From d91bfe93f289f522c83994b39c4543d7c6d7c40e Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Thu, 17 Aug 2023 05:54:03 -0600
Subject: [PATCH] Clear maps, rather than reset pointers.

---
 source/grid/tria.cc | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/source/grid/tria.cc b/source/grid/tria.cc
index 4b0c65fa41..83218e3631 100644
--- a/source/grid/tria.cc
+++ b/source/grid/tria.cc
@@ -16086,11 +16086,19 @@ void Triangulation<dim, spacedim>::clear_despite_subscriptions()
   // In 1d, also reset vertex-to-(boundary|manifold) maps to empty maps
   if (dim == 1)
     {
-      vertex_to_boundary_id_map_1d =
-        std::make_unique<std::map<unsigned int, types::boundary_id>>();
-      vertex_to_manifold_id_map_1d =
-        std::make_unique<std::map<unsigned int, types::manifold_id>>();
+      Assert(vertex_to_boundary_id_map_1d != nullptr, ExcInternalError());
+      vertex_to_boundary_id_map_1d->clear();
+
+      Assert(vertex_to_manifold_id_map_1d != nullptr, ExcInternalError());
+      vertex_to_manifold_id_map_1d->clear();
     }
+  else
+    {
+      // For dim>1, these maps should simply not exist.
+      Assert(vertex_to_boundary_id_map_1d == nullptr, ExcInternalError());
+      Assert(vertex_to_manifold_id_map_1d == nullptr, ExcInternalError());
+    }
+
 
   number_cache = internal::TriangulationImplementation::NumberCache<dim>();
 }
-- 
2.39.5