This isn't a question but rather a quick report for my future reference - I need to circle back and try to characterize this problem more fully when I'm not on deadline and can run some additional tests with Boost 1.32.0. Environment: - MS 7.1 compiler w/their STL distribution - Boost 1.31.0 (my client doesn't want to update to 1.32.0 until after this release) Summary: boost::variant registered as an internal edge property map member on a BGL graph causes the resultant graph to be inaccessible due to what appears to be incorrect initialization of both the internal vertex and edge property maps. I SUSPECT THAT THE ROOT CAUSE OF THIS CAN BE TRACKED BACK TO A MS 7.1 COMPILER BUG due to the fact that attempts to compile my test code results in either of (a) an C1001 Internal Compiler Error (b) a error-free compile and a completely screwed runtime. Details: The boost::variant in question is bounded by several unique specializations of a fully-specialized class. As follows: // pseudocode class A; class B; class C; template <typename tail_T, typename head_T> class edge_exeuctor {}; template <> class edge_executor<A, B>; template <> class edge_exeuctor<A,C>; tempalte <> class edge_exeuctor<B,C>; template <> class edge_executor<B,A>; tempalte <> class edge_executor<C,A>; template <> class edge_executor<C,B>; typedef boost::variant< edge_executor<A,B>, edge_executor<A,C>, edge_executor<B,C>, edge_executor<B,A>, edge_executor<C,A>, edge_executor<C,B> > variant_edge_t; The graph in question is declared as: enum vertex_foo_property_t { vertex_foo_property = 801 }; enum edge_foo_property_t {edge_foo_property = 802 }; BOOST_INSTALL_PROPERTY(vertex, foo_property); BOOST_INSTALL_PROPERTY(edge, foo_property); typedef property<vertex_foo_property, int, boost::property<vertex_color_t, default_color_type> > vertex_properties_t; typedef property<edge_foo_property, variant_edge_t> edge_properties_t; typedef adjacency_list<listS, listS, bidirectionalS, vertex_properties_t, edge_properties_t> graph_t; typedef graph_traits<graph_t>::edges_size_type edges_size_t; Failure: // THE TEST CODE WILL NOT ALWAYS COMPILE W/MS 7.1 // HALF THE TIME IT BOMBS W/C1001 INTERNAL COMPILER ERROR // when it does compile, no errors are reported by the following runtime behavior is observed graph_t g; edges_size_t edge_count = num_edges(g); // <- protection fault // stepping into num_edges in a debug build reveals that both vertex and edge property maps point to uninitialized memory (0xcdcdcdcd) // removing variant_edge_t from edge_properties_t and replacing with an int works as expected... ---- - Chris