Info Catalog eintr: debug-on-entry eintr: Debugging eintr: edebug

eintr: debug-on-quit

 
 17.3 ‘debug-on-quit’ and ‘(debug)’
 ==================================
 
 In addition to setting ‘debug-on-error’ or calling ‘debug-on-entry’,
 there are two other ways to start ‘debug’.
 
    You can start ‘debug’ whenever you type ‘C-g’ (‘keyboard-quit’) by
 setting the variable ‘debug-on-quit’ to ‘t’.  This is useful for
 debugging infinite loops.
 
    Or, you can insert a line that says ‘(debug)’ into your code where
 you want the debugger to start, like this:
 
      (defun triangle-bugged (number)
        "Return sum of numbers 1 through NUMBER inclusive."
        (let ((total 0))
          (while (> number 0)
            (setq total (+ total number))
            (debug)                         ; Start debugger.
            (setq number (1= number)))      ; Error here.
          total))
 
    The ‘debug’ function is described in detail in The Lisp
 Debugger (elisp)Debugger.
 

Info Catalog eintr: debug-on-entry eintr: Debugging eintr: edebug