Re: [boost] [smart_ptr] Some questions

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-04-09 13:40:05

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On Wednesday 09 April 2008 08:07 am, Daniel Frey wrote:
> Before the change, I even wondered if the weak_ptr could be replaced by
> a detail::weak_count, which would reduce the overhead from two plain
> pointers to only one plain pointer, since shared_from_this always has
> *this.

But *this inside enable_shared_from_this<T> is not a T*, it is a 
enable_shared_from_this<T>*.  To downcast it to a T* requires a dynamic_cast 
for the general case, which requires a vtable.  Not that I consider a vtable 
to be significant overhead (I know, it's a horrifiying opinion for a C++ 
programmer but there it is).

- -- 
Frank
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