Re: [Discuss-gnuradio] QT Gui FFT resizing Segfault

[Marcus Müller]

I think it's going wrong in getActionFromSize, which easy as it
looks[1], I don't get the hang of.
Why do we need a specific QAction based on the FFT length we're setting?
And why does an FFT size of 4 lead to negative indices in a QList?

Anyway, the actual bug was on my side, as I was constantly setting an
FFT size of 4. Which seemingly doesn't work.
@LD: try
<callback>set_fft_size(max(int($fftsize),32))</callback>
instead. I was then able to change the displayed FFT on the fly using QT
Gui sliders [2].

Greetings,
Marcus

[1] gr-qtgui/include/gnuradio/qtgui/form_menus.h
[2] https://gist.github.com/marcusmueller/edfef568a92821261f9f , the
adjustable_qtgui_fft.grc file should load nicely in a 3.7.4 GNU Radio, I
think it should work with 3.7.x
On 04.06.2014 09:21, Marcus Müller wrote:
> Hi!
>
> Alfredo: Jep, did that. GDB was how I figured out things went wrong in
> FreqDisplayForm::setFFTSize() in the first place :).
> Jörg: Interesting; but the error is quite reproducibly at the same
> place; I'll try to set a breakpoint at the kernel call and see if that
> happens again. But that will require some gdb magic (so that GDB only
> interrupts program flow when the fft size changes), and that's
> definitively something that would be worthwhile to learn, however I'm
> postponing this for now for reasons of time available.
>
> Greetings,
> Marcus
>
> On 04.06.2014 08:48, Jan Krämer wrote:
>> Hey,
>>
>> I know another GSoC Student has problems with the a GT GUI sink as
>> well. It would randomly SEGFAULT in a volk multiply kernel. I think it
>> is the volk_32_fc_32f_multiply_32fc kernel used in
>> waterfall_sink_X_impl::fft(). This kernel takes the FFT size as an
>> input argument, so it could be related to your problem. I just had a
>> quick glance at it so I am not sure though. I'll ask him to post his
>> exact problem when he arrives at the lab. Maybe he can shed a bit more
>> light on this problem
>>
>> -Jan
>>
>>
>> On 04.06.2014 01:43, Alfredo Muniz wrote:
>>> On Tue, Jun 3, 2014 at 4:35 PM, Marcus Müller <address@hidden
>>> <mailto:address@hidden>> wrote:
>>>
>>>     I hope someone more familiar with the qtgui infrastructure might
>>>     chime in.
>>>
>>>
>>> Hey Marcus,
>>>
>>> Did you try debugging the SEGFAULT using gdb? This is a good
>>> reference to try:
>>> http://www.unknownroad.com/rtfm/gdbtut/gdbsegfault.html
>>>
>>>
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>>> Discuss-gnuradio mailing list
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>>
>>
>>
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