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