Author: Julia Lawall <Julia.Lawall@lip6.fr> for_each_child_of_node performs an of_node_put on each iteration, so putting an of_node_put before a continue results in a double put. The semantic match that finds this problem is as follows (http://coccinelle.lip6.fr): // @@ expression root,e; local idexpression child; iterator name for_each_child_of_node; @@ for_each_child_of_node(root, child) { … when != of_node_get(child) * of_node_put(child); … …