On 11/2/05, Michael D. Crawford <crawford@goingware.com> wrote: 0. Am I correct in what I say about the various Boost smart pointers? I
say shared_ptr isn't thread safe. Am I right? If so, does
No. See Peter's response. 3. Can you pick any nits with my assertions about C++ or the various
smart pointers? Do you agree with me that the following is a case where auto_ptr is the best choice? Can you think of others?
http://www.goingware.com/tips/smart-pointers-and-automated-testing/#when-to-...
You say in this section that shared_ptr doesn't have a reset() method. It does. See: http://boost.org/libs/smart_ptr/shared_ptr.htm#Synopsis So it would work just as well as auto_ptr in this situation. There's also a typo in the comment at the top of the sample app: * ... and scoped_ptr, which permits them * by using reference counting" This should be "shared_ptr" not "scoped_ptr" (which you mention first). Also, I think the example could use some rewriting so it more clearly illustrates the strengths of the smart pointer approach. I'd suggest throwing an exception and using a class with a "noisy" ctor/dtor so the user can see what is happening without using valgrind. I'm attaching a stab at this to this message. 4. I say early on that neither auto_ptr nor the Boost smart pointers
provide all the different kinds of smart pointers one would want. What other kinds can you think of? How would they be implemented? I already have a couple completely implemented, and keep thinking of more, but I'd like ideas for others to discuss in my next installment. I won't tell you my answers yet because I want to stimulate discussion.
There is a flexible policy-based smart pointer ("policy_ptr") scheduled for review soon that provides customization options for things like the reference count implementation, copy semantics, etc. I suspect you've implemented some similar things. 6. If you were a sinner before you came to my soup kitchen's service,
have I saved your soul? If not, how could I have made my case more effectively? Was your free, hot supper satisfying? Would you come back for more?
I'd suggest correcting the factual errors, and linking to some other resources on smart pointers (e.g. Sutter, Alexandrescu, et al) before I could say I would walk away from the table feeling full :) Sutter on auto_ptr: http://www.gotw.ca/publications/using_auto_ptr_effectively.htm Alexandrescu on Smart Pointers: http://www.informit.com/articles/article.asp?p=31529 -- Caleb Epstein caleb dot epstein at gmail dot com