[Boost-bugs] [Boost C++ Libraries] #8023: Error using iterator traits with coroutine iterator

Subject: [Boost-bugs] [Boost C++ Libraries] #8023: Error using iterator traits with coroutine iterator
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-02-10 05:39:45

#8023: Error using iterator traits with coroutine iterator
-------------------------------------+--------------------------------------
 Reporter:  nathanridge              |       Owner:  olli     
     Type:  Bugs                     |      Status:  new      
Milestone:  To Be Determined         |   Component:  coroutine
  Version:  Boost Development Trunk  |    Severity:  Problem  
 Keywords:                           |  
-------------------------------------+--------------------------------------
 I am getting compiler errors when using std::iterator_traits with a
 coroutine's iterator type:

 {{{

 #include <boost/coroutine/coroutine.hpp>
 #include <boost/iterator/iterator_traits.hpp>

 typedef boost::coroutines::coroutine<int()> coroutine_type;
 typedef std::iterator_traits<coroutine_type::iterator>::pointer pointer;
 }}}

 The errors are (with gcc 4.7.2):


 {{{

 In file included from boost/boost/coroutine/coroutine.hpp:31:0,
                  from test.cpp:1:
 boost/boost/coroutine/detail/coroutine_op.hpp: In instantiation of 'class
 boost::coroutines::detail::coroutine_op<int(),
 boost::coroutines::coroutine<int()>, int, 0>::iterator':
 c++/bits/stl_iterator_base_types.h:143:1:   recursively required from
 'constexpr const bool
 std::__has_iterator_category_helper<boost::coroutines::detail::coroutine_op<int(),
 boost::coroutines::coroutine<int()>, int, 0>::iterator>::value'
 c++/bits/stl_iterator_base_types.h:143:1:   required from 'struct
 std::__has_iterator_category<boost::coroutines::detail::coroutine_op<int(),
 boost::coroutines::coroutine<int()>, int, 0>::iterator>'
 c++/bits/stl_iterator_base_types.h:160:12:   required from 'struct
 std::iterator_traits<boost::coroutines::detail::coroutine_op<int(),
 boost::coroutines::coroutine<int()>, int, 0>::iterator>'
 test.cpp:5:55:   required from here
 boost/boost/coroutine/detail/coroutine_op.hpp:84:73: error: no type named
 'pointer' in 'struct
 std::iterator_traits<boost::coroutines::detail::coroutine_op<int(),
 boost::coroutines::coroutine<int()>, int, 0>::iterator>'
 boost/boost/coroutine/detail/coroutine_op.hpp:85:73: error: no type named
 'reference' in 'struct
 std::iterator_traits<boost::coroutines::detail::coroutine_op<int(),
 boost::coroutines::coroutine<int()>, int, 0>::iterator>'
 }}}

 The problem is the following typedefs in the iterator class:

 {{{

 typedef typename std::iterator_traits< iterator >::pointer      pointer_t;
 typedef typename std::iterator_traits< iterator >::reference
 reference_t;
 }}}

 If the iterator class is instantiated in the context of instantiating
 iterator_traits<iterator>, as is the case in my example code, these
 typedefs cause a recursive instantiation of iterator_traits<iterator>. In
 the recursive instantiation, 'iterator' is incomplete, and thus does not
 have the required members.

 A solution is to express the underlying type of these typedefs more
 directly, for example:

 {{{

 typedef typename iterator::pointer      pointer_t;
 typedef typename iterator::reference    reference_t;
 }}}

 The coroutine's const_iterator has a similar problem.

 Attached is a patch with the above fix.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8023>
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