Re: [boost] is_virtual_base_of ?

Subject: Re: [boost] is_virtual_base_of ?
From: Daniel Frey (d.frey_at_[hidden])
Date: 2009-03-11 14:02:36

On 11.03.2009, at 19:18, Robert Ramey wrote:

> My current version - checked into the trunk at
> boost/serialization/is_virtual_base_of.hpp is attached.  I think it
> addresses the points mentioned here.
>
> I can fix the case that causes me problems by adding a default  
> constructor
> which is never called.  That doesn't help for the generic case  
> though.  I'm
> guessing that type traits has lots of situations where members are  
> declared
> and never called.

You probably misunderstood the idea, as it is really generic. The idea  
is to add a declaration (without a definition) of X's ctor (or any  
other generated methods that cause you trouble). To be more precise:

Index: boost/serialization/is_virtual_base_of.hpp
===================================================================
--- boost/serialization/is_virtual_base_of.hpp	(revision 51709)
+++ boost/serialization/is_virtual_base_of.hpp	(working copy)
@@ -29,7 +29,7 @@
  template<typename Base, typename Derived>
  struct is_virtual_base_of_impl
  {
-    struct X : Derived, virtual Base {};
+    struct X : Derived, virtual Base { X(); };
      BOOST_STATIC_CONSTANT(bool, value = sizeof(X)==sizeof(Derived));
  };

HTH, Daniel