On Monday 05 May 2014 20:55:08 Bjorn Reese wrote:

According to [1]:

"The compare_exchange_weak/compare_exchange_strong variants taking four parameters differ from the three parameter variants in that they allow a different memory ordering constraint to be specified in case the operation fails."

According to std::atomic there are some constaints on failure_order. Is this also the case for boost::atomic?

Yes, as boost::atomic aims to implement the standard interface as close as possible. The requirements are not enforced with asserts yet, but they will be.