Re: [Boost-users] Compilation error using boost::filtered_graph when trying to access graph properties via boost::graph_bundle

Subject: Re: [Boost-users] Compilation error using boost::filtered_graph when trying to access graph properties via boost::graph_bundle
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-02-28 14:15:29

On Mon, 28 Feb 2011, Tony Cook wrote:

>
> Hi, The following test program highlights an compilation error issue when using a boost::filtered_graph to access
> graph properties.  I am using Boost 1.46.0
>
> #include <boost/graph/adjacency_list.hpp>
> #include <boost/graph/filtered_graph.hpp>
>
>
> class TestGraph
> {
>   class VertexProperties { public: bool mFlag ; } ;
>   class EdgeProperties   { public: bool mFlag ; } ;
>   class GraphProperties  { public: bool mFlag ; } ;
>
>   typedef boost::adjacency_list
>      <boost::vecS, boost::listS, boost::undirectedS, EdgeProperties, VertexProperties, GraphProperties> GraphType ;
>
>   template <typename GraphType>
>   class EdgePredicate
>   {
>      public: EdgePredicate () : mpGraph (0) {}
>      public: EdgePredicate (GraphType& vrGraph) : mpGraph (&vrGraph) {}
>      public: template <typename EdgeType>
>              bool operator()(const EdgeType& vEdge) const { return (*mpGraph)[vEdge].mFlag ; }
>      private: GraphType* mpGraph ;
>   } ;
>
>   template <typename GraphType>
>   class VertexPredicate
>   {
>      public: VertexPredicate () : mpGraph (0) {}
>      public: VertexPredicate (GraphType& vrGraph) : mpGraph (&vrGraph) {}
>      public: template <typename VertexType>
>              bool operator()(const VertexType& vVertex) const { return (*mpGraph)[vVertex].mFlag ; }
>      private: GraphType* mpGraph ;
>   } ;
>
>   typedef boost::filtered_graph<GraphType, EdgePredicate<GraphType>, VertexPredicate<GraphType> > FilteredGraphType ;
>
>   ...
>
>
>   void foo ()
>   {
>      GraphType graph ;
>      FilteredGraphType filter (graph, EdgePredicate<GraphType> (graph), VertexPredicate<GraphType> (graph)) ;
>
>      graph  [boost::graph_bundle].mFlag = true ;
>      filter [boost::graph_bundle].mFlag ;        // ***** Does not compile - see below
>      ...
>   }
> }
>
> ...
>
> gcc 4.5.2 issues the following error message
>
> In member function 'typename boost::graph::detail::bundled_result<Graph, Descriptor>::type& boost::filtered_graph<Graph, EdgePredicate, VertexPredicate>::operator[](Descriptor)
> [with Descriptor = boost::graph_bundle_t,
>      Graph = boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, TestGraph::EdgeProperties, TestGraph::VertexProperties, TestGraph::GraphProperties>,
>      EdgePredicate = TestGraph::EdgePredicate<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, TestGraph::EdgeProperties, TestGraph::VertexProperties, TestGraph::GraphProperties> >,
>      VertexPredicate = TestGraph::VertexPredicate<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, TestGraph::EdgeProperties, TestGraph::VertexProperties, TestGraph::GraphProperties> >,
>      typename boost::graph::detail::bundled_result<Graph, Descriptor>::type = TestGraph::VertexProperties]':
>
>
> Visual Studio 2005 issues this error at the same line (see above)
>
> error C2440: 'return' : cannot convert from 'TestGraph::GraphProperties' to 'TestGraph::VertexProperties &'
> test-graph-types.h(78) : see reference to function template instantiation 'TestGraph::VertexProperties &boost::filtered_graph<Graph,EdgePredicate,VertexPredicate>::operator []<boost::graph_bundle_t>(Descriptor)' being compiled
> with
> [
>   Graph=TestGraph::GraphType,
>   EdgePredicate=TestGraph::EdgePredicate<TestGraph::GraphType>,
>   VertexPredicate=TestGraph::VertexPredicate<TestGraph::GraphType>,
>   Descriptor=boost::graph_bundle_t
> ]
>
>
> The error originates in boost filtered_graph.hpp line 201
>
> 199    // Bundled properties support
> 200    template<typename Descriptor>
> 201    typename graph::detail::bundled_result<Graph, Descriptor>::type&
> 201    operator[](Descriptor x)
> 203    { return const_cast<Graph&>(this->m_g)[x]; }
>
> The bug appears to be that using Descriptor = boost::graph_bundle somehow selects the wrong return type for operator[](Descriptor) selecting TestGraph::VertexProperties instead of the expected TestGraph::GraphProperties
>
> This is confirmed by redeclaring the GraphType as
>
>   typedef boost::adjacency_list
>      <boost::vecS, boost::listS, boost::undirectedS, EdgeProperties, VertexProperties, VertexProperties> GraphType ;
>
> i.e. the type for the graph properties happens to be the same as that used for the Vertex properties.
>
> Now it compiles cleanly!!
>
> Can someone help me locate the origin of this problem. I need to patch this quickly :(
>
> It should be noted that there are no problems accessing vertex and edge bundled properties via a filtered_graph - only the graph bundled properties exhibit this issue.

This is probably a bug -- I'll look at it later this afternoon.

-- Jeremiah Willcock