InterlockedCompareExchange64 function (winnt.h)

Performs an atomic compare-and-exchange operation on the specified values. The function compares two specified 64-bit values and exchanges with another 64-bit value based on the outcome of the comparison.

LONG64 InterlockedCompareExchange64(
  [in, out] LONG64 volatile *Destination,
  [in]      LONG64          ExChange,
  [in]      LONG64          Comperand
);

[in, out] Destination

A pointer to the destination value.

[in] ExChange

The exchange value.

[in] Comperand

The value to compare to Destination.

The function returns the initial value of the Destination parameter.

The function compares the Destination value with the Comparand value. If the Destination value is equal to the Comparand value, the Exchange value is stored in the address specified by Destination. Otherwise, no operation is performed.

The variables for this function must be aligned on a 64-bit boundary; otherwise, this function will behave unpredictably on multiprocessor x86 systems and any non-x86 systems. See _aligned_malloc.

The interlocked functions provide a simple mechanism for synchronizing access to a variable that is shared by multiple threads. This function is atomic with respect to calls to other interlocked functions.

This function is implemented using a compiler intrinsic where possible. For more information, see the WinBase.h header file and _InterlockedCompareExchange64.

This function generates a full memory barrier (or fence) to ensure that memory operations are completed in order.

Itanium-based systems:  For performance-critical applications, use InterlockedCompareExchangeAcquire64 or InterlockedCompareExchangeRelease64 instead.

Interlocked Variable Access

InterlockedCompare64Exchange128

InterlockedCompareExchange

InterlockedCompareExchange128

InterlockedCompareExchange16

InterlockedCompareExchange16Acquire

InterlockedCompareExchange16NoFence

InterlockedCompareExchange16Release

InterlockedCompareExchangeAcquire

InterlockedCompareExchangeAcquire64

InterlockedCompareExchangeNoFence

InterlockedCompareExchangeNoFence64

InterlockedCompareExchangePointer

InterlockedCompareExchangePointerAcquire

InterlockedCompareExchangePointerNoFence

InterlockedCompareExchangePointerRelease

InterlockedCompareExchangeRelease

InterlockedCompareExchangeRelease64

Synchronization Functions