  Null pointer exceptions (NPE) are the number one cause of uncaught crashing
exceptions in production. In this paper, we aim at exploring the search space
of possible patches for null pointer exceptions with metaprogramming. Our idea
is to transform the program under repair with automated code transformation, so
as to obtain a metaprogram. This metaprogram contains automatically injected
hooks, that can be activated to emulate a null pointer exception patch. This
enables us to perform a fine-grain analysis of the runtime context of null
pointer exceptions. We set up an experiment with 16 real null pointer
exceptions that have happened in the field. We compare the effectiveness of our
metaprogramming approach against simple templates for repairing null pointer
exceptions.
