How to avoid an error from displaying?

Question

How to avoid an error from displaying the little Windows error box?
Try and Except dont work because the error isnt showned by Delphi but from Program or I think from Windows.

try
Size:=TFileStream.Create(BitFile,fmOpenRead);
except on E: EFCreateError
do EC.Add('Error: ' + IntToStr(GetLastError));
end;

Answer 1

Is the error shown in your application? Otherwise put, is it an unhandled exception? Or is it a box displayed by Windows or by an external application?

You say 'event', but event handlers can contain try..except blocks too.

If it is an exception, and you don't know where it's coming from, you can use the TApplicationEvents class to attach the Application.OnException event. It will fire on all unhandled exceptions. There you can catch it, or rather, set a breakpoint and use the stack trace to see where the exception is coming from.

Answer 2

An error box doesn't imply an exception has been raised. An error box can be explicitly shown in code.

So, it seems your question is "How can I prevent 3rd party code from working As Designed?". Beside decompiling the binaries, I'm afraid I can't suggest much, especially if you don't have the source.

If you have the source code and know the routine that needs to be replaced, you could write your own replacement and "hijack" the routine at runtime. This is the method used by, for example, the fastcode project to replace delphi's routine without recompiling the VCL. You can see the implementation in their project.

http://fastcode.sourceforge.net/

Unit: FastcodePatch.pas

Answer 3

Here it is

 private
    { Private declarations }
  public
   procedure MyExceptionHandler(Sender : TObject; E : Exception ); //define exception handler
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.MyExceptionHandler(Sender:TObject;E:Exception);
begin
    //Do nothing
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Application.OnException := MyExceptionHandler;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  //Generate an exception
  asm
  mov eax,8272
  mov [eax],$2FFFFF
  end 
end;