Getting Constrint information..??

Help!

Can anyone tell me what wrong with the following codesnippet. I nuke the
server when called (stored procedure)

... some VALID spi_exec call :-) has been done ...

TupleDesc tupdesc = SPI_tuptable->tupdesc;
TupleConstr *tupconstr = SPI_tuptable->tupdesc->constr;
ConstrCheck *check = tupconstr->check;
SPITupleTable *tuptable = SPI_tuptable;
char *ccbin;

char buf[8192];
int i;

for (i = 1, buf[0] = 0; i <= tupdesc->natts; i++) {
ccbin = check[i].ccbin;
sprintf(buf + strlen (buf), "%s, %s",
SPI_fname(tupdesc,i),
ccbin);
elog (NOTICE, "%s", buf);
}

I have not had any luck :-( I'm a C beginner thou, so maybe i screw up when
accessing the structures

Any help is appreciated

/Steffen Nielsen