Regards, Helge! This is the fragment of $(BOOST_ROOT)/boost/memory_order.hpp: namespace boost { enum memory_order { memory_order_relaxed = 0, memory_order_acquire = 1, memory_order_release = 2, memory_order_acq_rel = 3, // acquire | release memory_order_seq_cst = 7 // acq_rel | 4 }; } // namespace boost My questions: 1) Where is the memory_order_consume constant? I failed to compile your "Double Check Singleton Pattern" sample, because it uses "memory_order_consume" constant. 2) How soon Boost.Atomic will be included into Boost release? Best, Andrew. -- View this message in context: http://old.nabble.com/Thread-safe-singleton-pattern-tp27315850p27344594.html Sent from the Boost - Dev mailing list archive at Nabble.com.