common/iso_8601.cc: Make return expression Clang compatible

Signed-off-by: Willem Jan Withagen <wjw@digiware.nl>

diff --git a/src/common/iso_8601.cc b/src/common/iso_8601.cc
index dcf43be9413658c11dbba2ca8e7498afac3129b5..39e00e0b31f9c648d79b54c7e94fbab56b83ca67 100644 (file)
--- a/src/common/iso_8601.cc
+++ b/src/common/iso_8601.cc
@@ -41,7 +41,8 @@ optional<real_time> calculate(const tm& t, uint32_t n = 0) {
     return none;
   }
 
-  return real_clock::from_time_t(tt) + nanoseconds(n);
+  return boost::make_optional<real_time>(real_clock::from_time_t(tt)
+                                         + nanoseconds(n));
 }
 }