From 40f4e6ed2f3310acf1f13b26945b22dfdcfda6c4 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Fri, 19 May 2017 18:11:29 +0100
Subject: [PATCH] Disable <chrono> for older clang versions.

---
 include/boost/config/stdlib/libstdcpp3.hpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/boost/config/stdlib/libstdcpp3.hpp b/include/boost/config/stdlib/libstdcpp3.hpp
index 91ecccba..152435fc 100644
--- a/include/boost/config/stdlib/libstdcpp3.hpp
+++ b/include/boost/config/stdlib/libstdcpp3.hpp
@@ -161,6 +161,15 @@ extern "C" char *gets (char *__s);
 #if BOOST_LIBSTDCXX_VERSION < 40800
 #  define BOOST_NO_CXX11_THREAD_LOCAL
 #endif
+//
+// Early clang versions can handle <chrono>, not exactly sure which versions
+// but certainly up to clang-3.4 and gcc-4.6:
+//
+#if (__clang_major__ < 3) || ((__clang_major__ == 3) && (__clang_minor__ < 5))
+#  if BOOST_LIBSTDCXX_VERSION < 50000
+#     define BOOST_NO_CXX11_HDR_CHRONO
+#  endif
+#endif
 
 //
 //  GCC 4.8 and 9 add working versions of <atomic> and <regex> respectively.