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lib: graph: fix deletions

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Iterating over an array while deleting items needs to consider
interactions between the iteration position and deletion.  The previous
code completely ignored that problem, leading to memleaks (graph_delete
skipping half of the nodes) and dangling pointers (if parallel edges
exist in graph_remove_edge).

Iterating backwards is safe and reduces "move to fill hole" overhead in
deletion.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Cc: Quentin Young <qlyoung@cumulusnetworks.com>
This commit is contained in:
David Lamparter 2017-01-25 04:13:14 +01:00
parent 1e78204400
commit 72d98ee943
1 changed files with 3 additions and 3 deletions
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6
lib/graph.c
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@ -117,11 +117,11 @@ void
graph_remove_edge (struct graph_node *from, struct graph_node *to)
{
// remove from from to->from
for (unsigned int i = 0; i < vector_active (to->from); i++)
for (unsigned int i = vector_active (to->from); i--; /**/)
if (vector_slot (to->from, i) == from)
vector_remove (to->from, i);
// remove to from from->to
for (unsigned int i = 0; i < vector_active (from->to); i++)
for (unsigned int i = vector_active (from->to); i--; /**/)
if (vector_slot (from->to, i) == to)
vector_remove (from->to, i);
}
@ -130,7 +130,7 @@ void
graph_delete_graph (struct graph *graph)
{
// delete each node in the graph
for (unsigned int i = 0; i < vector_active (graph->nodes); i++)
for (unsigned int i = vector_active (graph->nodes); i--; /**/)
graph_delete_node (graph, vector_slot (graph->nodes, i));
vector_free (graph->nodes);