Re: Question on BIGGEST_ALIGNMENT in GCC on NetBSD/m68k

John Paul Adrian Glaubitz <[email protected]> Mon, 26 May 2025 20:50:12 +0200

Newsgroups	gmane.os.netbsd.ports.m68k,gmane.linux.debian.ports.68k,gmane.linux.ports.m68k
Message-ID	<db71b12ac8ad8dabce6b0781e42e1fc2d5fbc0fe.camel@physik.fu-berlin.de>

Hi Jason,

On Mon, 2025-05-26 at 11:25 -0700, Jason Thorpe wrote:
> > On May 26, 2025, at 8:05 AM, John Paul Adrian Glaubitz <[email protected]> wrote:
> > 
> > Now I'm wondering whether why some types on NetBSD such as double have 8 bytes
> > alignment on a 32-bit system. Does anyone know the reasoning for that?
> 
> Because that’s what is specified in the System V ABI for m68k.
> 
>      https://m680x0.github.io/ref/sysv-m68k-abi-part1.pdf
> 
> See Figure 3-1.  “double” and “long double” are explicitly 8-byte aligned.

OK, that clarifies it, thank you!

FWIW, I have scanned the whole SysV ABI specification in case someone needs it:

https://people.debian.org/~glaubitz/m68k-sysv-abi.pdf

Adrian

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