diff --git a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Algebraic_curve_kernel_2.h b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Algebraic_curve_kernel_2.h
index 52da564cb0c..2e2d76d3462 100644
--- a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Algebraic_curve_kernel_2.h
+++ b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Algebraic_curve_kernel_2.h
@@ -411,8 +411,8 @@ public:
 			     
 
        result_type operator() (const argument_type& arg) const {
-	 CGAL_assertion(_inner);
-	 CGAL_assertion(_outer);
+	 CGAL_assertion(bool(_inner));
+	 CGAL_assertion(bool(_outer));
 	 return _outer.get()(_inner.get()(arg));
        }
     private:
diff --git a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_analysis_2.h b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_analysis_2.h
index f1e3954f54c..945b743c907 100644
--- a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_analysis_2.h
+++ b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_analysis_2.h
@@ -651,7 +651,7 @@ public:
 
     //! Returns the defining polynomial
     Polynomial_2 polynomial_2() const {
-        CGAL_precondition(this->ptr()->f);
+        CGAL_precondition(bool(this->ptr()->f));
         return this->ptr()->f.get();
     }
 
@@ -664,7 +664,7 @@ public:
      * the curve's defining equation is returned.
      */
     size_type number_of_status_lines_with_event() const {
-        CGAL_precondition(this->ptr()->f);
+        CGAL_precondition(bool(this->ptr()->f));
 #if CGAL_ACK_USE_SPECIAL_TREATMENT_FOR_CONIX
         if(CGAL::degree(polynomial_2(),1)==2) {
             return this->conic_number_of_status_lines_with_event();
@@ -1739,7 +1739,7 @@ private:
         if(! this->ptr()->intermediate_values) {
             // This is created during event_coordiantes()
             event_coordinates();
-            CGAL_assertion(this->ptr()->intermediate_values);
+            CGAL_assertion(bool(this->ptr()->intermediate_values));
         }
         return this->ptr()->intermediate_values.get();
     }
diff --git a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_pair_analysis_2.h b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_pair_analysis_2.h
index a9c39bf9126..24fa4de491c 100644
--- a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_pair_analysis_2.h
+++ b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Curve_pair_analysis_2.h
@@ -556,7 +556,7 @@ public:
         if(! this->ptr()->resultant) {
             compute_resultant();
         }
-        CGAL_assertion(this->ptr()->resultant);
+        CGAL_assertion(bool(this->ptr()->resultant));
         return this->ptr()->resultant.get();
     }
 
@@ -564,7 +564,7 @@ public:
         if(! this->ptr()->resultant_roots) {
             compute_resultant_roots_with_multiplicities();
         }
-        CGAL_assertion(this->ptr()->resultant_roots);
+        CGAL_assertion(bool(this->ptr()->resultant_roots));
         return this->ptr()->resultant_roots.get();
     }
 
@@ -578,7 +578,7 @@ public:
         if(! this->ptr()->multiplicities_of_resultant_roots) {
             compute_resultant_roots_with_multiplicities();
         }
-        CGAL_assertion(this->ptr()->multiplicities_of_resultant_roots);
+        CGAL_assertion(bool(this->ptr()->multiplicities_of_resultant_roots));
         return this->ptr()->multiplicities_of_resultant_roots.get();
     }    
     
@@ -598,7 +598,7 @@ public:
 	       resultant_roots().end(),
 	       std::back_inserter(this->ptr()->stripe_values.get()));
         }
-        CGAL_assertion(this->ptr()->stripe_values);
+        CGAL_assertion(bool(this->ptr()->stripe_values));
         return this->ptr()->stripe_values.get();
     }
 
@@ -606,7 +606,7 @@ public:
         if(! this->ptr()->event_x_coordinates) {
             compute_event_x_coordinates_with_event_indices();
         }
-        CGAL_assertion(this->ptr()->event_x_coordinates);
+        CGAL_assertion(bool(this->ptr()->event_x_coordinates));
         return this->ptr()->event_x_coordinates.get();
     }
 
