Update to Harfbuzz 8.1.1

Pick-to: 5.15 6.2 6.5 6.6
Change-Id: I886bc7d385e62ff0c9546c18bb7bb9273ef1cbd1
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

9 files changed, 204 insertions, 83 deletions

diff --git a/src/3rdparty/harfbuzz-ng/src/graph/classdef-graph.hh b/src/3rdparty/harfbuzz-ng/src/graph/classdef-graph.hh
index c2e24a7067..c1432883ff 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/classdef-graph.hh
+++ b/src/3rdparty/harfbuzz-ng/src/graph/classdef-graph.hh
@@ -72,7 +72,7 @@ struct ClassDef : public OT::ClassDef
     class_def_link->width = SmallTypes::size;
     class_def_link->objidx = class_def_prime_id;
     class_def_link->position = link_position;
-    class_def_prime_vertex.parents.push (parent_id);
+    class_def_prime_vertex.add_parent (parent_id);
 
     return true;
   }
@@ -94,7 +94,13 @@ struct ClassDef : public OT::ClassDef
     }
 
     hb_bytes_t class_def_copy = serializer.copy_bytes ();
-    c.add_buffer ((char *) class_def_copy.arrayZ); // Give ownership to the context, it will cleanup the buffer.
+    if (!class_def_copy.arrayZ) return false;
+    // Give ownership to the context, it will cleanup the buffer.
+    if (!c.add_buffer ((char *) class_def_copy.arrayZ))
+    {
+      hb_free ((char *) class_def_copy.arrayZ);
+      return false;
+    }
 
     auto& obj = c.graph.vertices_[dest_obj].obj;
     obj.head = (char *) class_def_copy.arrayZ;
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/coverage-graph.hh b/src/3rdparty/harfbuzz-ng/src/graph/coverage-graph.hh
index 49d0936315..4f44e076d1 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/coverage-graph.hh
+++ b/src/3rdparty/harfbuzz-ng/src/graph/coverage-graph.hh
@@ -96,7 +96,7 @@ struct Coverage : public OT::Layout::Common::Coverage
     coverage_link->width = SmallTypes::size;
     coverage_link->objidx = coverage_prime_id;
     coverage_link->position = link_position;
-    coverage_prime_vertex.parents.push (parent_id);
+    coverage_prime_vertex.add_parent (parent_id);
 
     return (Coverage*) coverage_prime_vertex.obj.head;
   }
@@ -118,7 +118,13 @@ struct Coverage : public OT::Layout::Common::Coverage
     }
 
     hb_bytes_t coverage_copy = serializer.copy_bytes ();
-    c.add_buffer ((char *) coverage_copy.arrayZ); // Give ownership to the context, it will cleanup the buffer.
+    if (!coverage_copy.arrayZ) return false;
+    // Give ownership to the context, it will cleanup the buffer.
+    if (!c.add_buffer ((char *) coverage_copy.arrayZ))
+    {
+      hb_free ((char *) coverage_copy.arrayZ);
+      return false;
+    }
 
     auto& obj = c.graph.vertices_[dest_obj].obj;
     obj.head = (char *) coverage_copy.arrayZ;
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/graph.hh b/src/3rdparty/harfbuzz-ng/src/graph/graph.hh
index 294a999918..0680958190 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/graph.hh
+++ b/src/3rdparty/harfbuzz-ng/src/graph/graph.hh
@@ -43,12 +43,28 @@ struct graph_t
   {
     hb_serialize_context_t::object_t obj;
     int64_t distance = 0 ;
-    int64_t space = 0 ;
-    hb_vector_t<unsigned> parents;
+    unsigned space = 0 ;
     unsigned start = 0;
     unsigned end = 0;
     unsigned priority = 0;
-
+    private:
+    unsigned incoming_edges_ = 0;
+    unsigned single_parent = (unsigned) -1;
+    hb_hashmap_t<unsigned, unsigned> parents;
+    public:
+
+    auto parents_iter () const HB_AUTO_RETURN
+    (
+      hb_concat (
+	hb_iter (&single_parent, single_parent != (unsigned) -1),
+	parents.keys_ref ()
+      )
+    )
+
+    bool in_error () const
+    {
+      return parents.in_error ();
+    }
 
