Fix w32 bug with call-process-region.

* callproc.c (Fcall_process_region): Pass nil, not "/dev/null",
to Fcall_process when the input is empty.  This simplifies the
code a bit.  It makes no difference on POSIXish platforms but
apparently it fixes a bug on w32.

Fixes: debbugs:14885

src/ChangeLog

 2013-07-16  Paul Eggert  <eggert@cs.ucla.edu>
 
-	Fix bug where Emacs tries to close a file twice (Bug#14839).
+	Fix w32 bug with call-process-region (Bug#14885).
+	* callproc.c (Fcall_process_region): Pass nil, not "/dev/null",
+	to Fcall_process when the input is empty.  This simplifies the
+	code a bit.  It makes no difference on POSIXish platforms but
+	apparently it fixes a bug on w32.
+
+	Fix bug where insert-file-contents closes a file twice. (Bug#14839).
 	* fileio.c (close_file_unwind): Don't close if FD is negative;
 	this can happen when unwinding a zapped file descriptor.
 	(Finsert_file_contents): Unwind-protect the fd before the point marker,

src/callproc.c

@@ -1093,7 +1093,7 @@ usage: (call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &r
   (ptrdiff_t nargs, Lisp_Object *args)
 {
   struct gcpro gcpro1;
-  Lisp_Object filename_string;
+  Lisp_Object infile;
   ptrdiff_t count = SPECPDL_INDEX ();
   Lisp_Object start = args[0];
   Lisp_Object end = args[1];
@@ -1111,10 +1111,8 @@ usage: (call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &r
       empty_input = XINT (start) == XINT (end);
     }
 
-  filename_string = (empty_input
-		     ? build_string (NULL_DEVICE)
-		     : create_temp_file (nargs, args));
-  GCPRO1 (filename_string);
+  infile = empty_input ? Qnil : create_temp_file (nargs, args);
+  GCPRO1 (infile);
 
   if (nargs > 3 && !NILP (args[3]))
     Fdelete_region (start, end);
@@ -1129,7 +1127,7 @@ usage: (call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &r
       args[0] = args[2];
       nargs = 2;
     }
-  args[1] = filename_string;
+  args[1] = infile;
 
   RETURN_UNGCPRO (unbind_to (count, Fcall_process (nargs, args)));
 }