=== modified file 'include/obstack.h'
--- include/obstack.h	2011-10-22 01:35:29 +0000
+++ include/obstack.h	2012-05-30 01:18:36 +0000
@@ -538,6 +538,40 @@ __extension__								\
 
 #endif /* not __GNUC__ or not __STDC__ */
 
+
+/* The MARK operation allows you to save the state of the obstack by pushing
+   a special marker onto the stack. When you RELEASE that marker the obstack
+   returns to its previous state which means all memory allocated after the
+   marker is free'd, and most importantly if you were growing an object before
+   pushing the marker, you can now continue growing it. Needless to say that
+   the marker is destroyed if you release/free an earlier marker/object. */
+static inline void *obstack_mark (struct obstack *o)
+{
+  void **old_base, **p;
+
+  /* Rellocation may happen when growing...*/
+  obstack_blank (o, sizeof (void *));
+  /* ...so save object_base afterwards... */
+  old_base = (void **) o->object_base;
+  /* ...and save the end of the previous object to return it. */
+  p = (void **) & o->next_free [-1 * sizeof (void *)];
+
+  /* Finally make it possible to start growing new objects */
+  obstack_finish (o);
+  /* and store saved state in the new space we grew. */
+  *p = old_base;
+
+  return p;
+}
+
+static inline void obstack_release (struct obstack *o, void *p)
+{
+  void *old_base = *(void **) p;
+  obstack_free (o, p);
+  o->object_base = (char *) old_base;
+}
+
+
 #ifdef __cplusplus
 }	/* C++ */
 #endif