iterator_adaptor and operator-> for input iterators

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-08-07 16:16:59

I wrote an iterator to do recursive directory iteration.  The heart of it 
is:

     template< typename Predicate >
     class recursive_directory_iterator
       : public boost::iterator_adaptor<
          boost::shared_ptr< detail::rdi_imp< Predicate > >,
          detail::rdi_policies,
          const boost::filesystem::path,
          const boost::filesystem::path &,
          const boost::filesystem::path *,
          std::input_iterator_tag,
          std::ptrdiff_t >
     { ... };

Works fine as long as you stay away from operator->.

For example,

   fs::recursive_directory_iterator<pred_type> rdi( dir , dummy );
   fs::recursive_directory_iterator<pred_type> rdi_end;

   for ( ; rdi != rdi_end; ++rdi )
   {
//  std::cout << rdi->generic_path() << std::endl;
     std::cout << (*rdi).generic_path() << std::endl;
   }

works as expected.  But if you uncomment the commented line, the program 
fails in the call to operator->.  What "fails" means depends on the 
execution environment; whatever is happening seems to confuse the debugger, 
stepping doesn't shed much light on the problem.  Same symptoms with both 
VC++7 and Intel 6.0.

I suppose I'm doing something stupid, but don't have a clue as to what.

I notice in iterator_adaptor_test.cpp that operator-> is not actually 
exercised. Is it possible there is a bug in it for input iterators? I've 
not had similar problems with iterator_adaptor for bidirectional iterators.

Any help appreciated,

--Beman