From d1bf1feeca3029d858452e0b8d44ceee0208c67f Mon Sep 17 00:00:00 2001
From: Roy Stogner <Roy.Stogner@inl.gov>
Date: Wed, 10 Dec 2025 23:20:44 -0600
Subject: [PATCH] GhostingFunctor clone is pure virtual

(at least in non-deprecated builds)
---
 include/ghosting/ghosting_functor.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/ghosting/ghosting_functor.h b/include/ghosting/ghosting_functor.h
index fa1fb62cee6..b9e5458d3a4 100644
--- a/include/ghosting/ghosting_functor.h
+++ b/include/ghosting/ghosting_functor.h
@@ -213,10 +213,12 @@ class GhostingFunctor : public ReferenceCountedObject<GhostingFunctor>
    * different meshes. The operations in  GhostingFunctor are mesh dependent.
    */
   virtual std::unique_ptr<GhostingFunctor> clone () const
-  // Let us return nullptr for backward compatibility.
-  // We will come back to mark this function as pure virtual
-  // once the API upgrade is done.
-  { return nullptr; }
+#ifndef LIBMESH_ENABLE_DEPRECATED
+  = 0;
+#else
+  // Return nullptr for backward compatibility.
+  { libmesh_deprecated(); return nullptr; }
+#endif
 
   /**
    * It should be called after cloning a ghosting functor.