$ valgrind -v --tool=memcheck --leak-check=full --trace-children=yes --track-origins=yes --time-stamp=yes --max-stackframe=4435592 --log-file=/tmp/zabbix_agentd_%p --leak-resolution=high --show-leak-kinds=all zabbix_agentd -t modbus.get[tcp://127.0.0.1]

==00:00:00:00.598 42628== 1,024 bytes in 1 blocks are definitely lost in loss record 11 of 12
==00:00:00:00.598 42628==    at 0x48407B4: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==00:00:00:00.598 42628==    by 0x16F20A: zbx_malloc2 (misc.c:152)
==00:00:00:00.598 42628==    by 0x1700F4: zbx_dvsprintf (common_str.c:72)
==00:00:00:00.598 42628==    by 0x170206: zbx_dsprintf (common_str.c:111)
==00:00:00:00.598 42628==    by 0x145396: modbus_read_data (modbus.c:552)
==00:00:00:00.598 42628==    by 0x145396: modbus_get (modbus.c:820)
==00:00:00:00.598 42628==    by 0x132948: zbx_execute_agent_check (sysinfo.c:1228)
==00:00:00:00.598 42628==    by 0x132DAB: zbx_test_parameter (sysinfo.c:970)
==00:00:00:00.598 42628==    by 0x11F4E2: main (zabbix_agentd.c:1545)