Info Catalog elisp: Error Debugging elisp: Debugger elisp: Function Debugging

elisp: Infinite Loops

 
 17.1.2 Debugging Infinite Loops
 -------------------------------
 
 When a program loops infinitely and fails to return, your first problem
 is to stop the loop.  On most operating systems, you can do this with
 ‘C-g’, which causes a “quit”.  Quitting.
 
    Ordinary quitting gives no information about why the program was
 looping.  To get more information, you can set the variable
 ‘debug-on-quit’ to non-‘nil’.  Once you have the debugger running in the
 middle of the infinite loop, you can proceed from the debugger using the
 stepping commands.  If you step through the entire loop, you may get
 enough information to solve the problem.
 
    Quitting with ‘C-g’ is not considered an error, and ‘debug-on-error’
 has no effect on the handling of ‘C-g’.  Likewise, ‘debug-on-quit’ has
 no effect on errors.
 
  -- User Option: debug-on-quit
      This variable determines whether the debugger is called when ‘quit’
      is signaled and not handled.  If ‘debug-on-quit’ is non-‘nil’, then
      the debugger is called whenever you quit (that is, type ‘C-g’).  If
      ‘debug-on-quit’ is ‘nil’ (the default), then the debugger is not
      called when you quit.
 

Info Catalog elisp: Error Debugging elisp: Debugger elisp: Function Debugging