John Maddock <john <at> johnmaddock.co.uk> writes:
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?
Yes, that's top of my list for this morning.
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
As Timmo says, it's so nothing can be moved before the read. It's OK to move stuff into a critical section, but never out. Anthony