A month ago, I wrote about Bozhidar Batsov’s post on debugging in Emacs. The idea was simple: if Emacs got an error, you could turn on debug-on-error and rerun the offending command. When the error occurs, Emacs will produce a backtrace to help you debug the problem. This can be helpful even for non-programmers.
Batsov is back with a followup post. In his latest post, he makes clear that Emacs is not just displaying a backtrace. What’s really happening is that you’ve been dumped into the bugger and you can query it for information on what happened.
Batsov provides a list of some of the things the debugger can provide and the (single letter) commands to invoke them. You can, for example, examine the current values of variables, evaluate expressions, step through code, continue execution, view help, or simply quit the debugger.
Programmers are, of course, comfortable with all of this but even less technical people can use it profitably. Take a look at Batsov’s post to help you get ready for the next time you have an unexplained Emacs error.