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<title>Issue 581: flush() not unformatted function</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="581"><a href="lwg-defects.html#581">581</a>. <code>flush()</code> not unformatted function</h3>
<p><b>Section:</b> 31.7.6.4 <a href="https://wg21.link/ostream.unformatted">[ostream.unformatted]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2006-06-14 <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#ostream.unformatted">issues</a> in [ostream.unformatted].</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 resolution of issue 60 changed <code>basic_ostream::flush()</code>
so as not  to require it to behave as  an unformatted output function.
That has at least two in my opinion problematic consequences:

        </p>
        <p>

First, <code>flush()</code>  now calls <code>rdbuf()->pubsync()</code>
unconditionally, without  regard to the  state of the stream.  I can't
think of any reason why <code>flush()</code> should behave differently
from the vast majority of stream functions in this respect.

        </p>
        <p>

Second, <code>flush()</code> is not  required to catch exceptions from
<code>pubsync()</code> or set  <code>badbit</code> in response to such
events. That doesn't seem right either, as most other stream functions
do so.

        </p>
    

    <p id="res-581"><b>Proposed resolution:</b></p>
        <p>

I  propose  to revert  the  resolution of  issue  60  with respect  to
<code>flush()</code>. Specifically,  I propose to  change 27.6.2.6, p7
as follows:

        </p>

<p>
Effects: <ins>Behaves as an  unformatted output function (as described
in 27.6.2.6, paragraph 1). </ins>If <code>rdbuf()</code> is not a null
pointer,  <ins>constructs a  sentry  object.  If  this object  returns
<code>true</code> when converted to a  value of type bool the function
</ins>calls <code>rdbuf()->pubsync()</code>.  If that function returns
-1    calls    <code>setstate(badbit)</code>    (which    may    throw
<code>ios_base::failure</code>  (27.4.4.3)).   <ins>Otherwise, if  the
sentry object returns <code>false</code>, does nothing.</ins><del>Does
not  behave  as  an  unformatted  output  function  (as  described  in
27.6.2.6, paragraph 1).</del>
</p>

    

<p><i>[
Kona (2007): Proposed Disposition: Ready
]</i></p>





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