"Peter Dimov" <[EMAIL PROTECTED]> wrote in message 00b201c2c6da$16c22e70$1d00a8c0@pdimov2">news:00b201c2c6da$16c22e70$1d00a8c0@pdimov2... > From: "Andrei Alexandrescu" <[EMAIL PROTECTED]> > [...] > > > > It should be noted that the constructor taking a custom deleter has many > > implementation efficiency consequences that are not mentioned in the > > Standards proposal nor in the shared_ptr doc. My feeling is that the > > documentation at > > http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1397.html and at > > http://www.boost.org/libs/smart_ptr/shared_ptr.htm is coy about mentioning > > that the added constructor requires quite some more overhead under the > > covers, including runtime polymorpshim, virtual calls, extra allocations, > > all those good things. > > The runtime polymorphism/virtual call issue is not exclusively mandated by > the two-argument constructor. It is necessary to capture the deallocation > information at construction time in order to support incomplete classes, > EXE/DLL heap mismatch, and shared_ptr<T>'s ability to call the right > destructor regardless of T.
I understand that. I also know not all people would need all that. [...] > I really don't understand why you consider policy-based smart pointers and > the current shared_ptr enemies, when in my opinion they perfectly complement > each other. But I've grown tired of asking. I guess I started feeling that way when I've been told that shared_ptr is everything everyone will ever need, so there's no need for policy-based smart pointers :o). In a language with template typedefs, there would be no complementarity - shared_ptr will be but one point in the design space allowed by smart_ptr. Andrei _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
