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

[Pierre Barbier de Reuille]

Some more details ...

I made some experiment and it appears that if I use an ob ject of the 
class :

******************************
class EmptyMean:
  def __init__(self,walls):
    self.walls = walls
  def __call__(self,cell):
    poly = self.walls.getCell(cell)
    l = len(poly)
    return vertex_type(l,l)
***********************************

as a parameter for my C++ method, it works. But if I use :

******************************
class EmptyMean:
  def __init__(self,walls):
    self.walls = walls
  def __call__(self,cell):
    poly = self.walls.getCell(cell)
    return poly[0]
***********************************

it crashes ! poly is an exported vector<vertex_type>. I exported it so 
that it has the same behaviour as a python list.
Here is the code of the __getitem__ method used to export the vector to 
python :

***************************************************************************
template <class ToExport>
typename container_trait<ToExport>::value_type
  list_getItem(ToExport* exp,
           typename container_trait<ToExport>::difference_type i)
{
  typename container_trait<ToExport>::iterator it;
  it = PosInRange(exp, i);
  return *it;
}

template <class ToExport>
typename container_trait<ToExport>::iterator
  PosInRange(ToExport *l,
         typename container_trait<ToExport>::difference_type i)
{
  typename container_trait<ToExport>::difference_type size = l->size();
  if((i >= size) || (i < -size))
    {
      PythonExc_IndexError ind;
      ind.error_str = "assignment index out of range";
      throw ind;
    }
  if(i < 0)
    {
      typename container_trait<ToExport>::difference_type size = l->size();
      i += size;
    }
  typename container_trait<ToExport>::iterator it = l->begin();
  advance(it, i);
  return it;
}
*********************************************************************

The template parameter ToExport is here std::vector<vertex_type>.
container_trait<std::vector<vertex_type> >::iterator is 
std::vector<vertex_type>::iterator
container_trait<std::vector<vertex_type> >::difference_type is 
std::vector<vertex_type>::difference_type
container_trait<std::vector<vertex_type> >::iterator is 
std::vector<vertex_type>::iterator


I'm still looking for more precise information, but I still have 
absolutely no clue abour what is going on ...

-- 
Pierre Barbier de Reuille

INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP
Botanique et Bio-informatique de l'Architecture des Plantes
TA40/PSII, Boulevard de la Lironde
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