Topic: Add std::make_shared template specialization for

Author: Andrew Dunn <ANDREW.A.DUNN@leidos.com>
Date: Fri, 10 Oct 2014 15:31:42 +1100 Raw View 
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    At the moment, <tt>std::make_shared</tt> will call the constructor
    of an instance descended from <tt>std::enable_shared_from_this</tt>
    before initialising the self referential <tt>weak_ptr</tt>.<br>
    <br>
    This makes it impossible to use <tt>shared_from_this()</tt> during
    the construction phase of the instance. The use case which I
    encountered is when constructing an instance which has member
    variables that keep a weak reference to the parent instance.<br>
    <br>
    My proposal is to set the self-referential <tt>weak_ptr</tt> before
    calling the constructor. This would allow <tt>shared_from_this()</tt>
    to be used in the constructor.<br>
    <br>
    In pseudocode it would look something like this:<br>
    <br>
    <tt>namespace std</tt><tt><br>
    </tt><tt>{</tt><tt><br>
    </tt><tt>=C2=A0=C2=A0=C2=A0 template &lt;typename T, typename... Params=
&gt;</tt><tt><br>
    </tt><tt>=C2=A0=C2=A0=C2=A0
      enable_if_t&lt;is_base_of&lt;enable_shared_from_this&lt;T&gt;, T
      &gt;::value,<br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 shared_ptr&lt;T&gt; &gt;</tt><tt><br>
    </tt><tt>=C2=A0=C2=A0=C2=A0 make_shared(Params&amp;&amp;... parameters)=
<br>
      =C2=A0=C2=A0=C2=A0 {</tt><tt><br>
    </tt><tt>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 </tt><tt>ALLOCATE M=
EMORY<br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 CREATE SHARED POINTER TO A=
DDRESS<br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 SET SELF-REFERENTIAL WEAK =
POINTER<br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 T(parameters...);<br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 RETURN SHARED POINTER<br>
      =C2=A0=C2=A0=C2=A0 }<br>
    </tt><tt>}</tt><br>
    <br>
    Any thoughts?<br>
    <br>
    <div class=3D"moz-signature">-- <br>
      <b>Andrew Dunn</b></div>
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