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Danny Hatt
17th August 2010, 16:35
Hello everyone.

I am attempting to make a qt program on Windows 7 that uses a MySQL plugin.

I have compiled both qt and the mysql plugin with no problems using my minGW 32bit compiler.

However, I keep on getting an error like this:



mingw32-make -f Makefile.Debug
mingw32-make[1]: Entering directory `C:/Users/dhatt/Desktop/testdb2'
g++ -c -g -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_SQL_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN - I"..\..\..\..\QT\qt\include\QtCore" -I"..\..\..\..\QT\qt\include\QtGui" -I"..\..\..\..\QT\qt\include\QtSql" -I"..\..\..\..\QT\qt\include" -I"..\..\..\..\MySQL\bin" -I"..\..\..\..\QT\qt\include\ActiveQt" -I"debug" -I"..\..\..\..\QT\qt\mkspecs\win32-g++" -o debug\database.o database.cpp
g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -Wl,-subsystem,windows -o debug\testdb2.exe debug/database.o -L"c:\QT\qt\lib" -lmingw32 -lqtmaind -L C:\MySQL\lib\opt -LC:/QT/qt/plugins/sqldrivers -lqsqlmysqld -lQtSqld4 -lQtGuid4 -lQtCored4 -LC:\MySQL\lib\opt
C:/qt/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../mingw32/bin/ld.exe: cannot find -lqsqlmysqld
collect2: ld returned 1 exit status
mingw32-make[1]: *** [debug\executable.exe] Error 1
mingw32-make[1]: Leaving directory `C:/Users/dhatt/Desktop/testdb2'
mingw32-make: *** [debug] Error 2


I apologize in advance for being very verbose of what I did, but I am doing this partly for troubleshooting, and partly so any other lost souls don't end up wasting three weeks on this particular problem. :)

Here are my specs:

Windows 7 Nokia's Open Source QT
Qt SDK for Windows (C:\Qt\2010.04\qt)
Linux MinGW Version 5.1.6 (C\Linux\MinGW)
MySQL5 with C++ files (C:\MySQL5)

If you want to know how I installed qt, just follow this site's instructions:

http://www.jiggerjuice.net/software/qt-sql-drivers.html

These other sites may hold some extra information tidbits:

http://doc.qt.nokia.com/4.6/sql-driver.html

http://www.rag.com.au/linux/qt4howto.html

http://qtnode.net/wiki?title=Qt4_on_Windows(yes, I did check with Nokia's docs!!!)

http://doc.trolltech.com/qq/qq10-windows-deployment.html

This fellow mentioned about remaking qmake, which I am not doing unless I have a good reason.

http://christopher.rasch-olsen.no/2009/04/14/qt-45-and-mysql-plugin-with-mingw-on-windows-xp/

I've already deleted the plugin cache once before, I hope I won't have to do it again...

http://doc.trolltech.com/4.2/plugins-howto.html#the-plugin-cache

http://ubuntuforums.org/showthread.php?t=1070155

If there is any confusion, between the two compilation option (creating the mysql libraries statically, or as a plugin), I chose for the plugin because it compiles quicker and I don't have to worry about licensing.

Generally, the big trouble of mysql to most people is to make a mingw compatible library. Generally, I did this with the mingw tools in ( https://olex.openlogic.com/packages/mingw-utils )...



c:\> cd MySQL\lib\opt
c:\mysql\lib\opt> reimp -d libmysql.lib
c:\mysql\lib\opt> dlltool --input-def libmysql.def --dllname libmysql.dll --output-lib libmysql.a -k


I should have done it right since in my C:\MySQL\lib\opt, it has the two files:

libmysql.a
libmysql.lib
LIBMYSQL.def (not a typo)

and in the C:\MySQL\bin directory, I have:

libmySQL.bin (not a typo)

I had compiled the mysql plugin beforehand:



cd %QTDIR%\src\plugins\sqldrivers\mysql
qmake "INCLUDEPATH+=C:\MySQL\include" "LIBS+=C:\MYSQL\lib\opt\libmysql.lib" mysql.pro
mingw32-make


As a result, I have in my C:\QT\qt\plugins\sqldrivers folder:

libqsqlmysql4.a
libqsqlmysqldq4.a
libqsqlodbc4.a
libqsqlodbcd4.a
qsqlmysql4.dll
qsqlmysqld4.dll
qsqlodbc4.dll
qsqlodbc4.dll

And in my C:\QT\bin folder

QtSql4.dll
QtSqld4.dll

So, I assume from this site ( http://www.qtforum.org/article/21352/how-to-compile-use-a-mysql-driver.html) that I got it right.


I didn't use the binaries of qt itself, I used the compiled qt files(also from Nokia), but reconfigured and recompiled them using mingw32-make. I had no errors. This was my configuration options for remaking qt.

-opensource
-nomake examples
-nomake demos
-no-sql-lite
-no-qt3support
-no-gif
-no-libpng
-no-libmng
-no-libtiff
-no-phonon
-no-phonon-backend
-no-multimedia
-no-audio-backend
-no-webkit
-no-script
-no-scripttools
-nodeclarative
-plugin-sql-mysql -l mysql -I C:\QT\qt\include -L C:\QT\qt\lib\opt


Here is my .pro file

LANGUAGE = C++

TEMPLATE = app
TARGET = executable
QT += core sql
QTPLUGIN += qsqlmysql
DEPENDPATH += .
INCLUDEPATH += C:\MySQL\bin
LIBS += -L C:\MySQL\lib\opt -lmysql

# Input
SOURCES += database.cpp

I installed the plugin described in here:

C:\QT\qt

My path variables are:

%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\Sy stem32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShel l\v1.0\;C:\Program Files (x86)\QuickTime\QTSystem\;C:\Python26;C:\Linux\Cyg win\bin;C:\mingw-utils-0.3\bin;C:\QT\qt\bin;C:\MySQL\bin;C:\MySQL\include ;C:\QT\mingw32\bin;C:\QT\mingw\bin;C:\QT\qt\plugin s\sqldrivers

The qt command prompt added a few extra though, so I did all of this in the command prompt.

Setting up a MinGW/Qt only environment...
-- QTDIR set to C:\QT\qt
-- PATH set to C:\QT\qt\bin
-- Adding C:\QT\bin to PATH
-- Adding C:\Windows\System32 to PATH
-- QMAKESPEC set to win32-g++ (mingw is my only compiler so, this is unnecessary)

Although I either did all that already, or it is redundant. I only add this for the sake of completeness.

Here is my code (database.cpp):



#include <QtSql>
#include <iostream>
using namespace std;

int main( int argc, char ** argv )
{
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("---.---.---.---");
db.setDatabaseName("--------");
db.setUserName("------------");
db.setPassword("------------");
if (!db.open()) cout << "Failed to connect to mysql" << endl;
else cout << "Works finally." << endl;
QSqlDatabase::removeDatabase("QMYSQL");
exit ( 0 );
}


Very simple, yes?

I went to my directory with the example code, run



mingw32-make distclean
qmake
mingw32-make


and get the error message above. I've tried building a version with the release version only (no debug), and it still shows the same message, but with "cannot find -lqsqlmysq", so it is not that.

I've tried many things, but where should I look next to solve it; maybe someone can narrow it down for me, set me on the right path, or even better, solve his annoying problem.

Also, I plan to use python bindings with my code (I need PyQT + MySQL). If the proposed solution would prevent me from doing so, let me know.