Qt6 / Cmake Link error while porting Qt chart example from .pro to cmake. Undefined reference to vtable

For experience, I'm importing chart.cpp and .h from the dynamic spline example (which works perfectly fine on its own) in my own CMake built app. The example is compiled with a .pro file.

I Tuned the CMakeLists.txt file to include the lib. The result is this file:

cmake_minimum_required(VERSION 3.5)

project(controlCenter VERSION 0.1 LANGUAGES CXX)


set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)

find_package(Qt6 REQUIRED COMPONENTS SerialPort)
find_package(Qt6 REQUIRED COMPONENTS charts)
find_package(Qt6 REQUIRED COMPONENTS gui)
       
set(PROJECT_SOURCES
        main.cpp
        mainwindow.cpp
        mainwindow.h
        mainwindow.ui
        chart.cpp
        chart.h
)

include_directories(PRIVATE "libraries" "autogenerated" ".")

if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)
    qt_add_executable(controlCenter
        MANUAL_FINALIZATION
        ${PROJECT_SOURCES}
    )
# Define target properties for Android with Qt 6 as:
#    set_property(TARGET controlCenter APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
#                 ${CMAKE_CURRENT_SOURCE_DIR}/android)
# For more information, see https://doc.qt.io/qt-6/qt-add-executable.html#target-creation
else()
    if(ANDROID)
        add_library(controlCenter SHARED
            ${PROJECT_SOURCES}
        )
# Define properties for Android with Qt 5 after find_package() calls as:
#    set(ANDROID_PACKAGE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/android")
    else()
        add_executable(controlCenter
            ${PROJECT_SOURCES}
        )
    endif()
endif()

target_link_libraries(controlCenter PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)
target_link_libraries(controlCenter PRIVATE Qt6::SerialPort)
target_link_libraries(controlCenter PRIVATE Qt6::Charts)

# Qt for iOS sets MACOSX_BUNDLE_GUI_IDENTIFIER automatically since Qt 6.1.
# If you are developing for iOS or macOS you should consider setting an
# explicit, fixed bundle identifier manually though.
if(${QT_VERSION} VERSION_LESS 6.1.0)
  set(BUNDLE_ID_OPTION MACOSX_BUNDLE_GUI_IDENTIFIER com.example.controlCenter)
endif()
set_target_properties(controlCenter PROPERTIES
    ${BUNDLE_ID_OPTION}
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

include(GNUInstallDirs)
install(TARGETS controlCenter
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)

if(QT_VERSION_MAJOR EQUAL 6)
    qt_finalize_executable(controlCenter)
endif()

With this settings, the linker fails with this error:

 ld.exe: CMakeFiles/controlCenter.dir/chart.cpp.obj:chart.cpp:(.rdata$.refptr._ZTV5Chart[.refptr._ZTV5Chart]+0x0): undefined reference to `vtable for Chart'

Chart class containes its destructor (files chart.h and chart.cpp are exactly like in the example):

#ifndef CHART_H
#define CHART_H

#include <QtCharts/QChart>
#include <QtCore/QTimer>

QT_BEGIN_NAMESPACE
class QSplineSeries;
class QValueAxis;
QT_END_NAMESPACE

QT_USE_NAMESPACE

//![1]
class Chart: public QChart
{
    Q_OBJECT
public:
    Chart(QGraphicsItem *parent = nullptr, Qt::WindowFlags wFlags = {});
    virtual ~Chart();

public slots:
    void handleTimeout();

private:
    QTimer m_timer;
    QSplineSeries *m_series;
    QStringList m_titles;
    QValueAxis *m_axisX;
    QValueAxis *m_axisY;
    qreal m_step;
    qreal m_x;
    qreal m_y;
};
//![1]

#endif /* CHART_H */

and :

#include "chart.h"
#include <QtCharts/QAbstractAxis>
#include <QtCharts/QSplineSeries>
#include <QtCharts/QValueAxis>
#include <QtCore/QRandomGenerator>
#include <QtCore/QDebug>

Chart::Chart(QGraphicsItem *parent, Qt::WindowFlags wFlags):
    QChart(QChart::ChartTypeCartesian, parent, wFlags),
    m_series(0),
    m_axisX(new QValueAxis()),
    m_axisY(new QValueAxis()),
    m_step(0),
    m_x(5),
    m_y(1)
{
    QObject::connect(&m_timer, &QTimer::timeout, this, &Chart::handleTimeout);
    m_timer.setInterval(1000);

    m_series = new QSplineSeries(this);
    QPen green(Qt::red);
    green.setWidth(3);
    m_series->setPen(green);
    m_series->append(m_x, m_y);

    addSeries(m_series);

    addAxis(m_axisX,Qt::AlignBottom);
    addAxis(m_axisY,Qt::AlignLeft);
    m_series->attachAxis(m_axisX);
    m_series->attachAxis(m_axisY);
    m_axisX->setTickCount(5);
    m_axisX->setRange(0, 10);
    m_axisY->setRange(-5, 10);

    m_timer.start();
}

Chart::~Chart()
{

}

What can be the reason?

Hummmm... Clean / cmake / build did it!