how can I understand my valgrind error message?

I am getting the follow error message from valgrind:

==1808== 0 bytes in 1 blocks are still reachable in loss record 1 of 1,734
==1808==    at 0x4A05E7D: malloc (vg_replace_malloc.c:309)
==1808==    by 0x4CC2BA9: hwloc_build_level_from_list (topology.c:1603)
==1808==    by 0x4CC2BA9: hwloc_connect_levels (topology.c:1774)
==1808==    by 0x4CC2F25: hwloc_discover (topology.c:2091)
==1808==    by 0x4CC2F25: opal_hwloc132_hwloc_topology_load (topology.c:2596)
==1808==    by 0x4C60957: orte_odls_base_open (odls_base_open.c:205)
==1808==    by 0x632FDB3: ???
==1808==    by 0x4C3B6B9: orte_init (orte_init.c:127)
==1808==    by 0x403E0E: orterun (orterun.c:693)
==1808==    by 0x4035E3: main (main.c:13)
==1808==
==1808== 0 bytes in 1 blocks are still reachable in loss record 2 of 1,734
==1808==    at 0x4A05E7D: malloc (vg_replace_malloc.c:309)
==1808==    by 0x4CC2BD5: hwloc_build_level_from_list (topology.c:1603)
==1808==    by 0x4CC2BD5: hwloc_connect_levels (topology.c:1775)
==1808==    by 0x4CC2F25: hwloc_discover (topology.c:2091)
==1808==    by 0x4CC2F25: opal_hwloc132_hwloc_topology_load (topology.c:2596)
==1808==    by 0x4C60957: orte_odls_base_open (odls_base_open.c:205)
==1808==    by 0x632FDB3: ???
==1808==    by 0x4C3B6B9: orte_init (orte_init.c:127)
==1808==    by 0x403E0E: orterun (orterun.c:693)
==1808==    by 0x4035E3: main (main.c:13)

I am not able to understand which kind of problem valgrind is reporting. Is there anybody willing to explain?

I have checked all new instances. All of them are properly deleted.

I am getting valgrind error messagges and a further error form mpi when the code ends:

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mpirun noticed that process rank 0 with PID 1811 on node laki.pi.ingv.it exited on signal 11 (Segmentation fault).
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