_InterlockedExchangePointer intrinsic functions

Article
08/03/2021

Microsoft Specific

Performs an atomic exchange operation, which copies the address passed in as the second argument into the first argument, and returns the original address of the first.

Syntax

void * _InterlockedExchangePointer(
   void * volatile * Target,
   void * Value
);
void * _InterlockedExchangePointer_acq(
   void * volatile * Target,
   void * Value
);
void * _InterlockedExchangePointer_rel(
   void * volatile * Target,
   void * Value
);
void * _InterlockedExchangePointer_nf(
   void * volatile * Target,
   void * Value
);
void * _InterlockedExchangePointer_HLEAcquire(
   void * volatile * Target,
   void * Value
);
void * _InterlockedExchangePointer_HLERelease(
   void * volatile * Target,
   void * Value
);

Parameters

Target
[in, out] Pointer to the pointer to the value to exchange. The function sets the value to Value and returns its previous value.

Value
[in] Value to be exchanged with the value pointed to by Target.

Return value

The function returns the initial value pointed to by Target.

Requirements

Intrinsic	Architecture	Header
`_InterlockedExchangePointer`	x86, ARM, x64, ARM64	<intrin.h>
`_InterlockedExchangePointer_acq`, `_InterlockedExchangePointer_rel`, `_InterlockedExchangePointer_nf`	ARM, ARM64	<intrin.h>
`_InterlockedExchangePointer_HLEAcquire`, `_InterlockedExchangePointer_HLERelease`	x64	<immintrin.h>

On the x86 architecture, _InterlockedExchangePointer is a macro that calls _InterlockedExchange.

Remarks

On a 64-bit system, the parameters are 64 bits and must be aligned on 64-bit boundaries. Otherwise, the function fails. On a 32-bit system, the parameters are 32 bits and must be aligned on 32-bit boundaries. For more information, see align.

On ARM platforms, use the intrinsics with _acq and _rel suffixes if you need acquire and release semantics, such as at the beginning and end of a critical section. The intrinsic with an _nf ("no fence") suffix doesn't act as a memory barrier.

On Intel platforms that support Hardware Lock Elision (HLE) instructions, the intrinsics with _HLEAcquire and _HLERelease suffixes include a hint to the processor that can accelerate performance by eliminating a lock write step in hardware. If these intrinsics are called on platforms that don't support HLE, the hint is ignored.

These routines are only available as intrinsics.

END Microsoft Specific