Qt5 with CMake - vtable error while AUTOMOC is ON

Question

I am trying to run simple Calculator example of Qt5 tutorials using CMake. The error I got is

[ 25%] Automatic moc and uic for target calculator
[ 25%] Built target calculator_automoc
Scanning dependencies of target calculator
[ 50%] Building CXX object CMakeFiles/calculator.dir/main.cpp.o
[ 75%] Linking CXX executable calculator
CMakeFiles/calculator.dir/main.cpp.o: In function `main':
main.cpp:(.text+0x45): undefined reference to `Calculator::Calculator(QWidget*)'
CMakeFiles/calculator.dir/main.cpp.o: In function `Calculator::~Calculator()':
main.cpp:(.text._ZN10CalculatorD2Ev[_ZN10CalculatorD5Ev]+0xf): undefined reference to `vtable for Calculator'
main.cpp:(.text._ZN10CalculatorD2Ev[_ZN10CalculatorD5Ev]+0x21): undefined reference to `vtable for Calculator'
collect2: error: ld returned 1 exit status
CMakeFiles/calculator.dir/build.make:123: recipe for target 'calculator' failed
make[3]: *** [calculator] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/calculator.dir/all' failed
make[2]: *** [CMakeFiles/calculator.dir/all] Error 2
CMakeFiles/Makefile2:79: recipe for target 'CMakeFiles/calculator.dir/rule' failed
make[1]: *** [CMakeFiles/calculator.dir/rule] Error 2
Makefile:118: recipe for target 'calculator' failed
make: *** [calculator] Error 2

Then I've found this and set CMAKE_AUTOMOC to ON, but it didn't help. It seems it's a basic CMakeLists.txt mistake but I cannot overcome for days.

Here are my files:

CMakeLists.txt

cmake_minimum_required(VERSION 2.8.11)

set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTOUIC ON)
# Find includes in corresponding build directories
set(CMAKE_INCLUDE_CURRENT_DIR ON)
# Tell CMake to create the calculator executable
add_executable(calculator main.cpp)

project(calculator)

SET(CMAKE_PREFIX_PATH $ENV{HOME}/software/Qt5.7.0/5.7/gcc_64)

# Find the QtWidgets library
find_package(Qt5Widgets)

# Use the Widgets module from Qt 5.
target_link_libraries(calculator Qt5::Widgets)

main.cpp

 #include <QApplication>    
 #include "calculator.h"

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     Calculator calc;

     calc.show();
     return app.exec();
 }

calculator.h

 #ifndef CALCULATOR_H
 #define CALCULATOR_H    
 #include <QWidget>

 class Calculator : public QWidget
 {
     Q_OBJECT

 public:
     Calculator(QWidget *parent = 0);
 };

 #endif

calculator.cpp

 #include <QtGui>    
 #include <math.h>    
 #include "calculator.h"

 Calculator::Calculator(QWidget *parent)
     : QWidget(parent)
 {
     QGridLayout *mainLayout = new QGridLayout;
     setWindowTitle(tr("Calculator"));
 }

Thanks for any help!

Make a minimal small example showing the problem. Don't just copy everything here. — The Quantum Physicist, Sep 08 '16 at 20:16

score 1 · Answer 1 · answered Sep 09 '16 at 05:04

This line in CMakeLists.txt:

add_executable(calculator main.cpp) #calculator.cpp button.cpp)

Possibly you are not aware of this, but the # specifies a comment. As a result cmake is not set up to make calculator.cpp or button.cpp compiled or linked into your executable.

Qt5 with CMake - vtable error while AUTOMOC is ON

1 Answers1