--- a/lisp/ChangeLog	Sun Mar 15 21:13:23 2015 +0000
+++ b/lisp/ChangeLog	Mon Mar 16 00:09:46 2015 +0000
@@ -1,3 +1,9 @@
+2015-03-16  Aidan Kehoe  <kehoea@parhasard.net>
+
+	* obsolete.el (max-char):
+	Make this available for compatiblity with GNU, implement it in
+	terms of char-code-limit.
+
 2015-03-15  Aidan Kehoe  <kehoea@parhasard.net>
 
 	* tty-init.el (make-frame-after-init-entry-point):

--- a/lisp/obsolete.el	Sun Mar 15 21:13:23 2015 +0000
+++ b/lisp/obsolete.el	Mon Mar 16 00:09:46 2015 +0000
@@ -485,5 +485,15 @@
 (make-obsolete 'remrassoc "use delete* with :test #'equal, :key #'cdr")
 (make-obsolete 'remrassq "use delete* with :test #'eq, :key #'cdr")
 
+(defun max-char ()
+  "Return a fixnum one less than `char-code-limit'.
+
+In contrast with GNU Emacs, this is not necessarily a valid character, but it
+is an inclusive upper bound on the possible values returned by `char-int'."
+  (1- char-code-limit))
+(make-compatible
+ 'max-char
+ "consider `char-code-limit', which gives an exclusive upper bound")
+
 (provide 'obsolete)
 ;;; obsolete.el ends here

--- a/man/ChangeLog	Sun Mar 15 21:13:23 2015 +0000
+++ b/man/ChangeLog	Mon Mar 16 00:09:46 2015 +0000
@@ -1,3 +1,8 @@
+2015-03-15  Aidan Kehoe  <kehoea@parhasard.net>
+
+	* lispref/strings.texi (Character Codes):
+	Document `char-code-limit' here too.
+
 2015-03-14  Aidan Kehoe  <kehoea@parhasard.net>
 
 	* lispref/help.texi (Help Functions):

--- a/man/lispref/strings.texi	Sun Mar 15 21:13:23 2015 +0000
+++ b/man/lispref/strings.texi	Mon Mar 16 00:09:46 2015 +0000
@@ -330,6 +330,17 @@
 @code{nil} is returned.
 @end defun
 
+@defvar char-code-limit
+This is a constant integer describing an exclusive upper bound on the
+results return by @code{char-int} and that set of integers (fixnums) for
+which @code{int-char} will give non-nil. Without @sc{mule}
+(internationalization) support this will be @code{#x100}, as described
+under @code{char-int}, but with @sc{mule} support the range of values is
+much bigger, at least 21 bits' worth.  If an integer is less than
+@var{char-code-limit}, it may still not have an associated character, it
+is still necessary to check with the next function, @code{char-int-p}.
+@end defvar
+
 @defun char-int-p object
 This function returns @code{t} if @var{object} is an integer that can be
 converted into a character.

--- a/src/ChangeLog	Sun Mar 15 21:13:23 2015 +0000
+++ b/src/ChangeLog	Mon Mar 16 00:09:46 2015 +0000
@@ -1,3 +1,12 @@
+2015-03-15  Aidan Kehoe  <kehoea@parhasard.net>
+
+	* text.h: Make CHAR_CODE_LIMIT available as a #define.
+	* text.h (valid_ichar_p): Use it.
+	* text.c: Make a fixnum Vchar_code_limit available here.
+	* text.c (non_ascii_valid_ichar_p): Use CHAR_CODE_LIMIT.
+	* text.c (vars_of_text): Make `char-code-limit' available to
+	Lisp.
+
 2015-03-14  Aidan Kehoe  <kehoea@parhasard.net>
 
 	* general-slots.h (Qno_character_typed): New error symbol.

