Re: [Gnavi-discuss] GWindows : GNAT 3.15p vs GNAT 2005 about exceptions

[Wiljan D. <wil...@ph...>]

Hello Gautier,

You wrote:
> I also noticed that the exception 
>appears, as if not caught, on a console (when the console has not been 
>disabled by the -mwindows linker argument of course).

I have run into the same problem. In general one wants an exception 
handler that catches these exceptions
and reports them so one has a traceback. That ususually helps a great deal 
finding the root cause.
Th latest gnat release have a different exception mechanism.
Exception do not progagate through the stack when there are pieces of non 
Ada code.
For this reason, I addapted Gwindows to establish an exception handler for 
these cases.
In the gwindows-base.ads I added:

   type Exception_Event is access
     procedure (Window : in out GWindows.Base.Base_Window_Type'Class;
                E : Ada.Exceptions.Exception_Occurrence);

   procedure On_Exception_Handler (Handler : Exception_Event);

The exception handler routine in store in a global variable:

   Exception_Handler : Exception_Event;
   procedure On_Exception_Handler (Handler : Exception_Event) is
   begin
      Exception_Handler := Handler;
   end On_Exception_Handler;

In the routines WndProc and WndProc_Control I use an exception handler in 
the following form:

   exception when E : others =>
      if Exception_Handler /= null then
         Exception_Handler (Win_Ptr.all, E);
      end if;
      raise;

This mechanism seems to be working fine and can catch all exceptions.
The application of cause needs to install such an exception handler.

Please anyone comment on these changes.

Greetings,

Wiljan