From 21b7d8be4c6f15726d91a8257fa8e93ba5466e1d Mon Sep 17 00:00:00 2001
From: msv <msv@opencascade.com>
Date: Thu, 11 Dec 2014 15:40:05 +0300
Subject: [PATCH] 0025453: SIGSEGV in BRepFill_Sweep::BuildShell

Fixed the bug causing exception when the first edge in generated sweep occurs to be degenerated.

Comments have been added.

Test-case for issue #25453
---
 src/BRepFill/BRepFill_Sweep.cxx | 30 ++++++++++++++++++++++++------
 tests/bugs/modalg_5/bug25453    | 22 ++++++++++++++++++++++
 2 files changed, 46 insertions(+), 6 deletions(-)
 create mode 100644 tests/bugs/modalg_5/bug25453

diff --git a/src/BRepFill/BRepFill_Sweep.cxx b/src/BRepFill/BRepFill_Sweep.cxx
index 99e7a04f55..ed78845b3e 100644
--- a/src/BRepFill/BRepFill_Sweep.cxx
+++ b/src/BRepFill/BRepFill_Sweep.cxx
@@ -2465,9 +2465,18 @@ BRepFill_Sweep::BRepFill_Sweep(const Handle(BRepFill_SectionLaw)& Section,
         }
      
 	if (uclose && (isec==NbLaw)) {
-	  UpdateEdge(TopoDS::Edge(UEdge(1, ipath)), 
-		     S, !exuv, ULast);
-	  UEdge(isec+1, ipath) = UEdge(1, ipath);
+          if (UEdge(1, ipath).IsNull()) //degenerated case
+          {
+            UEdge(isec+1, ipath) = BuildEdge(S, !exuv, ULast, 
+                                             Vertex(isec+1, ipath), 
+                                             Vertex(isec+1, ipath+1),
+                                             myTol3d);
+          }
+          else {
+            UpdateEdge(TopoDS::Edge(UEdge(1, ipath)), 
+		       S, !exuv, ULast);
+            UEdge(isec+1, ipath) = UEdge(1, ipath);
+          }
 	}
 	else {
           if (UEdge(isec+1, ipath).IsNull())
@@ -2502,9 +2511,18 @@ BRepFill_Sweep::BRepFill_Sweep(const Handle(BRepFill_SectionLaw)& Section,
 			S, exuv, VFirst);
 	
 	if (vclose && (ipath == NbPath)) {
-	  UpdateEdge(TopoDS::Edge(VEdge(isec, 1)), 
-		     S, exuv, VLast);
-	  VEdge(isec, ipath+1) = VEdge(isec, 1);
+          if (VEdge(isec, 1).IsNull()) //degenerated case
+          {
+            VEdge(isec, ipath+1) = BuildEdge(S, exuv, VLast, 
+					     Vertex(isec  , ipath+1), 
+                                             Vertex(isec+1, ipath+1),
+                                             myTol3d);
+          }
+          else {
+            UpdateEdge(TopoDS::Edge(VEdge(isec, 1)), 
+		       S, exuv, VLast);
+            VEdge(isec, ipath+1) = VEdge(isec, 1);
+          }
 	}
 	else if (VEdge(isec, ipath+1).IsNull())
 	  VEdge(isec, ipath+1) = BuildEdge(S, exuv, VLast, 
diff --git a/tests/bugs/modalg_5/bug25453 b/tests/bugs/modalg_5/bug25453
new file mode 100644
index 0000000000..49f7d154b1
--- /dev/null
+++ b/tests/bugs/modalg_5/bug25453
@@ -0,0 +1,22 @@
+puts "========"
+puts "OCC25453"
+puts "========"
+puts ""
+#########################################
+# SIGSEGV in BRepFill_Sweep::BuildShell
+#########################################
+
+smallview
+
+restore [locate_data_file OCC25453_sweep9-draw-Sketch001.brep] Sketch001
+explode Sketch001 E
+wire Sweep-0-spine Sketch001_1
+mksweep Sweep-0-spine
+setsweep -CF
+restore [locate_data_file OCC25453_sweep9-draw-Sketch.brep] Sketch
+trotate Sketch 0 0 0 1 0 0 90
+addsweep Sketch
+buildsweep Sweep -C
+
+fit
+set only_screen_axo 1