InterlockedExchangeAdd function (Windows)

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InterlockedExchangeAdd function

Applies to: desktop apps | Metro style apps

Performs an atomic addition of two 32-bit values.

To operate on 64-bit values, use the InterlockedExchangeAdd64 function.

Syntax

LONG __cdecl InterlockedExchangeAdd(
  __inout  LONG volatile *Addend,
  __in     LONG Value
);

Parameters

Addend [in, out]: A pointer to a variable. The value of this variable will be replaced with the result of the operation.
Value [in]: The value to be added to the variable pointed to by the Addend parameter.

Return value

The function returns the initial value of the Addend parameter.

Remarks

The function performs an atomic addition of Value to the value pointed to by Addend. The result is stored in the address specified by Addend. The function returns the initial value of the variable pointed to by Addend.

The variables for this function must be aligned on a 32-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 _InterlockedExchangeAdd

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 InterlockedExchangeAddAcquire instead.

Requirements

Minimum supported client	Windows XP
Minimum supported server	Windows Server 2003
Header	WinBase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll