there is byte order issue about mp->retval when session feature disabled, as follow:

(gdb) bt
#0 0x00000000004041b2 in vl_api_connect_uri_reply_t_handler (mp=0x3047f93c) at /home/wanghui/vpp_git/vpp/build-data/../src/uri/uri_tcp_test.c:491
#1 0x00007ffff7bc89b7 in msg_handler_internal (free_it=1, do_it=1, trace_it=<optimized out>, the_msg=0x3047f93c, am=0x7ffff7ddb2c0 <api_main>)
at /home/wanghui/vpp_git/vpp/src/vlibapi/api_shared.c:422
#2 vl_msg_api_handler (the_msg=0x3047f93c) at /home/wanghui/vpp_git/vpp/src/vlibapi/api_shared.c:545
#3 0x00007ffff7bc984a in vl_msg_api_queue_handler (q=q@entry=0x305e7ec0) at /home/wanghui/vpp_git/vpp/src/vlibapi/api_shared.c:721
#4 0x00007ffff7bcbf82 in rx_thread_fn (arg=<optimized out>) at /home/wanghui/vpp_git/vpp/src/vlibmemory/memory_client.c:92
#5 0x00007ffff7512df3 in start_thread () from /lib64/libpthread.so.0
#6 0x00007ffff6d363dd in clone () from /lib64/libc.so.6

(gdb) p/x mp->retval
$2 = 0xe2ffffff