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

Subject: Re: [boost] [parameter] Boost.Graph program not responding at run-time
From: Lorenzo Caminiti (lorcaminiti_at_[hidden])
Date: 2011-12-03 15:11:44

On Sat, Dec 3, 2011 at 2:28 PM, Jeremiah Willcock <jewillco_at_[hidden]> 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