Eric Jardim <ericjardim@gmail.com> writes:

Hi, all...

This is a simple question. I was reading the docs where it says about the "transfer of ownership" of a C++ object pointer. I am dealing exacly this situation, where the "with_custodian_and_ward" policy is not enough to prevent Python objects to delete C++ couterparts. The only hack is to hold references, but it is not a complete solution.

So, I read the FAQ entry where it explain how to deal with this issue: http://www.boost.org/libs/python/doc/v2/faq.html#ownership

But there, it speaks about using an "std::auto_ptr". On the other side, I am using "boost::shared_ptr" to hold my objects. I really do not know the difference between them, but I imagine they provide similar funcionality.

Yes, similar, but auto_ptr provides exclusive, as opposed to shared, ownership semantics. When an auto_ptr is copied or assigned, the source loses ownership and the destination acquires it.

So I will split my question in 3 parts: - Is it possible to take the ownership with "boost::shared_ptr",

Not if you mean to substitute it in the example in the FAQ, no.

or do I have to change my held types to "std::auto_ptr"?

That's a completely separate question. No, you don't need to change your held types.

- Is there any difference in practice, using boost's or std's smart pointers?

Yes, there are lots of differences. However you haven't been very specific about what you're interested in; you'd have to read the documentation for each of them to grasp all of the differences.

I just use them for holding Boost.Python extensions.

- As those functions with smart pointers do not exists, I suppose that I will have to write wrappers like:

void b_insert(B& b, std::auto_ptr<A> a) { b.insert(a.get()); a.release(); }

Is there any special reason for this to be a non-const reference to "b"?

Yes, all free functions that are going to be wrapped as class methods should take a non-const reference as their first argument.

Could it be a const reference

That would allow an implicit conversion from some other type to B to take place when calling the method, since const references can bind to rvalues

or a const/non-const pointer to "b"?

That would allow None to be passed as the first argument, resulting in a NULL pointer. -- Dave Abrahams Boost Consulting www.boost-consulting.com