> >>> It strikes to me now that the matter is not so subtle at all, since
> >>> add_vertex()
> >>> with vecS is very likely to invalidate vertex_iterators (clearly contrary
> >>> to
> >>> the
> >>> documentation). In my case the issue was a bit obscured since it is not
> >>> perfectly clear that source(edge_descriptor) and target(edge_descriptor)
> >>> use
> >>> vertex_iterators. I had expected that edge_descriptor stores two
> >>> vertex_descriptors.
> >> The problem is not with edge_descriptor it is in the operator++() of the
> >> edge_iterator class.
> >
> > I think that edge_iterators are not directly affected, and its still save
> > to
> > use them to access, e.g., edge properties. Its also save to use
> > operator++().
> > The problem is that calling source(...) on an edge descriptor dereferences a
> > vertex_iterator, and THAT one may have been invalidated. Is that right?
>
> Well, you can try to remove source() and target() calls from your
> example and to see if the problem is still reproducible.
The problem is with the documentation - not the code. The edge_iterator IS invalidated after add_vertex() because the edge_iterator retains a pair ouf out_edge_iterators that refer to the current out edge being visited of the current vertex. The add_vertex() call may not invalidate vertex descriptors but it will invalidate out_edge_iterators since the memory they pointed to no longer exsts (i.e., copied and deleted). The cascading effect is that it will also invalidate the edge_iterator. Hence, the failure of g[*i].