Problem using FFT-class in my own written block

Hi all,

I wrote my own block in C++, and used gr-modtool to do all the ‘things’
around it as described in the tutorial “Out-of-tree modules”.

I included ‘fft/fft.h’ in the C++ source code of the block, and used the
class ‘fft_complex’. Then after:

cmake ../

everything compiles/builds without error, and after:

make install

the block is available in GNU Radio Companion.

However, when trying to run a design using this block, I get the
following error:

ImportError /usr/local/ undefined symbol:


I tried executing “sudo ldconfig” but this doesn’t solve the problem.
So, does anybody know how to solve this? Please note:

* I use a USB-stick environment by Ettus R., GNU C++ version

* I am an absolute beginner regarding Linux and GNU Radio etc. So if
files need to be modified please let me know which files, where it
should (can) be located etc…

Thanks for reading,


On Tue, Nov 26, 2013 at 8:57 AM, [email protected] wrote:




That tutorial you mentioned doesn’t give you the whole picture about
configuring your OOT module with different needs like yours. Also read
through this one:

And note the subtle change between 3.7.2 versus later (currently only
on git) versions. You’re going to have to go in and edit your
CMakeLists.txt files in both the root directory of your OOT module and
the lib directory. Right now, what’s likely happening is that you
aren’t linking against the libraries you need. This tutorial will
explain how to find and link against


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