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    CWG Issue 2921</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="2921"></A><H4>2921.
  
Exporting redeclarations of entities not attached to a named module
</H4>
<B>Section: </B>10.2&#160; [<A href="https://wg21.link/module.interface">module.interface</A>]
 &#160;&#160;&#160;

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

 <B>Submitter: </B>Tomasz Kami&#324;ski
 &#160;&#160;&#160;

 <B>Date: </B>2024-06-20<BR>


<P>[Accepted as a DR at the November, 2024 meeting.]</P>



<P>Consider:</P>

<PRE>
  export module mod;
  extern "C++" void func();
  export extern "C++" {
    void func();
  }
</PRE>

<P>Per 10.2 [<A href="https://wg21.link/module.interface#6">module.interface</A>] paragraph 6, this is currently
ill-formed, but implementation treatment varies and there seems to be
little rationale why this should be ill-formed for entities not
attached to a named module.</P>

<P>The rule also makes the following example ill-formed, which was
intended to be well-formed:</P>

<PRE>
  export module M;
  namespace N { //<SPAN CLASS="cmnt"> external linkage, attached to global module, not exported</SPAN>
    void f();
  }
  namespace N { //<SPAN CLASS="cmnt"> error: exported namespace, redeclares non-exported namespace</SPAN>
    export void g();
  }
</PRE>

<P>The mental model here is that for an entity not attached to a named
module, exportedness is not a meaningful property of that entity.</P>

<P><B>Proposed resolution (approved by CWG 2024-08-16):</B></P>

<P>Change in 10.2 [<A href="https://wg21.link/module.interface#6">module.interface</A>] paragraph 6 as follows:</P>

<BLOCKQUOTE>

A redeclaration of an entity X is implicitly exported if X was
introduced by an exported declaration; otherwise it shall not be
exported <INS>if it is attached to a named module</INS>.

</BLOCKQUOTE>

<P><B>Additional notes (January, 2025)</B></P>

<P>Partially reverted in <A HREF="2990.html">issue 2990</A>.</P>

<BR><BR>
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