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<title>Issue 331: bad declaration of destructor for ios_base::failure</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="331"><a href="lwg-defects.html#331">331</a>. bad declaration of destructor for ios_base::failure</h3>
<p><b>Section:</b> 31.5.2.2.1 <a href="https://wg21.link/ios.failure">[ios.failure]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> PremAnand M. Rao <b>Opened:</b> 2001-08-23 <b>Last modified:</b> 2021-06-06</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#ios.failure">issues</a> in [ios.failure].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>
With the change in 16.4.6.14 <a href="https://wg21.link/res.on.exception.handling">[res.on.exception.handling]</a> to state
   "An implementation may strengthen the exception-specification for a
    non-virtual function by removing listed exceptions."
(issue <a href="lwg-defects.html#119" title="Should virtual functions be allowed to strengthen the exception specification? (Status: TC1)">119</a><sup><a href="https://cplusplus.github.io/LWG/issue119" title="Latest snapshot">(i)</a></sup>)
and the following declaration of ~failure() in ios_base::failure
</p>
<pre>
    namespace std {
       class ios_base::failure : public exception {
       public:
           ...
           virtual ~failure();
           ...
       };
     }
</pre>
<p>the class failure cannot be implemented since in 17.7.3 <a href="https://wg21.link/type.info">[type.info]</a> the destructor of class exception has an empty
exception specification:</p>
<pre>
    namespace std {
       class exception {
       public:
         ...
         virtual ~exception() throw();
         ...
       };
     }
</pre>


<p id="res-331"><b>Proposed resolution:</b></p>
<p>Remove the declaration of ~failure().</p>


<p><b>Rationale:</b></p>
<p>The proposed resolution is consistent with the way that destructors
of other classes derived from <code>exception</code> are handled.</p>






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