bug#16160: [PATCH] define-derived-mode clobbers syntax tables

[Daniel Colascione <dancol@dancol.org>]

Repro:

1) Visit shell script with comments. See comments fontified properly.
2) M-x find-library sh-script RET
3) M-x eval-buffer
4) Return to shell script buffer
5) C-x C-v RET
6) Observe that comments are no longer fontified as comments.

The define-derived-mode macro in sh-script.el emits code that clobbers 
sh-mode-syntax-table because we don't have a :syntax-table argument. I 
think the following patch changes the code to the expected behavior.

~/edev/trunk
$ bzr diff
=== modified file 'lisp/emacs-lisp/derived.el'
--- lisp/emacs-lisp/derived.el	2013-05-27 16:12:52 +0000
+++ lisp/emacs-lisp/derived.el	2013-12-16 11:09:41 +0000
@@ -206,11 +206,11 @@
         ,(if declare-syntax
  	    `(progn
  	       (unless (boundp ',syntax)
-		 (put ',syntax 'definition-name ',child))
-	       (defvar ,syntax (make-syntax-table))
-	       (unless (get ',syntax 'variable-documentation)
-		 (put ',syntax 'variable-documentation
-		      (purecopy ,(format "Syntax table for `%s'." child))))))
+		 (put ',syntax 'definition-name ',child)
+                 (defvar ,syntax (make-syntax-table))
+                 (unless (get ',syntax 'variable-documentation)
+                   (put ',syntax 'variable-documentation
+                        (purecopy ,(format "Syntax table for `%s'." 
child)))))))
         ,(if declare-abbrev
  	    `(progn
  	       (put ',abbrev 'definition-name ',child)


That is, we shouldn't touch the syntax table variable at all unless the 
variable is unbound.