I'm not sure, but from what I've read, I believe the non-underscore version
is only for use in Obj-C declarations (methods, properties), where the
double-underscore is for C declarations, including functions and variables
(local, global, or, I would expect, instance).

I don't know why there would be an issue with multiple levels of pointers
in a method declaration. Perhaps when everyone's recovered from WWDC,
someone else will chime in to help out. :-)


On 13 June 2015 at 18:00, Jonathan Schleifer <[email protected]>
wrote:

> Ah, thanks, that indeed works :). I was grepping `strings clang` for
> objc_null, that explains why I didn't find anything.
>
> Also, since there's no real documentation yet, what's the difference
> between __nullable and nullable and __nonnull and nonnull? What I found
> online reads like it's basically the same, with the one without the __
> being only usable in a method declaration. However, I noticed that there
> are cases where the one without __ doesn't work in a method declaration,
> e.g. when you have two layers of pointers.
>
> --
> Jonathan
>
> > Am 13.06.2015 um 17:59 schrieb Michael Hackett <
> [email protected]>:
> >
> > I believe it's:
> >
> >     #if
> >  __has_feature(nullability)
> >
> >
> >
> > On 13 June 2015 at 11:54, Jonathan Schleifer <[email protected]>
> wrote:
> > Hi!
> >
> > I saw that there's a __has_feature() for objc_generics and objc_kindof,
> however, there doesn't seem to be objc_nullability or similar. Since the
> sources for the Clang from Xcode 7 haven't been released, I grepped through
> `strings clang`, however, I could not find anything useful.
> >
> > What is the best way to check if the compiler supports nullability, so
> that if not I can #define nonnull and friends to nothing?
> >
> > PS: I also found objc_generics_variance - what's that?
> >
> > --
> > Jonathan
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