Hi, I have changed the ticket from threads to thread As this works as expected, Anthony could just add on the documentation why reentrant call_once functions are not a good idea. The explanation of Steven could be a good starting point: "I'll also point out that there is no good behavior for a recursive call to call_once. If it calls the function again, then f will be called twice. If it does not, then whatever initialization that call_once is doing may be incomplete. In either case, you have to know whether a call can be recursive and carefully design for it. If it happens accidentally, you're probably toast regardless of how it behaves. In the face of recursive calls it is impossible to maintain the post-condition that the function has run exactly once." After this modification IMO the ticket can be closed. Best, Vicente -- View this message in context: http://old.nabble.com/Boost-sprint%3A--3407-boost%3A%3Acall_once-not-re-entr... Sent from the Boost - Dev mailing list archive at Nabble.com.