGaist,

I have a new problem with QMysql, everything worked fine since today, actually when I executede this line

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

I have this error

libgcc_s.so.1 must be installed for pthread_cancel to work

I don't know why,

the plugin is correctly compiled without error, and using the ldd he found the libgcc_s.so.1

Can you help me please!

[SGaist]

Hi and welcome to devnet,

Which architecture are on ?

[fikou1335]

Hi and thanks for your quick response

I m working on Ubuntu 64bits
i got this

Precision-M4600:/usr/local/Trolltech/Qt-4.8.6/plugins/sqldrivers$ ldd libqsqlmysql.so 	linux-vdso.so.1 =>  (0x00007ffceb314000)
	libmysqlclient.so.18 => /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18 (0x00007f7a884c6000)
	libQtSql.so.4 => /usr/local/Trolltech/Qt-4.8.6/lib/libQtSql.so.4 (0x00007f7a88285000)
	libQtCore.so.4 => /usr/local/Trolltech/Qt-4.8.6/lib/libQtCore.so.4 (0x00007f7a87d91000)
	libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f7a87a7f000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f7a87868000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f7a874a3000)
	libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f7a8728a000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f7a87086000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f7a86e68000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f7a86b62000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f7a8695a000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f7a88c10000)

and this

Precision-M4600:/usr/lib/x86_64-linux-gnu$ ldd libmysqlclient.so.18
	linux-vdso.so.1 =>  (0x00007ffe50bc0000)
	libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fe8f4940000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fe8f473c000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fe8f451e000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fe8f4218000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe8f3e53000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fe8f5091000)

If I comment the addBase line in my code everything works fine without connecting to the Database of course.
when I try to list the drivers using

QStringList driverlist =QSqlDatabase::drivers();

I got this

Databases: QSQLITE QMYSQL3 QMYSQL

Everything works fine Monday, I checked the database, I could write on it fine,, but yesterday, it crash my application
hope it can help!

[fikou1335]

I have just created a new app with the main function and it works and connect fine to my database.

In my code I comment all the last code that I added this week and SURPRISE it works as well.
the problem is probably due to a third library that i started to use this week. I ll check why it cause a crach to mysql o_O

[SGaist]

What new library did you add ?

[fikou1335]

This one Dahua SDK

You can check by yourslef, they have a source example, PTZControl that works fine, but try to add

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

and you should get the same error.

this sdk is used to control PTZ cams of Dahua brand.
I changed my code by creating a new app to control cameras and get the informations of position from my big application.

put this main instsead of it

#include <QtGui/QApplication>
#include "dialog.h"
#include <QTextCodec>
#include <QObject>
#include <QtSql/QSqlDatabase>
#include <QStringList>
#include <QtSql/QSqlQuery>
#include <QtSql/QSqlRecord>
#include <QVariant>
#include <iostream>



int main(int argc, char *argv[])
{
    QSqlDatabase DB;
    cout <<endl<< "try connect MYSQL "<< endl;
    try
    {
        DB = QSqlDatabase::addDatabase( "QMYSQL");
    }
    catch(...)
    {
        cout << "fatal error"<< endl;
    }
    cout << "add database"<< endl;
    DB.setDatabaseName( "intrusiondetection" );
    DB.setUserName( "root" );

    DB.setPassword( "root" );
    cout << "1"<< endl;

    DB.setHostName( "" );

    cout << "try to connect"<< endl;
    if (DB.open())
    {
        cout << "QMYSQL correctly connected "<< endl;
    }
    else
    {
        cout << "QMYSQL not connected "<< endl;
    }


    QApplication a(argc, argv);
    QTextCodec::setCodecForCStrings(QTextCodec::codecForName("UTF-8"));
    Dialog w;
    w.show();

    return a.exec();
}

tell me if you got the same error.?

[SGaist]

One thing that you should first correct: move the database initialization code after the QApplication object creation.

[fikou1335]

i already tried every configuration but doesn't work! just a question by the way:
Is the QDbus available on the Ubuntu system since they said it is Unix only library..? I try to communicate between PTZcontrol process and my application

[SGaist]

Ubuntu is a unix based OS since it's based on the Debian distribution. QDBus is available on Linux, OS X and Windows (the two later requires that you install dbus by hand)

[Hervinsen]

Thanks to your guide, it is working on Kubuntu 16 with Qt 5.8
here is my output :

• /opt/Qt5.8.0/5.8/gcc_64/plugins/sqldrivers$ ldd libqsqlmysql.so
  linux-vdso.so.1 => (0x00007ffcf0bf4000)
  libQt5Sql.so.5 => /opt/Qt5.8.0/5.8/gcc_64/plugins/sqldrivers/./../../lib/libQt5Sql.so.5 (0x00007f28a7452000)
  libQt5Core.so.5 => /opt/Qt5.8.0/5.8/gcc_64/plugins/sqldrivers/./../../lib/libQt5Core.so.5 (0x00007f28a6d32000)
  libmysqlclient.so.20 => /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20 (0x00007f28a66fa000)
  libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f28a6372000)
  libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f28a5fa2000)
  libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f28a5d82000)
  libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f28a5a72000)
  libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f28a585a000)
  libicui18n.so.56 => /opt/Qt5.8.0/5.8/gcc_64/plugins/sqldrivers/./../../lib/libicui18n.so.56 (0x00007f28a53ba000)
  libicuuc.so.56 => /opt/Qt5.8.0/5.8/gcc_64/plugins/sqldrivers/./../../lib/libicuuc.so.56 (0x00007f28a5002000)
  libicudata.so.56 => /opt/Qt5.8.0/5.8/gcc_64/plugins/sqldrivers/./../../lib/libicudata.so.56 (0x00007f28a361a000)
  libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f28a3412000)
  librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f28a320a000)
  libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f28a2fea000)
  libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007f28a2de2000)
  libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f28a2aca000)
  /lib64/ld-linux-x86-64.so.2 (0x0000560448d0b000)
  libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f28a285a000)

[Amit Talbot]

im using qt 5.9 on mac this piece of code worked like charm for me

brew install mysql-connector-c