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    CWG Issue 2387</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="2387"></A><H4>2387.
  
Linkage of const-qualified variable template
</H4>
<B>Section: </B>6.7&#160; [<A href="https://wg21.link/basic.link">basic.link</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD5
 &#160;&#160;&#160;

 <B>Submitter: </B>John Spicer
 &#160;&#160;&#160;

 <B>Date: </B>2018-09-28<BR>


<P>[Accepted as a DR at the February, 2019 meeting.]</P>

<P>The list in 6.7 [<A href="https://wg21.link/basic.link#3">basic.link</A>] paragraph 3 specifying which
entities receive internal linkage does not mention variable templates,
so presumably a variable template has external linkage.
Clause 13 [<A href="https://wg21.link/temp#6">temp</A>] paragraph 6 gives the impression that a
specialization of a template with external linkage also has external
linkage. However, current implementations appear to give internal
linkage to specializations of const-qualified variable templates.
Should const-qualified variable templates have internal linkage?</P>

<P><B>Notes from the December, 2018 teleconference:</B></P>

<P>CWG felt that a <TT>const</TT> type should not affect the
linkage of a variable template or its instances.</P>

<P><B>Proposed resolution (February, 2019):</B></P>

<P>Change 6.7 [<A href="https://wg21.link/basic.link#3">basic.link</A>] paragraph 3 as follows:</P>

<BLOCKQUOTE>

<P>A name having namespace scope (6.4.6 [<A href="https://wg21.link/basic.scope.namespace">basic.scope.namespace</A>])
has internal linkage if it is the name of</P>

<UL>
<LI><P>a variable, <INS>variable template,</INS>
function or function template that is explicitly
declared <TT>static</TT>; or,</P></LI>

<LI><P>a non-inline <INS>non-template</INS>
variable of non-volatile const-qualified
type that is neither explicitly declared <TT>extern</TT> nor
previously declared to have external linkage; or</P></LI>

<LI><P>a data member of an anonymous union.</P></LI>

</UL>

<P><INS>[<I>Note:</I> An instantiated variable template that
has const-qualified type can have external linkage, even if
not declared <TT>extern</TT>. &#8212;<I>end
note</I>]</INS></P>

</BLOCKQUOTE>

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