Top_block start not returning

Hi,

I have a simple connection with a null source and sink, but when I try
to start the top_block, the start function doesn’t return. I’m simply
using the GrTemplate project for Android. I don’t see the “Exiting
FgStart function message,” any idea why?

gr::top_block_sptr tb = gr::make_top_block(“fg”);
gr::blocks::null_source::sptr src =
gr::blocks::null_source::make(sizeof(gr_complex));
gr::blocks::throttle::sptr thr =
gr::blocks::throttle::make(sizeof(gr_complex), 10000);
gr::blocks::null_sink::sptr snk =
gr::blocks::null_sink::make(sizeof(gr_complex));

tb->connect(src, 0, thr, 0);
tb->connect(thr, 0, snk, 0);

GR_INFO(“fg”, “FgStart Called”);
tb->start();
GR_INFO(“fg”, “Exiting FgStart function”);