Qt Undefined Reference to vtable

**Archimedes** · 24th February 2010, 21:30

What are the differences with the code you'll find in the .zip??
Also did you rerun qmake?

**ctote** · 24th February 2010, 21:35

Ok, here's what happened -- I ran your code and it compiled fine but no command line popped up, so I ran it again... now I get the same error every time with your code. I tried to run qmake, but it keeps saying unknown command.

This is frustrating

Also, I just noticed our .pro files are different... not sure if that matters:

mine:

Qt Code:

Switch view

# -------------------------------------------------
# Project created by QtCreator 2010-02-24T13:23:24
# -------------------------------------------------
QT += network
QT -= gui
TARGET = jausCommandLine
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp \
    jaus.cpp
HEADERS += jaus.h

# -------------------------------------------------
# Project created by QtCreator 2010-02-24T13:23:24
# -------------------------------------------------
QT += network
QT -= gui
TARGET = jausCommandLine
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp \
    jaus.cpp
HEADERS += jaus.h

To copy to clipboard, switch view to plain text mode

yours:

Qt Code:

Switch view

QT       += network
 
TARGET = jaus
TEMPLATE = app
 
 
SOURCES += main.cpp\
        jaus.cpp
 
HEADERS  += jaus.h

QT       += network

TARGET = jaus
TEMPLATE = app


SOURCES += main.cpp\
        jaus.cpp

HEADERS  += jaus.h

To copy to clipboard, switch view to plain text mode

**ctote** · 24th February 2010, 21:43

Just changed my .pro file for yours (except I added the CONFIG section for my command line) -- it's working great now. Why? I'm very new to Qt and don't quite understand the requirements in the .pro file (as well as the requirements for object creation e.g., Q_OBJECT).

**squidge** · 24th February 2010, 22:24

Typically, if you get "Undefined Reference to vtable" whilst building a project you need to ensure MOC is being run. The easiest way to ensure this is to simply run qmake from the QtCreator menu bar and then rebuild the project. Q_OBJECT is only required if your class needs signals or slots - these are then read by MOC and parsed into another file that it creates and automatically adds to your project. Without this file, you get the vtable error.