[boost] [thread] Use of _ReadWriteBarrier

From: John Maddock (john_at_[hidden])
Date: 2007-10-07 13:14:45

Anthony,

Just a couple of quick questions/comments regarding the use of 
_ReadWriteBarrier in the latest Boost.Thread code:

First up _ReadWriteBarrier is a VC++ compiler intrinsic: it's not supported 
by the Borland or MingW compilers, so these fail to link with unresolved 
externals to _ReadWriteBarrier.  Can interlocked_read_acquire be written in 
terms of InterlockedCompareExchange(pointer, 0, 0) and 
InterlockedCompareExchangePointer(pointer-to-pointer, 0, 0) in these cases?

Secondly, I'm a bit confused why the barrier is *after* the read, shouldn't 
it be before?  I'm not saying it should be, I just wondered :-)

Thanks, John.