# (no subject)

**URL:** <https://www.ruby-forum.com/t/no-subject/241328>\
**Category:** GNU Radio\
**Created:** [March 30, 2015, 9:40am UTC](https://www.ruby-forum.com/t/no-subject/241328 "2015-03-30T09:40:50Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [March 30, 2015, 9:40am UTC](https://www.ruby-forum.com/t/no-subject/241328/1 "2015-03-30T09:40:50Z")

</div>

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.