QSqlDatabase: QMYSQL driver not loaded / Build MySQL Plugin

[mattewre]

Hi,
I'm experiencing the same problem that happens to anybody that is not expert too much expert in QT setup and wants to use QMYSQL plugin.

There are a lot of topics on the forum but a 100% step-by-step guide is not found (and many things are changed during the time). Lots of people are asking help after trying to fix the problem by their self so they don't have a 100% clean / stock base. Instead I would like to receive assistance starting from a clean installation of the OS and QT.

How to (step-by-step guide):

• Clean Ubuntu 14.04 installation / Linux Mind 17 32bit
  if you are using 64bit, x86_64-linux-gnu would be the correct path for most things, instead of i386-linux-gnu as you are going to read in this thread

• Installed QT in the user Home from http://www.qt.io/download-open-source
  Useful for unexperienced future readers:
  chmod u+x qtInstallerName.run
  ./qtInstallerName.run

• During the installation select all "Source Components". This will download and install the sources useful to build plugins

• Install a compiler
  sudo apt-get install g++
  sudo apt-get install libgl1-mesa-dev libglu1-mesa-dev

• Write you project and you will face problems with:
  db = QSqlDatabase::addDatabase("QMYSQL");

• When you try to build your project you have this problem
  QSqlDatabase: QMYSQL driver not loaded
  QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7

• Understand the problem running the commands:
  cd /home/[yourUsername]/Qt/[QtVersion]/gcc/plugins/sqldrivers
  ldd libqsqlmysql.so

• Read this line of the output:
  libmysqlclient_r.so.16 => not found

• Install these packages
  sudo apt-get install libssl-dev
  sudo apt-get install libmysqlclient-dev

• Now you should build the MYSQL plugin, according to http://doc.qt.io/qt-5/sql-driver.html documentation:
  cd /home/[yourUsername]/Qt/[QtVersion]/Src/qtbase/src/plugins/sqldrivers/mysql
  Then use the qmake provided in your Qt5.5 installation
  /home/[yourUsername]/Qt/[QtVersion]/gcc/bin/qmake
  Finally,
  make
  But it gives this error:
  /usr/bin/ld: cannot find -lmysqlclient_r

• Make some symbolic links to make it working (please check mysql version, it could not be 18.1.0 in the future).
  sudo ln -s /usr/lib/i386-linux-gnu/libmysqlclient.so /usr/lib/i386-linux-gnu/libmysqlclient_r.so
  sudo ln -s /usr/lib/i386-linux-gnu/libmysqlclient.so /usr/lib/i386-linux-gnu/libmysqlclient_r.so.18
  sudo ln -s /usr/lib/i386-linux-gnu/libmysqlclient.so /usr/lib/i386-linux-gnu/libmysqlclient_r.so.18.1.0

• Run again:
  make
  It seems that the plugin have been built correctly. Last output is:
  mv -f libqsqlmysql.so ../../../../plugins/sqldrivers/
  and finally run:
  make install

• Test your application.

[mattewre]

Other resources (not required)
The old libmysqlclient_r.so.16
[32bit] http://launchpadlibrarian.net/75949497/libmysqlclient16_5.1.58-1ubuntu1_i386.deb
[64bit] http://launchpadlibrarian.net/94808408/libmysqlclient16_5.1.58-1ubuntu5_amd64.deb
And install with sudo dpkg -i [packageName].deb

---

I also tried to copy libmysqlclient.so.18 renaming to _r.so.16.
sudo cp /usr/lib/i386-linux-gnu/libmysqlclient.so.18 /usr/lib/i386-linux-gnu/libmysqlclient_r.so.16
But this method is not working, in fact ldd libqsqlmysql.so command says:
/usr/lib/i386-linux-gnu/libmysqlclient_r.so.16: version libmysqlclient_16 not found (required by Qt/5.5/gcc/plugins/sqldrivers/libqsqlmysql.so)
It seems it can understand it is not a true "version 16".

[SGaist]

Hi,

It's more than just a number in your file name.

Just rebuild the plugin using your currently installed MySQL library, it will be faster than trying to install version 16.

[mattewre]

This post is deleted!

[mattewre]

@SGaist updated the first post with the progress made with plugin build.

