memcmp((p1)->field, (p2)->field, ...) results in undefined behaviour if (p1)->field or (p2)->field is NULL. This holds also when tal_count((p1)->field) * sizeof(*(p1)->field) == 0.
memcmp((p1)->field, (p2)->field, ...) results in undefined behaviour if (p1)->field or (p2)->field is NULL. This holds also when tal_count((p1)->field) * sizeof(*(p1)->field) == 0.