From e6f508dc14a1cd1daf1dbb37b27b6f6464346b5f Mon Sep 17 00:00:00 2001
From: Henry Fredrick Schreiner <henry.fredrick.schreiner@cern.ch>
Date: Thu, 5 Apr 2018 13:13:51 +0200
Subject: [PATCH] Fix for redefinition warning

---
 include/CLI/Optional.hpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/CLI/Optional.hpp b/include/CLI/Optional.hpp
index 1b2db6a2..6370c45c 100644
--- a/include/CLI/Optional.hpp
+++ b/include/CLI/Optional.hpp
@@ -12,18 +12,24 @@
 #if defined(CLI11_CPP17) && __has_include(<optional>)
 #include <optional>
 #ifdef __cpp_lib_optional
+#ifndef CLI11_STD_OPTIONAL
 #define CLI11_STD_OPTIONAL
 #endif
 #endif
+#endif
 #if defined(CLI11_CPP14) && __has_include(<experimental/optional>)
 #include <experimental/optional>
+#ifndef CLI11_EXPERIMENTAL_OPTIONAL
 #define CLI11_EXPERIMENTAL_OPTIONAL
 #endif
+#endif
 #if __has_include(<boost/optional.hpp>)
 #include <boost/optional.hpp>
+#ifndef CLI11_BOOST_OPTIONAL
 #define CLI11_BOOST_OPTIONAL
 #endif
 #endif
+#endif
 // [CLI11:verbatim]
 
 namespace CLI {