BUG #13598: Hang forever, but must rollback (deadlock)

The following bug has been logged on the website:

Bug reference: 13598
Logged by: ImmortalDragon
Email address: immortaldragonm(at)gmail(dot)com
PostgreSQL version: 9.4.4
Operating system: windows
Description:

table:
CREATE TABLE t1(id integer primary key);

libpq code:

c1 = PQconnectdb(conninfo);
c2 = PQconnectdb(conninfo);

res1 = PQexec(c1, "BEGIN");
PQclear(res1);

res1 = PQexec(c1, "INSERT INTO t1 (id) VALUES (104)");
PQclear(res1);

res2 = PQexec(c2, "BEGIN");
PQclear(res2);

res2 = PQexec(c2, "INSERT INTO t1 (id) VALUES (104)"); //hang here
PQclear(res2);

res2 = PQexec(c2, "END");
PQclear(res2);

res1 = PQexec(c1, "END");
PQclear(res1);

I use different connection in one thread (like different programs, as i
undestand).

I think, that postgres must detect deadlock and rollback one of transaction
with error. But it hang forever. Why? i think it's bug.

deadlock_timeout - default (1s)

i check other version of postgres, same result.