build_set
a = build_set("a", va, sizeof(va) / sizeof(va[0]),
aa = build_set("aa", vaa, sizeof(vaa) / sizeof(vaa[0]), 0);
b = build_set("b", vb, sizeof(vb) / sizeof(vb[0]), 1);
c = build_set("c", vc, sizeof(vc) / sizeof(vc[0]), 1);
empty = build_set("empty", NULL, 0, 0);