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<title>Issue 1339: uninitialized_fill_n should return the end of its range</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#C++11">C++11</a> status.</em></p>
<h3 id="1339"><a href="lwg-defects.html#1339">1339</a>. <code>uninitialized_fill_n</code> should return the end of its range</h3>
<p><b>Section:</b> 26.11.7 <a href="https://wg21.link/uninitialized.fill">[uninitialized.fill]</a> <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> Jared Hoberock <b>Opened:</b> 2010-07-14 <b>Last modified:</b> 2017-06-15</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++11">C++11</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3092.pdf">N3092's</a>
specification of <code>uninitialized_fill_n</code> discards useful information and
is inconsistent with other algorithms such as <code>fill_n</code> which accept an
iterator and a size.  As currently specified, <code>unintialized_fill_n</code>
requires an additional linear traversal to find the end of the range.
</p>

<p>
Instead of returning <code>void</code>, <code>unintialized_fill_n</code> should return
one past the last iterator it dereferenced.
</p>

<p><i>[
Post-Rapperswil:
]</i></p>


<blockquote><p>
Moved to Tentatively Ready after 5 positive votes on c++std-lib.
</p></blockquote>

<p><i>[
Adopted at 2010-11 Batavia
]</i></p>




<p id="res-1339"><b>Proposed resolution:</b></p>
<p>
In section 20.2 <a href="https://wg21.link/memory">[memory]</a> change:,
</p>

<blockquote><pre>
template &lt;class ForwardIterator, class Size, class T&gt;
  <del>void</del> <ins>ForwardIterator</ins> uninitialized_fill_n(ForwardIterator first, Size n, const T&amp; x);
</pre></blockquote>


<p>
In section  [uninitialized.fill.n] change,
</p>

<blockquote><pre>
template &lt;class ForwardIterator, class Size, class T&gt;
  <del>void</del> <ins>ForwardIterator</ins> uninitialized_fill_n(ForwardIterator first, Size n, const T&amp; x);
</pre>
<blockquote>
<p>
1 <i>Effects:</i>
</p>
<blockquote><pre>
for (; n--; ++first)
  ::new (static_cast&lt;void*&gt;(&amp;*first))
    typename iterator_traits&lt;ForwardIterator&gt;::value_type(x);
<ins>return first;</ins>
</pre></blockquote>
</blockquote>
</blockquote>






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