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Create a (unique) GUID (2) (Views: 100)


Problem/Question/Abstract:

I have a very simple piece of test code to generate and display a GUID on the screen every time a user clicks on a button on a form. When I compile the program and run the executable on my Windows 2000 machine, I get a unique GUID every time I click the button, which is what I expect from the documentation. However, when I run the same executable on any Windows 98 SE machine, and even a Windows NT 4.0 Server (with SP5), it simply generates the exact same GUID over, and over, and over again.

Answer:

Using RAW API:

{ ... }
var
  Form1: TForm1;
  UuidCreateFunc: function(var guid: TGUID): HResult; stdcall;

implementation

{$R *.DFM}

uses
  ComObj;

procedure TForm1.Button1Click(Sender: TObject);
var
  hr: HRESULT;
  m_TGUID: TGUID;
  handle: THandle;
begin
  handle := LoadLibrary('RPCRT4.DLL');
  @UuidCreateFunc := GetProcAddress(Handle, 'UuidCreate');
  hr := UuidCreateFunc(m_TGUID);
  if failed(hr) then
    RaiseLastWin32Error;
  ShowMessage(GUIDToString(m_TGUID));
end;

With WIN2K support:

{ ... }
var
  Form1: TForm1;
  UuidCreateFunc: function(var guid: TGUID): HResult; stdcall;

implementation

{$R *.DFM}

uses
  ComObj;

procedure TForm1.Button1Click(Sender: TObject);
var
  hr: HRESULT;
  m_TGUID: TGUID;
  handle: THandle;
  WinVer: _OSVersionInfoA;
begin
  handle := LoadLibrary('RPCRT4.DLL');
  WinVer.dwOSVersionInfoSize := sizeof(WinVer);
  getversionex(WinVer);
  if WinVer.dwMajorVersion >= 5 then {Windows 2000 }
    @UuidCreateFunc := GetProcAddress(Handle, 'UuidCreateSequential')
  else
    @UuidCreateFunc := GetProcAddress(Handle, 'UuidCreate');
  hr := UuidCreateFunc(m_TGUID);
  if failed(hr) then
    RaiseLastWin32Error;
  ShowMessage(GUIDToString(m_TGUID));
end;

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