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    CWG Issue 1751</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="1751"></A><H4>1751.
  
Non-trivial operations vs non-trivial initialization
</H4>
<B>Section: </B>6.8.4&#160; [<A href="https://wg21.link/basic.life">basic.life</A>]
 &#160;&#160;&#160;

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

 <B>Submitter: </B>Nico Josuttis
 &#160;&#160;&#160;

 <B>Date: </B>2013-09-15<BR>


<P>[Moved to DR at the November, 2014 meeting.]</P>



<P>The description of <TT>is_trivially_constructible</TT> in
21.3.6.4 [<A href="https://wg21.link/meta.unary.prop#3">meta.unary.prop</A>] paragraph 3 says,</P>

<BLOCKQUOTE>

<TT>is_constructible&lt;T, Args...&gt;::value</TT> is <TT>true</TT> and the
variable definition for <TT>is_constructible</TT>, as defined below, is
known to call no operation that is not trivial ( 6.9 [<A href="https://wg21.link/basic.types">basic.types</A>],
11.4.4 [<A href="https://wg21.link/special">special</A>]).

</BLOCKQUOTE>

<P>This risks confusion when compared with the wording in
6.8.4 [<A href="https://wg21.link/basic.life#1">basic.life</A>] paragraph 1,</P>

<BLOCKQUOTE>

An object is said to have non-trivial initialization if it is of a class or
aggregate type and it or one of its members is initialized by a constructor
other than a trivial default constructor. [<I>Note:</I> initialization by a
trivial copy/move constructor is non-trivial initialization. &#8212;<I>end
note</I>]

</BLOCKQUOTE>

<P>The latter was written long before &#8220;trivial&#8221; became an
important concept in its own right and uses the term differently from
how it is used elsewhere in the Standard (as evidenced by the note
referring to copy/move construction).  The intent is to capture the
idea that there is some actual initialization occurring; it should
be rephrased to avoid the potential of confusion with the usage of
&#8220;trivial&#8221; elsewhere.</P>

<P><B>Proposed resolution (February, 2014):</B></P>

<P>Change 6.8.4 [<A href="https://wg21.link/basic.life#1">basic.life</A>] paragraph 1 as follows:</P>

<BLOCKQUOTE>

<P>The <I>lifetime</I> of an object is a runtime property of the object. An
object is said to have <DEL>non-trivial
initialization</DEL> <INS><I>non-vacuous initialization</I></INS> if it is
of a class or aggregate type and it or one of its members is initialized by
a constructor other than a trivial default constructor. [<I>Note:</I>
initialization by a trivial copy/move constructor is <DEL>non-trivial</DEL>
<INS>non-vacuous</INS> initialization. &#8212;<I>end note</I>] The lifetime
of an object of type <TT>T</TT> begins when:</P>

<UL>
<LI><P>storage with the proper alignment and size for type <TT>T</TT>
is obtained, and</P></LI>

<LI><P>if the object has <DEL>non-trivial</DEL> <INS>non-vacuous</INS>
initialization, its initialization is complete.</P></LI>

</UL>

<P>The lifetime of an object...</P>

</BLOCKQUOTE>

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