Re: std::map question

From: David Hilsee (davidhilseenews_at_yahoo.com)
Date: 08/15/04 

Date: Sat, 14 Aug 2004 21:49:48 -0400

"Flzw" <flownz@wanadoo.fr> wrote in message
news:cflku0$3bl$1@news-reader4.wanadoo.fr...
> > It would be better not to *work around* this but to redesign the
> > implementation of CObject. The way it is right now, destruction of one
> > instance will invalidate all copies that exist somewhere else. This does
> > not only make the use of containers impossible but is somewhat dangerous
> > anyway.
>
> True.
>
> But I thought std containers were efficient. Here with this line, it
creates
> 4 instances of the object and deletes three... Is it really worth it ?
>
> I mean, I will switch to std::map <string, CObject*> from std::map
<string,
> CObject> and handle new / delete myself I won't need to introduce shared
> pointers and it will be MUCH faster (to code and to run).

If you are allocating memory dyanmically and it is possible for exceptions
to be thrown, it can be difficult to guarantee leak-free code unless there
is an object that is responsible for managing the memory. If you take the
"easy" route, then you will probably write code that can leak memory in
certain cases. Also, reference counted pointers can provide other benefits,
because they can alleviate the need to explicitly manage the lifetime of an
object, making the code simpler and more likely to be correct. I doubt that
your predictions about the improvement in the efficiency of the code will be
realized, especially when you consider that the string is probably managing
a dynamically allocated buffer and the object is managing a handle to an OS
resource. The overhead of the smart pointer will most likely be negligible
when compared to the rest of the code. Profile it and see if it's something
to be concerned about. 

-- 
David Hilsee

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