1 files changed, 31 insertions, 9 deletions

diff --git a/src/coding.c b/src/coding.c
index 58fe2a86fc9..9c18a9d3036 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -4370,6 +4370,7 @@ detect_coding_charset (coding, mask)
   int multibytep = coding->src_multibyte;
   int consumed_chars = 0;
   Lisp_Object attrs, valids;
+  int found = 0;
 
   coding = &coding_categories[coding_category_charset];
   attrs = CODING_ID_ATTRS (coding->id);
@@ -4385,12 +4386,14 @@ detect_coding_charset (coding, mask)
       ONE_MORE_BYTE (c);
       if (NILP (AREF (valids, c)))
         break;
+      if (c >= 0x80)
+        found = 1;
     }
   *mask &= ~CATEGORY_MASK_CHARSET;
   return 0;
 
  no_more_source:
-  return 1;
+  return (found || NILP (CODING_ATTR_ASCII_COMPAT (attrs)));
 }
 
 static void
@@ -6323,9 +6326,7 @@ detect_coding_system (src, src_bytes, highest, multibytep, coding_system)
           if (c & 0x80
               || (c < 0x20 && (c == ISO_CODE_ESC
                                || c == ISO_CODE_SI
-                               || c == ISO_CODE_SO
-                               /* Most UTF-16 text contains '\0'. */
-                               || !c)))
+                               || c == ISO_CODE_SO)))
             break;
         }
       coding.head_ascii = src - coding.source;
@@ -7471,6 +7472,8 @@ usage: (define-coding-system-internal ...)  */)
     XSTRING (safe_charsets)->data[XFASTINT (XCAR (tail))] = 0;
   CODING_ATTR_SAFE_CHARSETS (attrs) = safe_charsets;
 
+  CODING_ATTR_ASCII_COMPAT (attrs) = args[coding_arg_ascii_compatible_p];
+
   val = args[coding_arg_decode_translation_table];
   if (! NILP (val))
     CHECK_CHAR_TABLE (val);
@@ -7525,6 +7528,9 @@ usage: (define-coding-system-internal ...)  */)
           int dim = CHARSET_DIMENSION (charset);
           int idx = (dim - 1) * 4;
           
+          if (CHARSET_ASCII_COMPATIBLE_P (charset))
+            CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
+
           for (i = charset->code_space[idx];
                i <= charset->code_space[idx + 1]; i++)
             {
@@ -7611,6 +7617,8 @@ usage: (define-coding-system-internal ...)  */)
     {
       Lisp_Object bom, endian;
 
+      CODING_ATTR_ASCII_COMPAT (attrs) = Qnil;
+
       if (nargs < coding_arg_utf16_max)
         goto short_args;
 
@@ -7651,8 +7659,12 @@ usage: (define-coding-system-internal ...)  */)
           val = Faref (initial, make_number (i));
           if (! NILP (val))
             {
-              CHECK_CHARSET_GET_ID (val, id);
-              ASET (initial, i, make_number (id));
+              struct charset *charset;
+
+              CHECK_CHARSET_GET_CHARSET (val, charset);
+              ASET (initial, i, make_number (CHARSET_ID (charset)));
+              if (i == 0 && CHARSET_ASCII_COMPATIBLE_P (charset))
+                CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
             }
           else
             ASET (initial, i, make_number (-1));
@@ -7713,7 +7725,7 @@ usage: (define-coding-system-internal ...)  */)
     {
       if (EQ (args[coding_arg_charset_list], Qemacs_mule))
         ASET (attrs, coding_attr_emacs_mule_full, Qt);
-
+      CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
       category = coding_category_emacs_mule;
     }
   else if (EQ (coding_type, Qshift_jis))
@@ -7728,6 +7740,8 @@ usage: (define-coding-system-internal ...)  */)
       if (CHARSET_DIMENSION (charset) != 1)
         error ("Dimension of charset %s is not one",
                XSYMBOL (CHARSET_NAME (charset))->name->data);
+      if (CHARSET_ASCII_COMPATIBLE_P (charset))
+        CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
 
       charset_list = XCDR (charset_list);
       charset = CHARSET_FROM_ID (XINT (XCAR (charset_list)));
@@ -7755,6 +7769,8 @@ usage: (define-coding-system-internal ...)  */)
       if (CHARSET_DIMENSION (charset) != 1)
         error ("Dimension of charset %s is not one",
                XSYMBOL (CHARSET_NAME (charset))->name->data);
+      if (CHARSET_ASCII_COMPATIBLE_P (charset))
+        CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
 
       charset_list = XCDR (charset_list);
       charset = CHARSET_FROM_ID (XINT (XCAR (charset_list)));
@@ -7766,9 +7782,15 @@ usage: (define-coding-system-internal ...)  */)
       Vbig5_coding_system = name;
     }
   else if (EQ (coding_type, Qraw_text))
-    category = coding_category_raw_text;
+    {
+      category = coding_category_raw_text;
+      CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
+    }
   else if (EQ (coding_type, Qutf_8))
-    category = coding_category_utf_8;
+    {
+      category = coding_category_utf_8;
+      CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
+    }
   else if (EQ (coding_type, Qundecided))
     category = coding_category_undecided;
   else