can external C-function get multiple rows?

I want my external C-function 'triple(int4)' to return multiple rows as 'SETOF int4' in order to be used in the
sql-statement
'select a.plno,a.prod from ( select * from plprice_00_1 ) a, ( select triple(17366760) as plno ) b where
a.plno=b.plno'.

Table 'plprice_00_1' is

pl=# \d plprice_00_1         Table "plprice_00_1"Attribute |     Type      | Modifier  
-----------+---------------+-----------plno      | integer       | not nullprod      | varchar(512)  | 
Indices: i_prc_prod_00_1,        pk_prc_plno_00_1

with primary key

pl=# \d pk_prc_plno_00_1
Index "pk_prc_plno_00_1"Attribute |  Type   
-----------+---------plno      | integer
unique btree (primary key)

I created C-function as

#include <stdlib.h>
int
triple(int i)
{       int *n = (int *)malloc(3*sizeof(int));       n[0] = i;       n[1] = 2*i;       n[2] = 3*i;       return *n;
}

and compiledit on Solaris using

# gcc -fpic -c triple.c
# gcc -G -o triple.so triple.o

Creating function in psql made no error

# CREATE FUNCTION triple(int4) RETURNS SETOF int4 AS '/var/local/lib/pgsql/lib/triple.so' LANGUAGE 'C';
CREATE

And now it just hung up (after pressing ^C it came back with "Cancel request sent ERROR:  Query was cancelled.") when I
call

# select triple(1);

So, can C-function return multiple rows? And if yes, what was my error?

Thanks in advance.

P.S.: Excuse me for bad english.

-- 

Alexey Nalbat