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    CWG Issue 499</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="499"></A><H4>499.
  
Throwing an array of unknown size
</H4>
<B>Section: </B>14.2&#160; [<A href="https://wg21.link/except.throw">except.throw</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD2
 &#160;&#160;&#160;

 <B>Submitter: </B>Mike Miller
 &#160;&#160;&#160;

 <B>Date: </B>19 Jan 2005<BR>


<P>[Voted into the WP at the March, 2009 meeting.]</P>

<P>According to 14.2 [<A href="https://wg21.link/except.throw#3">except.throw</A>] paragraph 3,</P>

<BLOCKQUOTE>

The type of the <I>throw-expression</I> shall not be an incomplete
type, or a pointer to an incomplete type other than (possibly
cv-qualified) <TT>void</TT>.

</BLOCKQUOTE>

<P>This disallows cases like the following, because <TT>str</TT> has
an incomplete type (an array of unknown size):</P>

<PRE>
    extern const char str[];
    void f() {
        throw str;
    }
</PRE>

<P>The array-to-pointer conversion is applied to the operand of
<TT>throw</TT>, so there's no problem creating the exception object,
which is the reason for the restriction on incomplete types.  I
believe this case should be permitted.</P>

<P><B>Notes from the April, 2005 meeting:</B></P>

<P>The CWG agreed that the example should be permitted.  Note
that the reference to <I>throw-expression</I> in the cited text
is incorrect; a <I>throw-expression</I> includes the <TT>throw</TT>
keyword and is always of type <TT>void</TT>.  This wording problem
is addressed in the proposed resolution for <A HREF="475.html">issue 475</A>.</P>

<P><B>Proposed resolution (October, 2006)</B></P>

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

<BLOCKQUOTE>

...<DEL>The type of the <I>throw-expression</I> shall not</DEL> <INS>If the type
of the exception object would</INS> be an incomplete type,
or a pointer to an incomplete type other than (possibly cv-qualified)
<TT>void</TT> <INS>the program is ill-formed</INS>...

</BLOCKQUOTE>

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