graph: Re-fetch dst_node descriptor after src_node potential removal

The graph_t::disconnect(src_node, dst_node) function removes connections
(edges) from src_node to dst_node in the graph, and then removes the
nodes (vertices) if their degree is zero after removing the connections.

Because removing a vertex from the graph invalidates vertex descriptors,
the graph_t::_remove_node() function resynchronizes the node-to-vertex
descriptor map after removing the vertex.

However, in graph_t::disconnect(), the vertex descriptor corresponding
to dst_node was not being refetched after the potential removal of
src_node, which results in the incorrect removal of innocent nodes under
certain circumstances. This commit ensures that the node-to-vertex
descriptor is reconsulted for the vertex descriptor corresponding to
dst_node before removing it from the tree.

1 files changed, 3 insertions, 0 deletions

diff --git a/host/lib/rfnoc/graph.cpp b/host/lib/rfnoc/graph.cpp
index d4f2d37e7..2edf591b3 100644
--- a/host/lib/rfnoc/graph.cpp
+++ b/host/lib/rfnoc/graph.cpp
@@ -200,6 +200,9 @@ void graph_t::disconnect(node_ref_t src_node, node_ref_t dst_node, graph_edge_t
         _remove_node(src_node);
     }
 
+    // Re-look up the vertex descriptor for dst_node, as the act of removing
+    // src_node may have modified it
+    dst_vertex_desc = _node_map.at(dst_node);
     if (boost::degree(dst_vertex_desc, _graph) == 0) {
         _remove_node(dst_node);
     }