Re: [Vala] Locking null references

[Jürg Billeter <j bitron ch>]

Hi Andrés,

On Tue, 2010-03-30 at 11:47 +0200, "Andrés G. Aragoneses" wrote:
> El 30/03/10 11:35, Jürg Billeter escribió:
> > On Mon, 2010-03-29 at 18:30 -0700, Jim Nelson wrote:
> > > In Vala, I can lock a null reference.  Is this by design or a side-effect?
> >
> > It's by design (constrained by GObject). Unlike in C#/.NET, we don't
> > have a monitor available in every object. Due to this constraint, we've
>
> AFAIK, it's not that there's a Monitor available in every object. The
> lock statement is translated into a Monitor.Enter() call, but note that
> this is a static function call.

The runtime uses a per instance field to implement Monitor.Enter, as far
as I know.

> > decided to use different lock statement semantics compared to C#. The
> > only other option would have been to not support lock statements at
> > all .
>
> Well, I'm wondering about a 3rd option which would be a compromise: that
> vala translate every lock statement with a minimal null-check first, so
> if the condition is not met, an exception is raised? What do you think
> about this approach?

I fail to see what we would gain by doing that. The semantics would
still differ significantly from C#. I don't see a reason why the field
value should ever be relevant with Vala's lock statement semantics. For
example, you can also lock integer fields where the null check wouldn't
make any sense.

Jürg