# Debugging in gnuradio **URL:** \ **Category:** GNU Radio\ **Created:** [April 4, 2012, 4:08pm UTC](https://www.ruby-forum.com/t/debugging-in-gnuradio/218571 "2012-04-04T16:08:49Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\ **Post date:** [April 4, 2012, 4:08pm UTC](https://www.ruby-forum.com/t/debugging-in-gnuradio/218571/1 "2012-04-04T16:08:49Z")
Hi, I am having a hard time with a “segmentation fault” error. I am no expert in python (I just started to use it last week) but I find it difficult to believe that a segmentation fault error would appear in python code. However, I am not using any block made by me. So this is the part of my code where there is an segmentation fault: def measure\_callback(self,kv): print “Measuring!!” if self.state==SNR\_MEASURE: print “Measuring SNR” self.lock() self.disconnect((self.gr\_file\_source\_0, 0), (self.gr\_throttle\_0,0), self.fft\_sink) self.connect((self.gr\_file\_source\_0, 0), (self.gr\_complex\_to\_mag\_squared\_0, 0), (self.gr\_moving\_average\_ff\_1, 0), (self.gr\_multiply\_const\_ff\_0, 0), self.pwr\_measure) self.unlock() time.sleep(5) snr\_val=10\*math.log(self.pwr\_measure.level()) print "SNR measured = ", snr\_val self.lock() self.disconnect((self.gr\_file\_source\_0, 0),(self.gr\_complex\_to\_mag\_squared\_0, 0), (self.gr\_moving\_average\_ff\_1, 0), (self.gr\_multiply\_const\_ff\_0, 0), self.pwr\_measure) self.connect((self.gr\_file\_source\_0, 0), self.gr\_throttle\_0, self.fft\_sink) self.unlock() So basically I am reading a signal from a file\_source and showing its FFT on a graphical interface. Then when there is a callback from a button I made, this measure\_callback(self,kv) is called and I change my circuit to measure SNR. I used some prints and discovered that the “segmentation fault” happens at “time.sleep(5)”. Lol. Furthermore, the error doesn’t happen all the times I run this code. Unfortunately, I don’t know any type of debugging programs for gnuradio (I don’t know if there is one) but it would be very handy because with just a “Segmentation Fault” message with no traceback it is difficult to know what to do. So, any suggestion about what might be causing this problem? ## Francisco View this message in context: [http://old.nabble.com/Debugging-in-gnuradio-tp33557751p33557751.html](http://old.nabble.com/Debugging-in-gnuradio-tp33557751p33557751.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![frankist](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/e36b37/32.png) [@frankist](https://www.ruby-forum.com/u/frankist)\ **Post date:** [April 5, 2012, 11:12am UTC](https://www.ruby-forum.com/t/debugging-in-gnuradio/218571/2 "2012-04-05T11:12:22Z")
It seems I found the solution, in spite of not knowing the reason. I just have to re-assign a new block to each block variable every time I re-connect them. It seems that connecting and disconnecting the same blocks several times was the cause for the segmentation fault. frankist wrote: > def measure\_callback(self,kv): > time.sleep(5) > So basically I am reading a signal from a file\_source and showing its FFT > “Segmentation Fault” message with no traceback it is difficult to know > what to do. > > So, any suggestion about what might be causing this problem? > > Francisco – View this message in context: [http://old.nabble.com/Debugging-in-gnuradio-tp33557751p33568799.html](http://old.nabble.com/Debugging-in-gnuradio-tp33557751p33568799.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![frankist](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/e36b37/32.png) [@frankist](https://www.ruby-forum.com/u/frankist)\ **Post date:** [April 6, 2012, 12:17am UTC](https://www.ruby-forum.com/t/debugging-in-gnuradio/218571/3 "2012-04-06T00:17:43Z")
On Thu, Apr 5, 2012 at 5:11 AM, frankist [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > It seems I found the solution, in spite of not knowing the reason. > > I just have to re-assign a new block to each block variable every time I > re-connect them. It seems that connecting and disconnecting the same blocks > several times was the cause for the segmentation fault. You shouldn’t have to do that. What version of GNU Radio are you using, and are you on a 32-bit platform? This might be related to a bug in the disconnect/reconnect calls that was patched recently. You can use the following link as a guide to debugging segfaults when they occur: [http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#How-do-I-debug-GNU-Radio-in-Python](http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#How-do-I-debug-GNU-Radio-in-Python) Tom ---
**Author:** ![frankist](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/e36b37/32.png) [@frankist](https://www.ruby-forum.com/u/frankist)\ **Post date:** [April 10, 2012, 11:39am UTC](https://www.ruby-forum.com/t/debugging-in-gnuradio/218571/4 "2012-04-10T11:39:21Z")
Hmm… Thanks a lot. I think the problem may be related to the connects/disconnects. Even if I am always reconnecting blocks, some freezes happen sometimes in the disconnect() commands. Is the patch you are refering to the new gnu version 3.5.3? Also, I would like to know if there is a better method than the “sleep” commands I used for letting the circuit for a short period of time. I mean, I used a head block to select just a few samples at the end of the circuit, but if I don’t use the time.sleep(), the python script won’t wait until I get the number of samples I need. So what I am asking is a type of semaphore command that lets the python script know when the gnuradio graph has already finished. Tom R.-2 wrote: > > > However, I am not using any block made by me. > > > self.connect((self.gr\_file\_source\_0, 0), > > > self.connect((self.gr\_file\_source\_0, 0), > > > > > > “Segmentation Fault” message with no traceback it is difficult to know > > > Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). > > > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) – View this message in context: [http://old.nabble.com/Debugging-in-gnuradio-tp33557751p33660247.html](http://old.nabble.com/Debugging-in-gnuradio-tp33557751p33660247.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com).