BUG #16039: PANIC when activating replication slots in Postgres 12.0 64bit under Windows

The following bug has been logged on the website:

Bug reference:      16039
Logged by:          Hans Buschmann
Email address:      buschmann@nidsa.net
PostgreSQL version: 12.0
Operating system:   Windows Server 2019 64bit
Description:

We just moved our production cluster from pg 11.5 to pg 12.0 under windows
using pg_dump/initdb/pg_restore.

When we activated the replication slots by  

SELECT * FROM pg_create_physical_replication_slot('sam_repli_3');

and tried restarting the server, we got a PANIC in error log:

CPS PRD 2019-10-04 19:10:07 CEST  00000  1:> LOG:  database system was shut
down at 2019-10-04 19:10:02 CEST
CPS PRD 2019-10-04 19:10:07 CEST  XX000  2:> PANIC:  could not fsync file
"pg_replslot/sam_repli_3/state": Bad file descriptor
CPS PRD 2019-10-04 19:10:07 CEST  00000  6:> LOG:  startup process (PID
4028) was terminated by exception 0xC0000409
CPS PRD 2019-10-04 19:10:07 CEST  00000  7:> HINT:  See C include file
"ntstatus.h" for a description of the hexadecimal value.
CPS PRD 2019-10-04 19:10:07 CEST  00000  8:> LOG:  aborting startup due to
startup process failure
CPS PRD 2019-10-04 19:10:07 CEST  00000  9:> LOG:  database system is shut
down

We use the EDB distribution from the website under Windows Server 2019
(September 2019 patch level).

select version ();
                          version
------------------------------------------------------------
 PostgreSQL 12.0, compiled by Visual C++ build 1914, 64-bit
(1 Zeile)

This seems to me like a fatal bug which makes the streaming replication
unusable under Windows x64 /pg12.

The same configuration worked flawlessly under pg 11.x until pg 11.5

By searching on google we encountered a similar error from 2015 under pg
9.4.1 reported under BUG #13287:

https://www.postgresql.org/message-id/flat/20150514105514.2691.67352%40wrigleys.postgresql.org

We were able to remove the replication slot by deleting the directory
pg_replslot/sam_repli_3.

The server seems to be working fine now, but without streaming replication
of course.


BTW: Is it necessary to restart the cluster after creating the replication
slot or is it a consequence of the error, that the 
newly created slot is not active automatically?

select * from pg_replication_slots;
  slot_name  | plugin | slot_type | datoid | database | temporary | active |
active_pid | xmin | catalog_xmin | restart_lsn | confirmed_flush_lsn

-------------+--------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------
 sam_repli_3 |        | physical  |        |          | f         | f      |
           |      |              |             |
 sam_repli_5 |        | physical  |        |          | f         | f      |
           |      |              |             |
(2 Zeilen)


Many thanks!


Hans Buschmann