Folk,<div><br></div><div>I have an object which serves as a header to a &quot;page&quot; of memory which I serialize by simply writing out.  I deserialize by reading the page and then doing a bit of fixup.  I do this for performance (no copies other than the I/O in both directions).  The header has an intrusive list pointer.  </div>

<div><br></div><div>When I reload the page, I must clear the header from the intrusive list.  The page has  been relocated (it may not be in the same physical location as it was when it was written).  Thus, a simple unlink does not work.  I was unable to figure out how to re-init the pointer when I had a base_hook.  So, I switched to a member hook supposing that I could simply clear the contents of the hook (violating the abstraction) on the reload.  </div>

<div><br></div><div>Unfortunately, the headers are members of a hierarchy.  The member_hook is defined in the base class and it is used in a subclass.  I abstracted the problem into the following code:</div><div><br></div>

<div><div>#include &lt;boost/intrusive/list.hpp&gt;</div><div><br></div><div>class Foo {</div><div>    public:</div><div>        boost::intrusive::list_member_hook&lt;&gt; hook_;</div><div>};</div><div><br></div><div>class Bar : public Foo {</div>

<div>    public:</div><div>        int x;</div><div>};</div><div><br></div><div>class BigMess {</div><div><br></div><div>    typedef boost::intrusive::member_hook&lt;Bar, boost::intrusive::list_member_hook&lt;&gt;, &amp;Bar::hook_&gt; mho;</div>

<div>    typedef boost::intrusive::list&lt;Bar, mho&gt; BarList;</div><div><br></div><div>    BarList list;</div><div><br></div><div>};</div></div><div><br></div><div>This fails to compile using g++ (GCC) 4.4.0 on centos 2.6.18-128.1.16.el5 with:</div>

<div><br></div><div><div>foo.cpp:15: error: could not convert template argument ‘&amp;Foo::hook_’ to ‘boost::intrusive::list_member_hook&lt;&gt; Bar::*’</div></div><div><br></div><div>Clearly, the type of the base class is taken to not be compatible with the subclass.  It is not clear why, however.</div>

<div><br></div><div>Any thoughts would be appreciated as to how to either fix the inheritance problem or how to clear the base_hook case (which does compile and runs, by the way :-)</div><div><br></div><div>Thanks</div><div>

<br></div><div>-steve</div><div><br></div>