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    CWG Issue 1282</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="1282"></A><H4>1282.
  
Underspecified destructor <I>exception-specification</I>
</H4>
<B>Section: </B>14.5&#160; [<A href="https://wg21.link/except.spec">except.spec</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD3
 &#160;&#160;&#160;

 <B>Submitter: </B>Daniel Kr&#252;gler
 &#160;&#160;&#160;

 <B>Date: </B>2011-03-28<BR>


<P>[Voted into the WP at the February, 2012 meeting;
moved to DR at the October, 2012 meeting.]</P>



<P>It is not clear whether the unexpected handler will be invoked in
the following example:</P>

<PRE>
  #include &lt;iostream&gt;
  #include &lt;exception&gt;

  struct A { ~A() throw() { } };
  struct B { ~B() noexcept { } };
  struct C : A, B { ~C() { throw 0; } };

  void unexpected_observer() {
   std::cerr &lt;&lt; "unexpected called" &lt;&lt; std::endl;
   std::terminate();
  }

  int main() {
   std::set_unexpected(unexpected_observer);
   C c;
  }

</PRE>

<P>The problem is 14.5 [<A href="https://wg21.link/except.spec#14">except.spec</A>] paragraph 14 only says that
the <I>exception-specification</I> of <TT>C::~C</TT> &#8220;shall allow
no exceptions,&#8221; which could mean either <TT>throw()</TT> or
<TT>noexcept(true)</TT>.</P>

<P><B>Proposed resolution (August, 2011):</B></P>

<P>Change 14.5 [<A href="https://wg21.link/except.spec#14">except.spec</A>] paragraph 14 as follows:</P>

<BLOCKQUOTE>

<P>An implicitly declared special member function (11.4.4 [<A href="https://wg21.link/special">special</A>]) <DEL>shall have</DEL> <INS>has</INS> an
<I>exception-specification</I>.  If <TT>f</TT> is an implicitly
declared default constructor, copy constructor, move constructor,
destructor, copy assignment operator, or move assignment operator, its
implicit <I>exception-specification</I> specifies the <I>type-id</I> <TT>T</TT>
if and only if <TT>T</TT> is allowed by the
<I>exception-specification</I> of a function directly invoked by
<TT>f</TT>'s implicit definition; <TT>f</TT> <DEL>shall allow</DEL>
<INS>allows</INS> all exceptions if any function it directly invokes
allows all exceptions, and <TT>f</TT> <DEL>shall allow no
exceptions</DEL> <INS>has the <I>exception-specification</I>
<TT>noexcept(true)</TT></INS> if every function it directly invokes
allows no exceptions. [<I>Example:</I>
</P>

<PRE>
  struct A {
    A();
    A(const A&amp;) throw();
    A(A&amp;&amp;) throw();
    ~A() throw(X);
  };
  struct B {
    B() throw();
    B(const B&amp;) throw();
    B(B&amp;&amp;) throw(Y);
    ~B() throw(Y);
  };
  struct D : public A, public B {
      //<SPAN CLASS="cmnt"> Implicit declaration of </SPAN>D::D();
      //<SPAN CLASS="cmnt"> Implicit declaration of </SPAN>D::D(const D&amp;) <DEL>throw()</DEL> <INS>noexcept(true)</INS>;
      //<SPAN CLASS="cmnt"> Implicit declaration of </SPAN>D::D(D&amp;&amp;) throw(Y);
      //<SPAN CLASS="cmnt"> Implicit declaration of </SPAN>D::~D() throw(X, Y);
  };
</PRE>

<P>Furthermore, if...</P>

</BLOCKQUOTE>

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