[boost] [smart_ptr] enable_shared_from_this_light

From: Daniel Frey (d.frey_at_[hidden])
Date: 2008-04-11 17:44:50

Hi,

I attached a complete implementation of enable_shared_from_this_light
which has an overhead of a single plain pointer. It is compatible with
1.35.0's enable_shared_from_this, except for one feature: The optimized
version requires that the following static_cast is legal:

  enable_shared_from_this_light<T>* p;
  static_cast<T*>(p);

which means that enable_shared_from_this_light<T> must be a
*non-virtual* base class of T. If you need this feature, you might want
to use trunk's enable_shared_from_this (without _light), which
(currently) has an overhead of four plain pointers, one bool and it
adds/requires the class to have a vtable. The trunk version therefore
offers some advanced features.

The above repeats a few things for those people that haven't followed
the discussion in the "[smart_ptr] Some questions"-thread. For those
that did: The thing to note is that I added two more things to
shared_ptr: _internal_shared_count() and a ctor which takes a
detail::weak_count and the raw pointer.

Any feedback welcome.

Regards, Daniel