Forces reads from memory to complete at the point of the call.
The _ReadBarrier, _WriteBarrier, and _ReadWriteBarrier functions help ensure the proper operation of multithreaded programs that are optimized by the Visual C++ compiler. A correctly optimized program yields the same results when it executes on multiple threads as when it executes on a single thread.
To help ensure that the optimized program operates correctly, the _ReadBarrier function forces reads from memory to complete at the point of the call. After the call, other threads can access the memory without fear that the thread that made the call might have a pending read from the memory. For more information, see the remarks in _ReadWriteBarrier.