[C++-sig] Segfault when calling python method from C++

[Pierre Barbier de Reuille]

I have an embedded python in a C++ program. I extend python using boost in order to interact with C++. Some of my methods makes use of C++ function-object. So I implemented this class to encapsulate Python methods :

*****************************************************
struct PyCenterComp
{
  PyCenterComp( boost::python::object o );
  PyCenterComp( const PyCenterComp& copy );
  vertex_type operator()( Delaunay2D::cell_descriptor cell );
  boost::python::object method;
};

PyCenterComp::PyCenterComp( object o )
: method( o )
{
}

PyCenterComp::PyCenterComp( const PyCenterComp& copy )
: method( copy.method )
{
}

vertex_type PyCenterComp::operator()( Delaunay2D::cell_descriptor cell )
{
  std::cerr << "Call method ... " << endl;
  boost::python::object o( method( cell_descriptor( cell ) ) );
  std::cerr << "Called" << endl;
  extract<vertex_type> v( o );
  std::cerr << "Converted" << endl;
  if( v.check() )
    {
      return v();
    }
  return vertex_type();
}
*******************************************

The Delaunay2D::cell_descriptor being implemented as void*, it's encapsulated in a cell_descriptor structure which is exported in Python.
In the python interpreter I created a function object with this code :

*******************************************
class ProdMean:
  def __init__(self, walls):
    self.walls = walls
  def __call__(self,cell):
    poly = self.walls.getCell(cell)
    return self.mean(poly)
  def mean(self, poly):
    dx = 1
    dy = 1
    for i in poly:
      dx = dx * i.x()
      dy = dy * i.y()
    dx = dx ** (1.0/len(poly))
    dy = dy ** (1.0/len(poly))
    return vertex_type(dx,dy)
*******************************************

Then I can use this class with :

p = ProdMean(walls)
l = [p(i) for i in walls]

walls is a C++ object (a graph) and the getCell method returns a polygon (a vector of vertex). This little python code works well. But now, if I try to call p from C++ using the PyCenterComp object I get a segmentation fault when calling the method (I got this output:
Call method ... 
zsh: segmentation fault
)

If you want, I can give you the callstack when the crash occure, but it's quite huge (~50 elements ... ) so I'll do only if it's needed.

Thanks,

-- 
Pierre Barbier de Reuille

INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP
Botanique et Bio-informatique de l'Architecture des Plantes
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