InterlockedCompareExchange

InterlockedCompareExchange performs an atomic compare-and-exchange operation on the specified values. The function compares two specified 32-bit values and exchanges with another 64-bit value based on the outcome of the comparison.

Syntax

LONG InterlockedCompareExchange(
     LONG volatile *Destination,
     LONG           Exchange,
     LONG           Comparand  
  );

Parameters

Destination

A pointer to the destination value.

Exchange

The exchange value.

Comparand

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 parameters for this function must be aligned on a 32-bit boundary; otherwise, the function will behave unpredictably on multiprocessor x64 systems.

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. It is thread-safe.

This function is implemented using a compiler intrinsic where possible. This function generates a full memory barrier (or fence) to ensure that memory operations are completed in order.

Requirements

Minimum Supported Version	RTX64 2013
Header	windows.h
Library	Rtx_Rtss.lib