RE: [boost] SmartPtrs: Making Code Self-Describing. Do we need mo re SmartPtrs?

From: Martin Bonner (martin.bonner_at_[hidden])
Date: 2005-04-26 03:09:12

----Original Message----
From: Pavel Chikulaev [mailto:pavel.chikulaev_at_[hidden]]
Sent: 25 April 2005 16:36
To: boost_at_[hidden]
Subject: [boost] SmartPtrs: Making Code Self-Describing. Do we need
more SmartPtrs? 

> Please consider the following code which we IMO too often see in other
> libraries:
> class Foo;
> Foo * Bar(Foo *);
> 
> What can we say about this pretty C-like function? It gets pointer
> Foo and returns pointer Foo. That's all we can be sure about it.
> But that's not enough to start working with it. But without looking at
> documentation we can't say whether we should delete these pointers
> or function Bar will handle it. What if even documentation says
> anything about it, what to do then? 

Discuss the lack of documentation with the original developer.  (A 2x4 may
be useful).

... You can't use a function if you don't know what it does.  The
documentation might as well discuss lifetimes.

> Example 1:
> We are the developer of function Foo. And we need to mark somehow
> that returned pointer is property of Foo internals and it shouldn't be
> deleted by the client function. We can achieve this using weak_ptr, but
> what if Foo internals doesn't have any shared_ptr's ? What to return then?

What's wrong with returning a reference here?

> Example 2:
> 
> We are developer of function Foo again. And now we need to mark that
> pointer argument is needed only for time of execution of Foo (it
> wasn't collected anywhere), and user cares about deallocation. How
> are we going to write such code and make it self-describing at the same
> time? Plain pointer? No Way! That would be a C-style, but we need
> something like C++-style... This time we don't have even one std or
> boost candidate for such job.
Reference definitely.

> Do we need them? 
I don't think so.

> Or we've already have some alternative solution I didn't find?
I think so.

-- 
Martin Bonner
Martin.Bonner_at_[hidden]
Pi Technology, Milton Hall, Ely Road, Milton, Cambridge, CB4 6WZ,
ENGLAND Tel: [phone]