QThread created in other QThread not calling destructor - qt

Question

I have a code:
#include <QApplication>
#include <QThread>
#include <QDebug>
class ChildThread : public QThread {
Q_OBJECT
public:
ChildThread() {
connect(this, &QThread::finished, this, &ChildThread::deleteLater);
}
~ChildThread() {
qDebug() << "~TR()";
}
protected:
void run() {
qDebug() << "RUN";
}
};
class ParentThread : public QThread {
Q_OBJECT
public:
protected:
void run() {
for (int i = 0; i < 10; i++) {
ChildThread *t = new ChildThread();
t->start();
msleep(1000);
}
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
ParentThread *t = new ParentThread();
t->start();
for (int i = 0; i < 10; i++) {
ChildThread *t = new ChildThread();
t->start();
QThread::msleep(1000);
}
return a.exec();
}
And I havnt understand, why all of the ChildThread that created in the ParentThread after reaching end of run() function not ending and desctructor of the ChildThread not called, but if I create ChildThread outside of ParentThread, deststructor of ChildThread was called?
Thank You!

Answer 1

The thread will not be destroyed when the run() function due to the
fact that the deleteLater() function is called when the parent (main) loop
get back the control.
Creating the ChildThread from main(), the QThread::msleep() call
give back the control to the main loop, so the destructor can be
called.