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<title>Issue 564: stringbuf seekpos underspecified</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="564"><a href="lwg-defects.html#564">564</a>. <code>stringbuf</code> seekpos underspecified</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#C++11">C++11</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2006-02-23 <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#C++11">C++11</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The   effects  of  the   <code>seekpos()</code>  member   function  of
<code>basic_stringbuf</code>  simply say  that the  function positions
the  input and/or  output  sequences  but fail  to  spell out  exactly
how. This is in contrast  to the detail in which <code>seekoff()</code>
is described.
</p>

<p><i>[
2009-07 Frankfurt
]</i></p>


<blockquote><p>
Move to Ready.
</p></blockquote>



<p id="res-564"><b>Proposed resolution:</b></p>
        <p>

Change 27.7.1.3, p13 to read:

        </p>
<blockquote>
<p>
-13- <i>Effects:</i> <ins>Equivalent to <code>seekoff(off_type(<i>sp</i>), ios_base::beg,
<i>which</i>)</code>.</ins> <del>Alters the stream position within the controlled sequences,
if possible, to correspond to the stream position stored in <code><i>sp</i></code>
(as described below).</del>
</p>
<ul>
<li><del>If <code>(<i>which</i> &amp; ios_base::in) != 0</code>, positions the input sequence.</del></li>
<li><del>If <code>(<i>which</i> &amp; ios_base::out) != 0</code>, positions the output sequence.</del></li>
<li><del>If <code><i>sp</i></code> is an invalid stream position, or if the function
positions neither sequence, the positioning operation fails. If <code><i>sp</i></code>
has not been obtained by a previous successful call to one of the positioning
functions (<code>seekoff</code>, <code>seekpos</code>, <code>tellg</code>, <code>tellp</code>)
the effect is undefined.</del></li>
</ul>
</blockquote>


<p><i>[
Kona (2007): A <code>pos_type</code> is a position in a stream by
definition, so there is no ambiguity as to what it means. Proposed
Disposition: NAD
]</i></p>


<p><i>[
Post-Kona Martin adds:
I'm afraid I disagree
with the Kona '07 rationale for marking it NAD. The only text
that describes precisely what it means to position the input
or output sequence is in <code>seekoff()</code>. The <code>seekpos()</code> Effects
clause is inadequate in comparison and the proposed resolution
plugs the hole by specifying <code>seekpos()</code> in terms of <code>seekoff()</code>.
]</i></p>





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