Re: Question on BIGGEST_ALIGNMENT in GCC on NetBSD/m68k

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Adrian,

On Fri, 13 Jun 2025 at 14:00, John Paul Adrian Glaubitz
<glaubitz@physik.fu-berlin.de> wrote:
> On Fri, 2025-06-13 at 13:55 +0200, Geert Uytterhoeven wrote:
> > From its inception, Linux/m68k used an ABI compatible with SunOS,
> > which dates back to the MC68000, and was probably the most popular
> > UNIX OS running on m68k at that time.  Several other UNIX vendors
> > followed a similar path, starting from the MC68000.  E.g. the HP-UX
> > Portability Guide[1] states that HP-UX on HP9000/300 (based on SVR2
> > at that time, apparently) uses an alignment of 2 bytes, too.

> > Linux has a strong history of not breaking the ABI between kernel and
> > user space, so changing that ABI is a no-go.

> Okay and how does this now fix the problems we're having on Linux/m68k?
>
> https://wiki.debian.org/M68k/Alignment
>
> We're compatible to "fails to build from source" now. I'm not sure how this
> is any helpful.
>
> I'm not sure why several people are contributing to this discussion with
> the argument that this change would break the "Linux ABI" when the Linux
> ABI is currently broken and doesn't even allow for Python to be built without
> further modifications.

You mean Python is broken, as it makes assumptions that are not
guaranteed by the C standard (oops, which one? ;-) ? ;-)

Lots of older packages used to build fine on much more obscure systems
than Linux/m68k.  Unfortunately people stopped caring for anything
not 64-bit little endian.  Yes, I know saying that doesn't help...

> What is your suggested alternative? Do you expect me to patch broken packages
> into all eternity? If keeping 2 bytes alignment ABI is so important to so many
> people, I would expect proponents to come up with solutions.
>
> So far, I haven't seen any. Just arguments why my approach is wrong.

You are completely ignoring the last sentence I wrote...

> >  What you do in the layers
> > above (in the kernel), or above (in userspace) is something different...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds