I work on Delphi project who interac with many other small libraries. I use FastMM4 and I would like work with complex classes passed on dll parameter.

So for exemple I send my form to my dll. Into the dll I test the type of parameter with the operator "IS".

But into the Dll the operator "IS" return always "false"

Exemple

library Dll;

uses
     FastMM4,
     System.SysUtils,
     System.Classes,
     Vcl.Dialogs,
     Vcl.Forms;

{$R *.res}

procedure Complex(L : TObject);stdcall;
begin
     if L is TForm then
        showmessage('Ok')
     else
        showmessage('Pas ok') ;

     if L is TCustomFrame then
         showmessage('Ok')
     else
         showmessage('Pas ok')
end;

exports
  Complex;

begin
end.

And the call

procedure TffsIsOperator.Button2Click(Sender: TObject);
var
 MaDLL : THandle;
 Proc  : procedure (l : TForm);
begin
   try
      MaDLL := LoadLibrary(PChar('Dll.dll'));
      @Proc := GetProcAddress(MaDLL, 'Complex');
      Proc(self);
   finally
      FreeLibrary(MaDLL);
   end;
end;