Re: Chaining Up (GLib Tutorial Error)

[Yevgen Muntyan <muntyan tamu edu>]

Phil Lello wrote:
> According to the GObject tutorial, chaining-up in 
> constructor/dispose/finalize code should be handled as follows:
>
> static void
> b_method_to_call (B *obj, int a)
> {
>   BClass *klass;
>   AClass *parent_class;
>   klass = B_GET_CLASS (obj);
>   parent_class = g_type_class_peek_parent (klass);
>
>   /* do stuff before chain up */
>   parent_class->method_to_call (obj, a);
>   /* do stuff after chain up */
> }
>   

Yes, a tutorial mistake.
> (Unless there is something horribly wrong with my implementation of 
> _GET_CLASS...)
>
> This works fine until we create CClass, a direct descendant of BClass. 
> When CClass is using the default 'method_to_call' code, e.g. in 
> finalize, B_GET_CLASS actually returns CClass. parent_class is now 
> BClass, and 'method_to_call' invokes itself, leading eventually to stack 
> overflow.
>   

Yes.

> The solution I've used, and that I think should be in the tutorial is:
>
> klass = g_type_class_peek (MY_CLASS_TYPE);
>
> Should I submit sample code to reproduce / raise a bug, or is this email 
> sufficient? I can provide a patch to tut_howto.xml if wanted, but this 
> seems excessive for a 1 line change.
>   

It'd be better to use G_DEFINE_TYPE in the tutorial, IMO. A nice
macro, saves you from many troubles.

Best regards,
Yevgen