Re: strange gtk_set_data_full behavior ...

[Sven LUTHER <luther maxime u-strasbg fr>]

On Tue, Jun 08, 1999 at 01:51:07PM -0400, Owen Taylor wrote:
> 
> Sven LUTHER <luther@maxime.u-strasbg.fr> writes:
> 
> > i think i did found a bug in glib, don't know where to report it, so i will
> > write here.
> 
> GLib bug reports should be entered into the GNOME bug tracker
> for the package glib. See README file in GTK+ for more
> info.

Ok will do ... No so sure it is a bug now ...

> > i do the following :
> > 
> > char data1[] = "Hello";
> > char data2[] = "Bye";
> > char data3[] = "XXX";
> > void sven_free (gpointer data)
> > {
> >   printf ("Hello you %u.\n", data);
> >   printf ("Data is %s.\n", data);
> > }
> > 
> > ...
> > 
> >   printf ("Data1 = %u.\n", data1);
> >   printf ("Data2 = %u.\n", data2);
> >   printf ("Data3 = %u.\n", data3);
> >   gtk_object_set_data_full (GTK_OBJECT (drawing_area), "Sven_data",\
> >     (gpointer)data1, (GtkDestroyNotify)&sven_free);
> >   gtk_object_set_data_full (GTK_OBJECT (drawing_area), "Sven_data",\
> >     (gpointer)data2, (GtkDestroyNotify)&sven_free);
> >   gtk_object_set_data_full (GTK_OBJECT (drawing_area), "Sven_data",\
> >     (gpointer)data3, (GtkDestroyNotify)&sven_free);
> >   gtk_object_set_data_full (GTK_OBJECT (drawing_area), "Sven_data",\
> >     (gpointer)NULL, (GtkDestroyNotify)&sven_free);
> > 
> > and get the following output :
> > 
> > Data1 = 138616.
> > Data2 = 138624.
> > Data3 = 138632.
> > Hello you 138616.
> > Data is Hello.
> > Hello you 138624.
> > Data is Bye.
> > 
> > GLib-CRITICAL **: file gdataset.c: line 349 (g_datalist_id_set_data_full):
> > assertion `destroy_func == NULL' failed.
> > 
> > So : 
> > 
> > 1) sven_free does not get called when i exit the application (is it a modified
> >    scribble-simple, i quit hitting the Quit button who has a
> >    gtk_widget_destroy callback fixed to it.
> > 
> > 2) the last call to gtk_object_set_data_full should free the data, and is
> >    perfectly legal, or at least the tutorial and the header file claims so, but
> > 	does no such thing, and i get an error about NULL destroy function.
> 
> The warning is indicating that you can't set a destroy function
> for a NULL data pointer. (The reason for this is that
> gtk_object_set_data (object, key, NULL) actually removes
> that key from the list attached to the widget.

Why not just ignore the function then, and remove the data ? Why give an error
for that ? This mean that i cannot have a generic gtk_object_set_data_full
wrapper wich will set the function, and use it transparently as
gtk_object_set_data.

> I'm not quite sure why your destroy function isn't being
> called when the widget is destroyed; the fourth call
> should have absolutely no effect. (Other than printing
> the warning)
> 
> In fact, I tried putting your code into an example
> program, and the destroy function is in fact called...

Huh ??? could you send me the program ? i simply put this stuff in the
scribble-simple.c example, but then maybe the scribble-simple example is buggy
?

PS: is this kind of mail correct for this list, or should it go to gtk-list ?
I am not sure where to address my mails. I am writting a binding for the ocaml
language, not an application.

Friendly,

Sven LUTHER