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<title>Issue 460: Default modes missing from basic_fstream member specifications</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#CD1">CD1</a> status.</em></p>
<h3 id="460"><a href="lwg-defects.html#460">460</a>. Default modes missing from basic_fstream member specifications</h3>
<p><b>Section:</b> 31.10 <a href="https://wg21.link/file.streams">[file.streams]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Ben Hutchings <b>Opened:</b> 2004-04-01 <b>Last modified:</b> 2017-06-15</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#file.streams">issues</a> in [file.streams].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The second parameters of the non-default constructor and of the open
member function for basic_fstream, named "mode", are optional
according to the class declaration in 27.8.1.11 [lib.fstream].  The
specifications of these members in 27.8.1.12 [lib.fstream.cons] and
27.8.1.13 lib.fstream.members] disagree with this, though the
constructor declaration has the "explicit" function-specifier implying
that it is intended to be callable with one argument.
</p>


<p id="res-460"><b>Proposed resolution:</b></p>
<p>In 31.10.6.2 <a href="https://wg21.link/fstream.cons">[fstream.cons]</a>, change</p>
<pre>
  explicit basic_fstream(const char* s, ios_base::openmode mode); 
</pre>
<p>to</p>
<pre>
  explicit basic_fstream(const char* s,
                         ios_base::openmode mode = ios_base::in|ios_base::out);
</pre>
<p>In 31.10.6.4 <a href="https://wg21.link/fstream.members">[fstream.members]</a>, change</p>
<pre>
  void open(const char*s, ios_base::openmode mode); 
</pre>
<p>to</p>
<pre>
  void open(const char*s,
            ios_base::openmode mode = ios_base::in|ios_base::out);
</pre>





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