[Boost-users] [iostreams] how to flush mapped_file

Hi, I'm new to the iostreams library, how do you flush/sync a iostreams::mapped_file? iostreams::flush(mapped_file) doesn't seem to work, although it works with a normal file device. are mapped_file's not flushable? the documentation of concept Flushable strangly says that it is an implementation detail, if a device is flushable. it should result in a call to msync() on posix systems and must not be an implementation detail, but the flush must be guaranteed. is this not possible with iostreams? thank you