Problem compiling zip_iterator with clang and C++11

[jonathan.jones@…]

The following code fails to compile on OSX 10.8.5 with Xcode 5.0.1 and Boost 1.49.0. This is not real world code, but it demonstrates the problem I'm facing.

#include <boost/iterator/zip_iterator.hpp>

template<typename T>
void foo()
{
    boost::zip_iterator<boost::tuple<T*> > iter;
    std::fill(iter, iter, boost::make_tuple(T()));
}

void bar()
{
    foo<int>();
}

Here are the commands I used to compile (if I drop "-stdlib=libc++" from the compile line, the code compiles just fine):

setenv DEVELOPER_DIR /Applications/Xcode5.0.1.app/Contents/Developer
xcrun -sdk macosx10.8 clang++ -c zip_iterator.cpp -I<boost-path>/include -std=c++11 -stdlib=libc++

and here is a heavily formatted snippet of the key error:

/Applications/Xcode5.0.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/algorithm:1824:1:
note: candidate function
    [with _RandomAccessIterator = boost::zip_iterator<boost::tuples::tuple<int *> >, _Tp = boost::tuples::tuple<int>]
not viable: no known conversion from
    'typename iterator_traits<zip_iterator<tuple<int *> > >::iterator_category'
    (aka 'boost::detail::iterator_category_with_traversal<std::__1::input_iterator_tag, boost::random_access_traversal_tag>')
to
    'std::__1::random_access_iterator_tag'
for 4th argument
    __fill(_RandomAccessIterator __first, _RandomAccessIterator __last, const _Tp& __value_, random_access_iterator_tag)

It appears as if the zip_iterator is not being converted to the correct iterator tag, which is why no calls to std::fill match.

[jonathan.jones@…]

The core problem seems to be this:

boost::detail::facade_iterator_category<boost::random_access_traversal_tag, boost::tuple<T&>, boost::tuple<T&> >::type

evaluates to the type:

boost::detail::iterator_category_with_traversal<std::input_iterator_tag, boost::random_access_traversal_tag>

This is how zip_iterator instantiates it, with boost::tuple<T&> as both the value and the reference type.

The newest implementation of std::fill in Xcode has implementations specific to forward_iterator_tag and random_access_iterator_tag, but not input_iterator_tag, hence the failure to compile.