On Mon, 2024-10-28 at 04:07 +0100, Thorsten Glaser wrote:
On Sun, 27 Oct 2024, Arnd Bergmann wrote:
On Sun, Oct 27, 2024, at 06:16, Finn Thain wrote:
Right. And I don't think the problem is going to go away. One solution
that is sometimes raised is better tooling. I'm not sure how that would
No. You don’t understand the problem: applications are being
written that require natural alignment for at least 32-bit and
smaller quantities, some possibly for all quantities even. We
need these applications to work, and we cannot redesign them
(it’s common for them to store flags in the lowest pointer bits
and do other awful things).
Yep, that's exactly the problem. Plus, the maintainers of 99% of the upstream
projects don't care about the alignment peculiarities of the Linux/m68k port.
Could you please, if you cannot believe it yourself, accept the
word of those actually doing the porting that it is direly needed
in the current Linux ecosystem. Thank you.
Agreed 100%.
That struct is just 12 bytes for you then?
Right. i686 and m68k agree on that.
The other ones that have misaligned 'long long' variables are
arc
arm (OABI only)
csky
microblaze
nios2
openrisc
superh
i386
Okaaay. So, all “old” platforms or with low distro support.
For Debian, we have superh and i386, out of these. It is
entirely possible that Qt et al. can work with this, but
these all have natural alignment for quantities ≤ 32 bits.
I'm not aware of any serious issues with alignment on i386.
i386 was the original target for 90% of the software in Debian, so if
there are issues, developers have already addressed them.
Does Gentoo support more of them? Debian used to have arm
OABI, but that’s ages ago. I know things like OpenADK support
them, but that is very chiefly embedded.
Currently, Gentoo supports i386 out of that list.
The 32-bit architectures that use a natural 8-byte
alignment are
arm (EABI)
parisc
mips
powerpc
riscv
s390
sparc
xtensa
That’s majoritily represented in Debian. And ideally, we’d
use that for all new architectures.
I have a feeling that GCC’s -malign-int will only push us
into the former. I have no idea whether it’s feasible to
also change GCC for this; that will probably depend on both
the other “what parts of the toolchain need changing” and
whether GCC can be switched with little effort.
Did you see how Chewi implemented 32-bit alignment? He actually didn't
use -malign-int but directly patched GCC itself, see:
https://marc.info/?l=glibc-help&m=169303990426196&w=2
Adrian
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer
`. `' Physicist
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