BUG #14983: ERROR: duplicate key value violates unique constraint "oid_tbl_oid_key"

The following bug has been logged on the website:

Bug reference: 14983
Logged by: Tony Reix
Email address: tony(dot)reix(at)atos(dot)net
PostgreSQL version: 10.1
Operating system: AIX
Description:

This error randomly appears when PostgreSQL is compiled with -O2 .
With -O0, no error out of 100 tries.

This error appears with v9.6.6, v10.0, and v10.1 . With compiler XLC v13 or
v12 (last available versions). On AIX 6.1, 7.1, and 7.2 .

The test is part of the PostgreSQL regression tests: cd src/bin ; su pgstbf
; gmake -C pgbench check.

I'd like to know how to produce more detailed traces.
Since I port PostgreSQL, I do not know how to debug PostgreSQL. So, I'd like
to get help about how to find the root cause of this issue.

Errors appearing in logs:
1) src/bin/pgbench/tmp_check/log/001_pgbench_main.log :
2017-12-18 16:07:39.268 CET [12976136] t/001_pgbench.pl LOG: execute
P0_0: INSERT INTO oid_tbl SELECT FROM generate_series(1,1000);
2017-12-18 16:07:39.268 CET [13041676] t/001_pgbench.pl ERROR: duplicate
key value violates unique constraint "oid_tbl_oid_key"
2017-12-18 16:07:39.268 CET [13041676] t/001_pgbench.pl DETAIL: Key
(oid)=(100291) already exists.
2017-12-18 16:07:39.268 CET [13041676] t/001_pgbench.pl STATEMENT:
INSERT INTO oid_tbl SELECT FROM generate_series(1,1000);
2017-12-18 16:07:39.285 CET [12386468] t/001_pgbench.pl LOG: execute
P0_0: INSERT INTO oid_tbl SELECT FROM generate_series(1,1000);

2) src/bin/pgbench/tmp_check/log/regress_log_001_pgbench :

Success. You can now start the database server using:

pg_ctl -D
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/tmp_check/data_main_2SQ6/pgdata
-l logfile start

# Running:
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/../../../src/test/regress/pg_regress
--config-auth
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/tmp_check/data_main_2SQ6/pgdata
### Starting node "main"
# Running: pg_ctl -D
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/tmp_check/data_main_2SQ6/pgdata
-l
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/tmp_check/log/001_pgbench_main.log
start
waiting for server to start.... done
server started
# Postmaster PID for node "main" is 12845290
# Running: pgbench --no-vacuum --client=5 --protocol=prepared
--transactions=25 --file
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/tmp_check/data_main_2SQ6/pgbench_script
ok 1 - concurrent OID generation: exit code 0
not ok 2 - concurrent OID generation: no stderr

# Failed test 'concurrent OID generation: no stderr'
# at
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/../../../src/test/perl/TestLib.pm
line 304.
# got: 'client 3 aborted in command 0 of script 0; ERROR:
duplicate key value violates unique constraint "oid_tbl_oid_key"
# DETAIL: Key (oid)=(100291) already exists.
#
# '
# expected:
not ok 3 - concurrent OID generation: matches

# Failed test 'concurrent OID generation: matches'
# at
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/../../../src/test/perl/TestLib.pm
line 305.
# 'transaction type:
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/tmp_check/data_main_2SQ6/pgbench_script
# scaling factor: 1
# query mode: prepared
# number of clients: 5
# number of threads: 1
# number of transactions per client: 25
# number of transactions actually processed: 117/125
# latency average = 37.404 ms
# tps = 133.674197 (including connections establishing)
# tps = 134.614762 (excluding connections establishing)
# '
# doesn't match '(?^:processed: 125/125)'
### Stopping node "main" using mode immediate
# Running: pg_ctl -D
/home2/freeware/src/packages/BUILD/postgresql-10.1-xlc13-AvecO2/32bit/src/bin/pgbench/tmp_check/data_main_2SQ6/pgdata
-m immediate stop
waiting for server to shut down.... done
server stopped
# No postmaster PID for node "main"
# Looks like you failed 2 tests of 3.