InterlockedCompareExchangePointer function (winnt.h)

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

To operate on non-pointer values, use the InterlockedCompareExchange function.

PVOID InterlockedCompareExchangePointer(
  [in, out] PVOID volatile *Destination,
  [in]      PVOID          Exchange,
  [in]      PVOID          Comperand
);

[in, out] Destination

A pointer to 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.

On a 64-bit system, the parameters are 64 bits and must be aligned on 64-bit boundaries; otherwise, the function will behave unpredictably. On a 32-bit system, the parameters are 32 bits and must be aligned on 32-bit boundaries.

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 _InterlockedCompareExchangePointer.

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 InterlockedCompareExchangePointerAcquire or InterlockedCompareExchangePointerRelease instead.

Interlocked Variable Access

InterlockedCompare64Exchange128

InterlockedCompareExchange

InterlockedCompareExchange128

InterlockedCompareExchange16

InterlockedCompareExchange16Acquire

InterlockedCompareExchange16NoFence

InterlockedCompareExchange16Release

InterlockedCompareExchange64

InterlockedCompareExchangeAcquire

InterlockedCompareExchangeAcquire64

InterlockedCompareExchangeNoFence

InterlockedCompareExchangeNoFence64

InterlockedCompareExchangePointerAcquire

InterlockedCompareExchangePointerNoFence

InterlockedCompareExchangePointerRelease

InterlockedCompareExchangeRelease

InterlockedCompareExchangeRelease64

Synchronization Functions