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<title>Issue 1462: Ambiguous value assignment to atomic_bool</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#Resolved">Resolved</a> status.</em></p>
<h3 id="1462"><a href="lwg-defects.html#1462">1462</a>. Ambiguous value assignment to <code>atomic_bool</code></h3>
<p><b>Section:</b> 99 [atomics.types.integral] <b>Status:</b> <a href="lwg-active.html#Resolved">Resolved</a>
 <b>Submitter:</b> BSI <b>Opened:</b> 2010-08-25 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#atomics.types.integral">issues</a> in [atomics.types.integral].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Resolved">Resolved</a> status.</p>
<p><b>Duplicate of:</b> <a href="lwg-closed.html#1463" title="Inconsistent value assignment for atomic_bool (Status: Dup)">1463</a></p>
<p><b>Discussion:</b></p>
<p><b>Addresses GB-132, US-157</b></p>

<p>
The <code>atomic_<em>itype</em></code> types and <code>atomic_address</code> have two
overloads of <code>operator=</code>; one is <code>volatile</code> qualified, and the
other is not. <code>atomic_bool</code> only has the <code>volatile</code> qualified
version:
</p>
<blockquote><pre>
bool operator=(bool) volatile;
</pre></blockquote>
<p>
On a non-<code>volatile</code>-qualified object this is ambiguous with
the deleted copy-assignment operator
</p>
<blockquote><pre>
atomic_bool&amp; operator=(atomic_bool const&amp;) = delete;
</pre></blockquote>
<p>
due to the need for a single standard conversion in each
case when assigning a bool to an <code>atomic_bool</code> as in:
</p>
<blockquote><pre>
atomic_bool b;
b = true;
</pre></blockquote>
<p>
The conversions are: 
</p>
<blockquote><pre>
atomic_bool&amp; &rarr; atomic_bool volatile&amp;
</pre></blockquote>
<p>
 vs 
</p>
<blockquote><pre>
bool &rarr; atomic_bool
</pre></blockquote>

<p><i>[
Proposed resolution as of NB comment:
]</i></p>


<p>
Change 99 [atomics.types.integral] as indicated:
</p>
<blockquote><pre>
namespace std {
  typedef struct atomic_bool {
    [..]
    bool operator=(bool) volatile;
    <ins>bool operator=(bool);</ins>
  } atomic_bool;
  [..]
}
</pre></blockquote>

<p><i>[
2010-10-27 Daniel adds:
]</i></p>


<blockquote><p>
Accepting <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3164.html">n3164</a> would solve this issue
by replacing <code>atomic_bool</code> by <code>atomic&lt;bool&gt;</code>.
</p></blockquote>

<p><i>[
2010 Batavia
]</i></p>

<p>
Resolved by adoption of <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3193.htm">n3193</a>.
</p>


<p id="res-1462"><b>Proposed resolution:</b></p><p>
Solved by <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3193.htm">n3193</a>.
</p>




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