Safe way (gc friendly) to change the reference values of args

[jazlee]

Hello,

From Issue: #296 I know all arguments are passed by reference, question: what is the safe way (GC friendly) to replace value referenced by args into something else? ex: from int to string, from unknown to int. Is there any example I can use for

In my case, I need to write a function that returns multiple return values which this cannot be done using conventional function structure, so i want to use parameter as output argument.

for example in gravity:

func main() {
   var date_today = SysUtils.Today();  // 12-12-2023
   var year, month, day;
   SysUtils.DecodeDate(date_today, year, month, day);  // output: year = 2023, month = 12, day = 12
}

The decodedate function in native (object pascal language):

function gravity_decodedate(vm: Pgravity_vm; args: Pgravity_value_t; nargs: UInt16; rindex: UInt32): Boolean; cdecl;

  procedure REPLACE_TO_INT(AVal: Pgravity_value_t; value: Int64);
  begin
    AVal^.isa := GravityEng.gravity_class_int;
    AVal^.f2.n := value;
  end;
var
  Year, Month, Day: Pgravity_value_t; // gravity_value_t*
  AYear, AMonth, ADay: Word;
begin
  with GravityEng do
  begin
    if (nargs <> 5) then
      Result := RETURN_ERROR(vm, 'Incorrect number of arguments.', rindex)
    else
    begin
      // Get the reference pointer to year, month, day in args
      Year := Pgravity_value_t(NativeUInt(args) + 2 * SizeOf(gravity_value_t));
      Month := Pgravity_value_t(NativeUInt(args) + 3 * SizeOf(gravity_value_t));
      Day := Pgravity_value_t(NativeUInt(args) + 4 * SizeOf(gravity_value_t));

      // perform decoding date
      DecodeDate(VALUE_AS_FLOAT(GET_VALUE(args, 1)), AYear, AMonth, ADay);

      // replace value on reference params
      REPLACE_TO_INT(Year, AYear);
      REPLACE_TO_INT(Month, AMonth);
      REPLACE_TO_INT(Day, ADay);
      Result := RETURN_NOVALUE;
    end;
  end;
end;

Regards,

-Jaimy.