D/Objective-C, extern (Objective-C)

[Johannes Pfau]

Am Mon, 24 Jun 2013 22:30:56 +0200
schrieb Jacob Carlborg <doob at me.com>:

> On 2013-06-24 15:27, Michel Fortin wrote:
> 
> > Not necessarily. There's a couple of Objective-C classes that get
> > special treatment by the compiler (identified by a pragma). One
> > could do the same for an UDA so the compiler would know where to
> > get that value. I'd surely have implemented it as an UDA if such a
> > thing existed at the time.
> 
> The thing is that pragmas are tied to the compiler. It knows the 
> difference between pragma(foo) and pragma(bar). But for UDA's they
> are all treated the same, there's no difference between @(3),
> @("asd") and @foo from the compiler's point of view (as far as I
> understand). You could implement it as a new attribute (that is, not
> an UDA), but to implement it as an UDA would be a totally new thing.

Maybe it's new in dmd but gdc already has an UDA which is recognized by
the compiler:
https://github.com/D-Programming-GDC/GDC/blob/master/libphobos/libdruntime/gcc/attribute.d
https://github.com/D-Programming-GDC/GDC/commit/afb27a0048cbf51d40abc2810b85641d9e9af9dc

The benefit of an UDA is that it does not pollute the global namespace
like a normal attribute would.