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<title>Issue 846: No definition for constructor</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#CD1">CD1</a> status.</em></p>
<h3 id="846"><a href="lwg-defects.html#846">846</a>. No definition for constructor</h3>
<p><b>Section:</b> 32.5.8.2 <a href="https://wg21.link/atomics.types.operations">[atomics.types.operations]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Alisdair Meredith <b>Opened:</b> 2008-06-03 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#atomics.types.operations">active issues</a> in [atomics.types.operations].</p>
<p><b>View all other</b> <a href="lwg-index.html#atomics.types.operations">issues</a> in [atomics.types.operations].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The atomic classes and class templates (99 [atomics.types.integral] &#47;
99 [atomics.types.address]) have a constexpr
constructor taking a value of the appropriate type for that atomic.
However, neither clause provides semantics or a definition for this
constructor.  I'm not sure if the initialization is implied by use of
constexpr keyword (which restricts the form of a constructor) but even if
that is the case, I think it is worth spelling out explicitly as the
inference would be far too subtle in that case.
</p>

<p><i>[
San Francisco:
]</i></p>


<blockquote>
<p>
Lawrence will provide wording.
</p>
<p>
This issue is addressed in
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2783.htm">N2783</a>.
</p>
</blockquote>


<p id="res-846"><b>Proposed resolution:</b></p>

<p>
before the description of ...<code>is_lock_free</code>,
that is before 32.5.8.2 <a href="https://wg21.link/atomics.types.operations">[atomics.types.operations]</a> paragraph 4,
add the following description.
</p>

<blockquote>
<pre><code>
constexpr <var>A</var>::<var>A</var>(<var>C</var> desired);
</code></pre>
<dl>
<dt><i>Effects:</i></dt>
<dd>
Initializes the object with the value <code>desired</code>.
[<i>Note:</i>
Construction is not atomic.
&mdash;<i>end note</i>]
</dd>
</dl>
</blockquote>





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