Re: [Boost-users] [intrusive] unordered_set::iterator_to

Subject: Re: [Boost-users] [intrusive] unordered_set::iterator_to
From: Paul Rose (paul.d.rose_at_[hidden])
Date: 2011-02-14 14:48:44

Sorry to keep replying to myself.

To fix this I chaged:
    return
const_iterator(bucket_type::s_iterator_to(priv_value_to_node(const_cast<reference>(value))),
this);
to:
    return const_iterator(bucket_type::s_iterator_to(const_cast<node
&>(priv_value_to_node(value))), this);
in file
   boost/intrusive/hashtable.hpp:
(near line 1682 in version 1_38_0)

The original code appears to be trying to call the non-const version of
priv_value_to_node() by casting away the constness of the value parameter,
but it doesn't work because the 'this' pointer is still const.

So, the const version of priv_value_to_node() is called instead, returning a
const reference.

That const reference is passed to the const version of
bucket_type::s_iterator_to(), which returns a const bucket (slist) iterator.

Finally, a const_iterator is constructed from the const bucket iterator, but
there is no constructor to support this.

The lack of supporting iterator constructor seems to be by-design, because
the iterator's internal slist_it_ is always non const.

Either casting away the constness of the this this pointer when calling
priv_value_to_node(), or casting away the constness of the returned node
reference will fix the problem.

I added a const_cast to the return from priv_value_to_node() and got rid of
the const_cast on the input value reference (no longer necessary).

Thanks,
Paul Rose