Re: [Discuss-gnuradio] constellation soft decoder

[Marcus Müller]

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Well, after having a debug build and then adding a lot of "volatile"s
into the code at the crashing function, it looks as if the
d_pre_diff_code of the constellation has size 0; and thus, you can't
access the 0. (read: first) element. How this could happen with a QPSK
object is currently subject to my confusion. Stay tuned for more
confusing facts as the code unfolds :).

Greetings,
Marcus

On 16.12.2013 08:30, Miklos Maroti wrote:
> Hi Marcus,
> 
> I do not think it is a compiler bug, but something uninitialized. 
> Constellation_qpsk and constellation_calcdist does not crash (I
> did not verify if they work). However, if I generate the LUT for 
> constellation_qpsk, then it crashes.
> 
> # uname -a Linux maroti-t410 3.11.0-14-generic #21-Ubuntu SMP Tue
> Nov 12 17:04:55 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> 
> # gcc --version gcc (Ubuntu/Linaro 4.8.1-10ubuntu9) 4.8.1
> 
> Using latest master branch of gnuradio, hash 117058bac41c91, both 
> CMAKE_BUILD_TYPE=Debug and Release produces the same behavior
> 
> # gdb `which python` core Reading symbols from
> /usr/bin/python2.7...(no debugging symbols found)...done.
> 
> warning: core file may not match specified executable file. [New
> LWP 2249] [New LWP 2251] [New LWP 2240] [New LWP 2248] [New LWP
> 2247] [New LWP 2239] [New LWP 2250]
> 
> warning: Can't read pathname for load map: Input/output error. 
> [Thread debugging using libthread_db enabled] Using host
> libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". 
> Core was generated by `python ./constellation_simulation.py'. 
> Program terminated with signal 11, Segmentation fault. #0
> 0x00007f98dbbe01a7 in gr::digital::constellation::calc_soft_dec ( 
> this=0x48321c0, sample=..., npwr=<optimized out>) at
> /home/mmaroti/workspace/gnuradio/gr-digital/lib/constellation.cc:286
>
> 
286        for(int j = 0; j < k; j++) {
> 
> i stack #0  0x00007f98dbbe01a7 in
> gr::digital::constellation::calc_soft_dec ( this=0x48321c0,
> sample=..., npwr=<optimized out>) at
> /home/mmaroti/workspace/gnuradio/gr-digital/lib/constellation.cc:286
>
> 
#1  0x00007f98dbbe0f7e in gr::digital::constellation::soft_decision_maker (
> this=0x48321c0, sample=...) at
> /home/mmaroti/workspace/gnuradio/gr-digital/lib/constellation.cc:355
>
> 
#2  0x00007f98dbbe94dc in
> gr::digital::constellation_soft_decoder_cf_impl::work
> (this=0x4fb11a0, noutput_items=8190, input_items=...,
> output_items=...) at
> /home/mmaroti/workspace/gnuradio/gr-digital/lib/constellation_soft_decoder_cf_impl.cc:68
>
> 
#3  0x00007f98e1c5dd38 in gr::sync_interpolator::general_work (
> this=0x4fb11c0, noutput_items=<optimized out>, ninput_items=..., 
> input_items=..., output_items=...) at
> /home/mmaroti/workspace/gnuradio/gnuradio-runtime/lib/sync_interpolator.cc:67
>
>  You should be able to reproduce the problem quite easily, but if 
> needed I can provided a test program.
> 
> Best, Miklos
> 
> On Mon, Dec 16, 2013 at 7:59 AM, Marcus Müller <address@hidden>
> wrote:
>> Could you post the whole backtrace (as a github gist, pastebin
>> etc)? That would be very helpful, along with information such
>> as: Compiler (Gcc (version), VC++, clang ...), Platform (Linux,
>> win, mac,...), architecture (x86(64), ARMv9, IBM S7390,...) and
>> GNU Radio source version.
>> 
>> Thanks and happy hacking, Marcus
>> 
>> On 12/16/2013 01:05 AM, Miklos Maroti wrote:
>>> 
>>> Hi Guys,
>>> 
>>> Constellation soft decoder crashes for constellation_bpsk()
>>> and constellation_8psk(). I could not find the cause of this
>>> problem, the back trace on my machine points to
>>> 
>>> gnuradio/gr-digital/lib/constellation.cc:286 for(int j = 0; j <
>>> k; j++) {
>>> 
>>> which does not make any sense. Any idea what could go wrong?
>>> 
>>> Miklos
>>> 
>>> _______________________________________________ 
>>> Discuss-gnuradio mailing list address@hidden 
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>> 
>> 
>> 
>> _______________________________________________ Discuss-gnuradio
>> mailing list address@hidden 
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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