From: Chris Thomas <cjack@...>
Date: 2002-01-15T03:14:12+09:00
Subject: Re: [OT] Question about RubyCocoa and GnuStep

On 1/10/02 8:16 PM, "Chris Gehlker" <gehlker@fastq.com> wrote:

> On 1/10/02 2:50 PM, "Chris Thomas" <cjack@cjack.com> wrote:
> 
>>>> So, my question is:  Could RubyCocoa be used under GnuStep on Linux?
>>>> I suspect that the answer is no right now,
>> 
>> In theory, it's possible to do this, but it would be a significant amount of
>> work with things as they stand.
>> 
>> The big technical problem (assuming that GNUstep perfectly replicates the
>> Cocoa API, which I'm pretty sure it doesn't currently) is that the GNU
>> Objective-C runtime and the NeXT Objective-C runtime -- although
>> conceptually related -- are completely different in both API and
>> implementation.
> 
> I think this overstates. Foundation pretty much works. At least my code
> works. AppKit has a long way to go. But the GNUStep folks express a desire
> to close the gap in their mission statement. Of course the fact that
> Foundation works is big deal for ObjC programmers and probably a don't care
> for ruby programmers.

I should be a little more clear. The Objective-C runtime library is the
support code for manipulating the underlying data structures that support
the dynamism of the Objective-C language, the class definition hierarchy and
such. NeXT had an Objective-C runtime library (which Apple continues to
maintain), but -- for reasons unknown to me -- did not donate it to the FSF
along with the Objective-C compiler. There is an entirely different GNU
Objective-C library for use on non-Mac OS X platforms; it is conceptually
similar, but different in API and implementation from the NeXT-derived
library.

>> I suspect you'll need to wait until GNUstep's interface is a bit closer to
>> Cocoa, though.
> 
> It seems to depend. Apple claims in one of their tech notes that Cocoa is an
> extension to the OpenStep API rather than a replacement for it and code that
> conforms strictly to the OpenStep API should port. Some of the folks on the
> Mac oriented lists, particularly Cocoa Dev, have asserted that this is
> mostly true. 

I'm not an expert on the provenance of Cocoa, so I'll accept that. :)

>> (BTW, A "fat binary" in Mac OS X parlance is a binary archive that contains
>> one Mach-O file for each CPU architecture that the developer wants to
>> support. Linux uses ELF executables, not Mach-O, so fat binary support is
>> not helpful for this purpose.)
> 
> This may be getting OT for a Ruby list but I find it really interesting. I
> don't understand ELF but I've been told it's very close to PEF which is
> supported in MOSX through a vector library. Wouldn't the same technique work
> for ELF? How did OPENSTEP support multiple executable formats?

To the best of my knowledge, OpenStep did not support multiple executable
formats. PEF applications are supported on Mac OS X through a command-line
tool called LaunchCFMApp that understands the PEF file format and sets up
the vector libraries (every function called from a PEF app must transition
through vector glue to translate it into a Mach-O call).

ELF applications could theoretically be supported the same way, but that
would require someone to do the work of creating a LaunchELFApp tool and
related stuff to translate ELF to Mach-O. PEF shared libraries are not
directly accessible from Mach-O code, and neither would ELF libraries be.

Chris