[Boost-users] [ptr_map] container equality comparison doesn't compile

From: Rodolfo Lima (rodolfo_at_[hidden])
Date: 2008-06-01 15:59:22

Hi, is there any other reason (apart from begin a bug) that the 
following code doesn't compile with g++-4.3?

#include <boost/ptr_container/ptr_map.hpp>

int main()
{
     boost::ptr_map<int,int> m1, m2;

     m1.insert(1,std::auto_ptr<int>(new int(2)));
     m2.insert(1,std::auto_ptr<int>(new int(2)));

     return m1 == m2;
}

gcc spits the following errors (be seated...):

/usr/lib/gcc/i686-pc-linux-gnu/4.3.0/include/g++-v4/bits/stl_algobase.h: 
In static member function 'static bool 
std::__equal<_BoolType>::equal(_II1, _II1, _II2) [with _II1 = 
boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, _II2 = 
boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, bool _BoolType = false]':

/usr/lib/gcc/i686-pc-linux-gnu/4.3.0/include/g++-v4/bits/stl_algobase.h:818: 
   instantiated from 'bool std::__equal_aux(_II1, _II1, _II2) [with _II1 
= boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, _II2 = 
boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>]'

/usr/lib/gcc/i686-pc-linux-gnu/4.3.0/include/g++-v4/bits/stl_algobase.h:950: 
   instantiated from 'bool std::equal(_II1, _II1, _II2) [with _II1 = 
boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, _II2 = 
boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>]'

/usr/include/boost/ptr_container/detail/reversible_ptr_container.hpp:441: 
   instantiated from 'bool 
boost::ptr_container_detail::reversible_ptr_container<Config, 
CloneAllocator>::operator==(const 
boost::ptr_container_detail::reversible_ptr_container<Config, 
CloneAllocator>&) const [with Config = 
boost::ptr_container_detail::map_config<int, std::map<int, void*, 
std::less<int>, std::allocator<std::pair<const int, void*> > > >, 
CloneAllocator = boost::heap_clone_allocator]'
teste.cpp:10:   instantiated from here

/usr/lib/gcc/i686-pc-linux-gnu/4.3.0/include/g++-v4/bits/stl_algobase.h:789: 
error: no match for 'operator==' in 
'((boost::iterator_facade<boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, 
boost::ptr_container_detail::ref_pair<int, const int* const>, 
boost::bidirectional_traversal_tag, 
boost::ptr_container_detail::ref_pair<int, const int* const>, int>*)(& 
__first1))->boost::iterator_facade<I, V, TC, R, D>::operator* [with 
Derived = 
boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, Value = 
boost::ptr_container_detail::ref_pair<int, const int* const>, 
CategoryOrTraversal = boost::bidirectional_traversal_tag, Reference = 
boost::ptr_container_detail::ref_pair<int, const int* const>, Difference 
= int]() == 
((boost::iterator_facade<boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, 
boost::ptr_container_detail::ref_pair<int, const int* const>, 
boost::bidirectional_traversal_tag, 
boost::ptr_container_detail::ref_pair<int, const int* const>, int>*)(& 
__first2))->boost::iterator_facade<I, V, TC, R, D>::operator* [with 
Derived = 
boost::ptr_map_iterator<std::_Rb_tree_const_iterator<std::pair<const 
int, void*> >, int, const int* const>, Value = 
boost::ptr_container_detail::ref_pair<int, const int* const>, 
CategoryOrTraversal = boost::bidirectional_traversal_tag, Reference = 
boost::ptr_container_detail::ref_pair<int, const int* const>, Difference 
= int]()'
make: ** [teste] Erro 1

My guess it that boost::ptr_container_detail::ref_pair should have an 
equality operator (and a less than also) somehow.

In fact... by adding the following operator== to it the code compiles 
and behaves as expected:

// #include <boost/utility/compare_pointees.hpp at top of the file
bool operator==(const ref_pair &that) const
{
        return first==that.first
                && boost::equal_pointees(second, that.second);
}

Something equivalent should be done for operator<

Any objections?

Regards,
rod