bug#8619: 23.3.50; CCL coding system encoder doesn't run CCL_EOF_CODE on zero length string

[Kazuhiro Ito <kzhr@d1.dion.ne.jp>]

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I think the cause of the problem is that encode_codin_ccl() does not
call ccl_driver() for zero length string.  Please see the attached
patch.

> When I start emacs (emacs-23 branch and trunk) with -Q and evaluate
> below code, I receive unexpected result.
> 
> (let ((string ""))
>   (define-ccl-program ccl-test
>     '(1
>       ((read r0))
>       ((write "[EOF]"))))
>   (make-coding-system 'ccl-test-cs 4 ?T "CCL_EOF_BLOCK tester"
> 		      '(ccl-test . ccl-test))
>   (list
>    (ccl-execute-on-string 'ccl-test (make-vector 9 0) string)
>    (decode-coding-string string 'ccl-test-cs)
>    (encode-coding-string string 'ccl-test-cs)))
> 
> It returns
>   ("[EOF]" "[EOF]" "")
> But emacs22 returns
>   ("[EOF]" "[EOF]" "[EOF]")
> and I expect such result.

-- 
Kazuhiro Ito

[-- Attachment #2: coding.c.diff --]
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=== modified file 'src/coding.c'
--- src/coding.c	2011-05-09 09:59:23 +0000
+++ src/coding.c	2011-05-27 12:13:14 +0000
@@ -5325,7 +5325,7 @@
       && coding->mode & CODING_MODE_LAST_BLOCK)
     ccl->last_block = 1;
 
-  while (charbuf < charbuf_end)
+  do
     {
       ccl_driver (ccl, charbuf, destination_charbuf,
 		  charbuf_end - charbuf, 1024, charset_list);
@@ -5347,6 +5347,7 @@
 	  || ccl->status == CCL_STAT_INVALID_CMD)
 	break;
     }
+  while (charbuf < charbuf_end);
 
   switch (ccl->status)
     {