> Is there a way to tell the libpq connect function not to use a pgpass
> file?
No, as Tom already said.
I think you could effectively disable the pgpass file (for a given application) if the application always requires an explicit, non-blank password from the user.
libpq won't use .pgpass if the connection string passed to PQconnectdb() (or whatever connection function you happen to be using) includes a "password=foo" clause, right?
-- Korry