Re: [Vala] Can adding new virtual method break ABI?

[Jürg Billeter <j bitron ch>]

On Mon, 2011-12-12 at 12:12 +0100, Luca Bruno wrote:
> On Mon, Dec 12, 2011 at 12:01 PM, Jürg Billeter <j bitron ch> wrote:
>         On Sun, 2011-12-11 at 11:34 +0100, Luca Bruno wrote:
>         > 2011/12/11 Tal Hadad <tal_hd hotmail com>
>         >
>         > > This idea is based on the assumption that the size of
>         XClass struct
>         > > doesn't matter and can be changed(Am I right?).
>         > > Also, how does the virtual method order is currently done
>         by Vala? Is it
>         > > alphabetic or by the order of the decelerations?
>         > >
>         >
>         > The ordering does not matter, the padding does.
>         
>         Ordering matters as well. Vala uses declaration order.
>
> We're talking about virtual methods, aren't we? There's no ABI break
> if the order of N pointers is exchanged.

When a subclass overrides a virtual method, the class_init function uses
the offset of the virtual function pointer. If that offset changes, the
subclass will need to be recompiled to work again.

Jürg