From 96133c8dd904e98fe264fc8f558ced4494e3576e Mon Sep 17 00:00:00 2001
From: Takatoshi Kondo <redboltz@gmail.com>
Date: Thu, 10 May 2018 19:02:24 +0900
Subject: [PATCH] Fixed #658.

Added include file checking.
---
 include/msgpack/type.hpp               | 9 +++++----
 include/msgpack/v1/cpp_config_decl.hpp | 6 ++++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/include/msgpack/type.hpp b/include/msgpack/type.hpp
index 2ef6aa9e..24460347 100644
--- a/include/msgpack/type.hpp
+++ b/include/msgpack/type.hpp
@@ -42,12 +42,13 @@
 #include "adaptor/cpp11/unordered_map.hpp"
 #include "adaptor/cpp11/unordered_set.hpp"
 
-#if __cplusplus >= 201703
-
+#if MSGPACK_HAS_INCLUDE(<optional>)
 #include "adaptor/cpp17/optional.hpp"
-#include "adaptor/cpp17/string_view.hpp"
+#endif // MSGPACK_HAS_INCLUDE(<optional>)
 
-#endif // __cplusplus >= 201703
+#if MSGPACK_HAS_INCLUDE(<string_view>)
+#include "adaptor/cpp17/string_view.hpp"
+#endif // MSGPACK_HAS_INCLUDE(<string_view>)
 
 #endif // defined(MSGPACK_USE_CPP03)
 
diff --git a/include/msgpack/v1/cpp_config_decl.hpp b/include/msgpack/v1/cpp_config_decl.hpp
index 43a48600..c9752f23 100644
--- a/include/msgpack/v1/cpp_config_decl.hpp
+++ b/include/msgpack/v1/cpp_config_decl.hpp
@@ -128,4 +128,10 @@ MSGPACK_API_VERSION_NAMESPACE(v1) {
 
 #endif // MSGPACK_USE_CPP03
 
+#if defined(__has_include)
+#define MSGPACK_HAS_INCLUDE __has_include
+#else  // defined(__has_include)
+#define MSGPACK_HAS_INCLUDE(header) 0
+#endif // defined(__has_include)
+
 #endif // MSGPACK_V1_CPP_CONFIG_DECL_HPP