[strategies] prevent integer overflow during segment touch ratio calc…

…ulation

include/boost/geometry/strategies/cartesian/cart_intersect.hpp

@@ -214,7 +214,7 @@ struct relate_cartesian_segments
 
  sides.set<1>(side::apply(robust_a1, robust_a2, robust_b1),
  side::apply(robust_a1, robust_a2, robust_b2));
- 
+
  if (sides.same<1>())
  {
  // Both points are at same side of other segment, we can leave
@@ -258,15 +258,41 @@ struct relate_cartesian_segments
  robust_coordinate_type robust_da0, robust_da;
  robust_coordinate_type robust_db0, robust_db;
 
- cramers_rule(robust_dx_a, robust_dy_a, robust_dx_b, robust_dy_b,
- get<0>(robust_a1) - get<0>(robust_b1),
- get<1>(robust_a1) - get<1>(robust_b1),
- robust_da0, robust_da);
+ if (sides.get<0, 0>() == 0)
+ {
+ robust_da0 = 1;
+ robust_da = 0;
+ }
+ else if (sides.get<0, 1>() == 0)
+ {
+ robust_da0 = 1;
+ robust_da = 1;
+ }
+ else
+ {
+ cramers_rule(robust_dx_a, robust_dy_a, robust_dx_b, robust_dy_b,
+ get<0>(robust_a1) - get<0>(robust_b1),
+ get<1>(robust_a1) - get<1>(robust_b1),
+ robust_da0, robust_da);
+ }
 
- cramers_rule(robust_dx_b, robust_dy_b, robust_dx_a, robust_dy_a,
- get<0>(robust_b1) - get<0>(robust_a1),
- get<1>(robust_b1) - get<1>(robust_a1),
- robust_db0, robust_db);
+ if (sides.get<1, 0>() == 0)
+ {
+ robust_db0 = 1;
+ robust_db = 0;
+ }
+ else if (sides.get<1, 1>() == 0)
+ {
+ robust_db0 = 1;
+ robust_db = 1;
+ }
+ else
+ {
+ cramers_rule(robust_dx_b, robust_dy_b, robust_dx_a, robust_dy_a,
+ get<0>(robust_b1) - get<0>(robust_a1),
+ get<1>(robust_b1) - get<1>(robust_a1),
+ robust_db0, robust_db);
+ }
 
  math::detail::equals_factor_policy<robust_coordinate_type>
  policy(robust_dx_a, robust_dy_a, robust_dx_b, robust_dy_b);
@@ -450,7 +476,7 @@ struct relate_cartesian_segments
  int const a2_wrt_b = position_value(oa_2, ob_1, ob_2);
  int const b1_wrt_a = position_value(ob_1, oa_1, oa_2);
  int const b2_wrt_a = position_value(ob_2, oa_1, oa_2);
- 
+
  // fix the ratios if necessary
  // CONSIDER: fixing ratios also in other cases, if they're inconsistent
  // e.g. if ratio == 1 or 0 (so IP at the endpoint)
@@ -467,7 +493,7 @@ struct relate_cartesian_segments
  {
  ra_from.assign(1, 1);
  rb_to.assign(0, 1);
- } 
+ }
 
  if (a2_wrt_b == 1)
  {