function idNvl( v,v2:PDSC):PDSC;cdecl; export;
begin
	if not isnull(v) then
		result:= v else
	result:= v2;
end;

procedure copyparam( v,rc:PDSC);
  begin
       //code provided by Rudy Velthuis (TeamB)
       rc^ := v^;
       //GetMem(rc^.dsc_address, v^.dsc_length);
       Move(v^.dsc_address^, rc.dsc_address^, v^.dsc_length);
  end;

DECLARE EXTERNAL FUNCTION UR_TEST
    DESCRIPTOR,
    DESCRIPTOR
RETURNS PARAMETER 2
ENTRY_POINT 'Test' MODULE_NAME 'Test.dll';

procedure Test(AParam: PISC_DSC; ARes: PISC_DSC); cdecl;
begin
  WriteToLogFmt('Param: %p', [AParam]);
  WriteToLogFmt('Res  : %p', [ARes]);
end;

SELECT ur_test('ABC') FROM rdb$database;

SELECT ur_test(99) FROM rdb$database;

RETURNS PARAMETER 2

declare external function UR_TEST
descriptor,
CSTRING(1024) BY DESCRIPTOR
RETURNS PARAMETER 2
entry_point 'Test' module_name 'Test.dll';

declare external function UR_TEST
descriptor,
DESCRIPTOR
RETURNS PARAMETER 2
entry_point 'Test' module_name 'Test.dll';

CREATE PROCEDURE SP_D_TEST (
  in_param VARCHAR(64))
RETURNS (
  out_param VARCHAR(64))
AS
BEGIN
  out_param = ur_test(:in_param);
END

DECLARE EXTERNAL FUNCTION name [data_type ;
| CSTRING (int) | DESCRIPTOR [, data_type | CSTRING (int) ...] DESCRIPTOR]
RETURNS {data_type [BY VALUE] | CSTRING (int) | PARAMETER n}
[FREE_IT]
ENTRY_POINT 'entryname'
MODULE_NAME 'modulename';