Callback method not being provided in GR 3.10 OOT Block

[David Cherkus]

As earlier, I am porting an OOT that worked with GR 3.9 into GR 3.10.

I'm a C++ and CMake newbie, please keep that in mind.

When I run a flowgraph with my GR 3.10 block in it I get:

Traceback (most recent call last):
    from gnuradio import mxvii
    from .mxvii_python import *
ImportError: /home/dcherkus/radioconda/envs/radioconda/lib/python3.9/site-packages/gnuradio/mxvii/mxvii_python.cpython-39-x86_64-linux-gnu.so: undefined symbol: _ZN2gr5mxvii7encoder15set_destinationENSt7cxx1112basic_stringIcSt11char_traitsIcESaIcEEE

Then I use c++filt to demangle the undefined symbol:

$ c++filt _ZN2gr5mxvii7encoder15set_destinationENSt7cxx1112basic_stringIcSt11char_traitsIcESaIcEEE
gr::mxvii::encoder::set_destination(std::cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>)

This shows Python is trying to call a callback I'm providing in C++ to set one of the block's parameters.

Then I use nm to see what is being exported by the C++ shared library built by my OOT:

$ nm -C ~/radioconda/envs/radioconda/lib/libgnuradio-mxvii.so.1.0.0.0

The only methods being exported are:

gr::mxvii::encoder_impl::work()
gr::mxvii::encoder_impl::encoder_impl()
gr::mxvii::encoder_impl::~encoder_impl()
gr::mxvii::encoder::make()

Then I use nm to see what is being exported by the .o I am building:

$ nm -C build/lib/CMakeFiles/gnuradio-mxvii.dir/encoder_impl.cc.o 2>/dev/null | grep set_destination
0000000000000000 T gr::mxvii::encoder_impl::set_destination(std::cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >)

So the object file is providing a definition of the callback method, but it doesn't get included in the shared object.

What could be going wrong here?

Based on reading other people's yml I tried a redundant 'cxx_templates' block but it didn't seem to help:

templates:
  imports: from gnuradio import mxvii
  make: mxvii.encoder(${source_address}, ${destination_address})
  callbacks:
  - set_source(${source_address})
  - set_destination(${destination_address})

cxx_templates:
  callbacks:
  - set_source(${source_address})
  - set_destination(${destination_address})

Any clues?

Thanks,

Dave