re PR preprocessor/34866 (valgrind error indication in testsuite from…

re PR preprocessor/34866 (valgrind error indication in testsuite from errors.c:156:cpp_error with gcc.dg/cpp/Wmissingdirs.c)

	PR libcpp/34866:
	* errors.c (cpp_error): Don't reference a token before the start
	of the current run.

From-SVN: r134421

libcpp/ChangeLog

+2008-04-17  Tom Tromey  <tromey@redhat.com>
+
+	PR libcpp/34866:
+	* errors.c (cpp_error): Don't reference a token before the start
+	of the current run.
+
 2008-04-16  Tom Tromey  <tromey@redhat.com>
 
 	* Makefile.in (TAGS_SOURCES): New variable.

libcpp/errors.c

 /* Default error handlers for CPP Library.
    Copyright (C) 1986, 1987, 1989, 1992, 1993, 1994, 1995, 1998, 1999, 2000,
-   2001, 2002, 2004 Free Software Foundation, Inc.
+   2001, 2002, 2004, 2008 Free Software Foundation, Inc.
    Written by Per Bothner, 1994.
    Based on CCCP program by Paul Rubin, June 1986
    Adapted to ANSI C, Richard Stallman, Jan 1987
@@ -151,6 +151,15 @@ cpp_error (cpp_reader * pfile, int level, const char *msgid, ...)
 	  else
 	    src_loc = pfile->line_table->highest_line;
 	}
+      /* We don't want to refer to a token before the beginning of the
+	 current run -- that is invalid.  */
+      else if (pfile->cur_token == pfile->cur_run->base)
+	{
+	  if (pfile->cur_run->prev != NULL)
+	    src_loc = pfile->cur_run->prev->limit->src_loc;
+	  else
+	    src_loc = 0;
+	}
       else
 	{
 	  src_loc = pfile->cur_token[-1].src_loc;