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    CWG Issue 2271</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="2271"></A><H4>2271.
  
Aliasing <TT>this</TT>
</H4>
<B>Section: </B>11.4.5&#160; [<A href="https://wg21.link/class.ctor">class.ctor</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++17
 &#160;&#160;&#160;

 <B>Submitter: </B>Richard Smith
 &#160;&#160;&#160;

 <B>Date: </B>2016-06-20<BR>


<P>[Moved to DR at the November, 2016 meeting.]</P>

<P>The restrictions against aliasing <TT>this</TT> inside a constructor
should apply to all objects, not just to const objects.</P>

<P><B>Proposed resolution (June, 2016):</B></P>

<P>Change 11.4.5 [<A href="https://wg21.link/class.ctor#12">class.ctor</A>] paragraph 12 as follows:</P>

<BLOCKQUOTE>

<P>During the construction of <DEL>a <TT>const</TT></DEL> <INS>an</INS>
object, if the value of the object or any of its subobjects is accessed
through a glvalue that is not obtained, directly or indirectly, from the
constructor's <TT>this</TT> pointer, the value of the object or subobject
thus obtained is unspecified. [<I>Example:</I>
</P>

<PRE>
  struct C;
  void no_opt(C*);

  struct C {
    int c;
    C() : c(0) { no_opt(this); }
  };

  const C cobj;

  void no_opt(C* cptr) {
    int i = cobj.c * 100; //<SPAN CLASS="cmnt"> value of </SPAN>cobj.c<SPAN CLASS="cmnt"> is unspecified</SPAN>
    cptr-&gt;c = 1;
    cout &lt;&lt; cobj.c * 100  //<SPAN CLASS="cmnt"> value of </SPAN>cobj.c<SPAN CLASS="cmnt"> is unspecified</SPAN>
         &lt;&lt; '\n';
  }

<INS>  extern struct D d;
  struct D {
    D(int a) : a(a), b(d.a) {}
    int a, b;
  };
  D d = D(1);             //<SPAN CLASS="cmnt"> value of </SPAN>d.b<SPAN CLASS="cmnt"> is unspecified</SPAN></INS>
</PRE>

<P>&#8212;<I>end example</I>]</P>

</BLOCKQUOTE>

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