Error: "Assertion `px != 0' failed."

Hello,

I need some help with an error I’m getting.

python: /usr/include/boost/shared_ptr.hpp:419: T* boost::shared_ptr<
>::operator->() const [with T = db_base]:
Assertion `px != 0’ failed.

What could be causing this? The entire code is the following:

#!/usr/bin/env python
##################################################

Gnuradio Python Flow Graph

Title: Signal To Raw

Generated: Fri Feb 12 01:11:49 2010

##################################################

from gnuradio import eng_notation
from gnuradio import gr
from gnuradio.eng_option import eng_option
from gnuradio.gr import firdes
from grc_gnuradio import usrp as grc_usrp
from optparse import OptionParser
import datetime
import time

class signal_to_raw(gr.top_block):

def __init__(self):
    gr.top_block.__init__(self)


    today = datetime.datetime.now()
        print "Starting:  %s" % today.isoformat(' ')

    ##################################################
    # option parser
    ##################################################
        ### usage="%prog: [options] output_filename0 

output_filename1 "
parser = OptionParser(option_class=eng_option) ###,
usage=usage)
parser.add_option("-R", “–rx_subdev_spec0”, type=“subdev”,
default=(0,0),help=“first channel select USRP Rx side A or
B(default=A)”)
parser.add_option("-r", “–rx_subdev_spec1”, type=“subdev”,
default=(1,0),help=“second channel select USRP Rx side A or
B(default=A)”)
parser.add_option("-d", “–decim”, type=“int”,
default=256,help=“set fgpa decimation rate to DECIM[default=%default]”)
parser.add_option("-f", “–freq”, type=“eng_float”,
default=54.1e6,help=“set frequency to FREQ”, metavar=“FREQ”)
parser.add_option("-g", “–gain”, type=“eng_float”,
default=100,help=“set gain in dB (default is midpoint)”)
#parser.add_option("-N", “–nsamples”, type=“eng_float”,
default=9600000,help=“number of samples to collect[default=9600000]”)
parser.add_option("-t", “–time”, type=“eng_float”,
default=3540.0,help=“length of recording in seconds [default=0]”)
parser.add_option("-F", “–fft”, type=“int”,
default=-1,help=“display real-time FFT”)
#parser.add_option("-

         (options, args) = parser.parse_args ()
        if len(args) !=0:
           parser.print_help()
           raise SystemExit, 1


    ##################################################
    # File name
    ##################################################
    adc_rate = 64e6
            decim = options.decim
            usrp_rate = adc_rate/decim
    interp = 4 # this is the interpolation interval for the "one in 

N" function
outdir = ‘/home/tamember/radar/gr_jp/’
#basename = ‘grdata_’
today = datetime.datetime.now()
datestamp = today.strftime("%y%m%d%H%M%S")
gain = options.gain
gainset = ‘%d_’ % (gain)
freq = options.freq
in_kHz = freq/1000
freqn = ‘%dkHz_’ % (in_kHz)
rate = ‘%i’ % ((usrp_rate * 2)/interp)
filenamea = outdir + datestamp + “_” + gainset + freqn +
rate + 'cha.dat’
filenameb = outdir + datestamp + "
" + gainset + freqn +
rate + ‘_chb.dat’

    ##################################################
    # Blocks
    ##################################################
    self.gr_file_sink_A = gr.file_sink(gr.sizeof_gr_complex*1, 

“/gr_jp/filenamea”)
self.gr_file_sink_B = gr.file_sink(gr.sizeof_gr_complex*1,
“/gr_jp/filenameb”)
self.usrp_dual_source_x_0 = grc_usrp.dual_source_c(which=0,
rx_ant_a=‘RXA’, rx_ant_b=“RXB”)
self.usrp_dual_source_x_0.set_decim_rate(decim)
self.usrp_dual_source_x_0.set_frequency_a(freq, verbose=True)
self.usrp_dual_source_x_0.set_frequency_b(freq, verbose=True)
self.usrp_dual_source_x_0.set_gain_a(gain)
self.usrp_dual_source_x_0.set_gain_b(gain)

    ##################################################
    # Connections
    ##################################################
    self.connect((self.usrp_dual_source_x_0, 0), 

(self.gr_file_sink_A, 0))
self.connect((self.usrp_dual_source_x_0, 1),
(self.gr_file_sink_B, 0))

    print 'Sample rate is: %ikHz' % (usrp_rate*2/(1000*interp))
    print 'ADC rate is: %iMHz' % 

(usrp_dual_source_x_0.adc_rate()/1000000)
print “Gain: %i” % (gain)
print “Freq is set to: %sMHz” % (freq/float(1000000.0))
print “Decimation interval is: %i” %
(usrp_dual_source_x_0.decim_rate())
print “Interpolation interval is: %i” % (interp)

if name == ‘main’:
if gr.enable_realtime_scheduling() != gr.RT_OK:
print “Error: failed to enable realtime scheduling.”
tb = signal_to_raw()
tb.start()
raw_input('Press Enter to quit: ‘)
tb.stop()
today = datetime.datetime.now()
print “Ending: %s” % today.isoformat(’ ')
print “”

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