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    CWG Issue 438</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="438"></A><H4>438.
  
Possible flaw in wording for multiple accesses to object between sequence points
</H4>
<B>Section: </B>Clause 7&#160; [<A href="https://wg21.link/expr">expr</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>29 Oct 2003<BR>


<P>Lisa Lippincott mentioned this case to me:</P>
<PRE>
  A[0] = 0;
  A[A[0]] = 1;
</PRE>
<P>This seems to use the old value of A[0] other than to calculate the new
value, which is said to be undefined, but it also seems reasonable, since
the old value is used in order to select the object to modify, so there's
no ordering ambiguity.</P>

<P>
<U>Steve Adamczyk</U>: the ordering rule referred to is in
Clause 7 [<A href="https://wg21.link/expr#4">expr</A>] paragraph 4.</P>

<P><B>Notes from the March 2004 meeting:</B></P>

<P>Clark Nelson mentions that the C committee may have done something on
this.</P>

<P><B>Note (July, 2009):</B></P>

<P>This issue was resolved by the adoption of the &#8220;sequenced
before&#8221; wording.</P>

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