@@ -614,7 +614,7 @@ public:
         if(! this->ptr()->event_indices) {
             compute_event_x_coordinates_with_event_indices();
         }
-        CGAL_assertion(this->ptr()->event_indices);
+        CGAL_assertion(bool(this->ptr()->event_indices));
         return this->ptr()->event_indices.get();
     } 
 
@@ -642,7 +642,7 @@ private:
         if(! this->ptr()->intermediate_values) {
             compute_intermediate_values_and_slices();
         }
-        CGAL_assertion(this->ptr()->intermediate_values);
+        CGAL_assertion(bool(this->ptr()->intermediate_values));
         return this->ptr()->intermediate_values.get();
     }
 
@@ -650,7 +650,7 @@ private:
         if(! this->ptr()->intermediate_slices) {
             compute_intermediate_values_and_slices();
         }
-        CGAL_assertion(this->ptr()->intermediate_slices);
+        CGAL_assertion(bool(this->ptr()->intermediate_slices));
         return this->ptr()->intermediate_slices.get();
     }
 
@@ -661,7 +661,7 @@ private:
         if(! this->ptr()->subresultants) {
             compute_subresultants();
         }
-        CGAL_assertion(this->ptr()->subresultants);
+        CGAL_assertion(bool(this->ptr()->subresultants));
         return this->ptr()->subresultants.get();
     }
 
@@ -675,7 +675,7 @@ private:
         if(! this->ptr()->principal_subresultants) {
             compute_subresultants();
         }
-        CGAL_assertion(this->ptr()->principal_subresultants);
+        CGAL_assertion(bool(this->ptr()->principal_subresultants));
         return this->ptr()->principal_subresultants.get();
     }
 
@@ -690,7 +690,7 @@ private:
         if(! this->ptr()->coprincipal_subresultants) {
             compute_subresultants();
         }
-        CGAL_assertion(this->ptr()->coprincipal_subresultants);
+        CGAL_assertion(bool(this->ptr()->coprincipal_subresultants));
         return this->ptr()->coprincipal_subresultants.get();
     }
 
@@ -1040,7 +1040,7 @@ public:
         if(! this->ptr()->event_slices[i]) {
             this->ptr()->event_slices[i] = create_event_slice(i);
         }
-        CGAL_assertion(this->ptr()->event_slices[i]);
+        CGAL_assertion(bool(this->ptr()->event_slices[i]));
         return this->ptr()->event_slices[i].get();
     }
       
@@ -1084,7 +1084,7 @@ public:
                 }
             }
         }
-        CGAL_assertion(intermediate_values()[i]);
+        CGAL_assertion(bool(intermediate_values()[i]));
         return intermediate_values()[i].get();
 
     }
diff --git a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Status_line_CA_1.h b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Status_line_CA_1.h
index 99625a6f771..ed322c42498 100644
--- a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Status_line_CA_1.h
+++ b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Status_line_CA_1.h
@@ -560,7 +560,7 @@ public:
 
     //! Returns the isolator instance
     Bitstream_descartes& isolator() const {
-        CGAL_assertion(this->ptr()->isolator);
+        CGAL_assertion(bool(this->ptr()->isolator));
         return this->ptr()->isolator.get();
     }
 
diff --git a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Xy_coordinate_2.h b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Xy_coordinate_2.h
index 3a154f798b5..e5865037212 100644
--- a/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Xy_coordinate_2.h
+++ b/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Xy_coordinate_2.h
@@ -387,7 +387,7 @@ public:
                         (*candidates.begin())->high()
                 );
         }
-        CGAL_postcondition(this->ptr()->_m_y);
+        CGAL_postcondition(bool(this->ptr()->_m_y));
         return *this->ptr()->_m_y;
     }
     
