Hi All,

In my Lazarus application I use a TPanel descendant component (TMyPanel) which have subpanels (TMySubPanel) which are TPanel descendants also. The subpanels accessed through a TList. If add a new subpanel into the main panel added to the list with TList.Add if remove a subpanel from it remove from the list with TList.Remove then call TMySubPanel.Free. My main development platform is x86_64-Linux and the application works like a charm. But with the Windows version of the app (cross compiled to i386-Win32) got an "Access violation." at TMySubPanel.Free. If start with gdb got "Program received signal SIGSEGV, Segmentation fault. 0x004041c4 in fpc_check_object ()" at TMySubPanel.Free.

I completely don't understand what is the source of the problem and why the two platforms behaves differently.

Cannot have a simple test case just a dumb example.

procedure TForm1.FormCreate(Sender: TObject);
var
   x:TPanel;
begin
   x.Free;
end;

With Linux no error (x is Nil before the Free call), with Windows got SIGSEGV (x is not Nil before the Free call). Is it a Lazarus thing or come from FPC?

Gabor

Hello,

That's wrong for sure, x is not initialized to nil, not in Linux nor in Windows. Procedure variables must be always initialized by hand. With that code you will get a warning from the compiler about uninitialized variable use.

2017. 06. 14. 10:28 keltezéssel, José Mejuto írta:

That's wrong for sure, x is not initialized to nil, not in Linux nor in Windows.

With the below code caption of the form not changed on Linux for me.

procedure TForm1.FormCreate(Sender: TObject);
var
   x:TPanel;
begin
   if Assigned(x) then Caption:='Assigned';
end;

Gabor

"Gabor Boros" wrote

2017. 06. 14. 10:28 keltezéssel, José Mejuto írta: > > That's wrong for sure, x is not initialized to nil, not in Linux nor in

Windows.

In this example the content of "x" is undefined as it's a local variable. The value of it is simply what is currently on the stack which *can* be Nil.

Regards,
Sven