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/volatile (volatile Keyword Interpretation)

Specifies how the volatile keyword is to be interpreted.

/volatile:{iso|ms}

/volatile:iso

Selects strict volatile semantics as defined by the ISO-standard C++ language. Acquire/release semantics are not guaranteed on volatile accesses. If the compiler targets ARM, this is the default interpretation of volatile.

/volatile:ms

Selects Microsoft extended volatile semantics, which add memory ordering guarantees beyond the ISO-standard C++ language. Acquire/release semantics are guaranteed on volatile accesses. However, this option also forces the compiler to generate hardware memory barriers, which might add significant overhead on ARM and other weak memory-ordering architectures. If the compiler targets any platform except ARM, this is default interpretation of volatile.

We strongly recommend that you use /volatile:iso along with explicit synchronization primitives and compiler intrinsics when you are dealing with memory that is shared across threads. For more information, see volatile (C++).

If you port existing code or change this option in the middle of a project, it may be helpful to enable warning C4746 to identify code locations that are affected by the difference in semantics.

There is no #pragma equivalent to control this option.

To set the /volatile compiler option in Visual Studio

  1. Open the Property Pages dialog box for the project. For more information, see How to: Open Project Property Pages.

  2. Select the C/C++ folder.

  3. Select the Command Line property page.

  4. In the Additional options box, add /volatile:iso or /volatile:ms.

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