I have just found that lldb has a gui command that brings up a nice UI for command line debugging. However, I have no idea how to use it and could not find any reasonable documentation.
(llvm) gui
Brings up this kind of interface:
However, I cannot figure out how to interact with it, eg. send a command to step to the next line. Any idea? I am using Mac OSX Catalina, iterm2 and tmux.