     bool link_positions_valid (unsigned num_objects, bool removed_nil)
     {
@@ -143,7 +159,9 @@ struct graph_t
       hb_swap (a.obj, b.obj);
       hb_swap (a.distance, b.distance);
       hb_swap (a.space, b.space);
+      hb_swap (a.single_parent, b.single_parent);
       hb_swap (a.parents, b.parents);
+      hb_swap (a.incoming_edges_, b.incoming_edges_);
       hb_swap (a.start, b.start);
       hb_swap (a.end, b.end);
       hb_swap (a.priority, b.priority);
@@ -154,6 +172,7 @@ struct graph_t
     {
       hb_hashmap_t<unsigned, unsigned> result;
 
+      result.alloc (obj.real_links.length);
       for (const auto& l : obj.real_links) {
         result.set (l.position, l.objidx);
       }
@@ -163,22 +182,76 @@ struct graph_t
 
     bool is_shared () const
     {
-      return parents.length > 1;
+      return parents.get_population () > 1;
     }
 
     unsigned incoming_edges () const
     {
-      return parents.length;
+      if (HB_DEBUG_SUBSET_REPACK)
+       {
+	assert (incoming_edges_ == (single_parent != (unsigned) -1) +
+		(parents.values_ref () | hb_reduce (hb_add, 0)));
+       }
+      return incoming_edges_;
+    }
+
+    void reset_parents ()
+    {
+      incoming_edges_ = 0;
+      single_parent = (unsigned) -1;
+      parents.reset ();
+    }
+
+    void add_parent (unsigned parent_index)
+    {
+      assert (parent_index != (unsigned) -1);
+      if (incoming_edges_ == 0)
+      {
+	single_parent = parent_index;
+	incoming_edges_ = 1;
+	return;
+      }
+      else if (single_parent != (unsigned) -1)
+      {
+        assert (incoming_edges_ == 1);
+	if (!parents.set (single_parent, 1))
+	  return;
+	single_parent = (unsigned) -1;
+      }
+
+      unsigned *v;
+      if (parents.has (parent_index, &v))
+      {
+        (*v)++;
+	incoming_edges_++;
+      }
+      else if (parents.set (parent_index, 1))
+	incoming_edges_++;
     }
 
     void remove_parent (unsigned parent_index)
     {
-      unsigned count = parents.length;
-      for (unsigned i = 0; i < count; i++)
+      if (parent_index == single_parent)
       {
-        if (parents.arrayZ[i] != parent_index) continue;
-        parents.remove_unordered (i);
-        break;
+	single_parent = (unsigned) -1;
+	incoming_edges_--;
+	return;
+      }
+
+      unsigned *v;
+      if (parents.has (parent_index, &v))
+      {
+	incoming_edges_--;
+	if (*v > 1)
+	  (*v)--;
+	else
+	  parents.del (parent_index);
+
+	if (incoming_edges_ == 1)
+	{
+	  single_parent = *parents.keys ();
+	  parents.reset ();
+	}
       }
     }
 
@@ -199,20 +272,46 @@ struct graph_t
       }
     }
 
-    void remap_parents (const hb_vector_t<unsigned>& id_map)
+    bool remap_parents (const hb_vector_t<unsigned>& id_map)
     {
-      unsigned count = parents.length;
-      for (unsigned i = 0; i < count; i++)
-        parents.arrayZ[i] = id_map[parents.arrayZ[i]];
+      if (single_parent != (unsigned) -1)
+      {
+        assert (single_parent < id_map.length);
+	single_parent = id_map[single_parent];
+	return true;
+      }
+
+      hb_hashmap_t<unsigned, unsigned> new_parents;
+      new_parents.alloc (parents.get_population ());
+      for (auto _ : parents)
+      {
+	assert (_.first < id_map.length);
+	assert (!new_parents.has (id_map[_.first]));
+	new_parents.set (id_map[_.first], _.second);
+      }
+
+      if (new_parents.in_error ())
+        return false;
+
+      parents = std::move (new_parents);
+      return true;
     }
 
