If you think you may have found a bug in GNU Emacs, please read the
Bugs section of the Emacs manual for advice on

(1) how to tell when to report a bug, and
(2) how to write a useful bug report and what information it needs to have.

You can read the Bugs section of the manual from inside Emacs.
Start Emacs, and press
  C-h r       (to view the Emacs manual)
  m Bugs RET  (to go to the section on Bugs) 
Or you can use the standalone Info program:
  info emacs
  m Bugs RET
(Standalone Info is part of the Texinfo distribution, not part of the
Emacs distribution.)

Printed copies of the Emacs manual can be purchased from the Free
Software Foundation's online store at <http://shop.fsf.org/>.

If necessary, you can read the manual without an info program:

    cat info/emacs* | more "+/^File: emacs.*,  Node: Bugs,"


Please first check the file etc/PROBLEMS (e.g. with C-h C-p in Emacs) to
make sure it isn't a known issue.
