https://svn.boost.org/trac/boost/ticket/2551
--- boost/date_time/constrained_value.hpp~	2008-02-27 16:00:24.000000000 -0400
+++ boost/date_time/constrained_value.hpp	2008-11-29 16:54:16.000000000 -0400
@@ -39,6 +39,7 @@
     typedef typename value_policies::value_type value_type;
     //    typedef except_type exception_type;
     constrained_value(value_type value) 
+      : value_(value) // avoid uninitialized use of value_ on error
     {
       assign(value);
     };