[SGaist]

You need to install the sources using the maintenance tool and call qmake from your Qt 5.5

[mattewre]

@SGaist
Thank for the tip about qmake.
I have found and used the qmake from my Qt5.5 installation in /home/[myUsername]/Qt/5.5/gcc/bin/qmake
Then I managed to run make too, so I think I successfully built the plugin.

I have updated the first post, so other people can read it and follow step-by-step instruction. I'm not an expert of linux, so I you have some suggestion / improvements let me know and I'll edit the first post.

[SGaist]

You are doing something nasty: don't do the links to libmysqlclient_r yourself. You are missing the MySQL dev package. Install it and you're good to go.

[bionegative]

Thank you, i manage to build the driver on one of my develop machines. However when i am doing the same on my other Linux machine it doesnt list it as an avaible driver even?
[Qt run]
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC3 QODBC

~/Qt5.5.0/5.5/gcc_64/plugins/sqldrivers$ ls -l
-rwxr-xr-x 1 user user 73368 okt 9 06:48 libqsqlmysql.so
» shows its been newly built

ldd libqsqlmysql.so
libmysqlclient.so.18 => /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18 (0x00007f6565b28000)
» It have found the link

» It seems like Qt dosnt know about it afterall.
usualy qt's output list the driver atleast but doesnt show it as loaded untill its compiled.

Edit: I tried load it during runtime
[Qt]
QPluginLoader loader;
loader.load("TheFullFilePath");
loader.errorString();
» And it shows me this error: "The file '/home/..........libqsqlmysql.so' is not a valid Qt plugin.
So something when wrong during building.

FIXED:
» This error was kinda fun, there was a manually added path variable in qtcreator->Tools->Options->Build & Run->[Tab]Qt Versons. Where the Auto-detected where right and the Manual was pointing at an old qt4 version.
After deleting that and rebuild the driver it worked..

[Malhar]

Hi ,
i am facing a different kind of issue. after doing ldd to libqsqlmysql.so inside sqldrivers folder am unable to see
libmysqlclient_r.so.16 => not found this particular statement.
Please help and reply ASAP.

Thanks

[SGaist]

Hi and welcome to devnet,

Then, what do you see ?

[Malhar]

