Return setof values from C-function

[Yuriy Rusinov <yrusinov@xxxxxxxxx>]

Dear Colleagues !

I have to return setof values from C-function

I wrote

    FuncCallContext *funcctx;

    int call_cntr;

    int max_calls;

    AttInMetadata *attinmeta;

    unsigned long il;

    if (SRF_IS_FIRSTCALL())

    {

        MemoryContext   oldcontext;

        funcctx = SRF_FIRSTCALL_INIT();

        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        funcctx->max_calls = num;

        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)

            ereport(ERROR,

                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),

                     errmsg("function returning record called in context "

                            "that cannot accept type record")));

        attinmeta = 0;//TupleDescGetAttInMetadata(tupdesc);

        funcctx->attinmeta = 0;//attinmeta;

        MemoryContextSwitchTo(oldcontext);

        funcctx->tuple_desc = BlessTupleDesc( tupdesc );

        elog (INFO, "1st row");

    }

    funcctx = SRF_PERCALL_SETUP();

    call_cntr = funcctx->call_cntr;

    max_calls = funcctx->max_calls;

    attinmeta = funcctx->attinmeta;

    HeapTuple tuple;

    if (call_cntr < max_calls)

    {

        elog (INFO, "Rows");

        unsigned long il = call_cntr;

        Datum * hvalues = (Datum *)palloc (2*sizeof(Datum));

        double val = gsl_histogram_get (gHist, il);

        hvalues[0] = UInt32GetDatum (il);

        hvalues[1] = Float8GetDatum (val);

        bool * nulls = palloc( 2 * sizeof( bool ) );

        elog (INFO, "%lu", il);

        tuple = heap_form_tuple( tupdesc, hvalues, nulls);

        elog (INFO, "%lu", il);

        //BuildTupleFromCStrings (attinmeta, hvalues);

        pfree (nulls);

        pfree (hvalues);

        SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum( tuple ) );

    }

    else

    {

        SRF_RETURN_DONE(funcctx);

    }

as written in documentation, but my function drops on 

tuple = heap_form_tuple( tupdesc, hvalues, nulls);

Could you tell me, are there any errors ?

--
Best regards,
Sincerely yours,
Yuriy Rusinov.