--- /dev/null
+#include "config.h"
+
+#include <assert.h>
+
+#include <ccan/agar/agar.h>
+#include <ccan/container_of/container_of.h>
+#include <ccan/ptrint/ptrint.h>
+
+#include "simple-graphr.h"
+
+static const void *error_first_edge_r(const struct agar_graph *gr,
+ const void *nr)
+{
+ return int2ptr(1);
+}
+
+static const void *error_next_edge_r(const struct agar_graph *gr,
+ const void *nr, const void *e)
+{
+ assert(ptr2int(e) == 1);
+
+ return NULL;
+}
+
+static int error_edge_info_r(const struct agar_graph *gr,
+ const void *nr, const void *e,
+ struct agar_edge_info *eir)
+{
+ int fromindex = ptr2int(nr);
+
+ switch (fromindex) {
+ case 1:
+ eir->to = int2ptr(2);
+ break;
+
+ case 2:
+ eir->to = NULL;
+ break;
+
+ case 3:
+ eir->to = int2ptr(4);
+ break;
+
+ default:
+ return -1;
+ }
+
+ return 0;
+}
+
+void error_graphr_init(struct error_graphr *egr)
+{
+ agar_init_graph(&egr->gr, error_first_edge_r, error_next_edge_r,
+ error_edge_info_r);
+}