The following bug has been logged online:
Bug reference: 6210
Logged by: Norman Palardy
Email address: npalardy@great-white-software.com
PostgreSQL version: 9
Operating system: OS X
Description: Description of PQconnectdbParams in documentation
Details:
Description of PQconnectdbParams in documentation does not say what happens
if you send parameters that the server does not recognize.
More an oversight / shortcoming than anything.
It appears that sending "application_name" to a server that does not support
that results in a failed connection - but this is not explicitly documented.