How to translate optional parameters from C to Delphi?

Question

Delphi

When translating functions from C to Delphi, I encountered an interesting moment, in the header file in C, there is such a function declaration: The

question is how to correctly implement this function in Delphi (my version, only the first two parameters)?

function Vix_GetProperties(handle: VixHandle;
                           firstPropertyID: VixPropertyID
                           ): VixError; cdecl; external 'vix.dll';

Unfortunately, I did not find examples of how to transfer such things '...' as a parameter from C to Delphi...

Answer 1

function Vix_GetProperties(
  handle: VixHandle;
  firstPropertyID: VixPropertyID
): VixError; cdecl varargs; external 'vix.dll';

After cdecl add varargs. This allows the remote library to tell the compiler that we can pass arguments as a list.
Thank you all very much!

Answer 2

Only by passing parameters in an array.

procedure TForm1.Display(X: array of const);
var
  I: Integer;
begin
  for I := Low(X) to High(X) do
  ...
end;

Display([42, 1.234, 'A', 'Васек Трубачев', Form1, TButton]);

Answer 3

Vix_GetPropertiesworks similarly WriteLnwith a list.

Predefined constants, types, procedures, and functions (such as True, Integer, or Writeln) do not have actual declarations.Instead they are built into the compiler and are treated as if they were declared at the beginning of the System unit.