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    CWG Issue 2820</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="2820"></A><H4>2820.
  
Value-initialization and default constructors
</H4>
<B>Section: </B>9.5.1&#160; [<A href="https://wg21.link/dcl.init.general">dcl.init.general</A>]
 &#160;&#160;&#160;

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

 <B>Submitter: </B>Shafik Yaghmour
 &#160;&#160;&#160;

 <B>Date: </B>2023-10-31<BR>


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



<P>Subclause 9.5.1 [<A href="https://wg21.link/dcl.init.general#9">dcl.init.general</A>] paragraph 9 specifies:</P>

<BLOCKQUOTE>

To value-initialize an object of type T means:
<UL>
<LI>if T is a (possibly
cv-qualified) class type (Clause Clause 11 [<A href="https://wg21.link/class">class</A>]), then
<UL>
<LI>
if T has either no default constructor
(11.4.5.2 [<A href="https://wg21.link/class.default.ctor">class.default.ctor</A>]) or a default constructor that is
user-provided or deleted, then the object is default-initialized;
</LI>
<LI>
otherwise, the object is zero-initialized and the semantic
constraints for default-initialization are checked, and if T has a
non-trivial default constructor, the object is default-initialized;
</LI>
</UL>
</LI>
<LI>if T is an array type, ...
</LI>
</UL>

</BLOCKQUOTE>

<P>The specification about checking the semantic constraints and
invoking only non-trivial default constructors is overly convoluted.
Omitting a call to a trivial constructor is an as-if optimization that
should not be prescribed by the standard.</P>

<P><B>Proposed resolution (approved by CWG 2024-01-19):</B></P>

<P>Change in 9.5.1 [<A href="https://wg21.link/dcl.init.general#9.1.2">dcl.init.general</A>] bullet 9.1.2 as follows:</P>

<BLOCKQUOTE>

<UL>
<LI>...</LI>
<LI>
otherwise, the object is zero-initialized and <DEL>the semantic
constraints for default-initialization are checked, and if T has a
non-trivial default constructor, the object is</DEL> <INS>then</INS>
default-initialized;
</LI>
</UL>

</BLOCKQUOTE>

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