[Boost-users] BGL, swapping two graphs can invalidate vertex descriptors?

Subject: [Boost-users] BGL, swapping two graphs can invalidate vertex descriptors?
From: Paolo Bolzoni (paolo.bolzoni.brown_at_[hidden])
Date: 2015-10-24 05:19:11

Dear list,

I had to fix a bug in a program of mine using the boost graph library.
In the program I need to add and remove vertices quickly, so I used
listS both for edges and vertices.
Besides, I need to refer to vertices with special ids (that are
integers), so I added to each vertex a integer and to the graph itself
a map between the ids and the vertices. The interface ensures that
when vertices are added and this data structures are updated properly.
For reference I put the whole (minified) graph definition after the email.

Now, I had a crash when using boost::out_edges in some part of the
programs and not in others. After some debugging it really seems that
it happens that the vertex descriptors, that are addresses to the
vertices, change after a swap. Unfortunately I could not manage to
make this behaviour in a small example so I am still unsure and I
decided to ask here.

It is possible that swapping two graphs (with listS as OutEdgeList and
VertexList) invalidates the vertex descriptors?

Yours faithfully,
Paolo

#include <boost/graph/adjacency_list.hpp>

namespace graph_prop {
struct vertex {
    int id{}; };
struct edge { int lenght{}; };
struct graph;
}

typedef boost::adjacency_list<
    boost::listS,
    boost::listS,
    boost::undirectedS,
    graph_prop::vertex,
    graph_prop::edge,
    graph_prop::graph > Graph;

namespace graph_prop {
struct graph {
    std::unordered_map<int, Graph::vertex_descriptor> ids{}; }; }