Where to execute the compiled psql

Greetings,

I am writing some plugin for pq. After running ./configure and make, shall I 
just go to /src/bin/psql to execute my executable psql -U (usrname) dbname? 
It seems that my updates in the file parse_expr.c is not reflect in this 
executable? For example, I changed one line from
  if (NULL == tup)   ereport(ERROR, (errcode(ERRCODE_UNDEFINED_OBJECT),   errmsg("key value not found")));

-->
  if (NULL == tup)   ereport(ERROR, (errcode(ERRCODE_UNDEFINED_OBJECT),   errmsg("key value not found while building
relation")));

But the program still reports key value not found when it runs.

Best wishes,
John