Re: [Discuss-gnuradio] FFT Header SWIG Issues

[Michael Dickens]

Hi Shalom - Something to check / verify: In the top-level CMakeLists.txt file, when searching for GNU Radio, make sure to include the FFT module, not just RUNTIME. From the look of the error, libgnuradio-fft is not being linked into your OOT anywhere. This small tweak should do the trick if this is indeed the actual issue. Hope this helps! - MLD

On Mon, Apr 30, 2018, at 3:43 PM, Shalom Dubinsky wrote:

I'm not very experienced with c++ or with swig, so perhaps I'm missing something here, but I've got a problem and I can't figure it out.

I'm trying to replicate the signal_detector block in gr-inspector, and I can't seem to include the fft header so that swig detects it.  I can't find the difference between my code and the gr-inspector code, either.

I can reliably reproduce this by:

1. creating a new module.

2. creating a new block, with python qa code

3. including the fft header `#include <gnuradio/fft/fft.h>`

4. instantiating an fft_complex object `fft::fft_complex *d_fft = new fft::fft_complex(1024, true);`

5. running `make && ctest -V`

The second test will fail, and the relevant part of the error message is "ImportError: /home/reader/code/drones/drone-hacker/gr-mwe/build/lib/libgnuradio-mwe-1.0.0git.so.0.0.0: undefined symbol: _ZN2gr3fft11fft_complexC1Eibi".

Declaring the object without instantiating it - `fft::fft_complex *d_fft;` will work.