问题
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%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\QuickTime\QTSystem\;C:\Python26;C:\Linux\Cygwin\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\plugins\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.
回答1:
Well, I'm going to solve my own problem, again, so let's make this fun!
This is your last chance.
After this, there is no turning back.
You download the PyQT.exe, the story ends. You wake up in your bed and you believe whatever you want to believe. You modify the .pro file, you stay in wonderland. And, I show you how deep the rabbit hole goes.
I eventually gave up and downloaded the .exe, which does have MySQL support out of the box. If mysql does not work, your application is the problem, and I recommend you read this post here ( http://lists.trolltech.com/qt-interest/2006-06/thread00292-0.html ) or follow the quote below:
The issue is that you either have to use the addLibraryPath method or
create a QCoreApplication instance before your first call to loading a database
Believe me, manually installing PyQT+MySQL on Windows is a pain. But if you need some out of the way plugin to get at that the executable doesn't know, you have to go down the rabbit hole further.
Here is the new and improved .pro file:
LANGUAGE = C++
TEMPLATE = app
TARGET = executable
QT += core sql
QTPLUGIN += qsqlmysql
DEPENDPATH += .
INCLUDEPATH += C:\MySQL\bin
LIBS += -L C:\MySQL\lib\opt
# Input
SOURCES += database.cpp
Turns out I did have the right path to mysql, I was just confusing it with the .pro file that I had. After redownloading qt and following the steps above again, modifying my .pro file made all the difference.
But now I had to download SIP and PyQT. I followed the docs on there. There are a few more problems. Follow the links or the directions which are left there in case the information is removed.
If your SIP make install has an error where it is looking at Unix paths (/usr/bin) instead of DOS paths (C:\QT), look at this link http://old.nabble.com/Building-SIP-on-MinGW-:-problem-at-%22make-install%22-td28909249.html# (short version: the problem is the sh.exe in one of your other linux compilers like cygwin or msys, change the name temporarily to force the make install to use DOS path naming):
If you configure PyQT and it spits out a file error that has to do with QTCore
Google pexports and download. Go to %QTdir%/bin. Then follow instructions or link ( http://jeethurao.com/blog/?p=18 )
pexports QtCore4.dll > QtCore4.def
dlltool –dllname QtCore4.dll –def QtCore4.def –output-lib libQtCore4.a
move libQtCore4.a ..\lib
And now you know kung-fu.
P.S: I never tried this method myself. This is a different, but untested (by me) method of compiling PyQT, done up by the trolls at Trolltech: http://www.diotavelli.net/PyQtWiki/InstallingPyQTCommercialWin
来源：https://stackoverflow.com/questions/3494875/win7-mingw-qt-mysql-program-screams-cannot-find-lqsqlmysqld-where-is-the-mis