<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<TITLE>
    CWG Issue 1418</TITLE>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<STYLE TYPE="text/css">
  INS { text-decoration:none; font-weight:bold; background-color:#A0FFA0 }
  .INS { text-decoration:none; background-color:#D0FFD0 }
  DEL { text-decoration:line-through; background-color:#FFA0A0 }
  .DEL { text-decoration:line-through; background-color: #FFD0D0 }
  @media (prefers-color-scheme: dark) {
    HTML { background-color:#202020; color:#f0f0f0; }
    A { color:#5bc0ff; }
    A:visited { color:#c6a8ff; }
    A:hover, a:focus { color:#afd7ff; }
    INS { background-color:#033a16; color:#aff5b4; }
    .INS { background-color: #033a16; }
    DEL { background-color:#67060c; color:#ffdcd7; }
    .DEL { background-color:#67060c; }
  }
  SPAN.cmnt { font-family:Times; font-style:italic }
</STYLE>
</HEAD>
<BODY>
<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="1418"></A><H4>1418.
  
Type of <TT>initializer_list</TT> backing array </H4>
<B>Section: </B>9.5.5&#160; [<A href="https://wg21.link/dcl.init.list">dcl.init.list</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD3
 &#160;&#160;&#160;

 <B>Submitter: </B>Johannes Schaub
 &#160;&#160;&#160;

 <B>Date: </B>2011-11-19<BR>


<P>[Moved to DR at the October, 2012 meeting.]</P>



<P>According to 9.5.5 [<A href="https://wg21.link/dcl.init.list#5">dcl.init.list</A>] paragraph 5, the
elements of the backing array for an object of type
<TT>std::initializer_list&lt;E&gt;</TT> are of type
<TT>E</TT>.  This is contradicted by the wording of
17.11 [<A href="https://wg21.link/support.initlist#2">support.initlist</A>] paragraph 2.</P>

<P><B>Proposed resolution (February, 2012):</B></P>

<P>Change 9.5.5 [<A href="https://wg21.link/dcl.init.list#5">dcl.init.list</A>] paragraph 5 as follows:</P>

<BLOCKQUOTE>

<P>An object of type <TT>std::initializer_list&lt;E&gt;</TT> is
constructed from an initializer list as if the implementation
allocated an array of <I>N</I> elements of type <TT><INS>const</INS>
E</TT>, where <I>N</I> is the number of elements in the initializer
list.  Each element of that array is copy-initialized with the
corresponding element of the initializer list, and the
<TT>std::initializer_list&lt;E&gt;</TT> object is constructed to refer
to that array.  If a narrowing conversion is required to initialize
any of the elements, the program is ill-formed. [<I>Example:</I>
</P>

<PRE>
  struct X {
    X(std::initializer_list&lt;double&gt; v);
  };
  X x{ 1,2,3 };
</PRE>

<P>The initialization will be implemented in a way roughly equivalent
to this:</P>

<PRE>
  <INS>const</INS> double __a[3] = {double{1}, double{2}, double{3}};
  X x(std::initializer_list&lt;double&gt;(__a, __a+3));
</PRE>

<P>assuming that the implementation can construct an initializer_list
object with a pair of pointers. &#8212;<I>end example</I>]</P>

</BLOCKQUOTE>

<BR><BR>
</BODY>
</HTML>
