On Sat, Nov 15, 2008 at 2:49 AM, Thorsten Ottosen
wrote:
Brendan Miller skrev:
I've been interested in non nullable smart pointers for a while. I
noticed a thread I wanted to check if anyone was still interested in
doing it:
http://lists.boost.org/Archives/boost/2008/04/135616.php
This seems like a worthwhile activity. Null is a legacy element from C
that essentially breaks type safety.
FWIW, Boost.PtrContainer does not allow you to put nulls in containers; if
you want nulls you have to ask for it:
boost::ptr_vector< boost::nullable<T> > vec;
I'm always shocked how many good ideas have already been implemented in boost.
I guess it would be trivial to add something like
typedef boost::shared_ptr< boost::non_null<T> > ptr_type;
which would not be default constructible, and which would throw if you
inserted a null (rather than providing a check in operator->).
You're suggesting that there would be a specialization of shared_ptr
for shared_ptr? That's a good idea, but I have no
idea on whether the maintainers of shared_ptr are willing to accept
that much more complexity. Also, shared_ptr is really a
mouthful, but I guess when c++0x comes out you could just do a
template using to shared_ref<t> or something for those (such as
myself) who want to consistently prohibit null in their code to
promote type safety.
Really though, if you had a non-nullable reference counted pointer,
you'd also want a non-nullable unmanaged pointer, a non-nullable weak
pointer, a non-nullable scoped pointer and appropriate conversions,
i.e. you can assign a non-null unmanaged pointer to a non-null
reference counted pointer and vice versa without a runtime null check
being done.
That's why I was thinking of just rolling a separate set of pointers,
maybe taking shared_ptr and scoped_ptr as starting points. I don't
know who the maintainer is, but i wasn't sure whether they would
accept a patch with that much added complexity.
Brendan
