return NULL from deriveGraph to indicate failure

Related to #1801.

diff --git a/lib/fdpgen/layout.c b/lib/fdpgen/layout.c
index 46897b0bd9164504ce96bca5ec9a4867a7f83dfb..b491d6410b68f66731adef90cba880f9f33eedb7 100644 (file)
--- a/lib/fdpgen/layout.c
+++ b/lib/fdpgen/layout.c
@@ -467,7 +467,7 @@ static graph_t *deriveGraph(graph_t * g, layout_info * infop)
        if (!DNODE(n)) {
            if (PARENT(n) && PARENT(n) != GPARENT(g)) {
                agerr (AGERR, "node \"%s\" is contained in two non-comparable clusters \"%s\" and \"%s\"\n", agnameof(n), agnameof(g), agnameof(PARENT(n)));
-               longjmp (jbuf, 1);
+               return NULL;
            }
            PARENT(n) = g;
            if (IS_CLUST_NODE(n))