Re: xen bits broke x32 build

[Philippe Mathieu-Daudé]

On 11/4/23 19:30, Michael Tokarev wrote:
> 11.04.2023 15:09, Peter Maydell wrote:
> ..
> > Frankly I would prefer to just say "we don't support x32".
> > It's a weird non-standard configuration that as far as I'm
> > aware is very little used. Its stats in the debian
> > popularity-contest graphs peaked at 18 users in 2017, and
> > have mostly been fluctuating between 1 and 3 for the last
> > couple of years:
> > https://popcon.debian.org/stat/sub-x32.png
>
> x32 was a nice idea but it lacked some final steps for it
> to fly.

I used to use a FreeRTOS POSIX/ucontext port compiled in x32.
This was useful to mimic FreeRTOS baremetal ARM32 memory footprint.

I see having a x32 QEMU binary as a masochist experiment =)

> In my opinion anyway.  Its compactness and speed
> are fantastic, - qemu build is about 10..15% faster with
> x32 gcc than it is with x86_64 gcc.
>
> At the time debian picked it up, it was not very usable
> b/c too many things didn't work and needed care.  Today,
> much more software actually works on x32. It is more,
> today with debian multiarch setup, it is possible to install
> some *parts* of the system to be x32 while the rest being
> x86_64, either for parts which benefits from x32 the most,
> or the other way around, main x32 and some parts x86_64.
> But it *still* lacks some infrastructure in debian, so it
> is possible to do with stable or testing distribution, -
> right now it is possible with unstable only.  Maybe we
> can change that for bookworm+.
>
> The thing is that now, it is much more complete than it
> was in 2017, and it'd be really sad if it goes away.
>
> x32 reveals some interesting problems in the code such
> as type misuse, it already helped to find and fix some
> bugs in some software, - for example in samba, where
> a pointer was misused to store a time_t (which would
> break with past-2038 time_t).

Why wasn't this caught by other 32-bit target?

> qemu never said it supports x32, and no one demanded
> such support from it. It's interesting to have it working
> there still, I *think*, as long as it does not require
> extra efforts.
>
> I'm fine to maintain the change required to keep it at
> least buildable on x32 in debian - again as long as it
> does not require huge efforts.
>
> > We're currently planning to deprecate-and-drop 32-bit x86
> > hosts, which are much more widely used than this. I see
> > no reason why we should care about this oddball failed
> > experiment of an ABI...
>
> Thanks,
>
> /mjt