Getting Qt to work in Fedora 12

Question

Qt is installed by default in Fedora 12. Tried the hello world program:

 #include </usr/include/QtGui/QApplication>
 #include </usr/include/QtGui/QPushButton>

 int main(int argc, char *argv[])
 {
   QApplication app(argc, argv);
   QPushButton hello("Hello world!");
   hello.show();
   return app.exec();
}

With normal compilation g++ -o helloWorld helloWorld.cpp, it shows:

/tmp/ccfEv7zR.o: In function main': helloWorld.cpp:(.text+0x2a): undefined reference toQApplication::QApplication(int&, char**, int)' helloWorld.cpp:(.text+0x53): undefined reference to QPushButton::QPushButton(QString const&, QWidget*)' helloWorld.cpp:(.text+0x8b): undefined reference toQApplication::exec()' helloWorld.cpp:(.text+0x99): undefined reference to QPushButton::~QPushButton()' helloWorld.cpp:(.text+0xac): undefined reference toQPushButton::~QPushButton()' helloWorld.cpp:(.text+0xc0): undefined reference to QApplication::~QApplication()' helloWorld.cpp:(.text+0xdc): undefined reference toQApplication::~QApplication()' /tmp/ccfEv7zR.o: In function QString::QString(char const*)': helloWorld.cpp:(.text._ZN7QStringC1EPKc[QString::QString(char const*)]+0x1d): undefined reference toQString::fromAscii_helper(char const*, int)' /tmp/ccfEv7zR.o: In function QString::~QString()': helloWorld.cpp:(.text._ZN7QStringD1Ev[QString::~QString()]+0x2d): undefined reference toQString::free(QString::Data*)' collect2: ld returned 1 exit status bash: ./helloWorld: No such file or directory

and with

qmake -project;qmake;make

it shows:

/usr/lib64/qt-3.3/bin/moc /usr/include/QtGui/qapplication.h -o /usr/include/QtGui/moc_qapplication.cpp moc: Cannot create /usr/include/QtGui/moc_qapplication.cpp make: * [/usr/include/QtGui/moc_qapplication.cpp] Error 1

Any idea how to get it to work?

UPDATE:
My cpp was already in a non-read-only directory. Now I changed the header to

#include <QApplication>
#include <QPushButton>

and it shows this error:

g++ -c -pipe -Wall -W -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -DQT_NO_DEBUG -I/usr/lib64/qt-3.3/mkspecs/default -I. -I. -I/usr/lib64/qt-3.3/include -o helloWorld.o helloWorld.cpp
helloWorld.cpp:1:25: error:
QApplication: No such file or
directory helloWorld.cpp:2:24: error:
QPushButton: No such file or directory
helloWorld.cpp: In function ‘int
main(int, char*)’: helloWorld.cpp:7:
error: ‘QApplication’ was not declared
in this scope helloWorld.cpp:7: error:
expected ‘;’ before ‘app’
helloWorld.cpp:8: error: ‘QPushButton’
was not declared in this scope
helloWorld.cpp:8: error: expected ‘;’
before ‘hello’ helloWorld.cpp:9:
error: ‘hello’ was not declared in
this scope helloWorld.cpp:10: error:
‘app’ was not declared in this scope
helloWorld.cpp: At global scope:
helloWorld.cpp:5: warning: unused
parameter ‘argc’ helloWorld.cpp:5:
warning: unused parameter ‘argv’ make:
** [helloWorld.o] Error 1

Show us your PATH and QDIR environment variables. Did you do a "custom" qt install or compiled your own at one stage? — Derick Schoonbee
@Derick: Are you the downvoter? I just received the "Popular Question" badge for this question. I didn't do a custom qt installed. In the very first line of my post I had mentioned that it was already installed by default in Fedora. First time I'm working with QT. How would I know about QDIR? — Nav
Nope wasn't me :) I suggest that you update your OS and Qt. If not try to search for the Fedora packages that have the Qt documentation and example code. There you'll see some samples with code that compiles with Qt3. (Is there a reason why your are on an "old" Fedora? Maybe install a new box? Tried a virtual machine such as VirtualBox or even Vagrant?) — Derick Schoonbee

Derick Schoonbee Derick Schoonbee · Accepted Answer · 2011-04-05T11:03:11

The problem is that /usr/include/QtGui/ is "protected". (You do not have write permissions to that directory)

Move your helloworld.cpp to a directory that you have write access to. For example /home/yourusername/helloworld/helloworld.cpp

Change:

#include </usr/include/QtGui/QApplication>
#include </usr/include/QtGui/QPushButton>

To:

#include <QApplication>
#include <QPushButton>

Then try:

qmake -project
qmake
make

I suggest you read a bit up on using qmake. You will then understand why you had the first error: qmake helps you to get the includes and right libraries step by creating a Makefile for you.

Edit:

Another thing to check is to ensure qmake is in your path and optionally if the QTDIR environment variable is set.

Getting Qt to work in Fedora 12

2 Answers