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    CWG Issue 1240</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="1240"></A><H4>1240.
  
<TT>constexpr</TT> defaulted constructors
</H4>
<B>Section: </B>9.3.2&#160; [<A href="https://wg21.link/dcl.name">dcl.name</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++11
 &#160;&#160;&#160;

 <B>Submitter: </B>Jens Maurer
 &#160;&#160;&#160;

 <B>Date: </B>2011-02-02<BR>


<P>[Voted into the WP at the March, 2011 meeting.]</P>

<P>
<A HREF="1199.html">Issue 1199</A> proposes to add the capability
of defining a <TT>constexpr</TT> special function as deleted.  It
would be similarly useful to be able to mark a defaulted constructor
as <TT>constexpr</TT>.  (It should be noted that the existing text of
11.4.5 [<A href="https://wg21.link/class.ctor">class.ctor</A>] and the proposed resolution of
<A HREF="1224.html">issue 1224</A> already allow for implicitly-defined
constructors to be implicitly <TT>constexpr</TT>; this issue simply
proposes allowing the explicit use of the <TT>constexpr</TT>
specifier.)</P>

<P><B>Proposed resolution (February, 2011):</B></P>

<OL>
<LI><P>Change 9.2.6 [<A href="https://wg21.link/dcl.constexpr#3">dcl.constexpr</A>] paragraph 3 as follows:</P></LI>

<BLOCKQUOTE>

<UL>
<LI><P>...</P></LI>

<LI>
<P>its <I>function-body</I> shall be <TT>= delete</TT><INS>, <TT>=
default</TT>,</INS> or a <I>compound-statement</I> of the form</P>

<PRE>
  { return <I>expression</I> ; }
</PRE>

</LI>

<LI><P>...</P></LI>

</UL>

</BLOCKQUOTE>

<LI><P>Change 9.2.6 [<A href="https://wg21.link/dcl.constexpr#4">dcl.constexpr</A>] paragraph 4 as follows:</P></LI>

<BLOCKQUOTE>

<P>In the definition of a <TT>constexpr</TT> constructor, each of the
parameter types shall be a literal type or a reference to a literal
type.  In addition, either its <I>function-body</I> shall be <TT>=
delete</TT> <INS>or <TT>= default</TT></INS> or it shall satisfy the
following constraints:</P>

<UL>
<LI><P>...</P></LI>

</UL>

<P><DEL>A trivial copy/move constructor is also a <TT>constexpr</TT>
constructor.</DEL></P>

</BLOCKQUOTE>

</OL>

<I>[Note: this resolution assumes that the changes for
<A HREF="1199.html">issue 1199</A> have been applied.]</I>

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