Fix fault in assembler when passed a bogus input file.

PR gas/20902
	* read.c (next_char_of_string): Do end advance past the end of the
	buffer.

gas/ChangeLog

@@ -1,5 +1,9 @@
 2016-12-05  Nick Clifton  <nickc@redhat.com>
 
+	PR gas/20902
+	* read.c (next_char_of_string): Do end advance past the end of the
+	buffer.
+
 	PR gas/20904
 	* as.h (SKIP_ALL_WHITESPACE): New macro.
 	* expr.c (operand): Use it.

gas/read.c

@@ -5533,6 +5533,12 @@ next_char_of_string (void)
   c = *input_line_pointer++ & CHAR_MASK;
   switch (c)
     {
+    case 0:
+      /* PR 20902: Do not advance past the end of the buffer.  */
+      -- input_line_pointer;
+      c = NOT_A_CHAR;
+      break;
+
     case '\"':
       c = NOT_A_CHAR;
       break;
@@ -5629,6 +5635,12 @@ next_char_of_string (void)
 	  bump_line_counters ();
 	  break;
 
+	case 0:
+	  /* Do not advance past the end of the buffer.  */
+	  -- input_line_pointer;
+	  c = NOT_A_CHAR;
+	  break;
+
 	default:
 
 #ifdef ONLY_STANDARD_ESCAPES