Notorious QSqlDatabase: QMYSQL driver not loaded but available

fractal5

On a Gentoo system, I get the notorious Qt mysql error:

QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7
false

This has numerous posts on various forums, some of which are unresolved.

Simple code to reproduce the error is given in e.g. http://adamcavendish.is-programmer.com/posts/40431.html

@int main(int argc, char *argv[])
{
QApplication a(argc, argv);

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("localhost");
db.setDatabaseName("test");
db.setUserName("test");
db.setPassword("xxxxxxxxxx");
bool ok = db.open();
qDebug() << ok;
db.close();

MainWindow w;
w.show();

return a.exec&#40;&#41;;

}
@
I have in my project .pro file:

QT += sql

There are no compiler errors. However, as the link http://adamcavendish.is-programmer.com/posts/40431.html suggests, my issue is of this type:

Using ldd I see that:

$ ldd libqsqlmysql.so
./libqsqlmysql.so: /usr/lib64/libmysqlclient_r.so.16: version `libmysqlclient_16' not found (required by ./libqsqlmysql.so)

Simply giving it this file as a symlink to the newer version (18) doesn't work.

So in other words I'm assuming I need to recompile this libqsqlmysql.so to use the newer version?

How do I go about compiling the new version?

According to qtcreator/5.4/Src/README it is stated that: "A typical `configure; make' build process is used."

I do configure (in qtcreator/5.4/Src), everything seems fine.

I do make, and I get:

g++ -c -pipe -O2 -Wall -W -D_REENTRANT -DQT_BOOTSTRAPPED -DQT_LITE_UNICODE -DQT_NO_CAST_TO_ASCII -DQT_NO_CODECS -DQT_NO_DATASTREAM -DQT_NO_LIBRARY -DQT_NO_QOBJECT -DQT_NO_SYSTEMLOCALE -DQT_NO_THREAD -DQT_NO_UNICODETABLES -DQT_NO_USING_NAMESPACE -DQT_NO_DEPRECATED -DQT_NO_TRANSLATION -DQT_QMAKE_LOCATION="/usr/bin/qmake" -DQT_CRYPTOGRAPHICHASH_ONLY_SHA1 -DQT_NO_CAST_FROM_ASCII -DQT_NO_DEBUG -I/usr/share/qt4/mkspecs/linux-g++ -I. -I/usr/include/qt4 -I. -o qlatincodec.o ../../corelib/codecs/qlatincodec.cpp
../../corelib/codecs/qlatincodec.cpp:35:19: fatal error: qlist.h: No such file or directory
#include "qlist.h"

I've tried the following versions:

Qt Creator 3.1.2 (opensource) Based on Qt 5.3.1 (GCC 4.6.1, 64 bit)
Qt Creator 3.3.1 (opensource) Based on Qt 5.4.1 (GCC 4.6.1, 64 bit)

SGaist

Hi and welcome to devnet,

You are going to long way. You can just build the plugin itself against your MySQL version 18 library. See "here":http://doc.qt.io/qt-5/sql-driver.html#qmysql-for-mysql-4-and-higher

fractal5

[quote author="SGaist" date="1425248560"]Hi and welcome to devnet,

You are going to long way. You can just build the plugin itself against your MySQL version 18 library. See "here":http://doc.qt.io/qt-5/sql-driver.html#qmysql-for-mysql-4-and-higher[/quote]

Thanks for the advice.

I've attempted this procedure now, and sadly it fails. I think I'm giving incorrect arguments to qmake.

I'm trying:

$ qmake "INCLUDEPATH+=/usr/lib64" "LIBS+=-L/usr/lib64 -lmysqlclient_r" mysql.pro make
WARNING: /home/devel/programs/qtcreator/5.4/Src/qtbase/src/plugins/sqldrivers/qsqldriverbase.pri:4: Unable to find file for inclusion qt_plugin
Project MESSAGE: Warning: unknown QT: core-private
Project MESSAGE: Warning: unknown QT: sql-private
Cannot find file: make.

The directory /usr/lib64 contains libmysqlclient. I tried some other options for INCLUDEPATH, e.g. I tried passing the directory ~/qtcreator/5.4/gcc_64/include/QtSql but all of my attempts result in the same error.

SGaist

Which qmake are you using ? You system's qmake or the 5.4 qmake ?

fractal5

[quote author="SGaist" date="1425255019"]Which qmake are you using ? You system's qmake or the 5.4 qmake ?[/quote]

I used my system qmake.

When I use the one found at qtcreator/5.4/Src/qtbase/bin/qmake I get:

$ ~/programs/qtcreator/5.4/Src/qtbase/bin/qmake "INCLUDEPATH+=/usr/lib64" "LIBS+=-L/usr/lib64 -lmysqlclient_r" mysql.pro make
Project ERROR: No module claims plugin type 'sqldrivers'

SGaist

In what folder are you calling that ?

fractal5

[quote author="SGaist" date="1425328932"]In what folder are you calling that ?[/quote]

In qtcreator/5.4/Src/qtbase/src/plugins/sqldrivers/mysql

Full command with prompt:

~/programs/qtcreator/5.4/Src/qtbase/src/plugins/sqldrivers/mysql $ qmake "INCLUDEPATH+=/usr/lib64" "LIBS+=-L/usr/lib64 -lmysqlclient_r" mysql.pro make

SGaist

If I read your like correctly you are calling your system installed qmake, or did I miss something ?