[Peter Eisentraut <peter.eisentraut@enterprisedb.com>]

configure can report this:

configure: WARNING:
*** With OpenLDAP versions 2.4.24 through 2.4.31, inclusive, each backend
*** process that loads libpq (via WAL receiver, dblink, or postgres_fdw) and
*** also uses LDAP will crash on exit.

The source code also says

# PostgreSQL sometimes loads libldap_r and plain libldap into the same
# process.  Check for OpenLDAP versions known not to tolerate doing so; 
assume
# non-OpenLDAP implementations are safe.  The dblink test suite 
exercises the
# hazardous interaction directly.

The libldap installation that comes with the macOS operating system 
reports itself as version 2.4.28, so this warning comes up every time, 
but the dblink test suite passes without problem.

I looked into this a bit further.  I checked by installing openldap 
2.4.31 from source on an centos 7 instance, and indeed the dblink test 
suite crashes right away.  So the test is still good.  I think it's very 
likely that Apple has patched around in their libldap code without 
changing the version.

I wonder whether we can do something to not make this warning appear 
when it's not necessary.  The release of openldap 2.4.32 (the first good 
one) is now ten years ago, so seeing faulty versions in the wild should 
be very rare.  I'm tempted to suggest that we can just remove the 
warning and rely on the dblink test to catch any stragglers.  We could 
also disable the test on macOS only.  Thoughts?