     void remap_parent (unsigned old_index, unsigned new_index)
     {
-      unsigned count = parents.length;
-      for (unsigned i = 0; i < count; i++)
+      if (single_parent != (unsigned) -1)
+      {
+        if (single_parent == old_index)
+	  single_parent = new_index;
+        return;
+      }
+
+      const unsigned *pv;
+      if (parents.has (old_index, &pv))
       {
-        if (parents.arrayZ[i] == old_index)
-          parents.arrayZ[i] = new_index;
+        unsigned v = *pv;
+	parents.set (new_index, v);
+	parents.del (old_index);
       }
     }
 
@@ -359,7 +458,6 @@ struct graph_t
 
   ~graph_t ()
   {
-    vertices_.fini ();
     for (char* b : buffers)
       hb_free (b);
   }
@@ -401,9 +499,10 @@ struct graph_t
     return vertices_[i].obj;
   }
 
-  void add_buffer (char* buffer)
+  bool add_buffer (char* buffer)
   {
     buffers.push (buffer);
+    return !buffers.in_error ();
   }
 
   /*
@@ -419,7 +518,7 @@ struct graph_t
     link->width = 2;
     link->objidx = child_id;
     link->position = (char*) offset - (char*) v.obj.head;
-    vertices_[child_id].parents.push (parent_id);
+    vertices_[child_id].add_parent (parent_id);
   }
 
   /*
@@ -465,7 +564,7 @@ struct graph_t
     {
       unsigned next_id = queue.pop_minimum().second;
 
-      hb_swap (sorted_graph[new_id], vertices_[next_id]);
+      sorted_graph[new_id] = std::move (vertices_[next_id]);
       const vertex_t& next = sorted_graph[new_id];
 
       if (unlikely (!check_success(new_id >= 0))) {
@@ -493,8 +592,8 @@ struct graph_t
     check_success (!queue.in_error ());
     check_success (!sorted_graph.in_error ());
 
-    remap_all_obj_indices (id_map, &sorted_graph);
-    hb_swap (vertices_, sorted_graph);
+    check_success (remap_all_obj_indices (id_map, &sorted_graph));
+    vertices_ = std::move (sorted_graph);
 
     if (!check_success (new_id == -1))
       print_orphaned_nodes ();
@@ -605,7 +704,7 @@ struct graph_t
   {
     unsigned child_idx = index_for_offset (node_idx, offset);
     auto& child = vertices_[child_idx];
-    for (unsigned p : child.parents)
+    for (unsigned p : child.parents_iter ())
     {
       if (p != node_idx) {
         return duplicate (node_idx, child_idx);
@@ -688,12 +787,15 @@ struct graph_t
       subgraph.set (root_idx, wide_parents (root_idx, parents));
       find_subgraph (root_idx, subgraph);
     }
+    if (subgraph.in_error ())
+      return false;
 
     unsigned original_root_idx = root_idx ();
     hb_map_t index_map;
     bool made_changes = false;
     for (auto entry : subgraph.iter ())
     {
+      assert (entry.first < vertices_.length);
       const auto& node = vertices_[entry.first];
       unsigned subgraph_incoming_edges = entry.second;
 
@@ -732,8 +834,7 @@ struct graph_t
     remap_obj_indices (index_map, parents.iter (), true);
 
