在问这个问题之前，我已经想了很多，读了很多文章。这些文章都没有给我适当的答案。

How To Really, Truly Use QThreads; The Full Explanation

辅助对象具有新线程的亲和力。

1> Worker结束信号将在线程上调用quit()。这将结束线程的事件循环并启动线程完成信号。

2>工作程序完成信号连接到工作程序deleteLater()。根据deleteLater()文档

**Schedules this object for deletion.
The object will be deleted when control returns to the event loop. If the event loop is > not running

when this function is called (e.g. deleteLater() is called on an
object before QCoreApplication::exec()), the object will be deleted
once the event loop is started.

Note that entering and leaving a new
event loop (e.g., by opening a modal dialog) will not perform the
deferred deletion; for the object to be deleted, the control must
return to the event loop from which deleteLater() was called.

Note: It
is safe to call this function more than once; when the first deferred
deletion event is delivered, any pending events for the object are
removed from the event queue.**

因此，当没有事件循环时，由于线程已经退出并且已经发出完成信号，因此我们将不再再次启动同一线程。在这种情况下，将永远不会处理deleteLater()，因为事件循环不存在，并且完全不会删除worker对象。这不会造成内存泄漏吗？

如果我们认为交换两条线可以解决问题，那么我还有另一个问题。 QT明确指出，信号发射时插槽被调用的顺序不确定

在上面提到的文章链接中有很多评论。甚至作者也无法完全回答问题

QThread将在发送完成信号后执行QCoreApplication :: sendPostedEvents事件类型为QEvent :: DeferredDelete

换句话说，QThread将收集所有未决的deleteLater，并在run返回之后执行它们

来源：https://qt.gitorious.org/qt/qtbase/source/c657bb7b51115d6e1719166fb502bb0ca1dcf4e8:src/corelib/thread/qthread_win.cpp#L363-462