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Re: [Discuss-gnuradio] New block: Segfault thrown when calling self.conn


From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] New block: Segfault thrown when calling self.connect
Date: Tue, 27 Sep 2011 19:01:30 -0400
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.22) Gecko/20110906 Fedora/3.1.14-1.fc14 Thunderbird/3.1.14

On 09/27/2011 06:09 PM, Sebastian Götte wrote:
Hello,
I wrote a GNU Radio block using the template from here:
http://gnuradio.org/redmine/projects/gnuradio/wiki/Basic_block
which shall eventually become a source module providing access to a
low-speed electroencephalographic capture board I designed and built, in
order to "abuse" the GNU Radio framework for that kind of data analysis.
This is the test program I tried to run (generated with grc, modified by
hand):
https://github.com/jaseg/openmind-viewer/blob/master/apps/top_block.py
On each run the program throws a segfault in the second connect call on
line 55:
   self.connect((self.openmind_buspirate_source_0, 0),
(self.gr_interleaved_short_to_complex_0, 0))
When I follow the segfault using gdb or pdb I end up somewhere in the
gnuradio internals.
I have no idea what causes this segfault and would be glad for any hints.
The source files of the rest of the block are to be found here (I do not
know which are actually relevant to this question):
https://github.com/jaseg/openmind-viewer
Thanks in advance (hoping that I provided enough information)

Without looking too deeply into it, having looked-over your block source, I might suggest that a better approach to interfacing to your "buspirate" device would be to write an external program and have it communicate data over a named pipe, and your Gnu Radio "stuff" can simply use a 'file source' on the named-pipe. There's no real performance penalty for this--named pipes are quite fast, and your source looks like it runs at a paltry 115200Kbps, which is "way down in the noise" as far as sample rates go.

My suspicion is that there's something wrong with your I/O signatures which is causing the Gnu Radio flow-graph "organizer" to
  barf in a non-graceful way.




--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org





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