On Thu, Nov 22, 2012 at 09:29:43PM +0100, Florian Weimer wrote: > On 11/18/2012 07:06 PM, NightStrike wrote: > > >What's wrong with std::shared_ptr? > > The pointer needs two words, and the per-object overhead for the > reference counts etc. is four words, if I'm counting correctly. > > (Other forms of reference counting have less overhead, of course, > but you were asking about std::shared_ptr.)
Actually, this observation may favor a real garbage collector. Marking GC as simple as ggc+gengtype usually have one (or a few) mark bits, so can consume only a few bits (or perhaps a byte in some mark array) per object. Copying GC could avoid consuming any more storage per object. Of course useless object may stay in memory for a while -until the GC deletes them or reuse their memory- but that observation is also true with traditional C++ "GC" techniques like shared_ptr .... An object may be freed later than what should be possible. And some GC techniques are quite friendly with L1 or L2 caches on the processor chip. Regards. -- Basile STARYNKEVITCH http://starynkevitch.net/Basile/ email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359 8, rue de la Faiencerie, 92340 Bourg La Reine, France *** opinions {are only mines, sont seulement les miennes} ***
