selfintersection of wires during offsetting

Hi,

I am trying to offset a wire multiple no of times till no of obtained offset wires is achieved.But,instead of coming out of loop the code is crashing when it is achieved!

here is the code sample:

void CImportExportDoc::Offset(TopoDS_Wire &W)
{
const GeomAbs_JoinType Join=GeomAbs_Arc;
Handle(AIS_Shape) ais7=new AIS_Shape(W);
BRepOffsetAPI_MakeOffset off(W,GeomAbs_Arc);
Standard_Real dist2 = -200;
Standard_Real NoW,NoE;
do{
off.Perform(dist2); //the code crashes here
TopoDS_Shape S5= off.Shape();
ShapeAnalysis_ShapeContents SA; //to analyse the given shape
SA.Perform(S5);
NoW=SA.NbWires(); //no. of wires in the shape
NoE=SA.NbEdges(); //no. of edges in the wire
TopExp_Explorer Exp1;
for(Exp1.Init(S5,TopAbs_EDGE);Exp1.More();Exp1.Next()) //exploring the shape into edges
{
TopoDS_Edge l_edge = TopoDS::Edge(Exp1.Current());
Handle(Geom_Curve) aCurve = BRep_Tool::Curve(l_edge,u,v);
GeomAdaptor_Curve c(aCurve );
}
dist2=dist2-10;
}while(NoW!=0);
}