[Dynamite] ANSI C question

[Ian Holmes]

On Thu, 23 Mar 2000, Guy Slater wrote:

> > > Do either of you know if this is strict ANSI, i.e. can we be sure that the
> > > first two fields of _GArray (data & len) are mapped to the same memory
> > > locations as data and len in _GRealArray in all C compilers?
> > 
> > This is strict ANSI interestingly. (read the back of K&R about struct
> > layout).
> 
> Given that:
> 
>     o The first member must always have offset zero
>     o Other members have increasing offset
>     o Structure padding is implementation defined
> 
> It still isn't clear to me (from K&R) whether the padding
> has to be *consistent* throughout the implemenataion.

hmmmm

> 
> Anyway, I doubt the glib people wouldn't have used it if
> it wasn't safe - they seem to have gone to a lot of effort
> to ensure portability. 

maybe we want to be even more portable than GLib though...

> 
> > > If so it makes life a lot easier...
> 
> Saves much messing with offsetof() or somesuch ..

We *could* do inheritance this way as Ewan says GTK does.

We would have to decide fairly soon whether we wanted to do inheritance
this way or by the "derived interface has a pointer to base interface"
model that was in the code I posted the other day.

The GTK model is:

	* slightly more efficient
	* much less safe

I can't help feeling that we are seriously retreading ground here. Oh
well.

Ian