diff --git a/Arrangement_on_surface_2/include/CGAL/Curved_kernel_via_analysis_2/Point_2.h b/Arrangement_on_surface_2/include/CGAL/Curved_kernel_via_analysis_2/Point_2.h
index 5c2d80460eb..6e18d960fad 100644
--- a/Arrangement_on_surface_2/include/CGAL/Curved_kernel_via_analysis_2/Point_2.h
+++ b/Arrangement_on_surface_2/include/CGAL/Curved_kernel_via_analysis_2/Point_2.h
@@ -379,7 +379,7 @@ public:
      */
     inline 
     const Coordinate_2& xy() const {
-        CGAL_precondition_msg(this->ptr()->_m_xy,
+        CGAL_precondition_msg(bool(this->ptr()->_m_xy),
             "Denied access to the curve end lying at x/y-infinity");
         return *(this->ptr()->_m_xy);
     }
@@ -514,8 +514,8 @@ public:
     inline
     CGAL::Comparison_result compare_xy(const Kernel_point_2& q, 
                                        bool equal_x = false) const {
-        CGAL_precondition(this->ptr()->_m_xy);
-        CGAL_precondition(q.ptr()->_m_xy);
+        CGAL_precondition(bool(this->ptr()->_m_xy));
+        CGAL_precondition(bool(q.ptr()->_m_xy));
 
         CGAL_CKvA_2_GRAB_CK_FUNCTOR_FOR_POINT(Compare_xy_2, compare_xy_2)
         CGAL_precondition(dynamic_cast< const Kernel_point_2* >(this) != NULL);
@@ -534,7 +534,7 @@ public:
     bool is_on(
          const typename Curved_kernel_via_analysis_2::Curve_2& curve
     ) const {
-        CGAL_precondition(this->ptr()->_m_xy);
+        CGAL_precondition(bool(this->ptr()->_m_xy));
 
         CGAL_CKvA_2_GRAB_CK_FUNCTOR_FOR_POINT(Is_on_2, is_on_2)
         CGAL_precondition(dynamic_cast< const Kernel_point_2* >(this) != NULL);
diff --git a/Circular_kernel_2/include/CGAL/Circular_kernel_2/Line_arc_2.h b/Circular_kernel_2/include/CGAL/Circular_kernel_2/Line_arc_2.h
index 3d6de479d3e..aac75c56cf5 100644
--- a/Circular_kernel_2/include/CGAL/Circular_kernel_2/Line_arc_2.h
+++ b/Circular_kernel_2/include/CGAL/Circular_kernel_2/Line_arc_2.h
@@ -133,7 +133,7 @@ public:
     //typedef typename Root_of_2::RT RT_2;
     typename Intersection_traits<CK, Line_2, Line_2>::result_type 
       v = CGAL::internal::intersection(support, l1, CK());
-    CGAL_assertion(v);
+    CGAL_assertion(bool(v));
 
     const Point_2 *pt = CGAL::internal::intersect_get<Point_2>(v);
     CGAL_assertion(pt != NULL);
diff --git a/Intersections_3/include/CGAL/Triangle_3_Triangle_3_intersection.h b/Intersections_3/include/CGAL/Triangle_3_Triangle_3_intersection.h
index 162813a490f..124027f7440 100644
--- a/Intersections_3/include/CGAL/Triangle_3_Triangle_3_intersection.h
+++ b/Intersections_3/include/CGAL/Triangle_3_Triangle_3_intersection.h
@@ -69,7 +69,7 @@ void intersection_coplanar_triangles_cutoff(
         ::result_type 
         obj = intersection(Line_3(p,q),Line_3(*prev,curr),k);
       // assert "not empty"
-      CGAL_kernel_assertion(obj);
+      CGAL_kernel_assertion(bool(obj));
       const typename Kernel::Point_3* inter=intersect_get<typename Kernel::Point_3>(obj);
       CGAL_kernel_assertion(inter!=NULL);
       prev=&(* inter_pts.insert(it,*inter) );
diff --git a/Kinetic_data_structures/include/CGAL/Kinetic/Heap_pointer_event_queue.h b/Kinetic_data_structures/include/CGAL/Kinetic/Heap_pointer_event_queue.h
index c19832e5562..8a2007707c3 100644
--- a/Kinetic_data_structures/include/CGAL/Kinetic/Heap_pointer_event_queue.h
+++ b/Kinetic_data_structures/include/CGAL/Kinetic/Heap_pointer_event_queue.h
@@ -401,7 +401,7 @@ public:
   //! Access the time of a particular event
   const Priority& priority(const Key &item) const
   {
-    CGAL_precondition(item);
+    CGAL_precondition(bool(item));
     return item->time();
   }
 
