[Discuss-gnuradio] (no subject)

HI,

      I'm trying to build the costas loop block..but it showing the error like this while I execute the make command:

/home/lekha/gr-digital/lib/cost_impl.cc: In constructor

'gr::digital::cost_impl::cost_impl(float, int)':

/home/lekha/gr-digital/lib/cost_impl.cc:47:15: error: type 'gr::blocks::control_loop' is

not a direct or virtual base of 'gr::digital::cost_impl'

/home/lekha/gr-digital/lib/cost_impl.cc: In member function 'virtual int

gr::digital::cost_impl::work(int, gr_vector_const_void_star&, gr_vector_void_star&)':

what is problem?  thanks for your help.