Info Catalog elisp: Examples of Catch elisp: Nonlocal Exits elisp: Cleanups

elisp: Errors

 
 10.6.3 Errors
 -------------
 
 When Emacs Lisp attempts to evaluate a form that, for some reason,
 cannot be evaluated, it “signals” an “error”.
 
    When an error is signaled, Emacs’s default reaction is to print an
 error message and terminate execution of the current command.  This is
 the right thing to do in most cases, such as if you type ‘C-f’ at the
 end of the buffer.
 
    In complicated programs, simple termination may not be what you want.
 For example, the program may have made temporary changes in data
 structures, or created temporary buffers that should be deleted before
 the program is finished.  In such cases, you would use ‘unwind-protect’
 to establish “cleanup expressions” to be evaluated in case of error.
 (Cleanups.)  Occasionally, you may wish the program to continue
 execution despite an error in a subroutine.  In these cases, you would
 use ‘condition-case’ to establish “error handlers” to recover control in
 case of error.
 
    Resist the temptation to use error handling to transfer control from
 one part of the program to another; use ‘catch’ and ‘throw’ instead.
 Catch and Throw.
 

Menu

 
· Signaling Errors      How to report an error.
· Processing of Errors  What Emacs does when you report an error.
· Handling Errors       How you can trap errors and continue execution.
· Error Symbols         How errors are classified for trapping them.
 

Info Catalog elisp: Examples of Catch elisp: Nonlocal Exits elisp: Cleanups