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Re: [Discuss-gnuradio] Question on how to derive a class in an out-of-tr

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] Question on how to derive a class in an out-of-tree module based on a gnuradio class
Date: Tue, 07 Oct 2014 09:54:16 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0

This looks like a linker error.
In your main CMakeList.txt, you have to add DIGITAL to the line containing

If you already have that, sometimes make clean helps, when for some reason linker/ccache/black magic involving CMake failed.


On 07.10.2014 03:58, Zhe Feng wrote:
Dear all,

I'm trying to derive a *packet_header2* class in my own OOT module based on
*gr::digital::packet_header_default*. I followed the way in
*packet_heade_ofdm*  of gr-digital and made packet_header2.h and
packet_header2.cc in my own OOT module.

But when I tried to import my_oot in python, it returned an undefined
symbol error like this:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/my_oot/__init__.py", line
45, in <module>
    from my_oot_swig import *
  File "/usr/local/lib/python2.7/dist-packages/my_oot/my_oot_cdma.py", line
26, in <module>
    _my_oot_swig = swig_import_helper()
  File "/usr/local/lib/python2.7/dist-packages/cdma/cdma_swig.py", line 22,
in swig_import_helper
    _mod = imp.load_module('_my_oot_swig', fp, pathname, description)
ImportError: /usr/local/lib/libgnuradio-my_oot.so: undefined symbol:

I searched the list and found a previous answered question below

where Marcus suggested editing the CMakeList.txt files by adding the module
I needed. So I added


and then. This above error disappeared when I import my_oot again in
python. But this problem isn't solved. I tried to access some functions of
packet_header_default like formatter and base, it returned me an
AtrributeError like this:

AttributeError: 'packet_header2_sptr' object has no attribute 'formatter',
which means the packet_header2 wasn't really a derived class of

I confirmed my conjecture by checking the
/usr/local/lib/python2.7/dist-packages/my_oot/my_oot_swig.py where the
classes are stored in python.  I found that the class packet_header2 is
defined as *class packet_header2(object)*. So the packet_header2 *isn't*
installed as a derived class of *gr::digital::packet_header_default*.  what
I expected was *packet_header2(gr::digital::packet_header_default)*.

So I'm asking you that how to correctly derive my class (eg:
packet_header2) in my own oot module based on a class (eg:
packet_header_default) in an existing module (eg: gr-digital)?

My packet_header2.h and packet_header2.cc are attached for your reference.


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