MySQL plugin, mingw64 and Windows 8.1 - QMYSQL driver not loaded

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@SGaist I didn't build Qt - I just downloaded the pre-compiled binary.

I have been building my application in debug mode - which I assume is why qsqlmysqld.dll is been used.

I just tried building a release version and it results in all the same errors but with qsqlmysql.dll instead.

SGaist

Which version did you install exactly ?

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@SGaist The details from Qt Creator's option menu:


Name: Qt 5.6.0 (mingw64)
ABI: x86-windows-msys-pe-64bit
Source: C:\msys64\mingw64
mkspec: win32-g++
qmake: C:\msys64\mingw64\bin\qmake.exe
Default: debug
Version: 5.6.0
QMAKE_SPEC win32-g++
QMAKE_VERSION 3.0
QMAKE_XSPEC win32-g++
QT_HOST_BINS C:\msys64\mingw64\bin
QT_HOST_DATA C:\msys64\mingw64\share\qt5
QT_HOST_LIBS C:\msys64\mingw64\lib
QT_HOST_PREFIX C:\msys64\mingw64
QT_INSTALL_ARCHDATA C:\msys64\mingw64\share\qt5
QT_INSTALL_BINS C:\msys64\mingw64\bin
QT_INSTALL_CONFIGURATION 
QT_INSTALL_DATA C:\msys64\mingw64\share\qt5
QT_INSTALL_DEMOS C:\msys64\mingw64\share\qt5\examples
QT_INSTALL_DOCS C:\msys64\mingw64\share\qt5\doc
QT_INSTALL_EXAMPLES C:\msys64\mingw64\share\qt5\examples
QT_INSTALL_HEADERS C:\msys64\mingw64\include
QT_INSTALL_IMPORTS C:\msys64\mingw64\share\qt5\imports
QT_INSTALL_LIBEXECS C:\msys64\mingw64\share\qt5\bin
QT_INSTALL_LIBS C:\msys64\mingw64\lib
QT_INSTALL_PLUGINS C:\msys64\mingw64\share\qt5\plugins
QT_INSTALL_PREFIX C:\msys64\mingw64
QT_INSTALL_QML C:\msys64\mingw64\share\qt5\qml
QT_INSTALL_TESTS C:\msys64\mingw64\share\qt5\tests
QT_INSTALL_TRANSLATIONS C:\msys64\mingw64\share\qt5\translations
QT_SYSROOT 
QT_VERSION 5.6.0

SGaist

I meant where did you get that package ?

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@SGaist Oh, I used MSYS2 to install it with the command: pacman -Sy mingw-w64-{i686,x86_64}-qt5

Qt Creator is the GPL Windows version from the main site. (this is 32bit which I thought might cause problems but everything else seems to work - I can compile and run 64bit applications that don't use MySQL)

SGaist

For Qt Creator, no there's no influence. It only uses Qt, the architecture of it is of no importance for the functionality (unless of course you are building a plugin for it)

Silly question but: do you have a MinGW64 build of MySQL available on your machine ?

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@SGaist I don't have MySQL database installed on this machine (as I have another machine setup as a server with it)

I have a 64bit version of MySQL Workbench which was installed from the pre-compiled binaries. This contains the 64bit libmysql.dll which I am using.

Somehow I also have a 32bit version of libmysql.dll although I'm not quite sure where this came from. I've been using it for some time as it works when I compile a 32bit version of my application.

SGaist

Then I wonder if the 32bit version of libmysql is found before the 64bit version.

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@SGaist I don't think so. When I remove the 32bit libmysql.dll file the 32bit version of my app stops working but the 64bit version still doesn't work.

And when:
LoadLibraryExA("libmysql.dll", NULL, NULL);
is called, it successfully loads the library on both the 32bit and 64bit versions of my app.

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This is the dependences from qsqlmysql.dll (http://imgur.com/MUMHGfN)

Just noticed that it seems a bit odd that libmariadb.dll is needed but libmysql.dll isn't?

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And that was the problem. I added libmariadb.dll to the same folder as the executable (same place as libmysql.dll) and now it all works!

Why I need a MariaDB library to connect to a MySQL database is still a mystery to me though... In fact libmysql.dll isn't even used - I just removed it and it still works.

Thanks for the help anyway! (if I can work out how, I'll mark this thread as solved)

SGaist

MariaDB is a drop-in replacement for MySQL and AFAIK, you should be able to connect to MySQL servers through the MariaDB client libraries.