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

From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2008-06-03 05:43:12

Rodolfo Lima skrev:
> 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?

No, I'll add something to trunk soon.

Thanks

-Thorsten