Boost.Python | Symbol in .so file but I get ImportError: undefined symbol

Question

I'm using Boost.Python to embed C++ code in my Python app. The module builds fine with a few warnings. When I import the module in Python I get this error:

ImportError: .../cdtm_ext.so: undefined symbol: gsl_multimin_fdfminimizer_conjugate_fr

This symbol is defined in an external library (Gnu Scientific Library) header file, and the symbol exists in the .so file:

$ nm cdtm_ext.so | grep gsl_multimin_fdfminimizer_conjugate_fr
   U gsl_multimin_fdfminimizer_conjugate_fr

Here is my Jamroot file:

import python ;

if ! [ python.configured ]
{
    ECHO "notice: no Python configured in user-config.jam" ;
    ECHO "notice: will use default configuration" ;
    using python ;
}

use-project boost
  : ../../../.. ;

project
  : requirements 
    <library>/boost/python//boost_python
    <include>/usr/local/include/gsl
    ;

python-extension cdtm_ext : cdtm.boost.cpp cdtm/cdtm-model.cpp cdtm/corpus.cpp    cdtm/main.cpp cdtm/opt.cpp cdtm/utils.cpp : <library-path>/usr/local/include/gsl ;

install convenient_copy 
  : cdtm_ext 
  : <install-dependencies>on <install-type>SHARED_LIB <install-type>PYTHON_EXTENSION
    <location>. 
  ;

I had a similar problem when I wrote my own extension using low-level C++ interface. I fixed the problem there by adding the library name gsl in the libraries list of the Extension function call. module = Extension(... libraries = ['gsl', 'cblas'] ...). I have no idea how to do the same thing with Boost.Python.

Answer 1

The symbol gsl_multimin_fdfminimizer_conjugate_fr is not defined in cdtm_ext.so, it is referenced in cdtm_ext.so but undefined, that is what U stands for. You need to link to the library in your case gsl to define that symbol.

See http://www.boost.org/doc/libs/1_46_1/doc/html/bbv2/tutorial.html#bbv2.tutorial.prebuilt for how to link libraries with bjam.