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    CWG Issue 210</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="210"></A><H4>210.
  
What is the type matched by an exception handler?
</H4>
<B>Section: </B>14.4&#160; [<A href="https://wg21.link/except.handle">except.handle</A>]
 &#160;&#160;&#160;

 <B>Status: </B>TC1
 &#160;&#160;&#160;

 <B>Submitter: </B>Scott Douglass
 &#160;&#160;&#160;

 <B>Date: </B>6 Mar 2000<BR>



<P>14.4 [<A href="https://wg21.link/except.handle#3">except.handle</A>] paragraph 3 says,</P>

<BLOCKQUOTE>

A <I>handler</I> is a match for a <I>throw-expression</I> with an
object of type <TT>E</TT>...

</BLOCKQUOTE>

<P>This wording leaves it unclear whether it is the dynamic type of the
object being thrown or the static type of the expression that
determines whether a handler is a match for a given exception.  For
instance,</P>

<PRE>
    struct B { B(); virtual ~B(); };
    struct D : B { D(); };
    void toss(const B* b) { throw *b; }
    void f() { const D d; toss(&amp;d); }
</PRE>

<P>In this code, presumably the type to be matched is <TT>B</TT> and not
<TT>const D</TT> (14.2 [<A href="https://wg21.link/except.throw">except.throw</A>]).</P>

<P>
<B>Suggested resolution:</B> Replace the cited wording as follows:</P>

<BLOCKQUOTE>

A <I>handler</I> is a match for a <I>throw-expression</I> which
initialized a temporary (14.2 [<A href="https://wg21.link/except.throw">except.throw</A>]) of type
<TT>E</TT>...

</BLOCKQUOTE>

<P><B>Proposed resolution (10/00):</B></P>

<OL>

<LI>
<P>Change 14.2 [<A href="https://wg21.link/except.throw#3">except.throw</A>] paragraph 3 from</P>

<BLOCKQUOTE>

A <I>throw-expression</I> initializes a temporary object, the type of
which is determined...

</BLOCKQUOTE>

<P>to</P>

<BLOCKQUOTE>

A <I>throw-expression</I> initializes a temporary object, called the
<I>exception object</I>, the type of which is determined...

</BLOCKQUOTE>
</LI>

<LI>
<P>Change 14.4 [<A href="https://wg21.link/except.handle#3">except.handle</A>] paragraph 3 from</P>

<BLOCKQUOTE>

A <I>handler</I> is a match for a <I>throw-expression</I> with an
object of type <TT>E</TT> if...

</BLOCKQUOTE>

<P>to</P>

<BLOCKQUOTE>

A <I>handler</I> is a match for an exception object of type <TT>E</TT>
if...

</BLOCKQUOTE>
</LI>
</OL>

<BR><BR>
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