Re: [Boost-users] Warnings and boost

Lee Houghton wrote:

The problem appears to be when operator += is called on the iterator. Here, the difference_type of the iterator, boost::iterator_facade::difference_type, which is equal to boost::detail::counting_iterator_base::difference, is __int64.

OK, that actually makes sense. The typedef searches for the smallest type able to represent all differences between any two numbers of the given type. For signed integers, this is always the next larger signed type. The reason for this is simple: INT_MAX - INT_MIN == UINT_MAX, but INT_MIN - INT_MAX == -UINT_MAX, a number that can only be represented by the next larger signed type. I wonder if this problem is logically solvable, or if a hack (like a static_cast in iterator_adaptor::advance, or perhaps a warning disable) is necessary. Another question is whether this warning should be considered perhaps a bug in VC++. Whatever. Different workaround is to modify boost/iterator/iterator_adaptor.hpp: + #if defined(BOOST_MSVC) + #pragma warning(disable: 4244) + #endif void advance(typename super_t::difference_type n) { BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag) m_iterator += n; } + #if defined(BOOST_MSVC) + #pragma warning(default: 4244) + #endif This is potentially unsafe, of course - nothing prevents you from just passing a HUGE value to +=. The likelyhood, though ... well, it's just a workaround. Sebastian Redl