@SGaist After doing ldd libqmysqlclint.so got this

ldd libqsqlpsql.so
linux-vdso.so.1 => (0x00007ffd58adb000)
libpq.so.5 => /usr/lib/libpq.so.5 (0x00007f8a75afe000)
libQt5Sql.so.5 => /opt/Qt5.1.0/5.1.0/gcc_64/plugins/sqldrivers/./../../lib/libQt5Sql.so.5 (0x00007f8a758bf000)
libQt5Core.so.5 => /opt/Qt5.1.0/5.1.0/gcc_64/plugins/sqldrivers/./../../lib/libQt5Core.so.5 (0x00007f8a75236000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f8a74f32000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f8a74b6d000)
libssl.so.1.0.0 => /lib/x86_64-linux-gnu/libssl.so.1.0.0 (0x00007f8a7490e000)
libcrypto.so.1.0.0 => /lib/x86_64-linux-gnu/libcrypto.so.1.0.0 (0x00007f8a74533000)
libkrb5.so.3 => /usr/lib/x86_64-linux-gnu/libkrb5.so.3 (0x00007f8a74268000)
libcom_err.so.2 => /lib/x86_64-linux-gnu/libcom_err.so.2 (0x00007f8a74064000)
libgssapi_krb5.so.2 => /usr/lib/x86_64-linux-gnu/libgssapi_krb5.so.2 (0x00007f8a73e1e000)
libldap_r-2.4.so.2 => /usr/lib/x86_64-linux-gnu/libldap_r-2.4.so.2 (0x00007f8a73bcd000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f8a739af000)
libicui18n.so.51 => /opt/Qt5.1.0/5.1.0/gcc_64/plugins/sqldrivers/./../../lib/libicui18n.so.51 (0x00007f8a73596000)
libicuuc.so.51 => /opt/Qt5.1.0/5.1.0/gcc_64/plugins/sqldrivers/./../../lib/libicuuc.so.51 (0x00007f8a73210000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f8a7300c000)
libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007f8a72e0a000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f8a72c02000)
libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f8a728fa000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f8a725f4000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f8a723de000)
/lib64/ld-linux-x86-64.so.2 (0x00007f8a75f42000)
libk5crypto.so.3 => /usr/lib/x86_64-linux-gnu/libk5crypto.so.3 (0x00007f8a721af000)
libkrb5support.so.0 => /usr/lib/x86_64-linux-gnu/libkrb5support.so.0 (0x00007f8a71fa4000)
libkeyutils.so.1 => /lib/x86_64-linux-gnu/libkeyutils.so.1 (0x00007f8a71da0000)
libresolv.so.2 => /lib/x86_64-linux-gnu/libresolv.so.2 (0x00007f8a71b85000)
liblber-2.4.so.2 => /usr/lib/x86_64-linux-gnu/liblber-2.4.so.2 (0x00007f8a71976000)
libsasl2.so.2 => /usr/lib/x86_64-linux-gnu/libsasl2.so.2 (0x00007f8a7175b000)
libgssapi.so.3 => /usr/lib/x86_64-linux-gnu/libgssapi.so.3 (0x00007f8a7151d000)
libgnutls.so.26 => /usr/lib/x86_64-linux-gnu/libgnutls.so.26 (0x00007f8a7125f000)
libgcrypt.so.11 => /lib/x86_64-linux-gnu/libgcrypt.so.11 (0x00007f8a70fdf000)
libicudata.so.51 => /opt/Qt5.1.0/5.1.0/gcc_64/plugins/sqldrivers/./../../lib/libicudata.so.51 (0x00007f8a6f896000)
libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f8a6f658000)
libheimntlm.so.0 => /usr/lib/x86_64-linux-gnu/libheimntlm.so.0 (0x00007f8a6f44f000)
libkrb5.so.26 => /usr/lib/x86_64-linux-gnu/libkrb5.so.26 (0x00007f8a6f1c7000)
libasn1.so.8 => /usr/lib/x86_64-linux-gnu/libasn1.so.8 (0x00007f8a6ef26000)
libhcrypto.so.4 => /usr/lib/x86_64-linux-gnu/libhcrypto.so.4 (0x00007f8a6ecf3000)
libroken.so.18 => /usr/lib/x86_64-linux-gnu/libroken.so.18 (0x00007f8a6eade000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f8a6e8c5000)
libtasn1.so.6 => /usr/lib/x86_64-linux-gnu/libtasn1.so.6 (0x00007f8a6e6b1000)
libp11-kit.so.0 => /usr/lib/x86_64-linux-gnu/libp11-kit.so.0 (0x00007f8a6e46f000)
libgpg-error.so.0 => /lib/x86_64-linux-gnu/libgpg-error.so.0 (0x00007f8a6e26a000)
libwind.so.0 => /usr/lib/x86_64-linux-gnu/libwind.so.0 (0x00007f8a6e041000)
libheimbase.so.1 => /usr/lib/x86_64-linux-gnu/libheimbase.so.1 (0x00007f8a6de33000)
libhx509.so.5 => /usr/lib/x86_64-linux-gnu/libhx509.so.5 (0x00007f8a6dbea000)
libsqlite3.so.0 => /usr/lib/x86_64-linux-gnu/libsqlite3.so.0 (0x00007f8a6d931000)
libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f8a6d6f8000)
libffi.so.6 => /usr/lib/x86_64-linux-gnu/libffi.so.6 (0x00007f8a6d4f0000)

[Malhar]

@SGaist sorry man that was my mistake i did ldd to a different .so file.

Thanks

[Peter Van Grieken]

@mattewre: really good post! Tnx!
@SGaist: I've been reading the forums and noticed you've been answering a lot of question asked by beginners like me. Thank you for the support!!

This post really helped to understand this issue, but I've been trying to tackle the same problem for a few days now but for some reason I don't seem to be able to recompile the library "libqsqlmysql.so".

