how to debug the codes in the PostgresMain() from the begining of this function to the "for (;;)" loop that handles the connection?

how to debug the codes in the PostgresMain() from the begining of this function to the "for (;;)" loop that handles the connection?
if i use eclipse cdt to attach the postgres process forked by postmaster, this part of codes from the begining of this PostgresMain() to the "for (;;)" loop could not be debugged. So anybody know how to debug this part codes? thanks.

thanks