In pg_ctl, work around ERROR_SHARING_VIOLATION on the postmaster log file.
On Windows, we use CMD.EXE to redirect the postmaster's stdout/stderr
into a log file. CMD.EXE will open that file with non-sharing-friendly
parameters, and the file will remain open for a short time after the
postmaster has removed postmaster.pid. This can result in an
ERROR_SHARING_VIOLATION failure if we attempt to start a new postmaster
immediately with the same log file (e.g. during "pg_ctl restart").
This seems to explain intermittent buildfarm failures we've been seeing
on Windows machines.
To fix, just open and close the log file using our own pgwin32_open(),
which will wait if necessary to avoid the failure. (Perhaps someday
we should stop using CMD.EXE, but that would be a far more complex
patch, and it doesn't seem worth the trouble ... yet.)
Back-patch to v12. This only solves the problem when frontend fopen()
is redirected to pgwin32_fopen(), which has only been true since commit
0ba06e0bf. Hence, no point in back-patching further, unless we care
to back-patch that change too.
Diagnosis and patch by Alexander Lakhin (bug #16154).
Discussion: https://postgr.es/m/16154-
1ccf0b537b24d5e0@postgresql.org