Conflict between Boost.Format and filtered_graph in Boost.Graph

[Jan Hudec <bulb@…>]

I am using boost::format in my logging macros and some graphs from Boost.Graph. But whenever I include boost/graph/filtered_graph.hpp, GCC starts to complain that

boost/graph/graph_traits.hpp: In instantiation of 'struct boost::graph_traits<char>':
boost/graph/filtered_graph.hpp:131:57:   required from 'struct boost::filtered_graph_base<char>'
boost/graph/filtered_graph.hpp:141:9:   required from 'class boost::filtered_graph<char, std::char_traits<char>, std::allocator<char> >'
boost/format/feed_args.hpp:253:17:   required from 'void boost::io::detail::distribute(boost::basic_format<Ch, Tr, Alloc>&, T) [with Ch = char; Tr = std::char_traits<char>; Alloc = std::allocator<char>; T = const SomeWrapper<lots of boost::graph things here> &]'
boost/format/feed_args.hpp:263:9:   required from 'boost::basic_format<Ch, Tr, Alloc>& boost::io::detail::feed(boost::basic_format<Ch, Tr, Alloc>&, T) [with Ch = char; Tr = std::char_traits<char>; Alloc = std::allocator<char>; T = const SomeWrapper<lots of boost::graph things here> &]'
[... more required froms, don't seem relevant anymore ...]
boost/graph/graph_traits.hpp:33:52: error: 'char' is not a class, struct, or union type

The SomeWrapper is my class for customizing operator<<. It's template argument has few hundred characters. It is pair of iterators into something complex involving boost::directed_graph. The filtered_graph is not actually used, only included.

Both GCC 4.5.2 and 4.7.2 show the above error, but Visual C++ 15.00.30729.01 (Visual Studio 9 2008) compiles it just fine. I am not sure whether it is bug in GCC or whether MSVC considers SFINAE something that isn't, but it seems to be the later. The template from boost/graph/filtered_graph.hpp will be found by ADL and because the template parameters are provided explicitly, compiler must instantiate it to find out whether it is better candidate or not. That fails, but not in immediate context, so it is not SFINAE.

It can be worked around by qualifying the put in boost/format/feed_args.hpp, renaming it, or by modifying the templates in graph_traits and filtered_graph to make the failure SFINAE (might have some advantages elsewhere).

I had the problem with 1.51 and updated to 1.53, because there are some changes to graph_traits that looked like they may be relevant, but it didn't help.

[Jeremiah Willcock]

Would it make sense to just add a namespace qualification (boost::io::detail, most likely) to the call to put? Or does that need to use ADL, even with the explicit template arguments?

[James E. King, III]

Can you provide a concrete and minimal example of this?

[James E. King, III]

Sample code showing this failure is required as the explanation is complex.