libpq: large objects

hej,

I'm having some troubles importing/exporting large objects using the
libpq C interface. I wrote a simple test program to see where the error
might be, but not even this seems to work:
test.cpp should import a file /tmp/redball.gif, and just try to open the
large object.
then, there is a manually inserted object in the database which I want
to export as /tmp/redball1.gif.
All functions fail with errors.

However, when doing the same import/export procedure using the
psql commandline tool, there's no problem. do you have any suggestions
what might be wrong? is the large object interface of libpq still very
much under development? Did I forget anything of great importance?

postgres version is 7.0.2-2, compiled from source, under SuSE 6.4
(kernel 2.2.16; libc 2.1.3-91); program, database and psql tool are run
resp. owned by the user "webdev" (having all necessary access rights).

I'd gladly appreciate ANY help & suggestions,
Philipp Käser
pkaeser(at)obtree(dot)com

------ test.cpp - test program to import/export some data ------
// link/compile using
// g++ -I/usr/local/pgsql/include -L/usr/local/pgsql/lib -lpq test.cpp -o
test

#include "libpq-fe.h"
#include "libpq/libpq-fs.h"

PGconn *myconn;

void main(void)
{
int tmpid, lofd;

printf("opening db\n");
myconn = PQconnectdb("host=localhost port=5432 dbname=PGSQLTest
user=webdev password=oms98");

if (PQstatus(myconn) != CONNECTION_OK) {
printf("error\n");
exit(-1);
}

printf("trying to import object /tmp/redball.gif...");
tmpid = lo_import(myconn, "/tmp/redball.gif");
printf("done, at id = %d\n", tmpid);

printf("ERROR MESSAGE %s\n", PQerrorMessage(myconn));

printf("trying to open obj with id = %d...", tmpid);
lofd = lo_open(myconn, tmpid, INV_READ);
printf(" ... done, at lofd = %d\n", lofd);

tmpid = 75201;
printf("trying to export to file /tmp/redball1.gif, from oid = %d",
tmpid);
lofd = lo_export(myconn, tmpid, "/tmp/redball1.gif");
printf(" ... done, retval = %d\n", lofd);

printf("ERROR MESSAGE %s\n", PQerrorMessage(myconn));

printf("terminating db connection\n");
PQfinish(myconn);

}

------ output when test is run ------
opening db
trying to import object /tmp/redball.gif...done, at id = 0
ERROR MESSAGE lo_import: could not open inv object oid 82753
trying to open obj with id = 0... ... done, at lofd = -1
trying to export to file /tmp/redball1.gif, from oid = 75201 ... done,
retval = -1
ERROR MESSAGE lo_export: can't open inv object 75201
terminating db connection

------ how it looks when exporting the already existing data, using psql
------
PGSQLTest=# select lo_export(75201, '/tmp/redball.gif');
lo_export
-----------
1
(1 row)

PGSQLTest=#