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<title>Issue 169: Bad efficiency of overflow() mandated</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#TC1">TC1</a> status.</em></p>
<h3 id="169"><a href="lwg-defects.html#169">169</a>. Bad efficiency of <code>overflow()</code> mandated</h3>
<p><b>Section:</b> 31.8.2.5 <a href="https://wg21.link/stringbuf.virtuals">[stringbuf.virtuals]</a> <b>Status:</b> <a href="lwg-active.html#TC1">TC1</a>
 <b>Submitter:</b> Dietmar K&uuml;hl <b>Opened:</b> 1999-07-20 <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#stringbuf.virtuals">active issues</a> in [stringbuf.virtuals].</p>
<p><b>View all other</b> <a href="lwg-index.html#stringbuf.virtuals">issues</a> in [stringbuf.virtuals].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#TC1">TC1</a> status.</p>
<p><b>Discussion:</b></p>
<p>Paragraph 8, Notes, of this section seems to mandate an extremely
inefficient way of buffer handling for <code>basic_stringbuf</code>,
especially in view of the restriction that <code>basic_ostream</code>
member functions are not allowed to use <code>xsputn()</code> (see 31.7.6.2 <a href="https://wg21.link/ostream">[ostream]</a>): For each character to be inserted, a new buffer
is to be created.</p> 
<p>Of course, the resolution below requires some handling of
simultaneous input and output since it is no longer possible to update
<code>egptr()</code> whenever <code>epptr()</code> is changed. A possible
solution is to handle this in <code>underflow()</code>.</p>


<p id="res-169"><b>Proposed resolution:</b></p>
<p>In 31.8.2.5 <a href="https://wg21.link/stringbuf.virtuals">[stringbuf.virtuals]</a> paragraph 8, Notes, insert the words
&quot;at least&quot; as in the following:</p>
<blockquote>
  <p>To make a write position available, the function reallocates (or initially
  allocates) an array object with a sufficient number of elements to hold the
  current array object (if any), plus <b>at least</b> one additional write
  position.</p>
</blockquote>




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