Bern


As a guess its already been freed. Or at least that's what it usually means for me. I'd suggest an "if assigned(table) then table.free"

Roy Lambert

Roy Lambert wrote:

> Bern
>
>
> As a guess its already been freed. Or at least that's what it usually
> means for me. I'd suggest an "if assigned(table) then table.free"
>
> Roy Lambert

I thought about that and I am already doing that.
Bern

--

Roy, check out the source.  It is already checking for nil for you...

procedure TObject.Free;
asm
       TEST    EAX,EAX
       JE      @@exit
       MOV     ECX,[EAX]
       MOV     DL,1
       CALL    dword ptr [ECX].vmtDestroy
@@exit:
end;

--Bill Sparrow--

Bern,

<< For some reason I am randomly getting an AV when I free tables.  Here is
a snip from the bug report I am getting (I have also attached
the bug report in case it helps). Basically at line 8702 in my data module
I am doing a .free of the table then I get the AV. >>

Is there any chance that the data module's components are being improperly
shared between threads ?  That's where I would start looking.
--
Tim Young
Elevate Software
www.elevatesoft.com

Roy,

FreeAndNil(Table) would be more like it. AObject.Free won't
do anything if AObject = nil, so checking to see if is
assigned doesn't get you anything. Using FreeAndNil will set
the object reference to nil so you don't have a bad pointer
hanging around. Also, Assigned(AObject) returns true whether
or not the reference points to a valid object.

Try putting a single button on a form:

procedure TForm1.Button1Click(Sender: TObject);
var
  AObject: TObject;
begin
  AObject := TObject.Create;
  AObject.Free;
  if Assigned(AObject) then begin
     Button1.Caption := Button1.Caption + ' Assigned';
  end; {if assigned}
end;

Run the application and click the button. It will say
"Assigned" because the object reference is not nil even
though the object had been freed. Then replace AObject.Free
with FreeAndNil(AObject) and try again.

Sean


Roy Lambert wrote:

> Bern
>
>
> As a guess its already been freed. Or at least that's what it usually means for me. I'd suggest an "if assigned(table) then table.free"
>
> Roy Lambert
>

Tim Young [Elevate Software] wrote:

> Bern,
>
> << For some reason I am randomly getting an AV when I free tables.
> Here is a snip from the bug report I am getting (I have also attached
> the bug report in case it helps). Basically at line 8702 in my data
> module I am doing a .free of the table then I get the AV. >>
>
> Is there any chance that the data module's components are being
> improperly shared between threads ?  That's where I would start
> looking.

Each component is created dynamically in the data module to be thread
safe. But even so the procedure that is having the problem is not used
by a thread.

Bern

--

Bill


1. I never got into assembler - tried and failed
2. I that case why do I get AV's when trying to free an object that's already been freed?

Roy Lambert

Bern,

<< Each component is created dynamically in the data module to be thread
safe. But even so the procedure that is having the problem is not used by a
thread. >>

And there's no chance that there's a Free taking place on a previously-freed
or uninitialized object reference ?

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim Young [Elevate Software] wrote:

> Bern,
>
> << Each component is created dynamically in the data module to be
> thread safe. But even so the procedure that is having the problem is
> not used by a thread. >>
>
> And there's no chance that there's a Free taking place on a
> previously-freed or uninitialized object reference ?

Nope I checked the code and there is only 1 place where the table is
freed in the entire project.

BTW I see I did not put it in the orginal post, but this is random.

Bern

--