     // Update roots set with new indices as needed.
-    uint32_t next = HB_SET_VALUE_INVALID;
-    while (roots.next (&next))
+    for (auto next : roots)
     {
       const uint32_t *v;
       if (index_map.has (next, &v))
@@ -750,10 +851,10 @@ struct graph_t
   {
     for (const auto& link : vertices_[node_idx].obj.all_links ())
     {
-      const uint32_t *v;
+      hb_codepoint_t *v;
       if (subgraph.has (link.objidx, &v))
       {
-        subgraph.set (link.objidx, *v + 1);
+        (*v)++;
         continue;
       }
       subgraph.set (link.objidx, 1);
@@ -825,7 +926,7 @@ struct graph_t
     new_link->position = (const char*) new_offset - (const char*) new_v.obj.head;
 
     auto& child = vertices_[child_id];
-    child.parents.push (new_parent_idx);
+    child.add_parent (new_parent_idx);
 
     old_v.remove_real_link (child_id, old_offset);
     child.remove_parent (old_parent_idx);
@@ -869,18 +970,18 @@ struct graph_t
     clone->obj.tail = child.obj.tail;
     clone->distance = child.distance;
     clone->space = child.space;
-    clone->parents.reset ();
+    clone->reset_parents ();
 
     unsigned clone_idx = vertices_.length - 2;
     for (const auto& l : child.obj.real_links)
     {
       clone->obj.real_links.push (l);
-      vertices_[l.objidx].parents.push (clone_idx);
+      vertices_[l.objidx].add_parent (clone_idx);
     }
     for (const auto& l : child.obj.virtual_links)
     {
       clone->obj.virtual_links.push (l);
-      vertices_[l.objidx].parents.push (clone_idx);
+      vertices_[l.objidx].add_parent (clone_idx);
     }
 
     check_success (!clone->obj.real_links.in_error ());
@@ -1009,13 +1110,13 @@ struct graph_t
   {
     update_parents();
 
-    if (root().parents)
+    if (root().incoming_edges ())
       // Root cannot have parents.
       return false;
 
     for (unsigned i = 0; i < root_idx (); i++)
     {
-      if (!vertices_[i].parents)
+      if (!vertices_[i].incoming_edges ())
         return false;
     }
     return true;
@@ -1079,14 +1180,14 @@ struct graph_t
     parents_invalid = true;
     update_parents();
 
-    if (root().parents) {
+    if (root().incoming_edges ()) {
       DEBUG_MSG (SUBSET_REPACK, nullptr, "Root node has incoming edges.");
     }
 
     for (unsigned i = 0; i < root_idx (); i++)
     {
       const auto& v = vertices_[i];
-      if (!v.parents)
+      if (!v.incoming_edges ())
         DEBUG_MSG (SUBSET_REPACK, nullptr, "Node %u is orphaned.", i);
     }
   }
@@ -1118,6 +1219,8 @@ struct graph_t
 
   unsigned space_for (unsigned index, unsigned* root = nullptr) const
   {
+  loop:
+    assert (index < vertices_.length);
     const auto& node = vertices_[index];
     if (node.space)
     {
@@ -1126,14 +1229,15 @@ struct graph_t
       return node.space;
     }
 
-    if (!node.parents)
+    if (!node.incoming_edges ())
     {
       if (root)
         *root = index;
       return 0;
     }
 
-    return space_for (node.parents[0], root);
+    index = *node.parents_iter ();
+    goto loop;
   }
 
   void err_other_error () { this->successful = false; }
@@ -1157,12 +1261,8 @@ struct graph_t
   unsigned wide_parents (unsigned node_idx, hb_set_t& parents) const
   {
     unsigned count = 0;
-    hb_set_t visited;
-    for (unsigned p : vertices_[node_idx].parents)
+    for (unsigned p : vertices_[node_idx].parents_iter ())
     {
-      if (visited.has (p)) continue;
-      visited.add (p);
-
       // Only real links can be wide
       for (const auto& l : vertices_[p].obj.real_links)
       {
@@ -1192,20 +1292,18 @@ struct graph_t
     unsigned count = vertices_.length;
 
     for (unsigned i = 0; i < count; i++)
-      vertices_.arrayZ[i].parents.reset ();
+      vertices_.arrayZ[i].reset_parents ();
 
     for (unsigned p = 0; p < count; p++)
     {
       for (auto& l : vertices_.arrayZ[p].obj.all_links ())
-      {
-        vertices_[l.objidx].parents.push (p);
-      }
+        vertices_[l.objidx].add_parent (p);
     }
 
