为什么当我第二次尝试启动同一个线程时，应用程序会崩溃

main.cpp:

#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    cThread = new QThread(this);
    cObject = new MyObject();
    cObject->moveToThread(cThread);
    QObject::connect(ui->pushButton_3, SIGNAL(clicked()),
                     this, SLOT(close())
                     );
    QObject::connect(cThread, SIGNAL(started()),
                     cObject, SLOT(doWork())
                     );
    QObject::connect(ui->pushButton_4, SIGNAL(clicked()),
                     this, SLOT(runThreadSlot())
                     );
    QObject::connect(cThread, SIGNAL(finished()),
                     cThread, SLOT(deleteLater())
                     );
    QObject::connect(cThread, SIGNAL(finished()),
                     cObject, SLOT(deleteLater())
                     );
    QObject::connect(cObject, SIGNAL(setStatusBarSignal(QString)),
                     this, SLOT(setStatusBarSlot(QString))
                     );
}
MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::runThreadSlot()
{
    cThread->start();
}
void MainWindow::setStatusBarSlot(QString text)
{
    ui->statusBar->showMessage(text);
}

myobject.cpp:

#include "myobject.h"
MyObject::MyObject(QObject *parent) :
    QObject(parent)
{
}
void MyObject::doWork()
{
    emit setStatusBarSignal(QString::number((qint32) QThread::currentThreadId()));
    QThread::currentThread()->quit();
    return;
}

主窗口.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "myobject.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
private slots:
    void runThreadSlot();
    void setStatusBarSlot(QString);
private:
    Ui::MainWindow *ui;
    QThread* cThread;
    MyObject* cObject;
};
#endif // MAINWINDOW_H

myobject.h:

#ifndef MYOBJECT_H
#define MYOBJECT_H
#include <QtCore>
class MyObject : public QObject
{
    Q_OBJECT
public:
    explicit MyObject(QObject *parent = 0);
signals:
    void setStatusBarSignal(QString);
public slots:
    void doWork();
};
#endif // MYOBJECT_H

所以模式是：

pushButton_4单击((--->runThreadSlot((--->cThread start((

线程立即使用QThread::currentThread()->quit();自行终止，但当我再次单击pushButton_4时，应用程序崩溃。