From 868cb07578f432f99ecd2700c9564dbd02824bf4 Mon Sep 17 00:00:00 2001
From: Nikita Kniazev <nok.raven@gmail.com>
Date: Sun, 1 Dec 2019 17:26:58 +0300
Subject: [PATCH] Try to include std::swap from the most lightweight header

Based on Boost.Move idea
---
 include/boost/core/swap.hpp | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/boost/core/swap.hpp b/include/boost/core/swap.hpp
index eff6b97..9820d4a 100644
--- a/include/boost/core/swap.hpp
+++ b/include/boost/core/swap.hpp
@@ -23,10 +23,25 @@
 
 #include <boost/core/enable_if.hpp>
 #include <boost/config.hpp>
-#include <utility> //for std::swap (C++11)
-#include <algorithm> //for std::swap (C++98)
 #include <cstddef> //for std::size_t
 
+// try to include std::swap from the most lightweight header
+#if defined(BOOST_DINKUMWARE_STDLIB)
+# include <utility>
+#elif defined(_LIBCPP_VERSION) // since the first commit
+# include <type_traits>
+#elif defined(__GLIBCXX__) && __GLIBCXX__ > 20080621 // GCC 4.4
+# include <bits/move.h>
+#elif defined(__GLIBCXX__) && __GLIBCXX__ > 20071010 // GCC 4.3
+# include <bits/stl_move.h>
+#elif defined(__GLIBCXX__) || defined(__GLIBCPP__) // && __GLIBCPP__ > 20001005 // GCC 2.97
+# include <bits/stl_algobase.h>
+#elif __cplusplus >= 201103L
+# include <utility>
+#else // C++98/03 fallback
+# include <algorithm>
+#endif
+
 namespace boost_swap_impl
 {
   // we can't use type_traits here