     for (unsigned i = 0; i < count; i++)
       // parents arrays must be accurate or downstream operations like cycle detection
       // and sorting won't work correctly.
-      check_success (!vertices_.arrayZ[i].parents.in_error ());
+      check_success (!vertices_.arrayZ[i].in_error ());
 
     parents_invalid = false;
   }
@@ -1249,12 +1347,8 @@ struct graph_t
     // (such as a fibonacci queue) with a fast decrease priority.
     unsigned count = vertices_.length;
     for (unsigned i = 0; i < count; i++)
-    {
-      if (i == vertices_.length - 1)
-        vertices_.arrayZ[i].distance = 0;
-      else
-        vertices_.arrayZ[i].distance = hb_int_max (int64_t);
-    }
+      vertices_.arrayZ[i].distance = hb_int_max (int64_t);
+    vertices_.tail ().distance = 0;
 
     hb_priority_queue_t queue;
     queue.insert (0, vertices_.length - 1);
@@ -1274,15 +1368,15 @@ struct graph_t
       {
         if (visited[link.objidx]) continue;
 
-        const auto& child = vertices_[link.objidx].obj;
+        const auto& child = vertices_.arrayZ[link.objidx].obj;
         unsigned link_width = link.width ? link.width : 4; // treat virtual offsets as 32 bits wide
         int64_t child_weight = (child.tail - child.head) +
-                               ((int64_t) 1 << (link_width * 8)) * (vertices_[link.objidx].space + 1);
+                               ((int64_t) 1 << (link_width * 8)) * (vertices_.arrayZ[link.objidx].space + 1);
         int64_t child_distance = next_distance + child_weight;
 
-        if (child_distance < vertices_[link.objidx].distance)
+        if (child_distance < vertices_.arrayZ[link.objidx].distance)
         {
-          vertices_[link.objidx].distance = child_distance;
+          vertices_.arrayZ[link.objidx].distance = child_distance;
           queue.insert (child_distance, link.objidx);
         }
       }
@@ -1310,7 +1404,7 @@ struct graph_t
     unsigned old_idx = link.objidx;
     link.objidx = new_idx;
     vertices_[old_idx].remove_parent (parent_idx);
-    vertices_[new_idx].parents.push (parent_idx);
+    vertices_[new_idx].add_parent (parent_idx);
   }
 
   /*
@@ -1338,18 +1432,20 @@ struct graph_t
   /*
    * Updates all objidx's in all links using the provided mapping.
    */
-  void remap_all_obj_indices (const hb_vector_t<unsigned>& id_map,
+  bool remap_all_obj_indices (const hb_vector_t<unsigned>& id_map,
                               hb_vector_t<vertex_t>* sorted_graph) const
   {
     unsigned count = sorted_graph->length;
     for (unsigned i = 0; i < count; i++)
     {
-      (*sorted_graph)[i].remap_parents (id_map);
+      if (!(*sorted_graph)[i].remap_parents (id_map))
+        return false;
       for (auto& link : sorted_graph->arrayZ[i].obj.all_links_writer ())
       {
         link.objidx = id_map[link.objidx];
       }
     }
+    return true;
   }
 
   /*
@@ -1380,7 +1476,7 @@ struct graph_t
     for (const auto& l : v.obj.all_links ())
       find_connected_nodes (l.objidx, targets, visited, connected);
 
-    for (unsigned p : v.parents)
+    for (unsigned p : v.parents_iter ())
       find_connected_nodes (p, targets, visited, connected);
   }
 
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.cc b/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.cc
index b2044426d4..d66eb49cfd 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.cc
+++ b/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.cc
@@ -52,7 +52,11 @@ unsigned gsubgpos_graph_context_t::create_node (unsigned size)
   if (!buffer)
     return -1;
 
-  add_buffer (buffer);
+  if (!add_buffer (buffer)) {
+    // Allocation did not get stored for freeing later.
+    hb_free (buffer);
+    return -1;
+  }
 
   return graph.new_node (buffer, buffer + size);
 }
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.hh b/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.hh
index 9fe9662e64..26b7cfe4d4 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.hh
+++ b/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-context.hh
@@ -47,9 +47,9 @@ struct gsubgpos_graph_context_t
 
