wat is the max number of rows that can be returned

hi all,
i am using postgreSQL7.1.3 with libPQ C API.

suppose i create a table tbl (col int8 primary key) and populate the table
to the full.
Now if i retreive the result with

int a;
..
result = pqexec(conn, "select * from tbl");
a = PQntuples (result);
..

what will be the value of a.

The value must surely wrap around, i presume (PQntuples returns int).
Is this limitation because of C API??

When there is provision to insert that many rows, is there any ways to
obtain the correct number of rows. (thru' C API). Or is it possible in
any other API.

tia.
--
regards,
hari