[boost] on windows flyweight simple_locking is using std::mutex but it should be using std::recursive_mutex()

Dear All, On windows flyweight simple_locking is using std::mutex but it should be using std::recursive_mutex. I've got this firing an exception due to _Check_C_return() getting passed something else than success (number 3). I've checked by implementing my own locking policy and it definitely shows that the code is attempting to hold more than a single lock in parallel on the same mutex. The secured set.erase() can cause further flyweights to be destroyed given a suitable recursive use of flyweight. Kind Regards Peter Foelsche PS. Thanks for boost!