1. What I can see

• Compiling an application that uses mysql produces this output:

loaded library "/home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/libqsqlmysql.so"
QLibraryPrivate::loadPlugin failed on "/home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/libqsqlmysql.so" : "Cannot load library /home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/libqsqlmysql.so: (libmysqlclient_r.so.16: cannot open shared object file: No such file or directory)"
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7

• library:

I do have the file libmysqlclient_r.so.18 located in /usr/lib/
(note: I also have libmysqlclient_r.so.18.3.0 located in /usr/lib/ so during my frantic search for a solution I may have updated mysql again :-) ). I guess recompiling libqsqlmysql.so will link to the correct one?

• doublechecking library dependency

petervg@ubuntu:~/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers$ ldd libqsqlmysql.so
linux-vdso.so.1 => (0x00007ffc493bf000)
libmysqlclient_r.so.16 => not found
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f5ffbe74000)
libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f5ffbc3b000)
libnsl.so.1 => /lib/x86_64-linux-gnu/libnsl.so.1 (0x00007f5ffba21000)
libssl.so.10 => not found
libcrypto.so.10 => not found
libQt5Sql.so.5 => /home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/./../../lib/libQt5Sql.so.5 (0x00007f5ffb7e0000)
libQt5Core.so.5 => /home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/./../../lib/libQt5Core.so.5 (0x00007f5ffb09a000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f5ffae7b000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f5ffaaf9000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f5ffa7f1000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f5ffa5d9000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f5ffa20f000)
libicui18n.so.54 => /home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/./../../lib/libicui18n.so.54 (0x00007f5ff9da0000)
libicuuc.so.54 => /home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/./../../lib/libicuuc.so.54 (0x00007f5ff99f2000)
libicudata.so.54 => /home/petervg/Qt5.5.1/5.5/gcc_64/plugins/sqldrivers/./../../lib/libicudata.so.54 (0x00007f5ff7fc8000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f5ff7dc4000)
libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007f5ff7bc1000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f5ff79b9000)
libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f5ff76aa000)
/lib64/ld-linux-x86-64.so.2 (0x00005569bd500000)
libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f5ff743c000)

2. try to recompile libqsqlmysql.so from the source included with the offline installer.

petervg@ubuntu:~/Qt5.5.1/5.5/Src/qtbase/src/plugins/sqldrivers/mysql$ qmake
petervg@ubuntu:~/Qt5.5.1/5.5/Src/qtbase/src/plugins/sqldrivers/mysql$ make
rm -f libqsqlmysql.so
g++ -Wl,--no-undefined -Wl,-O1 -Wl,--enable-new-dtags -Wl,-rpath,/home/petervg/Qt5.5.1/5.5/gcc_64 -Wl,-rpath,/home/petervg/Qt5.5.1/5.5/gcc_64 -Wl,-rpath,/home/petervg/Qt5.5.1/5.5/gcc_64/lib -shared -o libqsqlmysql.so .obj/main.o .obj/qsql_mysql.o .obj/moc_qsql_mysql_p.o -rdynamic -L/usr/lib64/mysql -lz -lcrypt -lnsl -lm -lssl -lcrypto -L/home/petervg/Qt5.5.1/5.5/Src/qtbase/lib -lQt5Sql -L/usr/local/lib -lmysqlclient_r -lQt5Core -lpthread
/usr/bin/ld: cannot find -lQt5Sql
/usr/bin/ld: cannot find -lQt5Core
collect2: error: ld returned 1 exit status
Makefile:142: recipe for target '../../../../plugins/sqldrivers/libqsqlmysql.so' failed
make: *** [../../../../plugins/sqldrivers/libqsqlmysql.so] Error 1
petervg@ubuntu:~/Qt5.5.1/5.5/Src/qtbase/src/plugins/sqldrivers/mysql$

-> I'm not sure if this is relevant, but I can see the library Qt5Sql cannot be found even though in (1) i can see the library libQt5Sql.so.5 is found in /home/petervg/Qt5.5.1/5.5/gcc_64/lib.

