ffi_struct_fix.rb

      def enclosing_module
        begin
          mod = self.name.split("::")[0..-2].inject(Object) { |obj, c| obj.const_get(c) }
          if mod < FFI::Library || mod < FFI::Struct
            mod
          elsif mod.respond_to?(:find_type)
            arity = mod.method(:find_type).arity
            # Only consider a #find_type that accepts a single argument.
            # MakeMakefile#find_type from 'mkmf' needs 2 arguments and should be ignored.
            if arity == 1 || arity == -1 || arity == -2
              mod
            end
          end
        rescue Exception
          nil
        end
      end