   HB_INTERNAL unsigned create_node (unsigned size);
 
-  void add_buffer (char* buffer)
+  bool add_buffer (char* buffer)
   {
-    graph.add_buffer (buffer);
+    return graph.add_buffer (buffer);
   }
 
  private:
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-graph.hh b/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-graph.hh
index c170638409..303517f687 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-graph.hh
+++ b/src/3rdparty/harfbuzz-ng/src/graph/gsubgpos-graph.hh
@@ -166,7 +166,7 @@ struct Lookup : public OT::Lookup
     }
 
     if (all_new_subtables) {
-      add_sub_tables (c, this_index, type, all_new_subtables);
+      return add_sub_tables (c, this_index, type, all_new_subtables);
     }
 
     return true;
@@ -184,7 +184,7 @@ struct Lookup : public OT::Lookup
     return sub_table->split_subtables (c, parent_idx, objidx);
   }
 
-  void add_sub_tables (gsubgpos_graph_context_t& c,
+  bool add_sub_tables (gsubgpos_graph_context_t& c,
                        unsigned this_index,
                        unsigned type,
                        hb_vector_t<hb_pair_t<unsigned, hb_vector_t<unsigned>>>& subtable_ids)
@@ -200,7 +200,12 @@ struct Lookup : public OT::Lookup
     size_t new_size = v.table_size ()
                       + new_subtable_count * OT::Offset16::static_size;
     char* buffer = (char*) hb_calloc (1, new_size);
-    c.add_buffer (buffer);
+    if (!buffer) return false;
+    if (!c.add_buffer (buffer))
+    {
+      hb_free (buffer);
+     return false;
+    }
     hb_memcpy (buffer, v.obj.head, v.table_size());
 
     v.obj.head = buffer;
@@ -220,7 +225,7 @@ struct Lookup : public OT::Lookup
         if (is_ext)
         {
           unsigned ext_id = create_extension_subtable (c, subtable_id, type);
-          c.graph.vertices_[subtable_id].parents.push (ext_id);
+          c.graph.vertices_[subtable_id].add_parent (ext_id);
           subtable_id = ext_id;
         }
 
@@ -229,7 +234,7 @@ struct Lookup : public OT::Lookup
         link->objidx = subtable_id;
         link->position = (char*) &new_lookup->subTable[offset_index++] -
                          (char*) new_lookup;
-        c.graph.vertices_[subtable_id].parents.push (this_index);
+        c.graph.vertices_[subtable_id].add_parent (this_index);
       }
     }
 
@@ -239,6 +244,7 @@ struct Lookup : public OT::Lookup
     // The head location of the lookup has changed, invalidating the lookups map entry
     // in the context. Update the map.
     c.lookups.set (this_index, new_lookup);
+    return true;
   }
 
   void fix_existing_subtable_links (gsubgpos_graph_context_t& c,
@@ -309,7 +315,7 @@ struct Lookup : public OT::Lookup
     // Make extension point at the subtable.
     auto& ext_vertex = c.graph.vertices_[ext_index];
     auto& subtable_vertex = c.graph.vertices_[subtable_index];
-    ext_vertex.parents.push (lookup_index);
+    ext_vertex.add_parent (lookup_index);
     subtable_vertex.remap_parent (lookup_index, ext_index);
 
