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<title>Issue 3129: regex_token_iterator constructor uses wrong pointer arithmetic</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++20">C++20</a> status.</em></p>
<h3 id="3129"><a href="lwg-defects.html#3129">3129</a>. <code>regex_token_iterator</code> constructor uses wrong pointer arithmetic</h3>
<p><b>Section:</b> 28.6.11.2.2 <a href="https://wg21.link/re.tokiter.cnstr">[re.tokiter.cnstr]</a> <b>Status:</b> <a href="lwg-active.html#C++20">C++20</a>
 <b>Submitter:</b> Tim Song <b>Opened:</b> 2018-06-30 <b>Last modified:</b> 2021-02-25</p>
<p><b>Priority: </b>0
</p>
<p><b>View all other</b> <a href="lwg-index.html#re.tokiter.cnstr">issues</a> in [re.tokiter.cnstr].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++20">C++20</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The specification of <code>regex_token_iterator</code> for the overload taking a 
<code>const int (&amp;submatchs)[N]</code> uses the range <code>[&amp;submatches, &amp;submatches + N)</code>.
This is obviously incorrect; we want to perform pointer arithmetic on a pointer to the first element
of that array, not a pointer to the whole array.
</p>

<p><i>[2018-07-20 Status to Tentatively Ready after five positive votes on the reflector.]</i></p>

<p><i>[2018-11, Adopted in San Diego]</i></p>



<p id="res-3129"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/n4750">N4750</a>.
</p>

<ol>
<li>
<p>
Change 28.6.11.2.2 <a href="https://wg21.link/re.tokiter.cnstr">[re.tokiter.cnstr]</a> p3 as indicated:
</p>
<blockquote>
<pre>
regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                     const regex_type&amp; re,
                     int submatch = 0,
                     regex_constants::match_flag_type m = regex_constants::match_default);

regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                     const regex_type&amp; re,
                     const vector&lt;int&gt;&amp; submatches,
                     regex_constants::match_flag_type m = regex_constants::match_default);

regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                     const regex_type&amp; re,
                     initializer_list&lt;int&gt; submatches,
                     regex_constants::match_flag_type m = regex_constants::match_default);

template&lt;size_t N&gt;
  regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                       const regex_type&amp; re,
                       const int (&amp;submatches)[N],
                       regex_constants::match_flag_type m = regex_constants::match_default);
</pre>
<blockquote>
<p>
-2- <i>Requires:</i> [&hellip;]
<p/>
-3- <i>Effects:</i> The first constructor initializes the member <code>subs</code> to hold the single
value <code>submatch</code>. <del>The second constructor initializes the member <code>subs</code> to hold a
copy of the argument <code>submatches</code>.</del> The <ins>second,</ins> third and fourth constructors 
initialize the member <code>subs</code> to hold a copy of the sequence of integer values pointed to
by the iterator range <del><code>[submatches.begin(), submatches.end())</code> and <code>[&amp;submatches,
&amp;submatches + N)</code>, respectively</del><ins><code>[begin(submatches), end(submatches))</code></ins>.
<p/>
-4- [&hellip;]
</p>
</blockquote>
</blockquote>
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