id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
6782	call_once uses incorrect barrier intrinsic on Visual Studio	ybungalobill@…	viboes	"boost\thread\win32\interlocked_read.hpp uses _ReadWriteBarrier() as a barrier. However, [http://msdn.microsoft.com/en-us/library/f20w0x5e%28v=vs.100%29.aspx according to MSDN] and the machine code generated, it doesn't emit any memory barrier instructions at all:

> The _ReadBarrier, _WriteBarrier, and _ReadWriteBarrier compiler intrinsics prevent only compiler re-ordering. To prevent the CPU from re-ordering read and write operations, use the MemoryBarrier macro.

So one should use the MemoryBarrier() macro instead. In fact according [http://msdn.microsoft.com/en-us/library/windows/desktop/ms684208%28v=vs.85%29.aspx this page] _ReadWriteBarrier is not necessary for volatile variables access since VS2005.

Thanks,
Y. Galka."	Bugs	closed	Boost 1.57.0	thread	Boost 1.49.0	Problem	fixed