Core dump when I run a program that uses embedded sql

Hello.
I'm using postgres 7.1, and I'm on my first try to use embedded sql. Here's
my problem.

I'm trying to use an example I copied from the web:

/**************************************************
Example program
for embedded SQL: tryit.pgc
**************************************************/

#include <stdio.h>

EXEC SQL INCLUDE sqlca;

main () {
EXEC SQL BEGIN DECLARE SECTION;
int sup_id;
int sales;
int total;
float price;
VARCHAR cof_name[33];
EXEC SQL END DECLARE SECTION;

EXEC SQL CONNECT 'TarjetaDebito' ;
if(sqlca.sqlcode) {
printf("Error al connectar a la base de datos.\n");
exit(0);
}

printf("Solicitud: ");
scanf("%d", &sup_id);

EXEC SQL SELECT nombreenplastico, correlativo INTO :cof_name, :price
FROM tarjeta WHERE correlativo = :sup_id ;
if (sqlca.sqlcode==0) {
printf("Result: %s tarjeta con solicitud $%5.2f\n", cof_name.arr,
price);
}
else {
printf("Error #%d: %s\n", sqlca.sqlerrm.sqlerrml,
sqlca.sqlerrm.sqlerrmc);
}
}

Nothing fancy as you can see... (of course I changed the names of the tables
and the fields to be able to find them on my server).

Then I precompile it (ecpg ...) successfully, and after that I compile it
with gcc (also everything OK aparently), and when I try to run my program, I
get
SEGMENTATION FAULT (core dumped).

I don't know where to start. Could you help me?

Thank you.

Ligia Pimentel