From 27d700ec010840205256bf64336cf3535ed1ec3d Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Thu, 10 Jun 2021 09:54:51 +0300
Subject: [PATCH] Use non-const references in ignore_unused to avoid g++-11
 warning

---
 include/boost/core/ignore_unused.hpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/boost/core/ignore_unused.hpp b/include/boost/core/ignore_unused.hpp
index 994e5f6..03614c5 100644
--- a/include/boost/core/ignore_unused.hpp
+++ b/include/boost/core/ignore_unused.hpp
@@ -11,12 +11,22 @@
 
 namespace boost {
 
-#ifndef BOOST_NO_CXX11_VARIADIC_TEMPLATES
+#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+
+template <typename... Ts>
+BOOST_FORCEINLINE BOOST_CXX14_CONSTEXPR void ignore_unused(Ts&& ...)
+{}
+
+#else
 
 template <typename... Ts>
 BOOST_FORCEINLINE BOOST_CXX14_CONSTEXPR void ignore_unused(Ts const& ...)
 {}
 
+#endif
+
 template <typename... Ts>
 BOOST_FORCEINLINE BOOST_CXX14_CONSTEXPR void ignore_unused()
 {}