Smart Pointer CTOR
This calls handles.deque::push_back and, #ifndef NDEBUG,
no_duplicates.set::insert. The void* in set is actually a T*
where T is the T in recyclable_base, the base class for cyclic_ptr and
weak_ptr.
The purpose of the static std::deque handles (in
cyclic_ptr.cpp) is:
- to allow traversal of "all handles in deque three times to collect
garbage" (comment above 'void recycler::recycle() throw()' in
cyclic_ptr.cpp).
- to allow the user to specify a finalizer
(or, in cyclic_ptr's case, a "deleter") for each instance of the
pointee.
However, the no_duplicates actually must be used for production code
and as well as for debugging; otherwise, if the same pointer is contained
in 2 different cyclic_ptr's, then it will be deleted
twice.