Clang requires std::atomic content to have noexcept default constructor

https://stackoverflow.com/questions/29483120/program-with-noexcept-constructor-accepted-by-gcc-rejected-by-clang

So navitia::ptime inherits from boost's one and implements it, to be used "atomically".

ptime.h

@@ -0,0 +1,61 @@
+/* Copyright © 2001-2018, Canal TP and/or its affiliates. All rights reserved.
+
+This file is part of Navitia,
+    the software to build cool stuff with public transport.
+
+Hope you'll enjoy and contribute to this project,
+    powered by Canal TP (www.canaltp.fr).
+Help us simplify mobility and open public transport:
+    a non ending quest to the responsive locomotion way of traveling!
+
+LICENCE: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Stay tuned using
+twitter @navitia
+IRC #navitia on freenode
+https://groups.google.com/d/forum/navitia
+www.navitia.io
+*/
+
+#include <boost/date_time/posix_time/posix_time.hpp>
+
+namespace navitia {
+
+class ptime: public boost::posix_time::ptime
+{
+public:
+    // Forward constructors
+    ptime(boost::gregorian::date d,time_duration_type td) : boost::posix_time::ptime(d,td)
+    {}
+    explicit ptime(boost::gregorian::date d) : boost::posix_time::ptime(d)
+    {}
+    ptime(const time_rep_type& rhs): boost::posix_time::ptime(rhs)
+    {}
+    ptime(const boost::date_time::special_values sv) : boost::posix_time::ptime(sv)
+    {}
+
+    // Add (copy-)constructor from ancestor
+    ptime(const boost::posix_time::ptime& rhs): boost::posix_time::ptime(rhs)
+    {}
+
+#if !defined(DATE_TIME_NO_DEFAULT_CONSTRUCTOR)
+    // Add noexcept default constructor
+    // Cause: Clang requires std::atomic content to have noexcept default constructor
+    ptime() noexcept: boost::posix_time::ptime()
+    {}
+#endif // DATE_TIME_NO_DEFAULT_CONSTRUCTOR
+
+};
+
+} // namespace navitia