Re: [Vala] Various tests with the new contract support, but also with non-GLib.Object classes

[Jürg Billeter <j bitron ch>]

On Thu, 2008-04-24 at 01:31 +0200, Philip Van Hoof wrote:
> I also wonder where the memory for " t = test_new ();" is protected for
> the use in app_thread_func as "app_y". As far as I can see is "app_test"
> assigning app_y to t (and if app_y was not NULL, freeing app_y first).
>
> That's probably as a result of y = #t; where I demand an ownership
> transfer.

Yes, this statement transfers the ownership of the object references by
`t' completely to `App.y', i.e. it also sets `t' to `null'.

> But the last line of app_test is going to free my t, right? Leaving me
> with a broken app_y, which I will be using in app_thread_func later.

The last line won't free `t', as `t' is now `null'. The issue here is
that `App.y' won't ever get freed as it's a static field, which is kind
of problematic. For applications we could just free objects assigned to
static fields at the end of main but that won't work for libraries just
like that.

> Will this only ever work with GLib.Object inherited types (ones that
> have reference counting)?
>
> Why not replacing "test_free" with a "test_unref" and adding a member
> called ref_count to "struct _Test" and do it right in stead? When I make
> myself a class in vala, I kinda 'okay' valac to do such things for me.

Yes, we're planning to change this a bit. Classes that don't specify a
base class will be reference-counted GType foundation classes, i.e. they
will derive from GTypeInstance. Non-GType registered classes (without
reference counting) will still be possible but will require an
attribute.

Jürg