     return true;
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/pairpos-graph.hh b/src/3rdparty/harfbuzz-ng/src/graph/pairpos-graph.hh
index 1c13eb24f9..ad158cc9e8 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/pairpos-graph.hh
+++ b/src/3rdparty/harfbuzz-ng/src/graph/pairpos-graph.hh
@@ -215,7 +215,7 @@ struct PairPosFormat2 : public OT::Layout::GPOS_impl::PairPosFormat2_4<SmallType
     auto gid_and_class =
         + coverage->iter ()
         | hb_map_retains_sorting ([&] (hb_codepoint_t gid) {
-          return hb_pair_t<hb_codepoint_t, hb_codepoint_t> (gid, class_def_1->get_class (gid));
+          return hb_codepoint_pair_t (gid, class_def_1->get_class (gid));
         })
         ;
     class_def_size_estimator_t estimator (gid_and_class);
@@ -386,14 +386,14 @@ struct PairPosFormat2 : public OT::Layout::GPOS_impl::PairPosFormat2_4<SmallType
     auto klass_map =
     + coverage_table->iter ()
     | hb_map_retains_sorting ([&] (hb_codepoint_t gid) {
-      return hb_pair_t<hb_codepoint_t, hb_codepoint_t> (gid, class_def_1_table->get_class (gid));
+      return hb_codepoint_pair_t (gid, class_def_1_table->get_class (gid));
     })
     | hb_filter ([&] (hb_codepoint_t klass) {
       return klass >= start && klass < end;
     }, hb_second)
-    | hb_map_retains_sorting ([&] (hb_pair_t<hb_codepoint_t, hb_codepoint_t> gid_and_class) {
+    | hb_map_retains_sorting ([&] (hb_codepoint_pair_t gid_and_class) {
       // Classes must be from 0...N so subtract start
-      return hb_pair_t<hb_codepoint_t, hb_codepoint_t> (gid_and_class.first, gid_and_class.second - start);
+      return hb_codepoint_pair_t (gid_and_class.first, gid_and_class.second - start);
     })
     ;
 
@@ -419,7 +419,7 @@ struct PairPosFormat2 : public OT::Layout::GPOS_impl::PairPosFormat2_4<SmallType
     class_def_link->width = SmallTypes::size;
     class_def_link->objidx = class_def_2_id;
     class_def_link->position = 10;
-    graph.vertices_[class_def_2_id].parents.push (pair_pos_prime_id);
+    graph.vertices_[class_def_2_id].add_parent (pair_pos_prime_id);
     graph.duplicate (pair_pos_prime_id, class_def_2_id);
 
     return pair_pos_prime_id;
@@ -519,7 +519,7 @@ struct PairPosFormat2 : public OT::Layout::GPOS_impl::PairPosFormat2_4<SmallType
     auto klass_map =
     + coverage.table->iter ()
     | hb_map_retains_sorting ([&] (hb_codepoint_t gid) {
-      return hb_pair_t<hb_codepoint_t, hb_codepoint_t> (gid, class_def_1.table->get_class (gid));
+      return hb_codepoint_pair_t (gid, class_def_1.table->get_class (gid));
     })
     | hb_filter ([&] (hb_codepoint_t klass) {
       return klass < count;
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/serialize.hh b/src/3rdparty/harfbuzz-ng/src/graph/serialize.hh
index 2e0b845baa..06e4bf44d8 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/serialize.hh
+++ b/src/3rdparty/harfbuzz-ng/src/graph/serialize.hh
@@ -226,6 +226,9 @@ inline hb_blob_t* serialize (const graph_t& graph)
 {
   hb_vector_t<char> buffer;
   size_t size = graph.total_size_in_bytes ();
+
+  if (!size) return hb_blob_get_empty ();
+
   if (!buffer.alloc (size)) {
     DEBUG_MSG (SUBSET_REPACK, nullptr, "Unable to allocate output buffer.");
     return nullptr;
diff --git a/src/3rdparty/harfbuzz-ng/src/graph/test-classdef-graph.cc b/src/3rdparty/harfbuzz-ng/src/graph/test-classdef-graph.cc
index 55854ff5c2..266be5e2d4 100644
--- a/src/3rdparty/harfbuzz-ng/src/graph/test-classdef-graph.cc
+++ b/src/3rdparty/harfbuzz-ng/src/graph/test-classdef-graph.cc
@@ -27,7 +27,7 @@
 #include "gsubgpos-context.hh"
 #include "classdef-graph.hh"
 
-typedef hb_pair_t<hb_codepoint_t, hb_codepoint_t> gid_and_class_t;
+typedef hb_codepoint_pair_t gid_and_class_t;
 typedef hb_vector_t<gid_and_class_t> gid_and_class_list_t;