[Discuss-gnuradio] Topology error

[Matthew Burnham]

Having bitten the bullet and upgraded to gcc-3.3 and debian testing, I'm 
now getting somewhere...

I've got a relatively simple bit of code copied from one of the 
examples (see below). This compiles fine, but I get the following error: 
"Topology cannot be changed after inital setup." I'm assuing this is 
something to do with the way the different Source, Sink and SigProcs are 
connected together. Do I need to create the various source, sink and 
SigProcs in a particular order?

How can I solve this for this simple set-up?

int main(int argc, char **argv) {
  VrGUI *guimain = new VrGUI(argc, argv);
  VrGUILayout *horiz = guimain->top->horizontal();
  VrGUILayout *vert = horiz->vertical();

  VrSource<short> *source = new VrFileSource<short>(SAMPLING_FREQUENCY, 
"raw_audio.short");

  VrSink<short> *scope_sink = new GrSimpleScopeSink<short>(vert, -AMPLITUDE, 
AMPLITUDE, 1000);
  VrSigProc *sqr = new GrSquare<short, short>();
  VrSink<short> *scope_sink2 = new GrSimpleScopeSink<short>(vert, -AMPLITUDE, 
AMPLITUDE, 1000);

  NWO_CONNECT (source, scope_sink);
  NWO_CONNECT (source, sqr);
  NWO_CONNECT (sqr, scope_sink2);

  VrMultiTask *m = new VrMultiTask ();
  m->add (scope_sink);
  m->add (sqr);
  m->add (scope_sink2);
  m->start();

  guimain->start();

  while (1) {
    guimain->processEvents(10 /*ms*/);
    m->process();
  }
}