(gdb) bt full:
#0  0x00000000004063b7 in cmd_user_input (auth_socket_path=0x4117f8 "/usr/local/dovecot20/var/run/dovecot/auth-userdb", input=0x7fff41c65320) at doveadm-auth.c:41
        conn = 0x998f50
        pool = 0x997ac0
        username = 0x0
        fields = 0x0
        p = 0x0
        ret = -1
#1  0x0000000000406ab6 in auth_cmd_common (cmd=0x61a940, argc=2, argv=0x921048) at doveadm-auth.c:201
        first = false
        auth_socket_path = 0x0
        input = {username = 0x92107b "aaa", password = 0x0, info = {service = 0x4119da "doveadm", local_ip = {family = 0, u = {ip6 = {__in6_u = {__u6_addr8 = '\000' <repeats 15 times>, __u6_addr16 = {0, 0, 0, 
                      0, 0, 0, 0, 0}, __u6_addr32 = {0, 0, 0, 0}}}, ip4 = {s_addr = 0}}}, remote_ip = {family = 0, u = {ip6 = {__in6_u = {__u6_addr8 = '\000' <repeats 15 times>, __u6_addr16 = {0, 0, 0, 0, 0, 0, 
                      0, 0}, __u6_addr32 = {0, 0, 0, 0}}}, ip4 = {s_addr = 0}}}, local_port = 0, remote_port = 0}}
        c = -1
#2  0x0000000000406b3e in cmd_user (argc=2, argv=0x921048) at doveadm-auth.c:214
No locals.
#3  0x000000000040602f in doveadm_try_run (cmd_name=0x921076 "user", argc=2, argv=0x921048) at doveadm.c:83
        cmd__foreach_end = 0x986650
        cmd = 0x986590
#4  0x00000000004062da in main (argc=2, argv=0x921048) at doveadm.c:169
        set_roots = {0x413860, 0x0}
        service_flags = 10
        cmd_name = 0x921076 "user"
        error = 0x411685 "H\205\355t\034\061\333\017\037@"
        c = -1