From 170fcd715f586cfd6b9f741c0572d472e0abe8ed Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 22 Aug 2019 08:28:08 -0400
Subject: Extend C++17 feature checks to require std::optional

---
 Source/Checks/cm_cxx17_check.cpp |  5 ++++-
 bootstrap                        | 16 +++++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Source/Checks/cm_cxx17_check.cpp b/Source/Checks/cm_cxx17_check.cpp
index 593d9b2..29863b1 100644
--- a/Source/Checks/cm_cxx17_check.cpp
+++ b/Source/Checks/cm_cxx17_check.cpp
@@ -1,6 +1,7 @@
 #include <cstdio>
 #include <iterator>
 #include <memory>
+#include <optional>
 #include <unordered_map>
 
 #ifdef _MSC_VER
@@ -27,5 +28,7 @@ int main()
   IDispatchPtr disp(ptr);
 #endif
 
-  return *u + *ai + *(bi - 1) + (3 - static_cast<int>(ci));
+  std::optional<int> oi = 0;
+
+  return *u + *ai + *(bi - 1) + (3 - static_cast<int>(ci)) + oi.value();
 }
diff --git a/bootstrap b/bootstrap
index 4581239..17dc3e8 100755
--- a/bootstrap
+++ b/bootstrap
@@ -1146,6 +1146,20 @@ int check_cxx14()
 }
 #endif
 
+#if __cplusplus >= 201703L
+#include <optional>
+int check_cxx17()
+{
+  std::optional<int> oi = 0;
+  return oi.value();
+}
+#else
+int check_cxx17()
+{
+  return 0;
+}
+#endif
+
 class Class
 {
 public:
@@ -1156,7 +1170,7 @@ private:
 int main()
 {
   auto const c = std::unique_ptr<Class>(new Class);
-  std::cout << c->Get() << check_cxx14() << std::endl;
+  std::cout << c->Get() << check_cxx14() << check_cxx17() << std::endl;
   return 0;
 }
 ' > "${TMPFILE}.cxx"
-- 
cgit v0.12