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<title>Issue 2318: basic_string's wording has confusing relics from the copy-on-write era</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="2318"><a href="lwg-defects.html#2318">2318</a>. <code>basic_string</code>'s wording has confusing relics from the copy-on-write era</h3>
<p><b>Section:</b> 27.4.3 <a href="https://wg21.link/basic.string">[basic.string]</a> <b>Status:</b> <a href="lwg-active.html#Resolved">Resolved</a>
 <b>Submitter:</b> Stephan T. Lavavej <b>Opened:</b> 2013-09-21 <b>Last modified:</b> 2018-11-25</p>
<p><b>Priority: </b>4
</p>
<p><b>View other</b> <a href="lwg-index-open.html#basic.string">active issues</a> in [basic.string].</p>
<p><b>View all other</b> <a href="lwg-index.html#basic.string">issues</a> in [basic.string].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Resolved">Resolved</a> status.</p>
<p><b>Discussion:</b></p>
<p>
27.4.3.5 <a href="https://wg21.link/string.capacity">[string.capacity]</a>/8 specifies <code>basic_string::resize(n, c)</code> with:
</p>
<blockquote><p>
<i>Effects:</i> Alters the length of the string designated by <code>*this</code> as follows:
</p>
<ul>
<li><p>
If <code>n &lt;= size()</code>, the function replaces the string designated by <code>*this</code> with a string of length <code>n</code> whose 
elements are a copy of the initial elements of the original string designated by <code>*this</code>.
</p>
</li>
<li><p>
If <code>n &gt; size()</code>, the function replaces the string designated by <code>*this</code> with a string of length <code>n</code> whose 
first <code>size()</code> elements are a copy of the original string designated by <code>*this</code>, and whose remaining elements are all 
initialized to <code>c</code>.
</p>
</li>
</ul>
</blockquote>
<p>
This wording is a relic of the copy-on-write era. In addition to being extremely confusing, it has undesirable implications.  
Saying "replaces the string designated by <code>*this</code> with a string of length <code>n</code> whose elements are a copy" suggests 
that the trimming case can reallocate. Reallocation during trimming should be forbidden, like <code>vector</code>.
<p/>
At least 7 paragraphs are affected: 27.4.3.5 <a href="https://wg21.link/string.capacity">[string.capacity]</a>/8, 27.4.3.7.2 <a href="https://wg21.link/string.append">[string.append]</a>/9, 
27.4.3.7.3 <a href="https://wg21.link/string.assign">[string.assign]</a>/3 and /10, 27.4.3.7.4 <a href="https://wg21.link/string.insert">[string.insert]</a>/11, 27.4.3.7.5 <a href="https://wg21.link/string.erase">[string.erase]</a>/4, and 
27.4.3.7.6 <a href="https://wg21.link/string.replace">[string.replace]</a>/11 say "replaces the string [designated/controlled] by <code>*this</code>". (27.4.3.7.7 <a href="https://wg21.link/string.copy">[string.copy]</a>/3 
is different &mdash; it "replaces the string designated by <code>s</code>".)
<p/>
Of the affected paragraphs, <code>resize()</code> and <code>erase()</code> are the most important to fix because they should forbid 
reallocation during trimming.
</p>

<p>Resolved by the adoption of <a href="https://wg21.link/P1148">P1148</a> in San Diego.</p>


<p id="res-2318"><b>Proposed resolution:</b></p>





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