Re: PATCH: Merge objc-improvements-branch to mainline

[Ziemowit Laski]

On Thursday, Sep 25, 2003, at 09:50 US/Pacific, Alexander Malmberg 
wrote:

> Ziemowit Laski wrote:
> > On Wednesday, Sep 24, 2003, at 10:48 US/Pacific, Alexander Malmberg
> > wrote:
> [snip]
> >   - The new exception syntax brings us closer to what C++ and
> > Javaoffers in
> >     this regard.  Although presently ObjC exceptions rely on
> > _setjmp/_longjmp
> >     for binary compatibility with Foundation, in the future we may 
> > flip
> > the
> >     switch and make it interoperable with C++ EH/RTTI machinery -- or
> > with Java
> >     -- and just ask developers to recompile their code.
>
> This sounds worrying. Currently, your extensions are explicitly
> documented as not interacting with c++'s exceptions. Do you intend to
> change this?

At some unspecified point in the future, when it becomes possible to
break binary compatibility, we hope to be able to move to the C++ EH
model.

> Introducing a bunch of extensions only to change their semantics later
> does not seem like a particularly good idea. If it is so, I would
> suggest that you at least add a warning in the documentation that this
> part of the semantics should not be relied on since it might change.

The semantics will not change; the only thing that _may_ change
is the implementation thereof.

> [snip]
> > As for the sizeof(jmpbuf) issue, I don't think we're in any more
> > trouble than
> > any vanilla C program utilizing setjmp/longjmp. :-)
>
> A vanilla c program can simply include setjmp.h and get the right
> definition of the struct. How do you propose that the compiler figure
> out the size with no more trouble than that (and, as the comment says,
> without forcing setjmp.h to be included)? (I can think of several
> solutions, but none that wouldn't involve a lot trouble.)

Yes, I agree that having the user #include <setjmp.h> would be a far
cleaner way; this was shot down at Apple internally. :-(  Of course,
when you guys do the GNU runtime port, you can either (1) require
<setjmp.h> to be included, or (2) use C++ EH.  Failing that, a
'jmpbuf_size' target hook could be put in whereby different platforms
could inform us of their requirements.

--Zem
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Ziemowit Laski                 1 Infinite Loop, MS 301-2K
Mac OS X Compiler Group        Cupertino, CA USA  95014-2083
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