There is an open source implementation of OPC UA in written C (http://open62541.org). The single header file called open62541.h (version 0.1 is available for download from their website) throws an NPE in Result.java (215) - see attached console output. The UA_WorkItem struct was being processed.

I believe that the NPE is related to the empty UA_Server struct, because when I provide a dummy implementation of it (struct UA_Server { int i; };) in a header file that includes open62541.h, the NPE disappears.

Here's my config.jnaerator file:

-library Open62541
open62541.h
-mode Directory
-o .
-v
-runtime JNA
-arch win32
-emptyStructsAsForwardDecls

Note that I am using Microsoft Visual Studio 12 and Windows SDK version 7.1A.