Re: is_virtual_base<B, D> - possible?
On 1 Jun, 14:41, int...@gmail.com wrote:
struct is_virtual_base_impl
{
struct In : Derived, virtual Base
{
};
enum { value = sizeof(In) == sizeof(Derived) };
};
The sizeof() solution is the one I use currently, but it is horribly
hackish - there are no guarantees about how the size of objects
changes (or doesn't) with different flavors of inheritance. It seems
to work with two compilers here, but not only it may not work on some
other one, it can be easily broken by moving to a next version of
those same compilers, so I'm rather uncomfortable with it.
I'm not quite sure about this solution myself. Unfortunately
every deficiency I can think of is implementation specific
and not C++ standard issue. I was hoping that boost might have
some compiler specific implementations.
on the other hand, it will never answer true if the Base is not
virtually
inherited by Derived, so used in serialization library, it will
always produce correct, albeit maybe not most efficient, code.
The only thing I can find in Boost is a vague mention of
is_virtual_base in the TODO list for the next version of the
serialization library. No code though, neither in the latest release,
nor in the CVS (including sandbox).
hmm. that is not very encouraging to hear. Why not ask at
comp.lib.boost.devel . Maybe someone with more experience
with different compilers has a more general solution.
DS