Re: Plan needed for switching m68k to 32-bit alignment

On Fri, 2024-10-25 at 23:38 +0200, Thorsten Glaser wrote:
> On Fri, 25 Oct 2024, John Paul Adrian Glaubitz wrote:
> 
> > as m68k has supported 32-bit alignment through the "-malign-int"
> > switch for a long time.
> 
> That switch constitutes a fundamental ABI change, even if
> the effect is limited.
> 
> Question is, do we need a kernel change for this at all?
> Is there anything in the kernel/userland interface that
> gets affected by this, or do these APIs use sufficient
> explicit padding? Has anyone looked at this?

James Le Cuirot (chewi) has created a Gentoo/m68k chroot with 4-byte
alignment and most of the stuff just worked from what I remember.

> If we know that the answer is no, the plan could look
> different from a yes answer, so…
> 
> Additionally… has anyone done the simple “enable -malign-int
> in GCC, begin rebuilding stuff, first glibc, then others,
> see what breaks”? Is there sufficient effect that we cannot
> incrementally change over?

Yes, see above.

> (Another question: does -malign-int switch to natural
> alignment for all types, i.e. 64 bit for llong and double,
> etc. or are we going to have to change GCC first as well
> to avoid more surprises?)

I assume so. Chewi, can you answer that question?

Adrian

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