Index: boost/thread/detail/config.hpp
===================================================================
--- boost/thread/detail/config.hpp	(revision 83090)
+++ boost/thread/detail/config.hpp	(working copy)
@@ -161,6 +161,12 @@
 #define BOOST_THREAD_PROVIDES_ONCE_CXX11
 #endif
 
+// For C++11 call_once interface the compiler MUST support constexpr.
+// Otherwise once_flag would be initialized during dynamic initialization stage, which is not thread-safe.
+#if defined(BOOST_THREAD_PROVIDES_ONCE_CXX11) && defined(BOOST_NO_CXX11_CONSTEXPR)
+#undef BOOST_THREAD_PROVIDES_ONCE_CXX11
+#endif
+
 // THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE
 #if ! defined BOOST_THREAD_DONT_PROVIDE_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE \
  && ! defined BOOST_THREAD_PROVIDES_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE