Re: [Vala] _get_type() and G_GNUC_CONST

[Jan Hudec <bulb ucw cz>]

On Wed, Aug 18, 2010 at 22:43:27 +0200, Aleksander Wabik wrote:
> In glib doc for G_GNUC_CONST macro: "A const function doesn't examine
> any values except its parameters, and has no effects except its return
> value."
>
> In 10-years-old mail:
> http://mail.gnome.org/archives/gtk-devel-list/2001-May/msg00174.html
>
> "_get_type() functions do have side effects, that of registering
> a type upon first invocation."
>
> So... as far as I can remember get_type() functions still has effect of
> registering a type in the type system upon first call? So is
> G_GNUC_CONST in vala-generated code valid?

Yes, the code is valid.

The point is that the function does not have any side-effects for any
practical purposes as everything that may depend on the type being allocated
either gets it from the function, or at least depends on something else that
does.

What the annotation means to compiler is that it is free to change the number
of calls to the function, reorder it with respect to other calls and memoize
it's return value for reuse. All of these optimizations are valid with type
getters, so the annotation is correct there.

-- 
                                                 Jan 'Bulb' Hudec <bulb ucw cz>