[#BloombergLP-bsls-AtomicOperations-testAndSwapPtrAcqRel]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bsls.adoc[bsls]::xref:BloombergLP/bsls/AtomicOperations.adoc[AtomicOperations]::testAndSwapPtrAcqRel
:relfileprefix: ../../../
:mrdocs:

Conditionally swap `atomicPtr` with acquire&sol;release ordering&period;

== Synopsis

Declared in `&lt;bsls&lowbar;atomicoperations&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
static
void*
testAndSwapPtrAcqRel(
    xref:BloombergLP/bsls/Atomic_TypeTraits-0b/Pointer.adoc[AtomicTypes::Pointer]* atomicPtr,
    void* compareValue,
    void* swapValue);
----

== Description

Conditionally set the value of the specified `atomicPtr` to the specified `swapValue` if and only if the value of `atomicPtr` equals the value of the specified `compareValue`, and return the initial value of `atomicPtr`, providing the acquire&sol;release memory ordering guarantee&period; The whole operation is performed atomically&period;

== Return Value

initial value of `atomicPtr` before the operation

== Parameters

[cols="1,4"]
|===
| Name| Description
| *atomicPtr*
| atomic pointer to test and possibly update
| *compareValue*
| expected current value of `atomicPtr`
| *swapValue*
| value to store if the comparison succeeds
|===


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