Re: Fast enumeration

[Nicola Pero]

> > If you refer to for(id x in y) syntax, I believe you just need to  
> > use a compiler with objc2.0 support, as well as a sufficiently  
> > recent runtime.
>
> That, and support for the fast enumeration protocol in Base  
> collections. This exists at least in base-1.20.1.
>
> This doesn't actually resolve the question, though, it just restates  
> it.
>
> Which compilers support [this aspect of] Objective-C 2.0 outside of  
> Apple's platforms? Neither gcc nor clang provide sufficiently
> comprehensive release notes to determine this sort of thing reliably.

GCC up to 4.5 does not support it.  GCC 4.6 (currently frozen,  
preparing for release) does support it.

The GCC 4.6 release notes (http://gcc.gnu.org/gcc-4.6/changes.html)  
contain a complete list of all the changes in the Objective-C
compiler in GCC 4.6.  In particular, they state:

"The Objective-C 2.0 fast enumeration syntax is supported in Objective- 
C. This is currently not yet available in Objective-C++.
Fast enumeration requires support in the runtime, and such support has  
been added to the GNU Objective-C runtime library
(shipped with GCC)."

I hope these release notes are clear and comprehensive enough ;-)

> How do I detect, at build time, which runtime I'm using, and  
> precisely which version of what runtime has the necessary support?  
> This is the sort of information one might expect to find on the  
> ObjC2_FAQ wiki page, but one doesn't (and it's probably out of date  
> anyway).
>
> Basically, my choices are:
> * Test a rather large set of compiler, runtime and library versions  
> together under a VM.
> * Hope that someone (i.e. David) imparts Secret Lore.
> * Continue to use slow enumeration extensively throughout Oolite for  
> the next couple of years, except on 64-bit Mac OS X.

In the case of GCC, you can simply check for the macro __GNU_LIBOBJC__  
which is defined only
by the GNU Objective-C runtime shipped with GCC 4.6 (and onwards) and  
by no other runtime.

If that macro is #defined, you have fast enumeration support in the  
compiler+runtime.  If not, you don't unless you're using
clang+libobjc2 I guess, which should be possible to check using  
another macro.

Thanks

PS: Unfortunately, you are asking for a stable release, and GCC 4.6  
hasn't been released yet, and you need gnustep-base
from trunk (soon to be released too) to use GCC 4.6.  In a couple of  
months, you'll have it in stable releases :-)