diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 0e90821..3e01c11 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -393,6 +393,14 @@
      bother trying to do macro expansion and whatnot.  */
   unsigned char preprocessed;
 
+  /* Nonzero means we are tracking locations of tokens involved in
+     macro expansion. 1 Means we track the location in degraded mode
+     where we do not track locations of tokens resulting from the
+     expansion of arguments of function-like macro.  2 Means we do
+     track all macro expansions. This last option is the one that
+     consumes the highest amount of memory.  */
+  unsigned char track_macro_expansion;
+
   /* Nonzero means handle C++ alternate operator names.  */
   unsigned char operator_names;