[#BloombergLP-bsls-AtomicPointer-testAndSwapAcqRel]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bsls.adoc[bsls]::xref:BloombergLP/bsls/AtomicPointer.adoc[AtomicPointer]::testAndSwapAcqRel
:relfileprefix: ../../../
:mrdocs:

Conditionally swap this pointer with acquire/release ordering.

== Synopsis

Declared in `<bsls_atomic.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
TYPE*
testAndSwapAcqRel(
    TYPE const* compareValue,
    TYPE* swapValue);
----

== Description

Compare the value of this object to the specified `compareValue`. If they are equal, set the value of this atomic pointer to the specified `swapValue`, otherwise leave this value unchanged. Return the previous value of this atomic pointer, whether or not the swap occurred. Note that the entire test‐and‐swap operation is performed atomically and it provides the acquire/release memory ordering guarantee.

== Return Value

previous value of this object

== Parameters

[cols="1,4"]
|===
| Name| Description
| *compareValue*
| expected current value of this object
| *swapValue*
| pointer to store if the comparison succeeds
|===


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