undefined reference to `PQprepare' with postgresql-dev 7.4.7-6sarge2

Hello,

I'm trying to compile a libpq program under Debian 3.1r2 with these
packages installed:

$ dpkg -l | grep postgres
ii postgresql 7.4.7-6sarge2 object-relational SQL database management sy
ii postgresql-cli 7.4.7-6sarge2 front-end programs for PostgreSQL
ii postgresql-con 7.4.7-6sarge2 additional facilities for PostgreSQL
ii postgresql-dev 7.4.7-6sarge2 development files for libpq (PostgreSQL libr
ii postgresql-doc 7.4.7-6sarge2 documentation for the PostgreSQL database ma

That program compiles and works fine with OpenBSD
and Cygwin (I'm using PostgreSQL 8.x there though...)

On Debian it unfortunately doesn't link:

$ gcc build/pref.o build/message.o build/pgsql.o build/user.o
build/util.o build/table.o build/common.o build/array.o
build/xstring.o build/strlcpy.o build/strlcat.o build/daemon.o -o pref
-L /usr/lib -L /usr/lib/postgresql/lib -lpq
build/pgsql.o(.text+0x15b): In function `db_prepare':
server/pgsql.c:57: undefined reference to `PQprepare'
collect2: ld returned 1 exit status

$ pg_config --version
PostgreSQL 7.4.7

$ pg_config --libdir
/usr/lib

$ objdump -x /usr/lib/libpq.a | grep -i PQprepare
00000000 *UND* 00000000 pqPrepareAsyncResult
00001974 R_386_PLT32 pqPrepareAsyncResult
00000490 g F .text 0000007d pqPrepareAsyncResult
000012e5 R_386_PLT32 pqPrepareAsyncResult
0000130a R_386_PLT32 pqPrepareAsyncResult
00000000 *UND* 00000000 pqPrepareAsyncResult
00001841 R_386_PLT32 pqPrepareAsyncResult

There are very few hits for the "undefined reference PQprepare"
on Google (which I take a good sign :-)

Does anybody have an idea please, what could I be doing wrong?

Why doesn't objdump find PQprepare, but finds PQconnectdb?

$ objdump -x /usr/lib/libpq.a | grep -i PQconnectdb
00000000 g F .text 00000042 PQconnectdb

Thank you
Alex

PS: And here is the code failing to link (my server/pgsql.c)
probably nothing special:

#define DB_CONN_STR "host=/tmp user=XXX dbname=XXX"
#define SQL_FETCH_USER \
"select username, user_avatar from phpbb_users where user_active = 1 " \
"and user_id = $1 and user_password = $2 and user_id not in " \
"(select ban_userid from phpbb_banlist where ban_userid is not null)"
......
static void
db_reconnect()
{
PQreset(conn);

if (PQstatus(conn) != CONNECTION_OK) {
warn("Connection to db '%s' failed: %s",
DB_CONN_STR, PQerrorMessage(conn));
sleep(RETRY_INTERVAL);
return;
}

db_prepare("sql_fetch_user", SQL_FETCH_USER, 2);
}

void
db_prepare(const char *stname, const char *query, int nparams)
{
PGresult* res;

res = PQprepare(conn, stname, query, nparams, NULL);
if (PQresultStatus(res) != PGRES_COMMAND_OK) {
PQclear(res);
db_disconnect();
die("Preparing statement '%s' failed: %s",
query, PQerrorMessage(conn));
}

PQclear(res);
}
......

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