Re: Cross-Platform Windows plus Mac

In article <macdev-267894.01334708112007@[EMAIL PROTECTED]
>,
 Ben Artin <macdev@[EMAIL PROTECTED]
> wrote:

> > 
> > All they did was ensure that the layers were properly separated, i.e.
that 
> > they didn't pass exceptions across the Objective-C/C++ boundary.  By 
> > following that and a few other simple patterns, all of their logic
(and 
> > there 
> > was a ton of it) was in C++ as was most of their "high-level"
presentation 
> > code.  That in turn talked to Objective-C code which actually
implemented 
> > the 
> > behavior for the high-level presentation code.
> 
> I really disagree with the characterization of "properly separated" for
this; 
> I 
> think it's "suitably crippled".
> 
> Given a language feature that is semantically equivalent in two
languages 
> (such 
> as exceptions), not being able to use that feature across the two
languages 
> has 
> nothing to do with proper separation and everything to do with running
into a 
> limitation of the language bridge and sucking it up.


Except that they are not semantically equivalent - C++ exceptions call 
dtors as the stack is unwound, while Objective-C exceptions don't (since 
Objective-C is built on C which has no such notion, and was implemented 
via setjmp/longjmp).  They are two completely different models (stack 
unwinding with compiler generated tables for stack layout vs 
setjmp/longjmp) that share some similar concepts but im****tant semantic 
differences.

So when Objective-C++ came about, they could either use one exception 
model or the other - they chose to use the Objective-C version (to avoid 
breaking all existing Objective-C code, with the caveat that C++ needed 
to be "partitioned").  With 64 bit Objective-C++, since there was no 
existing Objective-C code to break, they could finally use the C++ style 
exceptions.