Minor improvements to make_formatted_string.

* alloc.c (make_formatted_string): Prefer int to ptrdiff_t
where int is good enough, as vsprintf returns an int.
* lisp.h (make_formatted_string): Add ATTRIBUTE_FORMAT_PRINTF.

src/ChangeLog

+2012-07-09  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Minor improvements to make_formatted_string.
+	* alloc.c (make_formatted_string): Prefer int to ptrdiff_t
+	where int is good enough, as vsprintf returns an int.
+	* lisp.h (make_formatted_string): Add ATTRIBUTE_FORMAT_PRINTF.
+
 2012-07-09  Dmitry Antipov  <dmantipov@yandex.ru>
 	Use make_formatted_string to avoid double length calculation.

src/alloc.c

@@ -2524,7 +2524,7 @@ Lisp_Object
 make_formatted_string (char *buf, const char *format, ...)
 {
   va_list ap;
-  ptrdiff_t length;
+  int length;
 
   va_start (ap, format);
   length = vsprintf (buf, format, ap);

src/lisp.h

@@ -2611,7 +2611,8 @@ extern Lisp_Object list5 (Lisp_Object, Lisp_Object, Lisp_Object, Lisp_Object,
 extern Lisp_Object allocate_misc (void);
 extern _Noreturn void string_overflow (void);
 extern Lisp_Object make_string (const char *, ptrdiff_t);
-extern Lisp_Object make_formatted_string (char *, const char *, ...);
+extern Lisp_Object make_formatted_string (char *, const char *, ...)
+  ATTRIBUTE_FORMAT_PRINTF (2, 3);
 extern Lisp_Object make_unibyte_string (const char *, ptrdiff_t);
 extern Lisp_Object make_multibyte_string (const char *, ptrdiff_t, ptrdiff_t);
 extern Lisp_Object make_event_array (int, Lisp_Object *);