Re: Question on BIGGEST_ALIGNMENT in GCC on NetBSD/m68k
Hello Geert,
On Fri, 2025-06-13 at 13:55 +0200, Geert Uytterhoeven wrote:
> "The official(!) ABI"...
>
> Official according to what and to who?
> There are de jure and de facto standards.
>
> There's a lot of discussion and talking next to each other about
> "the ABI", and which ABI applies to what...
>
> The SVR4 ABI applies to systems claiming compatibility with SVR4, which
> was (AFAIK) never a goal for Linux. Before that, there were other ABIs
> used by various UNIX systems (BSD, SYSV, ...) and non-Unix systems
> (AmigaOS, Atari TOS, MacOS, ...).
>
> 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.
>
> SVR4 was an attempt to consolidate the various flavors of UNIX at
> that time (with BSD and SYSV being the two largest flavours), and
> "rebooted" the ABI. Binary-compatibility with older versions was
> ignored, as the UNIX landscape was wildly differing anyway, and
> people cared mostly about source-compatibility.
>
> Linux has a strong history of not breaking the ABI between kernel and
> user space, so changing that ABI is a no-go. What you do in the layers
> above (in the kernel), or above (in userspace) is something different...
>
> [1] http://www.bitsavers.org/pdf/hp/9000_hpux/7.x/98794-90047_HP-UX_Portability_Guide_Sep89.pdf
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.
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.
Adrian
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer
`. `' Physicist
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