在调试区域只输出（lldb），没有其他消息

I got a rare problem that randomly when I ran my app in xcode, the simulator will stop and in the debug area only "(lldb)" is shown. It is random because when I ran again without modifying my code, it will run. What could have been the problem? I tried it in my other projects but still the same. Thank you.I got a rare problem that randomly when I ran m