3. try to recompile libqsqlmysql.so from the source I downloaded (qt-everywhere-opensource-src-5.5.1).

petervg@ubuntu:~/Downloads/qt-everywhere-opensource-src-5.5.1/qtbase/src/plugins/sqldrivers/mysql$ qmake
petervg@ubuntu:~/Downloads/qt-everywhere-opensource-src-5.5.1/qtbase/src/plugins/sqldrivers/mysql$ make
rm -f libqsqlmysql.so
g++ -Wl,--no-undefined -Wl,-O1 -Wl,--enable-new-dtags -Wl,-rpath,/home/petervg/Qt5.5.1/5.5/gcc_64 -Wl,-rpath,/home/petervg/Qt5.5.1/5.5/gcc_64 -Wl,-rpath,/home/petervg/Qt5.5.1/5.5/gcc_64/lib -shared -o libqsqlmysql.so .obj/main.o .obj/qsql_mysql.o .obj/moc_qsql_mysql_p.o -rdynamic -L/usr/lib64/mysql -lmysqlclient_r -lz -lcrypt -lnsl -lm -lssl -lcrypto -L/home/petervg/Downloads/qt-everywhere-opensource-src-5.5.1/qtbase/lib -lQt5Sql -lQt5Core -lpthread
/usr/bin/ld: cannot find -lQt5Sql
/usr/bin/ld: cannot find -lQt5Core
collect2: error: ld returned 1 exit status
Makefile:142: recipe for target '../../../../plugins/sqldrivers/libqsqlmysql.so' failed
make: *** [../../../../plugins/sqldrivers/libqsqlmysql.so] Error 1

-> identical results...

4. Conclusion

I've learned it's best to first make sure you have the latest mysql files installed before installing QT, so i guess I could completely reinstall Qt now, but I'ld like to learn what I have been doing wrong....

Any tips where I should look further?

With kind regards
Peter

[Peter Van Grieken]

(answering myself :-) )

i open the mysql.pro in qtcreator (Coming from windows... I like an ide a lot more than the command line... sorry :-) ) and I added folowing line to this file:

LIBS += -L/home/petervg/Qt5.5.1/5.5/gcc_64/lib

I did this because I knew libQt5Sql.so.5 was located in /home/petervg/Qt5.5.1/5.5/gcc_64/lib.

What I do need to look into, is WHY this works? In /etc/environment I added:

• "PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/petervg/Qt5.5.1/Tools/QtCreator/bin/:/home/petervg/Qt5.5.1/5.5/gcc_64/lib:/home/petervg/Qt5.5.1/Tools/QtCreator/lib/qtcreator:/usr/lib"/x86_64-linux-gnu"

and in /home/petervg/.profile I added:

• LIBRARY_PATH="/home/petervg/Qt5.5.1/5.5/gcc_64/lib:/home/petervg/Qt5.5.1/5.5/gcc_64/plugins:/usr/lib/x86_64-linux-gnu:$LIBRARY_PATH"
  LD_LIBRARY_PATH="/home/petervg/Qt5.5.1/5.5/gcc_64/lib:/home/petervg/Qt5.5.1/5.5/gcc_64/plugins:/usr/lib/x86_64-linux-gnu:$LD_LIBRARY_PATH"
  export LIBRARY_PATH
  export LD_LIBRARY_PATH

Neither of these solutions worked.

But my problem us finally solved, so up to the next one... If anybody could shed some light as to why adding the line in the .PRO file worked, but not when adding the path to the environment variables... I'll be glad to know...

Tnx!

[SGaist]

Hi,

The most simple way to ensure you're using the right qmake is to call it with the full path to the executable. One other problem comes from the fact that you also have Qt Creator's stuff in your PATH. Don't do it, Qt Creator comes with it's own build of Qt so that it's a complete autonomous application.

The LIBS += -L/path/ tells the linker where to look for libraries.

[Peter Van Grieken]

Thanks!

I'll take a good look at the PATH variable.

[SGaist]

Leave it clean, that way you ensure that you're not mixing things on your system while building the driver.

[RalfSchaefer]

