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<title>Issue 2530: Clarify observable side effects of releasing a shared state</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#Open">Open</a> status.</em></p>
<h3 id="2530"><a href="lwg-active.html#2530">2530</a>. Clarify observable side effects of releasing a shared state</h3>
<p><b>Section:</b> 32.10.5 <a href="https://wg21.link/futures.state">[futures.state]</a> <b>Status:</b> <a href="lwg-active.html#Open">Open</a>
 <b>Submitter:</b> Agust&iacute;n K-ballo Berg&eacute; <b>Opened:</b> 2015-09-03 <b>Last modified:</b> 2016-08-06</p>
<p><b>Priority: </b>3
</p>
<p><b>View all other</b> <a href="lwg-index.html#futures.state">issues</a> in [futures.state].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Open">Open</a> status.</p>
<p><b>Discussion:</b></p>
<p>
When a shared-state is released, it may be necessary to execute user defined code for the destructor of a 
stored value or exception. It is unclear whether the execution of said destructor constitutes an observable side effect.
</p>
<p>
While discussing N4445 in Lenexa, Nat Goodspeed pointed out that 32.10.5 <a href="https://wg21.link/futures.state">[futures.state]</a>/5.1 does not explicitly 
mention the destruction of the result, so implementations should be allowed to release (or reuse) a shared state ahead 
of time under the "as-if" rule.
<p/>
The standard should clarify whether the execution of destructors is a visible side effect of releasing a shared state.
</p>

<p><i>[2016-08-03 Chicago]</i></p>

<p>This is related to <a href="lwg-active.html#2532" title="Satisfying a promise at thread exit (Status: Open)">2532</a><sup><a href="https://cplusplus.github.io/LWG/issue2532" title="Latest snapshot">(i)</a></sup></p>
<p>Fri AM: Moved to Open</p>


<p id="res-2530"><b>Proposed resolution:</b></p>





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