From 74623847b72f77b9509ee88cfa9164981787dd48 Mon Sep 17 00:00:00 2001
From: Megidd Git <megiddgit@gmail.com>
Date: Sat, 11 Sep 2021 11:50:24 +0430
Subject: [PATCH] Mesh: fix infinite loop when repairing mesh facet indices

---
 src/Mod/Mesh/App/Core/Degeneration.cpp  | 9 ++++++---
 src/Mod/Mesh/App/Core/TopoAlgorithm.cpp | 8 +++++---
 src/Mod/Mesh/App/Core/TopoAlgorithm.h   | 2 +-
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/src/Mod/Mesh/App/Core/Degeneration.cpp b/src/Mod/Mesh/App/Core/Degeneration.cpp
index 440fb0bdeb..261c30c452 100644
--- a/src/Mod/Mesh/App/Core/Degeneration.cpp
+++ b/src/Mod/Mesh/App/Core/Degeneration.cpp
@@ -1249,9 +1249,12 @@ bool MeshFixCorruptedFacets::Fixup()
     if ( it->Area() <= FLOAT_EPS )
     {
       unsigned long uId = it.Position();
-      cTopAlg.RemoveCorruptedFacet(uId);
-      // due to a modification of the array the iterator became invalid
-      it.Set(uId-1);
+      bool removed = cTopAlg.RemoveCorruptedFacet(uId);
+      if (removed) {
+          // due to a modification of the array the iterator became invalid
+          it.Set(uId-1);
+      }
+      
     }
   }
 
diff --git a/src/Mod/Mesh/App/Core/TopoAlgorithm.cpp b/src/Mod/Mesh/App/Core/TopoAlgorithm.cpp
index 49176331dd..76f13a68f1 100644
--- a/src/Mod/Mesh/App/Core/TopoAlgorithm.cpp
+++ b/src/Mod/Mesh/App/Core/TopoAlgorithm.cpp
@@ -1474,9 +1474,9 @@ void MeshTopoAlgorithm::RemoveDegeneratedFacet(unsigned long index)
   }
 }
 
-void MeshTopoAlgorithm::RemoveCorruptedFacet(unsigned long index)
+bool MeshTopoAlgorithm::RemoveCorruptedFacet(unsigned long index)
 {
-  if (index >= _rclMesh._aclFacetArray.size()) return;
+  if (index >= _rclMesh._aclFacetArray.size()) return false;
   MeshFacet& rFace = _rclMesh._aclFacetArray[index];
 
   // coincident corners (topological)
@@ -1494,9 +1494,11 @@ void MeshTopoAlgorithm::RemoveCorruptedFacet(unsigned long index)
       rFace._aulNeighbours[1] = ULONG_MAX;
       rFace._aulNeighbours[2] = ULONG_MAX;
       _rclMesh.DeleteFacet(index);
-      return;
+      return true;
     }
   }
+
+  return false;
 }
 
 void MeshTopoAlgorithm::FillupHoles(unsigned long length, int level,
diff --git a/src/Mod/Mesh/App/Core/TopoAlgorithm.h b/src/Mod/Mesh/App/Core/TopoAlgorithm.h
index 06056c22fc..199ca6a4bd 100644
--- a/src/Mod/Mesh/App/Core/TopoAlgorithm.h
+++ b/src/Mod/Mesh/App/Core/TopoAlgorithm.h
@@ -240,7 +240,7 @@ public:
      * Removes the corrupted facet at position \a index from the mesh structure.
      * A facet is corrupted if the indices of its corner points are not all different.
      */
-    void RemoveCorruptedFacet(unsigned long index);
+    bool RemoveCorruptedFacet(unsigned long index);
     /**
      * Closes holes in the mesh that consists of up to \a length edges. In case a fit 
      * needs to be done then the points of the neighbours of \a level rings will be used.