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    CWG Issue 2613</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="2613"></A><H4>2613.
  
Incomplete definition of resumer
</H4>
<B>Section: </B>9.6.4&#160; [<A href="https://wg21.link/dcl.fct.def.coroutine">dcl.fct.def.coroutine</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++23
 &#160;&#160;&#160;

 <B>Submitter: </B>Jim X
 &#160;&#160;&#160;

 <B>Date: </B>2022-02-15<BR>


<P>[Accepted as a DR at the November, 2022 meeting.]</P>

<P>Subclause 9.6.4 [<A href="https://wg21.link/dcl.fct.def.coroutine#8">dcl.fct.def.coroutine</A>] paragraph 8 specifies:</P>

<BLOCKQUOTE>

A suspended coroutine can be resumed to continue execution by invoking
a resumption member function (17.13.4.6 [<A href="https://wg21.link/coroutine.handle.resumption">coroutine.handle.resumption</A>]) of a
coroutine handle (17.13.4 [<A href="https://wg21.link/coroutine.handle">coroutine.handle</A>]) that refers to the
coroutine. The function that invoked a resumption member function is
called the <I>resumer</I>.

</BLOCKQUOTE>

<P>However, non-functions can also resume a coroutine, for example:</P>

<PRE>
Task task() {
  std::cout &lt;&lt; "in task\n";
  int r = co_await Line();
  std::cout &lt;&lt; "resumed\n";
  co_return r;
}
auto r = task();
auto c = (r.coro_.resume(), 0); //<SPAN CLASS="cmnt"> #1</SPAN>
</PRE>

<P><B>Proposed resolution (approved by CWG 2022-08-26):</B></P>

<P>Change in 9.6.4 [<A href="https://wg21.link/dcl.fct.def.coroutine#8">dcl.fct.def.coroutine</A>] paragraph 8 as follows:</P>

<BLOCKQUOTE>

A suspended coroutine can be resumed to continue execution by invoking
a resumption member function (17.13.4.6 [<A href="https://wg21.link/coroutine.handle.resumption">coroutine.handle.resumption</A>]) of a
coroutine handle (17.13.4 [<A href="https://wg21.link/coroutine.handle">coroutine.handle</A>]) that refers to the
coroutine. The <DEL>function</DEL> <INS>evaluation</INS> that invoked a
resumption member function is called the <I>resumer</I>.

</BLOCKQUOTE>

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