[PATCH, libcpp] Do not decrease highest_location if the included file has be included twice.

[Dehao Chen]

This patch fixes the bug that when include a header file, if the
header file is already included (with #define _HEADER_H_), libcpp
should not decrease its highest_location, otherwise it'll cause
incorrect source location when source location numbers are large
enough to omit columns.

Passed regression test.

OK for trunk?

Thanks,
Dehao

libcpp/ChangeLog:

2013-05-31  Dehao Chen  <de...@google.com>

        * files.c (_cpp_stack_include): Fix the highest_location when header
        file is guarded by #ifndef and is included twice.


Index: libcpp/files.c
===================================================================
--- libcpp/files.c (revision 199416)
+++ libcpp/files.c (working copy)
@@ -1002,7 +1002,8 @@ _cpp_stack_include (cpp_reader *pfile, const char
      linemap_add is not called) or we were included from the
      command-line.  */
   if (file->pchname == NULL && file->err_no == 0
-      && type != IT_CMDLINE && type != IT_DEFAULT)
+      && type != IT_CMDLINE && type != IT_DEFAULT
+      && !(file->cmacro && file->cmacro->type == NT_MACRO))
     pfile->line_table->highest_location--;

   return _cpp_stack_file (pfile, file, type == IT_IMPORT);