From 4120846d18c1a7ce5a51169feb1babb0603bddc0 Mon Sep 17 00:00:00 2001
From: Marius Kintel <marius@kintel.net>
Date: Sat, 5 Nov 2011 18:07:56 +0100
Subject: Catch a CGAL assert caused by a subtraction resulting in non-manifold
 geometry. see testdata/scad/bugs/rotate-diff-nonmanifold-crash.scad


diff --git a/src/CGAL_Nef_polyhedron.cc b/src/CGAL_Nef_polyhedron.cc
index 975c9a4..ccfde24 100644
--- a/src/CGAL_Nef_polyhedron.cc
+++ b/src/CGAL_Nef_polyhedron.cc
@@ -25,8 +25,16 @@ CGAL_Nef_polyhedron& CGAL_Nef_polyhedron::operator*=(const CGAL_Nef_polyhedron &
 
 CGAL_Nef_polyhedron& CGAL_Nef_polyhedron::operator-=(const CGAL_Nef_polyhedron &other)
 {
-	if (this->dim == 2) (*this->p2) -= (*other.p2);
-	else if (this->dim == 3) (*this->p3) -= (*other.p3);
+  // Triggered by testdata/scad/bugs/rotate-diff-nonmanifold-crash.scad
+	CGAL::Failure_behaviour old_behaviour = CGAL::set_error_behaviour(CGAL::THROW_EXCEPTION);
+	try {
+		if (this->dim == 2) (*this->p2) -= (*other.p2);
+		else if (this->dim == 3) (*this->p3) -= (*other.p3);
+	}
+	catch (CGAL::Assertion_exception e) {
+		PRINTF("CGAL error in CGAL_Nef_polyhedron::operator-=(): %s", e.what());
+	}
+	CGAL::set_error_behaviour(old_behaviour);
 	return *this;
 }
 
diff --git a/testdata/scad/bugs/rotate-diff-nonmanifold-crash.scad b/testdata/scad/bugs/rotate-diff-nonmanifold-crash.scad
new file mode 100644
index 0000000..d7011d9
--- /dev/null
+++ b/testdata/scad/bugs/rotate-diff-nonmanifold-crash.scad
@@ -0,0 +1,4 @@
+difference() {
+  rotate_extrude($fn=5) translate([4,0,0]) square([10, 10], center=true);
+  translate([6,6,6]) sphere(r=10);
+}
-- 
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