学习官方示例 - System.RunError
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

var P: Pointer;

procedure TForm1.Button1Click(Sender: TObject);
begin
if P = nil then
RunError(204);
end;

end.