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    CWG Issue 2552</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="2552"></A><H4>2552.
  
Constant evaluation of non-defining variable declarations
</H4>
<B>Section: </B>7.7&#160; [<A href="https://wg21.link/expr.const">expr.const</A>]
 &#160;&#160;&#160;

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

 <B>Submitter: </B>Hubert Tong
 &#160;&#160;&#160;

 <B>Date: </B>2022-03-21<BR>


<P>[Accepted as a DR at the June, 2023 meeting.]</P>

<P>Paper
<A HREF="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2242r3.html">P2242</A>
(Non-literal variables (and labels and gotos) in constexpr functions)
added 7.7 [<A href="https://wg21.link/expr.const#5.2">expr.const</A>] bullet 5.2:</P>

<BLOCKQUOTE>

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<LI>
a control flow that passes through a declaration of a variable with
static (6.8.6.2 [<A href="https://wg21.link/basic.stc.static">basic.stc.static</A>]) or thread
(6.8.6.3 [<A href="https://wg21.link/basic.stc.thread">basic.stc.thread</A>]) storage duration;
</LI>
</UL>

</BLOCKQUOTE>

<P>It seems that block-scope extern (i.e. non-defining) declarations
are covered by the above bullet, but only definitions should be in
view here.</P>

<P><B>Proposed resolution (approved by CWG 2023-06-15):</B></P>

<OL>
<LI>

<P>Change in 7.7 [<A href="https://wg21.link/expr.const#5.2">expr.const</A>] bullet 5.2 as follows:</P>

<BLOCKQUOTE>

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<LI>
a control flow that passes through a declaration of a <INS>block</INS>
variable <INS>(6.4.3 [<A href="https://wg21.link/basic.scope.block">basic.scope.block</A>])</INS> with static
(6.8.6.2 [<A href="https://wg21.link/basic.stc.static">basic.stc.static</A>]) or thread
(6.8.6.3 [<A href="https://wg21.link/basic.stc.thread">basic.stc.thread</A>]) storage duration;
</LI>
</UL>

</BLOCKQUOTE>
</LI>

</OL>

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