Re: BUG #17083: [PATCH] PostgreSQL fails to build with OpenLDAP 2.5.x

Adrian Ho <ml+postgresql(at)03s(dot)net> writes:
> Thanks, Tom, that turned out to only require one additional line, since
> $LIBS is already being saved and restored around that block:

I poked at this a bit further and realized that it's got a showstopper
problem: in OpenLDAP 2.4, ldap_simple_bind() exists in both libldap.so
and libldap_r.so. Thus, if we were dealing with an installation that
does not have a thread-safe libldap, the patched configure would
incorrectly seize on libldap.so as being an acceptable substitute,
allowing weird hard-to-diagnose failures at runtime.

IOW, while it might look from our existing coding like there's something
about ldap_simple_bind() that is tied to reentrancy, there isn't. How
else can we determine whether an OpenLDAP library is reentrant, if we
can no longer depend on the _r suffix?

Maybe we can decide that in 2021 such situations no longer exist in
the wild, but I'm unsure.

regards, tom lane