(encode-coding-char): Fix for ASCII characters.

1 files changed, 25 insertions, 22 deletions

diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index 0d3f0b01404..2e9b1e100e8 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -2805,29 +2805,32 @@ If there's no description string for VALUE, return nil."
 (defun encode-coding-char (char coding-system)
   "Encode CHAR by CODING-SYSTEM and return the resulting string.
 If CODING-SYSTEM can't safely encode CHAR, return nil."
-  (let ((str1 (string-as-multibyte (string char)))
-        (str2 (string-as-multibyte (string char char)))
+  (let* ((str1 (string-as-multibyte (string char)))
+         (str2 (string-as-multibyte (string char char)))
+         (found (find-coding-systems-string str1))
         enc1 enc2 i1 i2)
-    (when (memq (coding-system-base coding-system)
-                (find-coding-systems-string str1))
-      ;; We must find the encoded string of CHAR.  But, just encoding
-      ;; CHAR will put extra control sequences (usually to designate
-      ;; ASCII charset) at the tail if type of CODING is ISO 2022.
-      ;; To exclude such tailing bytes, we at first encode one-char
-      ;; string and two-char string, then check how many bytes at the
-      ;; tail of both encoded strings are the same.
-
-      (setq enc1 (encode-coding-string str1 coding-system)
-            i1 (length enc1)
-            enc2 (encode-coding-string str2 coding-system)
-            i2 (length enc2))
-      (while (and (> i1 0) (= (aref enc1 (1- i1)) (aref enc2 (1- i2))))
-        (setq i1 (1- i1) i2 (1- i2)))
-
-      ;; Now (substring enc1 i1) and (substring enc2 i2) are the same,
-      ;; and they are the extra control sequences at the tail to
-      ;; exclude.
-      (substring enc2 0 i2))))
+    (if (and (consp found)
+             (eq (car found) 'undecided))
+        str1
+      (when (memq (coding-system-base coding-system) found)
+        ;; We must find the encoded string of CHAR.  But, just encoding
+        ;; CHAR will put extra control sequences (usually to designate
+        ;; ASCII charset) at the tail if type of CODING is ISO 2022.
+        ;; To exclude such tailing bytes, we at first encode one-char
+        ;; string and two-char string, then check how many bytes at the
+        ;; tail of both encoded strings are the same.
+
+        (setq enc1 (encode-coding-string str1 coding-system)
+              i1 (length enc1)
+              enc2 (encode-coding-string str2 coding-system)
+              i2 (length enc2))
+        (while (and (> i1 0) (= (aref enc1 (1- i1)) (aref enc2 (1- i2))))
+          (setq i1 (1- i1) i2 (1- i2)))
+
+        ;; Now (substring enc1 i1) and (substring enc2 i2) are the same,
+        ;; and they are the extra control sequences at the tail to
+        ;; exclude.
+        (substring enc2 0 i2)))))
 
 ;; Backwards compatibility.  These might be better with :init-value t,
 ;; but that breaks loadup.