Updating. Found why the vec was causing a core dump in some cases. It comes

from the fact that std::vector has no inheritance mechanism.

sources/core/common.h

@@ -28,11 +28,8 @@ class vec : public std::vector<double>
 		{
 			assign(dim, 0.0) ;
 		}
-		virtual ~vec() 
-		{
-        }
-
-        //! \brief get a subpart of the vector
+        
+		//! \brief get a subpart of the vector
         vec subvector(int start, int n) const
         {
             vec res(n);

sources/core/function.h

@@ -291,6 +291,7 @@ class compound_function: public nonlinear_function, public std::vector<nonlinear
 			{
 				nb_params += this->at(i)->nbParameters();
 			}
+			return nb_params;
 		}
 
 		//! Get the vector of parameters for the function