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    CWG Issue 1997</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="1997"></A><H4>1997.
  
Placement new and previous initialization
</H4>
<B>Section: </B>6.8.5&#160; [<A href="https://wg21.link/basic.indet">basic.indet</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD7
 &#160;&#160;&#160;

 <B>Submitter: </B>Jason Merrill
 &#160;&#160;&#160;

 <B>Date: </B>2014-09-08<BR>




<P>Given the following example,</P>

<PRE>
  #include &lt;new&gt;

  int main() {
    unsigned char buf[sizeof(int)] = {};
    int *ip = new (buf) int;
    return *ip; //<SPAN CLASS="cmnt"> </SPAN>0<SPAN CLASS="cmnt"> or undefined?</SPAN>
  }
</PRE>

<P>Should the preceding initializsation of the buffer carry over to
the value of <TT>*ip</TT>?  According to 6.8.5 [<A href="https://wg21.link/basic.indet#1">basic.indet</A>] paragraph 1,
</P>

<BLOCKQUOTE>

When storage for an object with automatic or dynamic storage
duration is obtained, the object has an <I>indeterminate value</I>,
and if no initialization is performed for the object, that
object retains an indeterminate value until that value is
replaced (7.6.19 [<A href="https://wg21.link/expr.assign">expr.assign</A>]).

</BLOCKQUOTE>

<P>In this case, no new storage is being obtained for the
<TT>int</TT> object created by the <I>new-expression</I>.</P>

<P><B>Additional notes (August, 2024)</B></P>

<P>According to the resolution of <A HREF="2721.html">issue 2721</A>, storage for the elements of <TT>buf</TT> is considered
reused and thus the lifetime of those elements ends when the
allocation function returns.  Out-of-lifetime objects cannot hold
values.</P>

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