From 948151bd7d1caf6de447313637e851920916c1d4 Mon Sep 17 00:00:00 2001
From: joaquintides <joaquin@tid.es>
Date: Mon, 24 Jul 2023 18:43:20 +0200
Subject: [PATCH] added RVO enabler

---
 include/boost/unordered/detail/foa/reentrancy_check.hpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/boost/unordered/detail/foa/reentrancy_check.hpp b/include/boost/unordered/detail/foa/reentrancy_check.hpp
index 289d161c..6db39f1a 100644
--- a/include/boost/unordered/detail/foa/reentrancy_check.hpp
+++ b/include/boost/unordered/detail/foa/reentrancy_check.hpp
@@ -62,8 +62,9 @@ public:
     header()=this;
   }
 
-  entry_trace(const entry_trace&)=delete;
-  entry_trace& operator=(const entry_trace&)=delete;
+  /* not used but VS in pre-C++17 mode needs to see it for RVO */
+  entry_trace(const entry_trace&);
+
   ~entry_trace(){clear();}
 
   void clear()