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    CWG Issue 1978</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="1978"></A><H4>1978.
  
Redundant description of explicit constructor use
</H4>
<B>Section: </B>11.4.8.2&#160; [<A href="https://wg21.link/class.conv.ctor">class.conv.ctor</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD4
 &#160;&#160;&#160;

 <B>Submitter: </B>Geoffrey Romer
 &#160;&#160;&#160;

 <B>Date: </B>2014-07-22<BR>


<P>[Moved to DR at the May, 2015 meeting.]</P>



<P>The conditions under which an <TT>explicit</TT> constructor will
be used are given in 11.4.8.2 [<A href="https://wg21.link/class.conv.ctor#2">class.conv.ctor</A>] paragraph 2:</P>

<BLOCKQUOTE>

An explicit constructor constructs objects just like
non-explicit constructors, but does so only where the
direct-initialization syntax (9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>]) or
where casts (7.6.1.9 [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>],
7.6.3 [<A href="https://wg21.link/expr.cast">expr.cast</A>]) are explicitly used. A default
constructor may be an explicit constructor; such a
constructor will be used to perform default-initialization
or value-initialization (9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>]).

</BLOCKQUOTE>

<P>The existence of this wording in normative text is confusing
and should probably simply say that <TT>explicit</TT> constructors
are used in direct initialization, with cross-references to
9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>] and 12.2.2.5 [<A href="https://wg21.link/over.match.copy">over.match.copy</A>],
possibly as a note.</P>

<P><B>Proposed resolution (April, 2015):</B></P>

<P>Change 11.4.8.2 [<A href="https://wg21.link/class.conv.ctor#2">class.conv.ctor</A>] paragraph 2 as follows:</P>

<BLOCKQUOTE>

<INS>[<I>Note:</I></INS> An explicit constructor constructs
objects just like non-explicit constructors, but does so only
where the direct-initialization syntax (9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>])
or where casts (7.6.1.9 [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>],
7.6.3 [<A href="https://wg21.link/expr.cast">expr.cast</A>]) are explicitly used<INS>; see also
12.2.2.5 [<A href="https://wg21.link/over.match.copy">over.match.copy</A>]</INS>. A default constructor may be
an explicit constructor; such a constructor will be used to
perform default-initialization or value-initialization
(9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>]). [<I>Example:</I> ...  &#8212;<I>end
example</I>] <INS>&#8212;<I>end note</I>]</INS>

</BLOCKQUOTE>

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