Delph Exception handling problem with multiple Exception handling blocks

Posted by Robert Oschler on Stack Overflow See other posts from Stack Overflow or by Robert Oschler
Published on 2010-03-31T22:20:17Z Indexed on 2010/03/31 22:23 UTC
Read the original article Hit count: 1050

Filed under:
|
|
|
|

I'm using Delphi Pro 6 on Windows XP with FastMM 4.92 and the JEDI JVCL 3.0. Given the code below, I'm having the following problem: only the first exception handling block gets a valid instance of E. The other blocks match properly with the class of the Exception being raised, but E is unassigned (nil).

For example, given the current order of the exception handling blocks when I raise an E1 the block for E1 matches and E is a valid object instance. However, if I try to raise an E2, that block does match, but E is unassigned (nil). If I move the E2 catching block to the top of the ordering and raise an E1, then when the E1 block matches E is is now unassigned. With this new ordering if I raise an E2, E is properly assigned when it wasn't when the E2 block was not the first block in the ordering. Note I tried this case with a bare-bones project consisting of just a single Delphi form.

Am I doing something really silly here or is something really wrong?

Thanks, Robert

type
    E1 = class(EAbort)
    end;

    E2 = class(EAbort)
    end;


procedure TForm1.Button1Click(Sender: TObject);
begin
    try
        raise E1.Create('hello');
    except
        On E: E1 do
        begin
            OutputDebugString('E1');
        end;

        On E: E2 do
        begin
            OutputDebugString('E2');
        end;

        On E: Exception do
        begin
            OutputDebugString('E(all)');
        end;
    end; // try()
end;

© Stack Overflow or respective owner

Related posts about delphi

Related posts about exception