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Asked: 2026-05-26T03:20:03+00:00

I’m following this tutorial for building a simple OpenGl application in C++ using QT.

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I’m following this tutorial for building a simple OpenGl application in C++ using QT.

I’m trying to compile the application using g++ and the command line but I get the following errors:

/tmp/ccH2KFoZ.o: In function `GLWidget::GLWidget(QWidget*)':
GLWidget.cpp:(.text+0x38): undefined reference to `QGLWidget::QGLWidget(QWidget*, QGLWidget const*, QFlags<Qt::WindowType>)'
GLWidget.cpp:(.text+0x41): undefined reference to `vtable for GLWidget'
GLWidget.cpp:(.text+0x4b): undefined reference to `vtable for GLWidget'
GLWidget.cpp:(.text+0x5e): undefined reference to `QGLWidget::setMouseTracking(bool)'
GLWidget.cpp:(.text+0x6f): undefined reference to `QGLWidget::~QGLWidget()'
/tmp/ccH2KFoZ.o: In function `GLWidget::GLWidget(QWidget*)':
GLWidget.cpp:(.text+0xbe): undefined reference to `QGLWidget::QGLWidget(QWidget*, QGLWidget const*, QFlags<Qt::WindowType>)'
GLWidget.cpp:(.text+0xc7): undefined reference to `vtable for GLWidget'
GLWidget.cpp:(.text+0xd1): undefined reference to `vtable for GLWidget'
GLWidget.cpp:(.text+0xe4): undefined reference to `QGLWidget::setMouseTracking(bool)'
GLWidget.cpp:(.text+0xf5): undefined reference to `QGLWidget::~QGLWidget()'
/tmp/ccH2KFoZ.o: In function `GLWidget::resizeGL(int, int)':
GLWidget.cpp:(.text+0x1e1): undefined reference to `gluOrtho2D'
/tmp/ccH2KFoZ.o: In function `GLWidget::keyPressEvent(QKeyEvent*)':
GLWidget.cpp:(.text+0x2dd): undefined reference to `QWidget::close()'
/tmp/ccDIuk1w.o: In function `main':
main.cpp:(.text+0x29): undefined reference to `QApplication::QApplication(int&, char**, int)'
main.cpp:(.text+0x6a): undefined reference to `QApplication::exec()'
main.cpp:(.text+0xa0): undefined reference to `QApplication::~QApplication()'
main.cpp:(.text+0xb8): undefined reference to `QApplication::~QApplication()'
/tmp/ccDIuk1w.o: In function `QWidget::resize(int, int)':
main.cpp:(.text._ZN7QWidget6resizeEii[QWidget::resize(int, int)]+0x2d): undefined reference to `QWidget::resize(QSize const&)'
/tmp/ccDIuk1w.o: In function `GLWidget::~GLWidget()':
main.cpp:(.text._ZN8GLWidgetD1Ev[GLWidget::~GLWidget()]+0x13): undefined reference to `vtable for GLWidget'
main.cpp:(.text._ZN8GLWidgetD1Ev[GLWidget::~GLWidget()]+0x1d): undefined reference to `vtable for GLWidget'
main.cpp:(.text._ZN8GLWidgetD1Ev[GLWidget::~GLWidget()]+0x28): undefined reference to `QGLWidget::~QGLWidget()'
collect2: ld returned 1 exit status

I’ve tried searching for a solution but all the solutions I can suggest altering a .pro file which I assume is something used by Netbeans or Codeblocks, neither of which I’m using.

What are the correct command line flags to pass to g++ so I can compile this application?

Here is the g++ command I’m currently using:

g++ *.cpp  -I/usr/include/qt4 -I/usr/include/qt4/Qt -I/usr/include/QtCore -I/usr/include/QtGui -lGL

Edit: I ended up using a project file that looks like this. 

TEMPLATE = app
TARGET = glQt
QT += opengl

HEADERS += \
    GLWidget.h

SOURCES += \
    GLWidget.cpp \
    main.cpp
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1 Answer

  1. Editorial Team

    The .pro file is needed by QMake, the make app distributed with Qt.
    This pro file specifies all the files needed to build your project, as well as the Qt modules.

    More about qmake and the .pro file here: http://qt-project.org/doc/qt-4.8/qmake-manual.html

    If you install the IDE QtCreator, the task of modifying the .pro file and compiling your app will be a bit easier.

    After you modify the .pro file, you usually build the Qt app using the command qmake, which produces a make file ready to be used by your system (on Windows it can also produce .sln solutions for Visual Studio)

    A short .pro file from one of my projects:

    TEMPLATE = app
TARGET = icat2browser
QT += network webkit <-- add here the opengl module
DEFINES += QT_LARGEFILE_SUPPORT

HEADERS += \
    qicat2networkaccessmanager.h \
    ctimeline.h \
    cobjectsview.h \
    cicat2WebResponse.h \
    cicat2usersdialog.h \
    cicat2previewdialog.h \
    cicat2login.h \
    cicat2clients.h \
    cicat2browser.h \

SOURCES += \
    qicat2networkaccessmanager.cpp \
    main.cpp \
    ctimeline.cpp \
    cobjectsview.cpp \
    cicat2WebResponse.cpp \
    cicat2usersdialog.cpp \
    cicat2previewdialog.cpp \
    cicat2login.cpp \
    cicat2clients.cpp \
    cicat2browser.cpp \
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