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<title>Issue 366: Excessive const-qualification</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#NAD">NAD</a> status.</em></p>
<h3 id="366"><a href="lwg-closed.html#366">366</a>. Excessive const-qualification</h3>
<p><b>Section:</b> 31 <a href="https://wg21.link/input.output">[input.output]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Walter Brown, Marc Paterno <b>Opened:</b> 2002-05-10 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#input.output">issues</a> in [input.output].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The following member functions are declared const, yet return non-const
pointers. We believe they are should be changed, because they allow code
that may surprise the user. See document N1360 for details and
rationale.
</p>

<p><i>[Santa Cruz: the real issue is that we've got const member
functions that return pointers to non-const, and N1360 proposes
replacing them by overloaded pairs.  There isn't a consensus about
whether this is a real issue, since we've never said what our
constness policy is for iostreams.  N1360 relies on a distinction
between physical constness and logical constness; that distinction, or
those terms, does not appear in the standard.]</i></p>




<p id="res-366"><b>Proposed resolution:</b></p>
<p>In 27.4.4 and 27.4.4.2</p>
<p>Replace</p>
<pre>
  basic_ostream&lt;charT,traits&gt;* tie() const;
</pre>
<p>with</p>
<pre>
  basic_ostream&lt;charT,traits&gt;* tie();
  const basic_ostream&lt;charT,traits&gt;* tie() const;
</pre>

<p>and replace</p>
<pre>
  basic_streambuf&lt;charT,traits&gt;* rdbuf() const;
</pre>
<p>with</p>
<pre>
  basic_streambuf&lt;charT,traits&gt;* rdbuf();
  const basic_streambuf&lt;charT,traits&gt;* rdbuf() const;
</pre>

<p>In 27.5.2 and 27.5.2.3.1</p>
<p>Replace</p>
<pre>
  char_type* eback() const;
</pre>
<p>with</p>
<pre>
  char_type* eback();
  const char_type* eback() const;
</pre>

<p>Replace</p>
<pre>
  char_type gptr() const;
</pre>
<p>with</p>
<pre>
  char_type* gptr();
  const char_type* gptr() const;
</pre>

<p>Replace</p>
<pre>
  char_type* egptr() const;
</pre>
<p>with</p>
<pre>
  char_type* egptr();
  const char_type* egptr() const;
</pre>

<p>In 27.5.2 and 27.5.2.3.2</p>
<p>Replace</p>
<pre>
  char_type* pbase() const;
</pre>
<p>with</p>
<pre>
  char_type* pbase();
  const char_type* pbase() const;
</pre>

<p>Replace</p>
<pre>
  char_type* pptr() const;
</pre>
<p>with</p>
<pre>
  char_type* pptr();
  const char_type* pptr() const;
</pre>

<p>Replace</p>
<pre>
  char_type* epptr() const;
</pre>
<p>with</p>
<pre>
  char_type* epptr();
  const char_type* epptr() const;
</pre>

<p>In 27.7.2, 27.7.2.2, 27.7.3 27.7.3.2, 27.7.4, and 27.7.6</p>
<p>Replace</p>
<pre>
  basic_stringbuf&lt;charT,traits,Allocator&gt;* rdbuf() const;
</pre>
<p>with</p>
<pre>
  basic_stringbuf&lt;charT,traits,Allocator&gt;* rdbuf();
  const basic_stringbuf&lt;charT,traits,Allocator&gt;* rdbuf() const;
</pre>

<p>In  27.8.1.5, 27.8.1.7, 27.8.1.8, 27.8.1.10, 27.8.1.11, and 27.8.1.13</p>
<p>Replace</p>
<pre>
  basic_filebuf&lt;charT,traits&gt;* rdbuf() const;
</pre>
<p>with</p>
<pre>
  basic_filebuf&lt;charT,traits&gt;* rdbuf();
  const basic_filebuf&lt;charT,traits&gt;* rdbuf() const;
</pre>


<p><b>Rationale:</b></p>
<p>The existing specification is a bit sloppy, but there's no
  particular reason to change this other than tidiness, and there are
  a number of ways in which streams might have been designed
  differently if we were starting today.  There's no evidence that the
  existing constness policy is harming users.  We might consider
  a different constness policy as part of a full stream redesign.</p>





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