Re: m68k MacOS target support?

[lars brinkhoff <lars@nocrew.org>]

Mark Mitchell <mark@codesourcery.com> writes:
> >>>>> "lars" == lars brinkhoff <lars@nocrew.org> writes:
>     lars> That's very interesting, because I'd like to know if the GCC
>     lars> maintainers are interested in the changes I would have to
>     lars> make to GCC for it to support the different PDP-10 pointer
>     lars> formats.
> I can only speak for me; I only get one vote on the SC, just like
> everybody else.  And I've been in the minority more than once before!
> So, you shouldn't take what I say as necessarily reprentative.

Is there something I can do to get the attention of the SC?  Other
than posting these letters, of course.

>     lars> It's my intention that the changes should be as
>     lars> non-intrusive as possible and make GCC easier to port to
>     lars> other architectures with unsusual pointer formats.  
> That sounds helpful.  Those kind of generic changes are probably
> welcome -- especially if they don't add much maintenance overhead, and
> if there are other architectures that have similarly unusual pointer
> formats.  (I don't know whether there are such beasts or not,
> honestly).

There are, such as some DSPs, but they seem rare.  In general, I think
all word-addressed machines belong to this group, for example the ADI
210xx SHARC DSP.  The bit-addressed TMS34010 also doesn't fit within
GCC's model of pointers.  Both have much-hacked GCC ports that
hopefully would have benefitted from more generic pointer handling.

> What's funny about these kinds of things is how hard it is to undo
> anything.  Whenever I propose getting rid of a "feature" in GCC, I
> find that people now rely on that feature, or that at least many
> people are afraid people rely on that feature.  Support for a platform
> is a feature.  Once support is in GCC, it will probably be somewhat
> difficult to remove that support.

If PDP-10 support in GCC would get to the same level as support for
the PDP-11, I'd be quite happy.  And the PDP-11 back end is not looked
after very much, it seems.

> If it were up to me, I would ask the same questions any commercial
> enterprise would ask before including a port to the PDP-10, or any
> other architecture.  How large is the likely userbase?

I'd have to admit the PDP-10 userbase is most likely miniscule.

> What are the likely costs?  What are the long-term maintenance
> costs?

Some research would be needed to answer those questions.  And before
making that research, I'd like to know if there's at least some chance
of the changes being included in GCC.

> The beauty of free software, of course, is that even if the answers to
> those questions were negative, you would still have the freedom to do
> what you want to do, and to make your work available to others.

The question is whether to go ahead and make generic changes suitable
for inclusion in GCC, or to just make the minimal changes needed to
support the PDP-10 and maintain that as a separate patch.