Hi,

i'm facing a similiar sort of problem, not completely solvable by the steps above.
I recompiled the QMYSQL-plugin and it's linked to the correct mysql-libraries.
After doing ldd /opt/Qt/5.5/gcc_64/plugins/sqldrivers/libqsqlmysql.so I got this:

ldd /opt/Qt/5.5/gcc_64/plugins/sqldrivers/libqsqlmysql.so 
       linux-vdso.so.1 (0x00007fffd7d83000)
       libmysqlclient.so.18 => /usr/lib64/libmysqlclient.so.18 (0x00007f9eb8607000)
        libz.so.1 => /lib64/libz.so.1 (0x00007f9eb83f0000)
        libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007f9eb81b5000)
        libnsl.so.1 => /lib64/libnsl.so.1 (0x00007f9eb7f9d000)
        libssl.so.1.0.0 => /lib64/libssl.so.1.0.0 (0x00007f9eb7d34000)
        libcrypto.so.1.0.0 => /lib64/libcrypto.so.1.0.0 (0x00007f9eb7941000)
        libQt5Sql.so.5 => /opt/Qt/5.5/gcc_64/lib/libQt5Sql.so.5 (0x00007f9eb7701000)
        libQt5Core.so.5 => /opt/Qt/5.5/gcc_64/lib/libQt5Core.so.5 (0x00007f9eb6fba000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f9eb6d9d000)
        libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00007f9eb6a1b000)
        libm.so.6 => /lib64/libm.so.6 (0x00007f9eb6719000)
        libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f9eb6502000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f9eb615b000)
        libdl.so.2 => /lib64/libdl.so.2 (0x00007f9eb5f56000)
        libicui18n.so.54 => /opt/Qt/5.5/gcc_64/lib/libicui18n.so.54 (0x00007f9eb5ae8000)
        libicuuc.so.54 => /opt/Qt/5.5/gcc_64/lib/libicuuc.so.54 (0x00007f9eb5739000)
        libicudata.so.54 => /opt/Qt/5.5/gcc_64/lib/libicudata.so.54 (0x00007f9eb3d0f000)
        libgthread-2.0.so.0 => /usr/lib64/libgthread-2.0.so.0 (0x00007f9eb3b0d000)
        librt.so.1 => /lib64/librt.so.1 (0x00007f9eb3904000)
        libglib-2.0.so.0 => /usr/lib64/libglib-2.0.so.0 (0x00007f9eb35f5000)
        /lib64/ld-linux-x86-64.so.2 (0x000055fc1f3d8000)
        libpcre.so.1 => /usr/lib64/libpcre.so.1 (0x00007f9eb338e000)

So, erverything looks fine here.

When I try to connect to the database, it still doesn't work. It seems, QSqlDatabase loads the plugin without problems, setting dabase specific stuff fails.

My code-snippet, containing additional debug-stuff:

    QPluginLoader loader;
    loader.setFileName("/opt/Qt/5.5/gcc_64/plugins/sqldrivers/libqsqlmysql.so");
    qDebug() << "PluginLoader worked =" << loader.load();
    qDebug() << "Plugin Loader error=" << loader.errorString();

    QStringList driverlist =QSqlDatabase::drivers();
    qDebug() << "Databases: ";
    for (int i = 0; i < driverlist.size(); ++i)
    {
        qDebug() << driverlist.at(i);
    }

    if (!db_opened)
    {
            db = new QSqlDatabase();
            qDebug() << "Step 1 - Database:    is valid=" << db->isValid();
            db->addDatabase("QMYSQL3","cooptimedb");
            qDebug() << "Step 2 - Database:    is valid=" << db->isValid();

            db->setHostName("localhost");
            db->setDatabaseName("cooptime");
            db->setUserName("cooptime");
            db->setPassword("...");
            db->setPort(3306);

            qDebug() << "Database\n========\nHostname: " << db->hostName() << "\nDatabasename: " << db->databaseName() << "\nUsername: " << db->userName() << "\nPassword: " << db->password()  << "\nPort: " << db->port();


            if (! db->open())
            {
                qDebug() << "db errorcode=" <<  db->lastError().nativeErrorCode();
                qDebug() << "db errormessage=" << db->lastError() .text();
            }

The output of the code above is:

PluginLoader worked = true
Plugin Loader error= "Unknown error"
Databases: 
"QSQLITE"
"QMYSQL"
"QMYSQL3"
"QPSQL"
"QPSQL7"
Step 1 - Database:    is valid= false
Step 2 - Database:    is valid= false
Database
========
Hostname:  "" 
Databasename:  "" 
Username:  "" 
Password:  "" 
Port:  -1
db errorcode= ""
db errormessage= "Driver not loaded Driver not loaded"

So it seems, the driver still doesn't load.

Any help would be very appreciated. Thanks in advance.

[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.