From e9a7ec7a2b92f85777462a56e8a5b5fe808125b9 Mon Sep 17 00:00:00 2001
From: nbv <nbv@opencascade.com>
Date: Fri, 16 Jun 2017 12:21:57 +0300
Subject: [PATCH] 0028849: [Regression to 7.1.0] Exception in Boolean operation

The reason of exception has been eliminated.
---
 .../IntPatch_ImpImpIntersection_4.gxx         |  2 +-
 tests/bugs/modalg_7/bug28849                  | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 tests/bugs/modalg_7/bug28849

diff --git a/src/IntPatch/IntPatch_ImpImpIntersection_4.gxx b/src/IntPatch/IntPatch_ImpImpIntersection_4.gxx
index 1a6cb9b87a..27c5f6acc8 100644
--- a/src/IntPatch/IntPatch_ImpImpIntersection_4.gxx
+++ b/src/IntPatch/IntPatch_ImpImpIntersection_4.gxx
@@ -3212,7 +3212,7 @@ static IntPatch_ImpImpIntersection::IntStatus
               Standard_Boolean isChanged = Standard_False;
               for (Standard_Integer i = 0; i < aNbWLines; i++)
               {
-                if (aWLFindStatus[i] == WLFStatus_Absent)
+                if ((aWLFindStatus[i] == WLFStatus_Absent) || (aWLine[i]->NbPnts() == 0))
                   continue;
 
                 Standard_Real aU1c = 0.0, aV1c = 0.0;
diff --git a/tests/bugs/modalg_7/bug28849 b/tests/bugs/modalg_7/bug28849
new file mode 100644
index 0000000000..08aea352c7
--- /dev/null
+++ b/tests/bugs/modalg_7/bug28849
@@ -0,0 +1,28 @@
+puts "======="
+puts "OCC28849"
+puts "======="
+puts ""
+##################################################
+# [Regression to 7.1.0] Exception in Boolean operation
+##################################################
+
+restore [locate_data_file bug28849_shape1.brep] s1
+restore [locate_data_file bug28849_shape2.brep] s2
+
+bsection result s1 s2
+
+regexp {nb alone Vertices : ([-0-9.+eE]+)} [checksection result] full nbv
+
+if { $nbv != 2 } { 
+  puts "Error : Section is incorrect" 
+} else {
+  puts "Section is correct" 
+}
+
+checkprops result -l 5.40612
+
+smallview
+don result
+fit
+
+checkview -screenshot -2d -path ${imagedir}/${test_image}.png
\ No newline at end of file
-- 
2.20.1