* lisp/abbrev.el (edit-abbrevs-mode): Use define-derived-mode.

(edit-abbrevs-mode-map): Rename from edit-abbrevs-map.

* lisp/epa.el (epa--encode-coding-string, epa--decode-coding-string)
(epa--select-safe-coding-system, epa--derived-mode-p): Make it obvious
that it's defined.
(epa-key-list-mode, epa-key-mode, epa-info-mode):
Use define-derived-mode.

* lisp/epg.el (epg-start-encrypt): Minor CSE simplification.

lisp/abbrev.el

@@ -67,13 +67,15 @@ be replaced by its expansion."
 (put 'abbrev-mode 'safe-local-variable 'booleanp)
 
 
-(defvar edit-abbrevs-map
+(defvar edit-abbrevs-mode-map
   (let ((map (make-sparse-keymap)))
     (define-key map "\C-x\C-s" 'abbrev-edit-save-buffer)
     (define-key map "\C-x\C-w" 'abbrev-edit-save-to-file)
     (define-key map "\C-c\C-c" 'edit-abbrevs-redefine)
     map)
   "Keymap used in `edit-abbrevs'.")
+(define-obsolete-variable-alias 'edit-abbrevs-map
+  'edit-abbrevs-mode-map "24.4")
 
 (defun kill-all-abbrevs ()
   "Undefine all defined abbrevs."
@@ -144,16 +146,6 @@ Otherwise display all abbrevs."
       (set-buffer-modified-p nil)
       (current-buffer))))
 
-(defun edit-abbrevs-mode ()
-  "Major mode for editing the list of abbrev definitions.
-\\{edit-abbrevs-map}"
-  (interactive)
-  (kill-all-local-variables)
-  (setq major-mode 'edit-abbrevs-mode)
-  (setq mode-name "Edit-Abbrevs")
-  (use-local-map edit-abbrevs-map)
-  (run-mode-hooks 'edit-abbrevs-mode-hook))
-
 (defun edit-abbrevs ()
   "Alter abbrev definitions by editing a list of them.
 Selects a buffer containing a list of abbrev definitions with
@@ -1013,6 +1005,11 @@ SORTFUN is passed to `sort' to change the default ordering."
            (sort entries (lambda (x y)
                 (funcall sortfun (nth 2 x) (nth 2 y)))))))
 
+;; Keep it after define-abbrev-table, since define-derived-mode uses
+;; define-abbrev-table.
+(define-derived-mode edit-abbrevs-mode special-mode "Edit-Abbrevs"
+  "Major mode for editing the list of abbrev definitions.")
+
 (provide 'abbrev)
 
 ;;; abbrev.el ends here