--- a/src/text.c	Sun Mar 15 21:13:23 2015 +0000
+++ b/src/text.c	Mon Mar 16 00:09:46 2015 +0000
@@ -1322,6 +1322,7 @@
 Lisp_Object QSin_char_byte_conversion;
 Lisp_Object QSin_internal_external_conversion;
 
+Fixnum Vchar_code_limit;
 
 /************************************************************************/
 /*                          qxestr***() functions                       */
@@ -4677,7 +4678,7 @@
   int f1, f2, f3;
 
   /* Must have only lowest 21 bits set */
-  if (ch & ~0x1FFFFF)
+  if (ch & ~(CHAR_CODE_LIMIT - 1))
     return 0;
 
   f1 = ichar_field1 (ch);
@@ -5143,6 +5144,14 @@
     build_defer_string ("(in internal-external conversion)");
   staticpro (&QSin_internal_external_conversion);
 
+  DEFVAR_CONST_INT ("char-code-limit", &Vchar_code_limit /*
+Exclusive upper bound on the values return by `char-int'.
+
+Note that not every fixnum with a value below `char-code-limit' has an
+associated character; check with `char-int-p' if necessary.
+*/);
+  Vchar_code_limit = CHAR_CODE_LIMIT;
+
 #ifdef ENABLE_COMPOSITE_CHARS
   /* #### not dumped properly */
   composite_char_row_next = 32;

--- a/src/text.h	Sun Mar 15 21:13:23 2015 +0000
+++ b/src/text.h	Mon Mar 16 00:09:46 2015 +0000
@@ -121,6 +121,8 @@
 #define rep_bytes_by_first_byte(fb) 1
 #define byte_ascii_p(byte) 1
 #define MAX_ICHAR_LEN 1
+/* Exclusive upper bound on character codes. */
+#define CHAR_CODE_LIMIT 0x100 
 
 #else /* MULE */
 
@@ -212,12 +214,12 @@
 
 #define ichar_ascii_p(c) (!ichar_multibyte_p (c))
 
-/* Maximum number of bytes per Emacs character when represented as text, in
- any format.
- */
-
+/* Maximum number of bytes per Ichar when represented as text. */
 #define MAX_ICHAR_LEN 4
 
+/* Exclusive upper bound on char codes. */
+#define CHAR_CODE_LIMIT 0x200000 
+
 #endif /* not MULE */
 
 #ifdef MULE
@@ -239,7 +241,7 @@
 
 /* This works when CH is negative, and correctly returns non-zero only when CH
    is in the range [0, 255], inclusive. */
-#define valid_ichar_p(ch) (! (ch & ~0xFF))
+#define valid_ichar_p(ch) (! (ch & ~(CHAR_CODE_LIMIT - 1)))
 
 #endif /* not MULE */
 

--- a/tests/ChangeLog	Sun Mar 15 21:13:23 2015 +0000
+++ b/tests/ChangeLog	Mon Mar 16 00:09:46 2015 +0000
@@ -1,3 +1,9 @@
+2015-03-15  Aidan Kehoe  <kehoea@parhasard.net>
+
+	* automated/mule-tests.el (test-chars):
+	Use char-code-limit explicitly here, instead of hardcoding the
+	corresponding values.
+
 2015-03-04  Aidan Kehoe  <kehoea@parhasard.net>
 
 	* automated/lisp-tests.el:

--- a/tests/automated/mule-tests.el	Sun Mar 15 21:13:23 2015 +0000
+++ b/tests/automated/mule-tests.el	Mon Mar 16 00:09:46 2015 +0000
@@ -46,10 +46,9 @@
 
 If FOR-TEST-HARNESS is specified, a temporary buffer is used, and
 the Assert macro checks for correctness."
-  (let ((max (expt 2 (if (featurep 'mule) 21 8)))
-	(list nil)
+  (let ((list nil)
 	(i 0))
-    (while (< i max)
+    (while (< i char-code-limit)
       (and (not for-test-harness)
 	   (zerop (% i 1000))
 	   (message "%d" i))