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    CWG Issue 2624</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="2624"></A><H4>2624.
  
Array delete expression with no array cookie
</H4>
<B>Section: </B>7.6.2.9&#160; [<A href="https://wg21.link/expr.delete">expr.delete</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++23
 &#160;&#160;&#160;

 <B>Submitter: </B>Blacktea Hamburger
 &#160;&#160;&#160;

 <B>Date: </B>2022-08-22<BR>


<P>[Accepted as a DR at the November, 2022 meeting.]</P>

<P>Consider:</P>

<PRE>
char *p = static_cast&lt;char*&gt;(operator new[](2));
p = new (p) char[2];  // #1
delete[] p;           // #2
</PRE>

<P>Subclause 7.6.2.8 [<A href="https://wg21.link/expr.new#16">expr.new</A>] paragraph 16 specifies:</P>

<BLOCKQUOTE>

... When a <I>new-expression</I> calls an allocation function and that
allocation has not been extended, the <I>new-expression</I> passes the
amount of space requested to the allocation function as the first
argument of type std::size_t. That argument shall be no less than the
size of the object being created; it may be greater than the size of
the object being created only if the object is an array and the
allocation function is not a non-allocating form
(17.6.3.4 [<A href="https://wg21.link/new.delete.placement">new.delete.placement</A>]). ...

</BLOCKQUOTE>

<P>Subclause 7.6.2.9 [<A href="https://wg21.link/expr.delete#2">expr.delete</A>] paragraph 2 specifies:</P>

<BLOCKQUOTE>

... In an array delete expression, the value of the operand
of <TT>delete</TT> may be a null pointer value or a pointer value that
resulted from a previous array <I>new-expression</I>. [ Footnote:
... ]  If not, the behavior is undefined.

</BLOCKQUOTE>

<P>The non-allocating form of the <I>new-expression</I> at #1 is
constrained not to place an array cookie at the start of the array.
Yet, the array delete appears to be expected to divine that fact.</P>

<P><B>Proposed resolution (approved by CWG 2022-10-07):</B></P>

<P>Change in 7.6.2.9 [<A href="https://wg21.link/expr.delete#2">expr.delete</A>] paragraph 2 as follows:</P>

<BLOCKQUOTE>

... In an array delete expression, the value of the operand
of <TT>delete</TT> may be a null pointer value or a pointer value that
resulted from a previous array <I>new-expression</I> <INS>whose
allocation function was not a non-allocating form
(17.6.3.4 [<A href="https://wg21.link/new.delete.placement">new.delete.placement</A>])</INS>. [ Footnote: ... ]  If not, the
behavior is undefined.

</BLOCKQUOTE>

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