Your recommended solution, using interface mapping does not work with Groovy, because Groovy has no Interface. My Groovy solution so far is:

       import com.sun.jna.NativeLibrary        import com.sun.jna.Platform

       public class Clib {          private static def libc = NativeLibrary.getInstance(Platform.isWindows() ? "msvcrt" : "c")

         def methodMissing(String name, args) {            def method = libc.getFunction(name)            if (method) {              if (args.getClass().isArray()) {                return method.invokeInt(args)              } else {                return method.invokeInt([args] as Object[])              }            } else {              throw new MissingMethodException(name, getClass(), args)            }          }        }

Groovy calls automatically the methodMissing with single Object args or array Object[], depending the number of args. What shall I use if not com.sun.jna.Function, in this case?