Re: [Boost-users] scoped_ptr faq

Bruno Martínez wrote:

On Wed, 23 Nov 2005 08:34:26 -0200, Peter Dimov wrote:

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Bruno Martínez wrote:

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Hi.

I had the same question that is answered there, but the answer didn't fit my problem. I'm using scoped_ptr<node> inside node itself, so node is incomplete at the point of use. That forbids using auto_ptr, IIUC.

You can use a scoped_ptr member with an incomplete type, as long as you include out of line default constructor (if you need one) and destructor.

I know. The problem is that I want incomplete types support *and* release member function.

Use std::auto_ptr and ensure that you obey Peter Dimov's recommendations. I know, that the standard says, in 5.3.5 "If the object being deleted has incomplete class type at the point of deletion and the complete class has a non-trivial destructor or a deallocation function, the behavior is undefined." and in 17.4.3.6 "if an incomplete type (3.9) is used as a template argument when instantiating a template component." There exists no special restriction on std::auto_ptr for incomplete classes and the main difference between std::auto_ptr and boost::scoped_ptr in this point is that the standard says, that "no diagnose is required", while boost will diagnose that due a safety belt in boost::checked_delete.

I don't seem to require a destructor in this case, for vc71 or gcc3.4:

#include

struct node { boost::scoped_ptr<node> next; };

int main() { node n; }

This snippet does not proof, that no d'tor is needed, because node::next is empty for the complete program run-time. Just assign a node to next, and you will see.... Greetings from Bremen, Daniel