coding.c: (Fdefine_coding_system_internal): Make an utf-8 base coding-system...

coding.c: (Fdefine_coding_system_internal): Make an utf-8 base coding-system ASCII compatible only when it does not produce BOM on encoding (Bug#10383).

src/ChangeLog

+2011-12-28  Kenichi Handa  <handa@m17n.org>
+
+	* coding.c (Fdefine_coding_system_internal): Make an utf-8 base
+	coding-system ASCII compatible only when it does not produce BOM
+	on encoding (Bug#10383).
+
 2011-12-26  Jan Djärv  <jan.h.d@swipnet.se>
 
 	* xmenu.c (x_menu_wait_for_event): Use xg_select for Gtk3 so menus

src/coding.c

@@ -9999,8 +9999,6 @@ usage: (define-coding-system-internal ...)  */)
     {
       Lisp_Object bom;
 
-      CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
-
       if (nargs < coding_arg_utf8_max)
 	goto short_args;
 
@@ -10014,6 +10012,8 @@ usage: (define-coding-system-internal ...)  */)
 	  CHECK_CODING_SYSTEM (val);
 	}
       ASET (attrs, coding_attr_utf_bom, bom);
+      if (NILP (bom))
+	CODING_ATTR_ASCII_COMPAT (attrs) = Qt;
 
       category = (CONSP (bom) ? coding_category_utf_8_auto
 		  : NILP (bom) ? coding_category_utf_8_nosig