debug is an interactive autoloaded compiled Lisp function in `debug.el'.

(debug &rest ARGS)

Enter debugger. `c' returns from the debugger.
Arguments are mainly for use when this is called from the internals
of the evaluator.

You may call with no args, or you may pass nil as the first arg and
any other args you like. In that case, the list of args after the
first will be printed into the backtrace buffer.