void MainWindow::slotTest()
{
    Looper r;
    r.execloop();
    qDebug() << "done";
}

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

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow *mainWin = new MainWindow();
    mainWin->show();
    return app.exec();
}

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtGui>
#include <QMainWindow>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow();

public slots:
    void slotTest();
};

#endif

#include "mainwindow.h"
#include "looper.h"

MainWindow::MainWindow()
{
    setAttribute(Qt::WA_DeleteOnClose);
    QMetaObject::invokeMethod(this, "slotTest", Qt::QueuedConnection);
}

void MainWindow::slotTest()
{
    Looper r(this);
    r.execloop();
    qDebug() << "done";
}

#ifndef LOOPER_H
#define LOOPER_H

#include <QObject>
#include <QEventLoop>

class Looper : public QObject
{
    Q_OBJECT
public:
    explicit Looper(QObject *parent = 0);
    void execloop();

private:
    QEventLoop loop;
};

#endif // LOOPER_H

#include <QDebug>
#include "looper.h"

Looper::Looper(QObject *parent) :
    QObject(parent)
{
    qDebug() << "obj" << this;
}

void Looper::execloop()
{
    qDebug() << "start loop";
    loop.exec();
    qDebug() << "end loop";
}

obj Looper(0x7fff5fbfe2c0) 
start loop 
crash(36249,0x7fff709ffcc0) malloc: *** error for object 0x7fff5fbfe2c0: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug