InterlockedExchange function (winnt.h)

Article
10/13/2021

Sets a 32-bit variable to the specified value as an atomic operation.

To operate on a pointer variable, use the InterlockedExchangePointer function.

To operate on a 16-bit variable, use the InterlockedExchange16 function.

To operate on a 64-bit variable, use the InterlockedExchange64 function.

Syntax

LONG InterlockedExchange(
  [in, out] LONG volatile *Target,
  [in]      LONG          Value
);

Parameters

[in, out] Target

A pointer to the value to be exchanged. The function sets this variable to Value, and returns its prior value.

[in] Value

The value to be exchanged with the value pointed to by Target.

Return value

The function returns the initial value of the Target parameter.

Remarks

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 _InterlockedExchange.

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 InterlockedExchangeAcquire instead.

Note This function is supported on Windows RT-based systems.

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)
Library	Kernel32.lib
DLL	Kernel32.dll