[GENERAL] C function returns null values

[Gregor Trefs]

Hello all,

I developed a C function which returns a record. The record contains 3 scalar 
values and 2 arrays. Randomly some record elements are null and I wonder why. I 
could trace down the problem to the point where the return record is created. 
Until this point everything is computed correctly. Below you see an excerpt of 
the relevant code. I use PostGres 8.4 on Ubuntu 10.10 (x64).

typedef struct {
    // Size of the array
    int size;
    // Values of the array
    double *values;
} array_d;

// Integer

typedef struct {
    // Size of the array
    int size;
    // Values of the array
    int *values;
} array_i;

typedef struct {
    interval_orders o;
    array_d *interval_weights;
    array_d *interval_borders;
    array_i *add_weights;
    double b;
} c_param_type;

void create_dati_from_result(Datum *values, c_param_type *param) {
    // Array creation
    ArrayType *weights, *borders;
    Datum *weights_elem;
    Datum *borders_elem;
    int16 typlen;
    bool typbyval;
    char typalign;

    int i;

    // Set values
    values[0] = Float8GetDatum(param->o.interval_weight);
    values[1] = Float8GetDatum(param->o.quantitiy);
    values[2] = Float8GetDatum(param->o.long_sql);
    // Create datum arrays
    weights_elem = palloc(param->interval_weights->size * sizeof (Datum));
    borders_elem = palloc(param->interval_borders->size * sizeof (Datum));
    for (i = 0; i < param->interval_weights->size; i++) {
        weights_elem[i] = Float8GetDatum((float8) 
param->interval_weights->values[i]);
    }
    for (i = 0; i < param->interval_borders->size; i++) {
        borders_elem[i] = Float8GetDatum((float8) 
param->interval_borders->values[i]);
    }
    // Create array type
    get_typlenbyvalalign(FLOAT8OID, &typlen, &typbyval, &typalign);
    weights = construct_array(weights_elem, param->interval_weights->size, 
FLOAT8OID, typlen, typbyval, typalign);
    borders = construct_array(borders_elem, param->interval_borders->size, 
FLOAT8OID, typlen, typbyval, typalign);
    values[3] = PointerGetDatum(borders);
    values[4] = PointerGetDatum(weights);
}

PG_FUNCTION_INFO_V1(insert_order);

Datum insert_order(PG_FUNCTION_ARGS) {
    // Variable declarations go here
    // ...
    // vars for result
    TupleDesc tupdesc;
    Datum *values;
    bool *nulls;
    int tuplen,i;
    HeapTuple res_tuple;
    // Look whether everything has been provided
    if (PG_ARGISNULL(0)) {
        ereport(ERROR, (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED), errmsg("First 
argument is NULL")));
        PG_RETURN_NULL();
    }
    // Allocate memory
    param = palloc(sizeof (c_param_type));
    // Get the HeapTupleHeader
    header = PG_GETARG_HEAPTUPLEHEADER_COPY(0);
    // Extract information from parameter
    if (!extract_information(param, header)) {
        PG_RETURN_NULL();
    }
    // Some more code goes here
    // ...

    // Set values
    param->o.long_sql = total_cost;
    param->o.quantitiy = weight;
    param->o.interval_weight = weight;

    // Create result tuple
    values = palloc(sizeof(Datum)*5);
    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        ereport(ERROR, (errcode(ERRCODE_SUCCESSFUL_COMPLETION), 
errmsg("function returning record called in context that cannot accept type 
record")));
    // Get Dati
    create_dati_from_result(values, param);
    // Init Tuple Desc
    tupdesc = BlessTupleDesc(tupdesc);
    // Size
    tuplen = tupdesc->natts;
    // Allocate enough memory for nulls
    nulls = palloc(tuplen * sizeof (bool));
    // Create tuple
    res_tuple = heap_form_tuple(tupdesc, values, nulls);
    // Free allocated memory
    pfree(nulls);
    // Return result
    PG_RETURN_DATUM(HeapTupleGetDatum(res_tuple));
}

I hope you can help me.

Regards,
Gregor