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.
Syntax
PVOID InterlockedCompareExchangePointer(
[in, out] PVOID volatile *Destination,
[in] PVOID Exchange,
[in] PVOID Comperand
);
Parameters
[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.
Return value
The function returns the initial value of the Destination parameter.
Remarks
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.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP [desktop apps | UWP apps] |
| Minimum supported server | Windows Server 2003 [desktop apps | UWP apps] |
| Target Platform | Windows |
| Header | winnt.h (include Windows.h) |
See also
InterlockedCompare64Exchange128
InterlockedCompareExchange16Acquire
InterlockedCompareExchange16NoFence
InterlockedCompareExchange16Release
InterlockedCompareExchangeAcquire
InterlockedCompareExchangeAcquire64
InterlockedCompareExchangeNoFence
InterlockedCompareExchangeNoFence64
InterlockedCompareExchangePointerAcquire
InterlockedCompareExchangePointerNoFence
InterlockedCompareExchangePointerRelease
InterlockedCompareExchangeRelease