Re: [boost] [parameter] Boost.Graph program not responding at run-time

3 Dec 2011

      On Sat, Dec 3, 2011 at 2:28 PM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote:
...
On Sat, 3 Dec 2011, Lorenzo Caminiti wrote:
...
If I move the call to boost::depth_first_search into a template
depth_first_search_impl and out of the Boost.Parameter function body,
the code compiles (both MSVC and GCC with latest Boost from trunk) but
the executable runs forever and prints nothing to cout... What am I
doing wrong?
I tried your code with GCC 4.6.0 and it worked just fine as you pasted it
below.  I get:
order of discovery: u v y x w z
order of finish: x y v u z w
as the result.  You are returning an invalid pointer from
default_color_map(), though; &colors[0] becomes invalid when colors is
destroyed at the end of the function.
Oops... thanks, that was actually the issue, after I fixed the invalid
pointer the code runs fine.

BTW, what's the best way to generate a default_color_map for
Boost.Graph like the one below?

template< typename Size, typename IndexMap >
boost::iterator_property_map<boost::default_color_type*, IndexMap,
        boost::default_color_type, boost::default_color_type&>
default_color_map ( Size const& num_vertices, IndexMap const& index_map )
{
    std::vector<boost::default_color_type> colors(num_vertices);
    return &colors[0]; // *** Error: invalid ptr... ***
}

BOOST_PARAMETER_NAME(graph)
BOOST_PARAMETER_NAME(visitor)
BOOST_PARAMETER_NAME(root_vertex)
BOOST_PARAMETER_NAME(index_map)
BOOST_PARAMETER_NAME(color_map)

BOOST_PARAMETER_FUNCTION(
    (void),
    depth_first_search,
    tag,
    (required
        (graph, *(is_incidence_and_vertex_list_graph<boost::mpl::_>))
    )
    (optional
        (visitor, *, boost::dfs_visitor<>())
        (root_vertex,
                (vertex_descriptor<tag::graph::_>),
                *boost::vertices(graph).first)
        (index_map,
                *(is_integral_property_map_of_key< boost::mpl::_,
                        vertex_descriptor<tag::graph::_> >),
                boost::get(boost::vertex_index, graph))
        (in_out(color_map),
                *(is_property_map_of_key< boost::mpl::_,
                        vertex_descriptor<tag::graph::_> >),
                default_color_map(boost::num_vertices(graph),
index_map)) // *** Note: color map used here ***
    )
) {
    return depth_first_search_impl<graph_type, visitor_type, root_vertex_type,
            index_map_type, color_map_type>(graph, visitor, root_vertex,
            index_map, color_map);
}

--Lorenzo