debugging libpq backend code

Hello All,

I'm trying to debug libpq backend code (files: auth.c, auth-sasl.c in
directory src/backend/libpq).
I followed: Developer FAQ - PostgreSQL wiki and attached postgres
process ( because connection is still in progress and I don't see
backend process yet when I try to connect through psql). I could set
the break-points but these are not hit while it must. I think I should
not be attaching postmaster parent process instead attach the backend
process but how? how do I get the backend process id? Please note that
ps -ef does not show backend process and also I can't run `select
pg_backend_pid()` as connection is not authorized yet.

Can you suggest how to debug this backend code? especially files:
auth.c, auth-sasl.c in directory src/backend/libpq).

Appreciate your help.

Thanks,
Mahendrakar.