pg_upgrade from 8.3 to 9.1 and Flag --disable-integer-datetimes

Hello all,

we want to upgrade our database from Postgres 8.3.23 to 9.1.12 using
pg_upgrade. The documentation on pg_upgrade
(http://www.postgresql.org/docs/9.1/static/pgupgrade.html) states the
following:

"Also, the default datetime storage format changed to integer after
PostgreSQL 8.3. pg_upgrade will check that the datetime storage format
used by the old and new clusters match. Make sure your new cluster is
built with the configure flag --disable-integer-datetimes."

We have a SLES 11 system. We installed Postgres 9.1.12 using Yast. We
assume that our installation was built WITHOUT --disable-integer-datetimes.

The pg_upgrade is running without any complaints. Since we assume that
our 9.1-server is built without disable-integer-datetimes, we expect
pg_upgrade to fail or giving some kind of notice.

What is the expected behavior of pg_upgrade in the case that 9.1-server
is not built with with disable-integer-datetimes?

How do we determine, whether or not a server is built with
disable-integer-datetimes?

Best regards

Meik Weißbach