[PostgreSQL-Hackers] Finding a flow when query is fired in postgresql

i edited postgreql file so that i can check the flow of .c files invoked when
we fire a query but only what i am getting is just parse trees ,rewritten
trees and plan but no names of .c files invoked...
plz help me asap ...its very important for me. what additional changes are
required to see the names of .c files when query is fired......