diff --git a/Operations_on_polyhedra/include/CGAL/intersection_of_Polyhedra_3_refinement_visitor.h b/Operations_on_polyhedra/include/CGAL/intersection_of_Polyhedra_3_refinement_visitor.h
index d684263d491..77c1f5f50aa 100644
--- a/Operations_on_polyhedra/include/CGAL/intersection_of_Polyhedra_3_refinement_visitor.h
+++ b/Operations_on_polyhedra/include/CGAL/intersection_of_Polyhedra_3_refinement_visitor.h
@@ -576,7 +576,7 @@ void sew_3_marked_darts( Combinatorial_map_3& final_map,
     darts_to_remove.insert(not_top);   darts_to_remove.insert(not_top->beta(1)); darts_to_remove.insert(not_top->beta(1)->beta(1));
     darts_to_remove.insert(not_top->beta(3));   darts_to_remove.insert(not_top->beta(3)->beta(1)); darts_to_remove.insert(not_top->beta(3)->beta(1)->beta(1));
     O_Dart_handle current_1=next_marked_dart_around_target_vertex(final_map,not_top,mark_index);
-    CGAL_precondition(current_1);
+    CGAL_precondition(bool(current_1));
     not_top=*current_1;
   }
   while(not_top!=start);
diff --git a/Straight_skeleton_2/demo/Straight_skeleton_2/straight_skeleton_2.cpp b/Straight_skeleton_2/demo/Straight_skeleton_2/straight_skeleton_2.cpp
index bc3f2362234..f832c7dc38e 100644
--- a/Straight_skeleton_2/demo/Straight_skeleton_2/straight_skeleton_2.cpp
+++ b/Straight_skeleton_2/demo/Straight_skeleton_2/straight_skeleton_2.cpp
@@ -241,7 +241,7 @@ private slots:
         builder.enter_contour((*bit)->begin(),(*bit)->end());
       }
       sskel = builder.construct_skeleton() ;
-      sskel_valid = sskel ;
+      sskel_valid = bool(sskel) ;
       if ( !sskel_valid )
         QMessageBox::critical( this, my_title_string,"Straight Skeleton construction failed." );
       widget->redraw();
@@ -284,7 +284,7 @@ private slots:
           builder.enter_contour(lFrame,lFrame+4);
           builder.enter_contour(lOuter.rbegin(),lOuter.rend());
           sskel = builder.construct_skeleton() ;
-          sskel_valid = sskel ;
+          sskel_valid = bool(sskel) ;
           if ( !sskel_valid )
             QMessageBox::critical( this, my_title_string,"Straight Skeleton construction failed." );
 
diff --git a/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/Polygon_offset_builder_2_impl.h b/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/Polygon_offset_builder_2_impl.h
index 7653f01bd9a..97b3f6b4284 100644
--- a/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/Polygon_offset_builder_2_impl.h
+++ b/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/Polygon_offset_builder_2_impl.h
@@ -226,7 +226,7 @@ void Polygon_offset_builder_2<Ss,Gt,Cont,Visitor>::AddOffsetVertex( FT
   if ( !lP )
     lP = mVisitor.on_offset_point_overflowed(aHook) ;
     
-  CGAL_postcondition(lP);
+  CGAL_postcondition(bool(lP));
   
   CGAL_POLYOFFSET_TRACE(1,"Found offset point p=" << p2str(*lP) << " at offset " << aTime << " along bisector " << e2str(*aHook) << " reaching " << v2str(*aHook->vertex()) ) ;