[Gnucash-changes] Eliminate a double free of memory.

[David Hampton]

On Thu, 2005-06-02 at 16:59 -0400, Chris Shoemaker wrote:
> 1) The gtk_destroy signal handler (gnc_customer_window_destroy_cb) does
> NOT emit the CM event.  
> (It should be calling gnc_close_gui_component(cw->component_id);)
> 
> 2) The CM destroy handler (gnc_customer_window_close_handler) does NOT
> destroy the dialog context.  Instead, that's actually done inside the
> gtk_destroy signal handler.
> 
> 
> The biggest hint that this is an abuse of the CM api is the fact that
> the close handler is not explicitly unregistering the component with
> the CM, instead relying on it happening as a side-effect of the
> gtk_destroy signal.  If the close handler wanted to do anything with
> the component after it destroyed the dialog (like, say, read the
> non-gui state) it would be screwed because the whole component has
> been freed!
> 
> I think all the confusion goes away when you do something like this:
> [warning: not even compile tested]
> 
> // This is the gtk_destroy signal handler
> void
> gnc_customer_window_destroy_cb (GtkWidget *widget, gpointer data)
> {
>   CustomerWindow *cw = data;
> 
>   gnc_close_gui_component(cw->component_id);
> 
> }
> 
> // This is the CM close handler
> static void
> gnc_customer_window_close_handler (gpointer user_data)
> {
>   CustomerWindow *cw = user_data;
>   GncCustomer *customer = cw_get_customer (cw);
> 
>   gnc_suspend_gui_refresh ();
> 
>   if (cw->dialog_type == NEW_CUSTOMER && customer != NULL) {
>     gncCustomerBeginEdit (customer);
>     gncCustomerDestroy (customer);
>     cw->customer_guid = *xaccGUIDNULL ();
>   }
> 
>   gnc_unregister_gui_component (cw->component_id);
> 
>   gtk_widget_destroy (cw->dialog);
>   cw->dialog = NULL;
>   g_free (cw);
> 
>   gnc_resume_gui_refresh ();
> }
> 
> Makes a heck of a lot more sense to me.  David?

I think this will work because gtk_widget_destroy correctly handles
recursive invocation.  If the widget is already in the process of being
destroyed then the call to gtk_widget_destroy from
gnc_customer_window_close_handler is a noop, otherwise it will actually
destroy the dialog.

David