Re: Adaptation of Federico La Roccas ISDB-T blocks for DVB-T

[Vasil Velichkov]

Hi Ralf,

> Thread 27 "dvbt_symbol_inn" received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x7fffc5ffb700 (LWP 1924)]
> 0x00007fffe61a2e0d in ?? () from 
> /lib/x86_64-linux-gnu/libgnuradio-dtv.so.3.8.3
> (gdb) bt
> #0  0x00007fffe61a2e0d in  () at 
> /lib/x86_64-linux-gnu/libgnuradio-dtv.so.3.8.3
> #1  0x00007ffff0f40d13 in gr::block_executor::run_one_iteration() () at 
> /lib/x86_64-linux-gnu/libgnuradio-runtime.so.3.8.3
> #2  0x00007ffff0f95eaa in 
> gr::tpb_thread_body::tpb_thread_body(boost::shared_ptr<gr::block>, 
> boost::shared_ptr<boost::barrier>, int) () at 
> /lib/x86_64-linux-gnu/libgnuradio-runtime.so.3.8.3
> #3  0x00007ffff0f84928 in  () at 
> /lib/x86_64-linux-gnu/libgnuradio-runtime.so.3.8.3

It seems you are using Debian/Ubuntu (or some derivative) and you are missing 
the debug info symbols for libgnuradio-runtime.so and libgnuradio-dtv.so 
libraries. I'm not a Debian/Ubuntu user and I'm not very familiar how to 
install the missing symbols. Read the following pages, install the debug 
symbols and then repeat the same procedure and you will get some more 
meaningful information like .cpp/.h file names and line numbers.

https://wiki.ubuntu.com/Debug%20Symbol%20Packages
https://wiki.ubuntu.com/DebuggingProgramCrash
https://wiki.debian.org/HowToGetABacktrace#Installing_the_debugging_symbols

Also tell us which Linux distribution do you use and which version? How did you 
install gnuradio and the exact version?

Regards,
Vasil 

On 10/12/2021 14.51, Ralf Gorholt wrote:
> Hi Vasil,
> 
> thank you for your message. As I have no experience with GNU Radio and
> command line debugging, your hints may be really helpful. I have
> attached the gdb and valgrind output to this email.
> 
> In the gdb output thread 27 that receives the SIGSEGV is the DVB-T
> "Symbol Inner Interleaver" that comes with GNU Radio, not one of my blocks.
> 
> As far as valgrind is concerned, it tells me for my block OFDM
> Synchronization: "Conditional jump or move depends on uninitialised
> value(s)". I will see if I can find out which variable is uninitialized
> and how I can get rid of this problem.
> 
> Kind regards,
> 
> Ralf
> 
> Am 10.12.2021 um 12:35 schrieb Vasil Velichkov:
>> Hi Ralf,
>>
>> On 10/12/2021 11.52, Ralf Gorholt wrote:
>>> Unfortunately, when I deactivate the original flowgraph, it does no
>>> longer work and I get a -11 return code.
>> The "-11" value means that you got a segmentation fault and the process was 
>> kill with signal 11 (SIGSEGV)
>>
>> https://docs.python.org/3.8/library/subprocess.html#subprocess.CalledProcessError.returncode
>> https://www.man7.org/linux/man-pages/man7/signal.7.html
>>
>> In my opinion the easiest way to debug segfaults is to run the flowgraph 
>> under gdb and valgrind. Open your flowgraph in the gnuradio-companion and 
>> then Generate (F5) but do not Execute (F6). The open a terminal, go where 
>> the flowgraph python (.py) file was generated and execute
>>
>>   gdb -ex run --args /usr/bin/python3 test.py
>>
>> and then when it stops execute `bt` command in the gdb's shell and provide 
>> the full output. To run it under valgrind execute
>>
>>   valgrind --tool=memcheck /usr/bin/python3 test.py
>>
>> Adjust the path to your python interpreter and its version if needed.
>>
>> Regards,
>> Vasil