From 258179a707d143f8ffcd62ed83bfd0a4b21faeee Mon Sep 17 00:00:00 2001
From: Simon Giraudot <simon.giraudot@geometryfactory.com>
Date: Tue, 30 Apr 2019 11:23:47 +0200
Subject: [PATCH] Prevent construction of line with NaN coordinates

---
 .../CGAL/Intersections_3/intersection_3_1_impl.h       | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/Intersections_3/include/CGAL/Intersections_3/intersection_3_1_impl.h b/Intersections_3/include/CGAL/Intersections_3/intersection_3_1_impl.h
index 9f65b83e86e..0526ffe257d 100644
--- a/Intersections_3/include/CGAL/Intersections_3/intersection_3_1_impl.h
+++ b/Intersections_3/include/CGAL/Intersections_3/intersection_3_1_impl.h
@@ -29,6 +29,7 @@
 #include <boost/next_prior.hpp>
 #include <CGAL/Intersection_traits_3.h>
 #include <CGAL/number_utils.h>
+#include <CGAL/utils_classes.h>
 
 namespace CGAL {
 
@@ -424,10 +425,13 @@ intersection(const typename K::Line_3 &l1,
   const Point_3 p4 = p2 + v2;
   if(!K().coplanar_3_object()(p1,p2,p3,p4)) return intersection_return<typename K::Intersect_3, typename K::Line_3, typename K::Line_3>();
   const Vector_3 v3 = p3 - p1;
- const Vector_3 v3v2 = cross_product(v3,v2);
+  const Vector_3 v3v2 = cross_product(v3,v2);
   const Vector_3 v1v2 = cross_product(v1,v2);
-  const FT t = ((v3v2.x()*v1v2.x()) + (v3v2.y()*v1v2.y()) + (v3v2.z()*v1v2.z())) /
-               (v1v2.squared_length());
+  const FT sl = v1v2.squared_length();
+  if(certainly(sl == FT(0)))
+    return intersection_return<typename K::Intersect_3, typename K::Line_3, typename K::Line_3>();
+  const FT t = ((v3v2.x()*v1v2.x()) + (v3v2.y()*v1v2.y()) + (v3v2.z()*v1v2.z())) / sl;
+  
   return intersection_return<typename K::Intersect_3, typename K::Line_3, typename K::Line_3>(p1 + (v1 * t));
 }