[Boost-bugs] [Boost C++ Libraries] #6782: call_once uses incorrect barrier intrinsic on Visual Studio

Subject: [Boost-bugs] [Boost C++ Libraries] #6782: call_once uses incorrect barrier intrinsic on Visual Studio
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-04-11 16:56:27

#6782: call_once uses incorrect barrier intrinsic on Visual Studio
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 Reporter:  ybungalobill@…          |       Owner:  anthonyw
     Type:  Bugs                    |      Status:  new     
Milestone:  To Be Determined        |   Component:  thread  
  Version:  Boost 1.49.0            |    Severity:  Problem 
 Keywords:                          |  
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 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.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/6782>
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