Re: [Boost-users] interprocess::list and destructors of storedobjects

From: talamar (talamar.lands_at_[hidden])
Date: 2006-12-01 19:22:37

Thanks, Ion!
Regards, 
Alexander.

----- Original Message ----- 
From: "Ion Gaztañaga" <igaztanaga_at_[hidden]>
To: "Boost User List" <boost-users_at_[hidden]>
Sent: Saturday, December 02, 2006 3:03 AM
Subject: Re: [Boost-users] interprocess::list and destructors of storedobjects

> alexmark wrote:
>> Hi to all!
>> 
>> For the container type 
>> 
>> boost::interprocess::list<T, A> I 
>> 
>> need the destructor of stored object T be called when erase() is called for a corresponding list item. By default the T destructor is not called, memory only is deallocated. What is the correct way to force boost::interprocess::list to invoke destructors for contained objects while list item or the container itself is deleted?
>> 
>> TYA.
> 
> Hi,
> 
> I've reviewed the code from the list.hpp CVS and I see that erase is 
> written as:
> 
> 
>    iterator erase(const_iterator position)
>    {
>       NodePtr next_node = position.get_ptr()->m_next;
>       NodePtr prev_node = position.get_ptr()->m_prev;
>       NodePtr node      = position.get_ptr();
>       prev_node->m_next = next_node;
>       next_node->m_prev = prev_node;
>       AllocHolder::destroy_node(node);
>       --this->m_size;
>       return iterator(next_node);
>    }
> 
> And
> 
>       AllocHolder::destroy_node(node);
> 
> is written as:
> 
>    void destroy_node(NodePtr node)
>    {
>       if(!node_has_trivial_destructor){
>          self_t::destroy(node);
>       }
>       NodeAlloc::deallocate(node, 1);
>    }
> 
> in theory, if the node has trivial destructor, the destructor shouldn't 
> be called. but this "node_has_trivial_destructor" is:
> 
>    enum {
>       node_has_trivial_destructor =
>          boost::has_trivial_destructor<NodePtr>::value |
>          boost::has_trivial_destructor<T>::value
>    };
> 
> which I think is wrong since it should be
> 
>    enum {
>       node_has_trivial_destructor =
>          boost::has_trivial_destructor<NodePtr>::value &&
>          boost::has_trivial_destructor<T>::value
>    };
> 
> that is, the node pointer should have trivial destructor AND the value 
> should have trivial destructor. Otherwise, the destructor is wrongly 
> ignored.
> 
> I've uploaded the change to CVS. You can change your list.hpp code to 
> see if this works. The same bug is present in slist.hpp. Thanks for the 
> bug report!
> 
> Regards,
> 
> Ion
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