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POHow does an exception specification affect virtual destructor overriding?
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  1. POHow does an exception specification affect virtual destructor overriding?
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    copied!<p>The C++ Standard states the following about virtual functions that have exception specifications:</p> <blockquote> <p>If a virtual function has an <em>exception-specification</em>, all declarations, including the definition, of any function that overrides that virtual function in any derived class shall only allow exceptions that are allowed by the <em>exception-specification</em> of the base class virtual function (C++03 §15.4/3).</p> </blockquote> <p>Thus, the following is ill-formed:</p> <pre><code>struct B { virtual void f() throw() { } // allows no exceptions }; struct D : B { virtual void f() { } // allows all exceptions }; </code></pre> <p>(1) Does this rule apply to destructors? That is, is the following well-formed? </p> <pre><code>struct B { virtual ~B() throw() { } }; struct D : B { virtual ~D() { } }; </code></pre> <p>(2) How does this rule apply to an implicitly declared destructor? That is, is the following well-formed?</p> <pre><code>struct B { virtual ~B() throw() { } }; struct D : B { // ~D() implicitly declared }; </code></pre> <p>While in the general case one should <a href="http://www.gotw.ca/publications/mill22.htm" rel="noreferrer">never write an exception specification</a>, this question has practical implications because the <code>std::exception</code> destructor is virtual and has an empty exception specification.</p> <p>Since it is good practice not to allow an exception to be thrown from a destructor, let's assume for the sake of simplifying any examples that a destructor either allows all exceptions (that is, it has no exception specification) or it allows no exceptions (that is, it has an empty exception specification).</p>
 

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