From b27653493a12e0668cf0d86630909e51fce82f49 Mon Sep 17 00:00:00 2001
From: Lukas Matena <lukasmatena@seznam.cz>
Date: Fri, 25 Nov 2022 13:45:23 +0100
Subject: [PATCH] Measurement: prevent ending up in an infinite loop with
 broken models

---
 src/libslic3r/Measure.cpp     | 16 ++++++++++++++--
 src/libslic3r/SurfaceMesh.hpp |  9 +++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/libslic3r/Measure.cpp b/src/libslic3r/Measure.cpp
index a9cea06bd..37bf68e83 100644
--- a/src/libslic3r/Measure.cpp
+++ b/src/libslic3r/Measure.cpp
@@ -189,10 +189,16 @@ void MeasuringImpl::update_planes()
                     he = sm.next_around_target(he);
                     if (he.is_invalid())
                         goto PLANE_FAILURE;
+
+                    // For broken meshes, the iteration might never get back to he_orig.
+                    // Remember all halfedges we saw to break out of such infinite loops.
+                    boost::container::small_vector<Halfedge_index, 10> he_seen;
+
                     while ( (int)m_face_to_plane[sm.face(he)] == plane_id && he != he_orig) {
+                        he_seen.emplace_back(he);
                         he = sm.next_around_target(he);
-                        if (he.is_invalid())
-                        goto PLANE_FAILURE;
+                        if (he.is_invalid() || std::find(he_seen.begin(), he_seen.end(), he) != he_seen.end())
+                            goto PLANE_FAILURE;
                     }
                     he = sm.opposite(he);
                     if (he.is_invalid())
@@ -210,6 +216,12 @@ void MeasuringImpl::update_planes()
                     visited[face_it - facets.begin()][he.side()] = true;
 
                     last_border.emplace_back(sm.point(sm.source(he)).cast<double>());
+
+                    // In case of broken meshes, this loop might be infinite. Break
+                    // out in case it is clearly going bad.
+                    if (last_border.size() > 3*facets.size())
+                        goto PLANE_FAILURE;
+
                 } while (he != he_start);
 
                 if (last_border.size() == 1)
diff --git a/src/libslic3r/SurfaceMesh.hpp b/src/libslic3r/SurfaceMesh.hpp
index 9e547eec4..93eb9fdaa 100644
--- a/src/libslic3r/SurfaceMesh.hpp
+++ b/src/libslic3r/SurfaceMesh.hpp
@@ -4,6 +4,8 @@
 #include <admesh/stl.h>
 #include <libslic3r/TriangleMesh.hpp>
 
+#include "boost/container/small_vector.hpp"
+
 namespace Slic3r {
 
 class TriangleMesh;
@@ -115,11 +117,18 @@ public:
 
     size_t degree(Vertex_index v) const
     {
+        // In case the mesh is broken badly, the loop might end up to be infinite,
+        // never getting back to the first halfedge. Remember list of all half-edges
+        // and trip if any is encountered for the second time.
         Halfedge_index h_first = halfedge(v);
+        boost::container::small_vector<Halfedge_index, 10> he_visited;
         Halfedge_index h = next_around_target(h_first);
         size_t degree = 2;
         while (! h.is_invalid() && h != h_first) {
+            he_visited.emplace_back(h);
             h = next_around_target(h);
+            if (std::find(he_visited.begin(), he_visited.end(), h) == he_visited.end())
+                return 0;
             ++degree;
         }
         return h.is_invalid() ? 0 : degree - 1;