From 44a0006e0d5fea9b2420f7c3289b5e75ccac9cb0 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 22 Nov 2018 14:48:56 +0200
Subject: Fix <optional> availability detection for Mac OS

It still has it in <experimental/optional>.
---
 libbutl/optional.mxx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libbutl/optional.mxx b/libbutl/optional.mxx
index 33ee3d3..4f34a78 100644
--- a/libbutl/optional.mxx
+++ b/libbutl/optional.mxx
@@ -30,10 +30,12 @@
    // the latter we will check for the presence of the <optional> header which
    // only appeared in GCC 7. Also assume both are only available in C++17.
    //
+   // Note that on Mac OS it can still be <experimental/optional>.
+   //
 #  if __cplusplus >= 201703L
 #    if __has_include(<__config>)
 #      include <__config>          // _LIBCPP_VERSION
-#      if _LIBCPP_VERSION >= 4000
+#      if _LIBCPP_VERSION >= 4000 && __has_include(<optional>)
 #        define LIBBUTL_STD_OPTIONAL
 #      endif
 #    elif __has_include(<optional>)
-- 
cgit v1.1