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<title>Issue 1249: basic_ios default ctor</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="1249"><a href="lwg-defects.html#1249">1249</a>. <code>basic_ios</code> default ctor</h3>
<p><b>Section:</b> 31.5.4.2 <a href="https://wg21.link/basic.ios.cons">[basic.ios.cons]</a> <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2009-10-25 <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#basic.ios.cons">issues</a> in [basic.ios.cons].</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 <code>basic_ios</code> default ctor is required to leave the objects members
uninitialized (see below). The paragraph says the object must be
initialized by calling <code>basic_ios::init()</code> before it's destroyed but
I can't find a requirement that it be initialized before calling
any of the class other member functions. Am I not looking in the
right place or that an issue?
</p>

<p><i>[
2009-10-25 Daniel adds:
]</i></p>


<blockquote>
<p>
I agree, that your wording makes that clearer, but suggest to write
</p>

<blockquote><p>
... calling <code>basic_ios::init<del>()</del></code> before ...
</p></blockquote>

<p>
Doing so, I recommend to adapt that of <code>ios_base();</code> as well, where
we have:
</p>

<blockquote><p>
<i>Effects:</i> Each <code>ios_base</code> member has an indeterminate value
after construction. These members shall be initialized by calling
<code>basic_ios::init</code>. If an <code>ios_base</code> object is destroyed
before these initializations have taken place, the behavior is
undefined.
</p></blockquote>
</blockquote>

<p><i>[
Post-Rapperswil:
]</i></p>


<blockquote><p>
Moved to Tentatively Ready after 5 positive votes on c++std-lib.
</p></blockquote>

<p><i>[
Adopted at 2010-11 Batavia
]</i></p>




<p id="res-1249"><b>Proposed resolution:</b></p>
<p>
Change 31.5.2.8 <a href="https://wg21.link/ios.base.cons">[ios.base.cons]</a> p1:
</p>

<blockquote><pre>
ios_base();
</pre>
<blockquote><p>
<i>Effects:</i> Each <code>ios_base</code> member has an indeterminate value
after construction. <del>These</del> <ins>The object's</ins> members shall be initialized by calling
<code>basic_ios::init</code> <ins>before the object's first use or before
 it is destroyed, whichever comes first; otherwise the behavior
 is undefined.</ins>. <del>If an <code>ios_base</code> object is destroyed
before these initializations have taken place, the behavior is
undefined.</del>
</p></blockquote>
</blockquote>

<p>
Change 31.5.4.2 <a href="https://wg21.link/basic.ios.cons">[basic.ios.cons]</a> p2:
</p>

<blockquote><pre>
basic_ios();
</pre>
<blockquote><p>
<i>Effects:</i> Constructs an object of class <code>basic_ios</code>
(27.5.2.7) leaving its member objects uninitialized. The object shall be
initialized by calling <del>its</del>
<code><ins>basic_ios::</ins>init</code> <ins>before its first
use or before it is destroyed, whichever comes first; otherwise the
behavior is undefined.</ins> <del>member function. If it is destroyed
before it has been initialized the behavior is undefined.</del>
</p></blockquote>
</blockquote>





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