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.
Syntax
LONG64 InterlockedCompareExchange64(
[in, out] LONG64 volatile *Destination,
[in] LONG64 ExChange,
[in] LONG64 Comperand
);
Parameters
[in, out] Destination
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.
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.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows Vista [desktop apps | UWP apps] |
| Minimum supported server | Windows Server 2003 [desktop apps | UWP apps] |
| Target Platform | Windows |
| Header | winnt.h (include Windows.h) |
| Library | Kernel32.lib |
| DLL | Kernel32.dll |
See also
InterlockedCompare64Exchange128
InterlockedCompareExchange16Acquire
InterlockedCompareExchange16NoFence
InterlockedCompareExchange16Release
InterlockedCompareExchangeAcquire
InterlockedCompareExchangeAcquire64
InterlockedCompareExchangeNoFence
InterlockedCompareExchangeNoFence64
InterlockedCompareExchangePointer
InterlockedCompareExchangePointerAcquire
InterlockedCompareExchangePointerNoFence
InterlockedCompareExchangePointerRelease
InterlockedCompareExchangeRelease