On Wed, 2008-04-09 at 14:18 -0400, Frank Mori Hess wrote:
On Wednesday 09 April 2008 14:13 pm, Daniel Frey wrote:
static_cast<T*>(this) should be legal AFAIK (and doesn't need a vtable)
It works in some cases, but it will fail the smart_ptr/test/shared_from_this_test.cpp test for example.
You are right. Which makes the optimization possible only for cases where enable_shared_from_this<T> is not a virtual base class of T. What do you (and others) think about branching enable_shared_from_this<T> into two classes: low_overhead_enable_shared_from_this<T> and feature_rich_enable_shared_from_this<T> Yes, the names are crap, we need better ones :) Apart from that, I think it might be worth it. The first one would be the classic one plus the limitation you pointed out for virtual base classes, with an overhead of just 4 bytes, while the second one is the trunk version which offers a lot more features but currently has an overhead of 4 pointers, a vtable and a bool. Note that I don't think that one of the classes is "better" than the other, I just think that each class has valid use cases which can not be satisfied by the other class. Regards, Daniel