urgent: kol+freelibrary - access violation

← →
Riton (2005-09-07 19:06) [0]

Hello,

I used the Demo "DemoVCL2KOLDLL" (kol website : downloads > demos > ModalVCL2KOLDLL) and tried to modify it so that the dll becomes dynamic.

I encountered a problem by using Freelibrary !
When I quit the application "VCLProject1.exe", the error message which occurs is :
Access Violation at the address 00AF3DD8. Read of address 00AF3DD8.
What happens ?

Here is the code with the modifications in VCLUnit.pas :

unit VCLUnit1;

interface

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

type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

//procedure CallKOLFormModal; external "KOLDll.dll" name "CallKOLFormModal";
var
CallKOLFormModal: procedure;
dll:thandle;

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
// CallKOLFormModal;
dll:=loadlibrary("KOLDLL.dll");
CallKOLFormModal:=GetProcAddress(dll,"CallKOLFormModal");
CallKOLFormModal;
Freelibrary(dll);//if I use freelibrary, problem is "Access Violation"!
end;

end.

Thank you very much for resolving this problem.
Riton.

← →
Wiz@rd (2005-09-07 23:59) [1]

Try use Freelibrary on program terminating

← →
Thaddy (2005-09-08 16:07) [2]

If you have the error address, why do you not use the debugger?
The example as such does not contain erronious code.
Strategy one:
Check if the library is still loaded!
Check the call stack!

Strategy two:
Steps:
1. write down error address.
2. press F7 to start debugging session (step through mode)
3. press alt+G and enter address.

Look where it jumps to.

If this doesn"t work, compile in full debug mode and repeat the above.

I am afraid you will not get any serious answer here before you properly debug your code yourself.

← →
Riton (2005-09-08 19:52) [3]

Thanks very much for your help Wiz@rd and Thaddy.

Maybe a solution ?
The dll is unloaded when application is destroying.

There is anyway no more error with this procedure. I hope that it is a good way to solve the problem with freelibrary.

procedure TForm1.Form1Destroy(Sender: TObject);
begin
Freelibrary(dll);
end;

← →
Thaddy (2005-09-08 20:36) [4]

Yes. Or an example if you don"t need it after it was modal and to save resources:
procedure TForm1.Button1Click(Sender: TObject); var dll:THandle; begin // CallKOLFormModal; dll:=loadlibrary("KOLDLL.dll"); if dll <> 0 {or really >=32 i think, no win32.hlp on my GSM ;) } then begin CallKOLFormModal:=GetProcAddress(dll,"CallKOLFormModal"); if CallKOLFormModal <> 0 then CallKOLFormModal; Freelibrary(dll); end; end;

← →
Riton (2005-09-09 18:34) [5]

Alas, it doesn"t work.

- On the one hand there is a type compatibility problem with the following code :
if CallKOLFormModal <> 0 then CallKOLFormModal;

- On the other hand, if I suppress this code, I find again the access violation error :
Access Violation at the address 00AF3DD8. Read of address 00AF3DD8.

Sorry that your code doesn"t work.

If you want or have time to, I can send a zip file to you where the modifications are brought by me.

Riton.

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