Hi, Andrew Sutton escribió:
the documentation of adjacency_list states, that a call to add_vertex() does not invalidate any iterators nor descriptors. However, following code segfaults, because retrieving vertex
[]
This is a nice, subtle problem that you've found :) Remember that an adjacency list stores a list of incident edges for each vertex.
Adding a
vertex (with VertexSet == vecS) can cause a reallocation of the underlying buffer, causing all of those incident edge lists to be reallocated and copied. The edge iterator stores actually stores a pair of iterators into the out-edge list of some vertex... The unfortunate side-effect seems to be that adding a vertex *can* in fact invalidate an edge iterator. I guess the documentation is wrong.
Note that this probably won't be the case with VertexSet != vecS since additions don't cause re-allocations.
I don't see any possible way to work around this other than deferring all of your vertex additions til after the loop.
In the provided example g.m_vertices.reserve(6) helps. --Dmitry