Boost.Python - Exposing a class

Question

I have the following class called "Wav" which is stored in another directory, with the files "Wav.h" and "Wav.cpp" and looks like the following:

enum ReadType {
   NATIVE = 0,
   DOUBLE,
};

namespace AudioLib {
    class Wav : public Signal {
        public: 

           Wav(); 
           Wav(const int M, const int N);

           ///...  ->
    };
 };

The .cpp file contains the implementation of this class, everything compiles well.

I'm trying to implement a Python wrapper using boost.python and have the following file:

#include <boost/python.hpp>
#include "../src/Wav/Wav.h"

using namespace boost::python;

BOOST_PYTHON_MODULE(Wav)
{       
    class_<AudioLib::Wav>("Wav", 
          init<const int, const int>());
}

In my Makefile, I am compiling the Wav.cpp:

# Compile the .wav Python and Cpp file 
$(WAV_TARGET).so: $(WAV_TARGET).o
g++ -shared -Wl,--export-dynamic $(WAV_TARGET).o -L$(BOOST_LIB) -lboost_python -
    lboost_python -L/usr/lib/python$(PYTHON_VERSION)/config -lpython$(PYTHON_VERSION) -o 
    $(WAV_TARGET).so

$(WAV_TARGET).o: $(WAV_TARGET).cpp
g++ $(CFLAGS) ../src/Wav/Wav.cpp -I$(PYTHON_INCLUDE) -I$(BOOST_INC) -fPIC -c 
        $(WAV_TARGET).cpp 

And whenever I try to import into Python I get the following:

ImportError: Wav.so: undefined symbol: _ZN8AudioLib3WavC1Eii

Where am I going wrong?

Answer 1

It looks like you have failed to define the second constructor:

Wav(const int M, const int N);

I can replicate the error message by making a working (but simplified) copy of your example with in-line definitions and just removing the definition of that constructor. So my advice would be to check carefully for the definition in Wav.cpp and try creating an in-line definition to experiment.

If the definition does exist, maybe the linker flags are not right.